Port Coldwell area - Geology Ontario
Port Coldwell area - Geology Ontario
Port Coldwell area - Geology Ontario
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ONTARIO DEPARTMENT OF MINES<br />
GEOLOGICAL BRANCH .<br />
OPEN FILE REPORT<br />
No. SOU<br />
GEOLOGY OF<br />
PORT COLDWELL AREA<br />
DISTRICT OF THUNDER BAY<br />
ONTARIO<br />
DEC. 4, 1967
DEP/vrrv.- M T "; VMM FS<br />
Open-file Reports<br />
Open-file reports are made available to the<br />
public subject to certain conditions. Anyone using them<br />
shall be deemed to have agreed to these conditions which<br />
are as follows:<br />
This report is unedited. Discrepancies may<br />
occur for which the Department does not<br />
assume liability.<br />
Open-file copies may be read at the following<br />
places:<br />
The Library (Room 1433, Whitney<br />
Block), Department of Mines,<br />
Parliament Buildings, Toronto.<br />
The office of the Resident Geologist in<br />
whose district the <strong>area</strong> covered by this<br />
report is located.<br />
A report cannot be taken out of these offices.<br />
Handwritten notes and sketches may be made<br />
from it. This particular report is on file in<br />
the Resident Geologist's office located at:<br />
179 South Algoma St. ,<br />
<strong>Port</strong> Arthur<br />
Open-file reports cannot be handed out for<br />
office reading until a card, giving the name<br />
and address of the applicant, is filed with the<br />
Resident Geologist or Librarian.<br />
A copy of this report is available for interlibrary<br />
loan.<br />
The Department cannot supply photocopies.<br />
Arrangements may be made for photocopying<br />
by an outside firm at the user l s expense. The<br />
Librarian or Resident Geologist will supply<br />
information about these arrangements.<br />
The right to reproduce this report is reserved<br />
by the <strong>Ontario</strong> Department of Mines. Permis<br />
sion for other reproduction must be obtained in<br />
writing from the Director, Geological di ranch.<br />
J, E. Thomson,<br />
Director, Geological Branch.
ONTARIO<br />
DEPARTMENT OF MINES<br />
GEOLOGY OF<br />
PORT COLDWELL AREA<br />
DISTRICT OF THUNDER BAY<br />
ONTARIO<br />
by<br />
Frank P. Puskas
Table of Contents<br />
Page<br />
Abstract .......................... *...... *............. v<br />
Introduction ........................................... l<br />
Mapping Methods ..................................... 2<br />
Acknowledgments ..................................... 3<br />
ireviou- Geological Investigation ................... 4<br />
To -jogra^ay ... ....... ...... .... . ... . . .. .............. 5<br />
Ncrural Resources ................................... 8<br />
General <strong>Geology</strong> ........................................ 9<br />
Table of formations .............................. 14<br />
Metavolcanic-Metasedimentary Assemblage ............. 16<br />
Mafic to Intermediate Metavolcanics .............. 16<br />
Felsic Metavolcanics ............................. 19<br />
Metasediments .................................... 22<br />
Mecagreywacke ................................. 22<br />
Early Granitic Rocks ................................ 23<br />
Late Mafic Intrusive Rocks .......................... 24<br />
<strong>Port</strong> <strong>Coldwell</strong> Alkalic Complex ....................... 25<br />
Introduction ..................................... 25<br />
f Main f Series ................................. 26<br />
"Chilled 1 Gabbro ........................ 26<br />
Massive Gabbro .......................... 28<br />
Layered Gabbro .......................... 30<br />
Laurvikites ............................. 32<br />
Layered Laurvikite ................... 33<br />
Laurvikite, massive .................. 34<br />
Laurvikite, pegmatites ............... 34<br />
Laurvikite, porphyritic varieties .... 36<br />
'Secondary* Series ............................ 36<br />
Syenodiorite ............................ 37<br />
Nordmarkite . .. ..... .... ................. 37<br />
Nepheline Syenites ...................... 38<br />
Natrolite-Perthite Dikes ................ 40<br />
Analcite Tinguaite Dikes ................ 40<br />
Lamprophyre Dikes ............................. 40<br />
Perthosite Dikes .............................. 41<br />
Late Granitic Rocks ................................. 41<br />
Little Pic River Granite ......................... 41<br />
Pleistocene and Recent ................................. 42<br />
Structural <strong>Geology</strong> ..................................... 43<br />
Introduction ........................................ 43<br />
Structural Elements within the Metavolcanic-<br />
Metasedimentary Sequences ....... 44<br />
Fold Structures .................................. 44
Page<br />
Foliation and Lineation ............................ 45<br />
Faulting ........................................... 46<br />
Jointing ........................................... 46<br />
Accumulation and Interpretation of Joint data ... 47<br />
Joints in Metavolcanic-Metasedimentary Sequences. 48<br />
Structures Related to the Granitic Intrusions ......... 50<br />
Jointing ........................................... 50<br />
Conclusion ...................................... 53<br />
Structures Related to <strong>Port</strong> <strong>Coldwell</strong> Alkalic Complex ... 54<br />
Glossary of Terms .................................. 54<br />
Layering in the 'Main 1 Series ...................... 56<br />
Rhythmic Layering ............................... 56<br />
Discontinuous and/or Disturbed Layering ......... 57<br />
Inch-Scale Layering ............................. 57<br />
Cryptic Layering ......................,......... 58<br />
Igneous Lamination in the 'Main 1 Series ............ 58<br />
Jointing in the 'Main 1 Series ...................... 59<br />
Layering in the 'Secondary' Series ................. 60<br />
Jointing in the 'Secondary' Series .........ooo..... 60<br />
Lineaments ......................................... 62<br />
Summary ............................................ 62<br />
Economic <strong>Geology</strong> ..................................o...... 64<br />
Introduction ...........*.............................. 64<br />
Iron ....................o.............**..*..........* 65<br />
Zebe Renshaw ............o. 0 ............*.....o..... 66<br />
George Olson ......................o................ 67<br />
Empire Explorations Ltd. ..........................o 68<br />
Non-Ferrous Base Metals ............................... 70<br />
Moneta Porcupine Mines Limited ..................... 71<br />
Lakehead Mines Limited ............................. 76<br />
Conwest Exploration Company Limited ................ 79<br />
Anaconda American Brass Limited .................... 82<br />
Falconbridge Nickel Mines Limited .................. 85<br />
Building Stone ........................................ 86<br />
Cold Spring Granite Company ......................*. 86<br />
Lake Superior Stone Syndicate ...................... 88<br />
Nepheline ............................................. 88<br />
Denison Mines Limited .............................. 89<br />
Sand and Gravel ....................................... 91<br />
Selected Bibliography ...................................o 92<br />
- iii -
Figures*<br />
1. Contour diagram of joints in Precambrian metavolcanicmetasedimentary<br />
sequences in the <strong>Port</strong> <strong>Coldwell</strong> <strong>area</strong>,<br />
lower hemisphere plot of 1300 poles.<br />
2. Contour diagram of joints in Jim Lake granite, lower<br />
hemisphere plot of 700 poles.<br />
3. Dilation features exhibited by the lamprophyre dikes<br />
emplaced along the extension joints in the Jim Lake<br />
granite.<br />
4. Contour diagram of joints in the 'main 1 series of rocks<br />
of the <strong>Port</strong> <strong>Coldwell</strong> Alkalic Complex. Lower hemisphere<br />
plot of 1900 poles.<br />
5. Contour diagram of joints in Coubran Lake metavolcanic<br />
roof pendant, lower hemisphere plot of 861 poles.<br />
6. Contour diagram of joints in the larger bodies of<br />
nepheline syenite, lower hemisphere plot of 683 poles.<br />
7. Sketch illustrating the presence of nepheline syenite<br />
veins along pre-existing joints, in the metavolcanics,<br />
which have been reactivated during emplacement. From<br />
portion of Coubran Lake metavolcanic roof pendant, 4<br />
miles northeast of <strong>Port</strong> <strong>Coldwell</strong> station, along the<br />
Trans Canada Highway 17.<br />
8. Sketch illustrating the repeated reactivation of jointing<br />
with concomitant intrusion of feldspathoidal syenite<br />
dikes.<br />
9. Surface geological plan of part of the property of Moneta<br />
Porcupine Mines Limited showing the relative locations<br />
of gossan zones and diamond drill holes (modified from<br />
a plan by G. Perrault).<br />
10. Diagram of sections along a specimen of nephelinized<br />
mafic metavolcanic. Note the brecciation and partial<br />
assimilation (shown by stippling) of the metavolcanics.<br />
Veinlets of nepheline syenite are joint controlled.<br />
* These figures follow page 94, at the back of this report.<br />
- iv -
Preliminary Map*<br />
(Back pocket)<br />
P.114 <strong>Port</strong> <strong>Coldwell</strong> Area, Scale l inch to \ mile<br />
* Preliminary maps may be purchased at Publications Office, <strong>Ontario</strong><br />
Department of Mines, Whitney Block, Parliament Buildings, Toronto.
ABSTRACT<br />
The map-<strong>area</strong>, in the District of Thunder Bay, is dominated<br />
by the <strong>Port</strong> <strong>Coldwell</strong> Alkalic Complex.<br />
The Complex is Precambrian<br />
(1000+ m.y.), approximately 580 square kilometres in <strong>area</strong>,<br />
more or less circular in outline, and lies within a metavolcanicmetasedimentary<br />
belt which extends westward from White Lake<br />
along the northern shore of Lake Superior.<br />
The <strong>Port</strong> <strong>Coldwell</strong> Alkalic Complex is composed of two<br />
series of rocks: A 'main 1 series which includes gabbros and<br />
laurvikites, and a 'secondary 1<br />
series which includes syenodiorites,<br />
nordmarkites and feldspathoidal rock types.<br />
Within the 'main* series a zonation has been recognized<br />
which is as follows:<br />
Upper Zone:<br />
Lower Zone:<br />
Inner Border Zone f b f<br />
Inner Border Zone 'a 1<br />
Outer Border Zone:<br />
Laurvikite<br />
Layered laurvikite<br />
Layered gabbro<br />
Massive gabbro<br />
Chilled gabbro<br />
The rhythmic layering (Skaergaard type) in the gabbro and<br />
laurvikite dips inwards at moderate angles.<br />
Lensoid bodies<br />
of titanomagnetite-apatite up to 50 feet wide are generally<br />
concordant with the attitude of layering.<br />
The Little Pic River granite has intruded the northwestern<br />
part of the <strong>Port</strong> <strong>Coldwell</strong> Complex.<br />
Inclusions of gabbro,<br />
laurvikite and mafic metavolcanics are abundant within the
granite or hybrid phases thereof.<br />
The <strong>area</strong> has been investigated for iron and non-ferrous<br />
base metals, but there has been no production to date.<br />
Analyses to date indicate a fairly large concentration of<br />
titanium in the ilmenomagnetite bands. Base metal mineralization<br />
is predominantly restricted to the massive gabbros, a zone<br />
approximately 300 metres wide. Detailed drilling of the<br />
sulphide-bearing gabbro, by various companies, more or less<br />
including all portions of the zone exposed, has indicated a<br />
limited or large tonnage of fairly low-grade copper ore.<br />
Continued exploration in the <strong>area</strong> and changing market demands<br />
may eventually lead to the development of an ore deposit.<br />
- vi -
- l -<br />
<strong>Geology</strong> of the <strong>Port</strong> <strong>Coldwell</strong> Area<br />
District of Thunder Bay<br />
By F. P. Puskas 1<br />
INTRODUCTION<br />
The <strong>Port</strong> <strong>Coldwell</strong> <strong>area</strong> is between approximate longitudes<br />
860 17 f and 86O40'W and latitudes 48o41 f and 48O54 f N and comprises<br />
all or parts of the following townships: Pic, 76, 77, 78,<br />
79, and 80, in the District of Thunder Bay, <strong>Port</strong> Arthur Mining<br />
Division.<br />
The <strong>area</strong> lies on the north shore of Lake Superior<br />
which in most cases is rocky and precipitous and generally<br />
offers but limited opportunity for safe disembarkation.<br />
Protected harbours can be found at <strong>Port</strong> Monroe, <strong>Port</strong> <strong>Coldwell</strong><br />
and Marathon.<br />
The south part of the <strong>area</strong> is traversed by the Canadian<br />
Pacific Railway line and Trans-Canada Highway 17 with both<br />
right-of-ways running very close to the shoreline. The<br />
panoramic view along this stretch of the coast is almost<br />
unrivalled for scenic beauty.<br />
The northwest parts of the <strong>area</strong> were reached by vehicle<br />
by way of Killala Lake road which has a reasonably good gravel<br />
surface up to the Little Pic River bridge.<br />
Maintenance costs<br />
I<br />
Postgraduate student, Department of <strong>Geology</strong>, Lehigh University,<br />
Allentown, Penna., Manuscript received by the Chief Geologist,<br />
6 Jan. 1967.
- 2 -<br />
were formerly met by revenue received from tolls but with<br />
discontinuance (in 1958) of tolling the various bridges,<br />
including the Little Pic River bridge, have been closed to<br />
vehicle traffic.<br />
The north parts of the map-<strong>area</strong> are<br />
accessible by means of the Gordie Lake-Coubran Lake-Wullie<br />
Lake waterway system and by means of the Pic and Little Pic<br />
rivers which can be navigated by canoe from their mouths<br />
northward for distances up to 50 miles.<br />
A few short portages<br />
are necessary during low-water season.<br />
The airstrip, belonging to Marathon Pulp and Paper<br />
Company, is located near the Highway 17 turnoff to the Marathon<br />
townsite and is adequate for medium-range, twin-engine aircraft,<br />
Mapping Methods<br />
The present geological survey was carried out during the<br />
summers of 1958 and 1959 by a field party consisting of two<br />
senior geologists, and two assistants, and during the summer of<br />
1960 by a two-man party.<br />
The geology was plotted on perfatrace overlays on aerial<br />
photographs at a scale of l inch to 1/4 mile.<br />
All exposures<br />
along the shorelines, power lines, railway and highway were<br />
examined and plotted; intervening forest-covered country was<br />
mapped by running pace-and-compass surveys generally at 1/4
- 3 -<br />
mile intervals. Data from the overlays were transferred to a<br />
base map prepared by the Cartography Unit of the <strong>Ontario</strong><br />
Department of Mines. In transferring data to the base map<br />
care was taken to minimize marginal distortions by recording<br />
only that data centrally located in each respective overlay.<br />
A preliminary geological map (P.114) on the scale of l inch<br />
to % mile was issued in 1961. A revised edition shows the<br />
outcrop <strong>area</strong>s.<br />
Acknowledgments<br />
Much of the early mapping was done by H. V. Tuominen and<br />
N. T. Irvine in 1958 and 1959. In 1960 the author and<br />
H. V. Tuominen were assisted by T. Wade and W. Shorten; in<br />
1961 the author was assisted by T. Wade.<br />
The author received all possible assistance from the<br />
mining companies that own properties in the <strong>area</strong> and his<br />
indebtedness to them is hereby acknowledged. As well it is an<br />
equal pleasure to record the assistance given by various<br />
residents of the Marathon <strong>area</strong>, and various members of the<br />
<strong>Ontario</strong> Department of Mines, in particular; E.G. Pye, resident<br />
geologist at <strong>Port</strong> Arthur; and J.E. Thomson, Chief Geologist;<br />
and M.E. Hurst, Director.
- 4 -<br />
Previous Geological Investigation<br />
As early as 1846 the presence of syenite had been<br />
reported (Logan 1846-7, p.29-30) and mention of nepheline<br />
syenite was made by 1863 (Logan 1863,p.80-81, 480, 647).<br />
A brief account of the early investigations up to 1910 has<br />
been given by Kerr (1910, p. 194-232) to which the reader<br />
is referred.<br />
The first reconnaissance investigation of the region<br />
was carried out by Kerr (1910) during the fall of 1906 and<br />
1907. In all a period in the order of ten weeks was spent<br />
in the mapping of the geology along the shore line, along<br />
the Canadian Pacific Railway, and along five north-south<br />
traverses. The high standard of Kerr 1 s investigation cannot<br />
be denied regardless of the early date at which the work was<br />
done, and despite the obvious retarding factors, such as the<br />
adverse weather conditions encountered, the limited field time<br />
available, and the absence of modern mapping aids and highway<br />
cuts.<br />
The west limit of the map-<strong>area</strong> was mapped by Walker<br />
(1956) and the east limit of the <strong>area</strong> was examined by Thomson<br />
(1931) and Milne (1964).
- 5 -<br />
Topography<br />
The highest hills in the <strong>area</strong> are found within the <strong>Port</strong><br />
<strong>Coldwell</strong> Complex and are generally capped by volcanic flows<br />
and (or) their metamorphic equivalents.<br />
These hills can be<br />
considered as belonging to one of two categories; namely,<br />
hills f peripheral 1<br />
to, and those hills associated with, the<br />
more extensive and centrally located metavolcanic roof pendant<br />
(presently named the Coubran Lake roof pendant).<br />
The<br />
1 peripheral 1 hills have elevations in the order of 900 to 1300<br />
feet above mean sea level.<br />
The centrally located hills have<br />
elevations which are 1300 to 1500 feet and in places nearly<br />
1600 feet above mean sea level.<br />
The relative differences in elevation of the rocks within<br />
the <strong>Port</strong> <strong>Coldwell</strong> Complex are distinctive and appear significant<br />
in that the feldspathoidal syenites, which characteristically<br />
occur associated with the Coubran Lake roof pendant, consistently<br />
exhibit the highest elevations.<br />
Most hills in the <strong>Port</strong> <strong>Coldwell</strong> <strong>area</strong> have a north-south<br />
profile represented by a moderately gentle dipping north slope<br />
and a more or less rounded top, followed by a precipitous slope<br />
to the south.
- 6 -<br />
Since the mean water level of Lake Superior is 602 feet<br />
above mean sea level, the available relief in the <strong>area</strong> is<br />
considerably higher than the general elevation of the<br />
surrounding Shield <strong>area</strong>s.<br />
The high relief in the <strong>area</strong> may be<br />
attributed to rapid post-glacial uplift and older (i.e. pre-<br />
Pleistocene) downfaulting associated with and (or) related to<br />
the formation of the Lake Superior basin.<br />
The <strong>area</strong> is dissected by numerous lineaments and valleys,<br />
the more prominent of which are:<br />
(1) south-trending valleys of the Pic and<br />
Little Pic River, Redsucker Cove lineament, east<br />
Wullie Lake lineament, Jim Lake lineament;<br />
(2) northwest-trending valleys of Bamoos Lake, Knob lake,<br />
Coubran Lake;<br />
(3) northeast-trending valleys of Seeley and Lacobeer lakes<br />
and Pic Island;<br />
(4) east-west trending valleys.<br />
Many valleys, but mainly those which trend to the south, were enlarged<br />
during Pleistocene time.<br />
Ice moving southwestward, as indicated<br />
by the direction of glacial striae was partly channelled along<br />
the relatively straight courses of many of these valleys.<br />
The<br />
valley floors are relatively flat and generally occupied by<br />
lake(s), rivers and (or) streams, and (or) alluvium.
- 7 -<br />
A broad clay terrace generally flanks and trends parallel<br />
to the present course of the Pic River for a distance of more<br />
than 50 miles (Farrand 1960). Varved clay banks are approximately<br />
60 feet in height.<br />
Extensive sand and gravel deposits occur near the mouths<br />
of the Pic and Little Pic rivers. Within the vicinity of the<br />
Pic, southwest of Trans-Canada Highway 17, there are numerous<br />
depressions up to 400 feet in diameter. This pitted outwash<br />
plain merges into the coastal beach deposits which extend<br />
westward, discontinuously, beyond Middleton station.<br />
The beach deposits are predominantly gravels with minor<br />
pebbles and cobbles. The deposits have been built on<br />
dissected topography, but are themselves undissected and<br />
remarkably fresh. Hough (1958, chap.11) considers these<br />
beaches to be Nipissing and not Algonquin in age.<br />
The elevation<br />
of the beach at Marathon is given by Hough (1958, Table 16,<br />
p. 257) as 710 feet above mean sea level, or 108 feet above<br />
the present surface of Lake Superior. This beach extends<br />
northward for a distance of approximately 2% miles and<br />
represents a fairly large sand and gravel deposit.<br />
There are at least six beach levels at Marathon (see also<br />
Thomson 1931). The vertical interval between the terraces is<br />
5 to 45 feet. Walker (1961) states that the vertical interval
- 8 -<br />
between terraces occurring 20 or more miles to the west is<br />
5 to 10 feet. This relationship may indicate a substantial<br />
increase in the rate of post-glacial isostatic adjustment<br />
in the Marathon <strong>area</strong> than that to the west.<br />
It is interesting to note that in 1884, at a site 600 feet<br />
east of Pic River along the Canadian Pacific Railroad track,<br />
a copper hook, or gaff, and some charcoal were found in the<br />
bottom of a rock cavity under 18 feet of clay topped with<br />
gravel. Hough (1958, p. 258) states that:<br />
"The most reasonable interpretation of this information is that<br />
the archeological material was emplaced sometime during a<br />
pre-Nipissing low-water stage and that the site was flooded<br />
by water rising to the Nipissing level." In the past years<br />
archeological investigations in-the <strong>area</strong> have been carried<br />
out by parties organized and directed by various staff members<br />
from the University of Toronto.<br />
Natural Resources<br />
The entire <strong>area</strong> is forest-covered and timber of commercial<br />
value is obtained from large stands approximately 40 miles north<br />
from the mouth of the Pic River.<br />
The stands are generally mixed<br />
soft and hardwood and include spruce, black spruce, balsam,<br />
jackpine, balsam fir, balsam poplar, tamarack, white birch and
- 9 -<br />
cedar.<br />
Most of the trees are less than 12 inches in diameter<br />
at the base.<br />
Pulp drives which were so common along the Pic<br />
River in the past may eventually be supplanted by the direct<br />
pipelining of chips to the mill site.<br />
Moose, black bear, fox, rabbit, beaver, and skunk are<br />
common in the <strong>area</strong>.<br />
Moose were observed during most of the<br />
summer along the edge of lakes and rivers.<br />
Numerous beaver<br />
dams occur in the streams, and generally made travel difficult<br />
owing to flooding.<br />
Because of poor fur prices trapping in<br />
the <strong>area</strong> has fallen off considerably.<br />
Whitefish, pickerel, pike, and lake trout can be caught<br />
in Lake Superior; and many <strong>area</strong>s, such as Mink Creek and<br />
Gordie Lake contain speckled trout.<br />
In the past commercial<br />
fishing was carried out from <strong>Port</strong> <strong>Coldwell</strong>.<br />
GENERAL GEOLOGY<br />
Although this report deals mainly with the larger unit<br />
comprising the entire map-<strong>area</strong>, namely the <strong>Port</strong> <strong>Coldwell</strong> Complex,<br />
it cannot neglect the granitic-metavolcanic country rocks,<br />
expecially when the overall geological history is being considered*<br />
All the bedrock in the map-<strong>area</strong> is Precambrian in age and<br />
includes intrusions, extrusive rocks with minor amounts of<br />
associated tuffaceous pyroclastic rocks and metasediments.
- 10 -<br />
The metavolcanic-metasedimentary sequences comprise the<br />
oldest formations.<br />
The metavolcanics are composed primarily<br />
of mafic lavas, porphyritic varieties of intermediate to<br />
felsic composition, and non-porphyritic felsic varieties<br />
comprising rhyolite agglomerate, tuff and banded tuff agglomerate,<br />
The metasediments, predominantly laminated argillites and<br />
metagreywackes, are intercalated with the extrusive rocks and<br />
characteristically the contact between the magmatic rocks and<br />
metasediments is sharp.<br />
The metasediments predominate in the north part of the<br />
map-<strong>area</strong> and consistently occur as the younger member in<br />
synclinal structures.<br />
The metavolcanics predominate in the<br />
south part of the map-<strong>area</strong>.<br />
Outcrops of the more mafic lavas<br />
generally exhibit pillow structures in varying degrees of<br />
development.<br />
The metavolcanic-metasedimentary sequences have been<br />
intruded, apparently to a minor degree by dikes, sills and<br />
irregular bodies of diorite.<br />
Upon deformation the rocks were<br />
isoclinally folded to a near-vertical attitude.<br />
The folds<br />
strike approximately N70OE and plunge gently eastward.<br />
This<br />
major period of deformation was closely followed by the<br />
emplacement of a biotite-homblende-quartz f eye f<br />
granite into<br />
and along the crestal region of an anticlinal fold.<br />
This
- 11 -<br />
granite, hereafter called the Jim Lake granite, resembles the<br />
Owl Lake - Cairngorm Lake granite described by Walker (1961).<br />
A body of trondhjemite, exhibiting earlier more-syenitic phases,<br />
has intruded the metasediments at Wullie Lake. It is possible<br />
itthat these rocks represent more mafic and syenitic phases of<br />
the Jim Lake granite. This granite is cut by two sets of<br />
lamprophyric dikes striking approximately NIO 0^ and N30OE.<br />
These dikes are predominantly contained within the trondhjemitegranite<br />
bodies to which they are believed to be genetically<br />
related.<br />
The folded metavolcanics-trondhjemite-granite association<br />
has been cut by porphyritic and non-porphyritic diabase dikes.<br />
Diabase dikes exhibiting a porphyritic texture trend<br />
approximately N400W, whereas more predominant non-porphyritic<br />
diabase dikes trend approximately N30OE.<br />
Intersections were<br />
not found but in nearby <strong>area</strong>s where the diabase dikes exhibit<br />
the same general trends and textures the porphyritic variety<br />
is older.<br />
All the aforementioned rock types comprise the host rock<br />
for the <strong>Port</strong> <strong>Coldwell</strong> Complex which is a circular body,<br />
approximately 580 square kilometres in size. The host rocks<br />
have undergone various metamorphic and (or) assimilative<br />
phenomena related to the emplacement of the Complex. Part<br />
of the Complex is overlain by a volcanic roof pendant,
- 12 -<br />
predominantly of mafic composition, to which the name Coubran<br />
Lake roof pendant has been given.<br />
The rocks of the <strong>Port</strong> <strong>Coldwell</strong> Complex can be considered<br />
as members of one of two series, namely; a f main f series and<br />
a f secondary 1 series generally found associated with the<br />
inclusions, in particular the Coubran Lake roof pendant.<br />
The rocks of the f main t series include the gabbros and<br />
laurvikites and their respective differentiated and layered<br />
phases. Mineralogically, these rocks are predominantly<br />
composed of olivine, pyroxene, feldspar, amphibole,<br />
titanomagnetite, apatite and sulphides.<br />
The rocks of the f secondary 1 series include a mediumgrained<br />
red hornblende syenite (syenodiorite) - red quartz<br />
syenite (nordmarkite), and feldspathoidal syenites.<br />
The<br />
metavolcanic-syenodiorite-nordmarkite suite exhibit gradational<br />
and (or) diffuse contacts whereas the metavolcanic-feldspathoidal<br />
syenites suite exhibit sharp intrusive contacts and (or)<br />
gradational contacts or both.<br />
Mineralogically these rocks are<br />
predominantly composed of alkalic feldspar, nepheline or<br />
natrolite or analcite, amphibole and (or) biotite and quartz<br />
in the syenodiorites-nordmarkites.<br />
The youngest rock in the complex is a set of perthosite<br />
pegmatite dikes that radiate from the Coubran Lake roof pendant.
- 13 -<br />
These dikes transect the suite of lamprophyre dikes associated<br />
with the alkalic complex.<br />
The youngest rock in the map-<strong>area</strong> is an undelimited granite<br />
body given the name Little Pic River granite.<br />
This granite has<br />
invaded the Complex, more or less solely within the northwest<br />
quadrant.<br />
The rocks belonging to the Complex have been<br />
variably granitized and brecciated.<br />
The accompanying table outlines the general sequence of<br />
formations in the <strong>area</strong>, from youngest to oldest* Terms, such<br />
as Keewatin, Timiskaming etc., for rocks pre-dating the<br />
Grenville orogeny (i.e. 1,000 + m.y.) have been purposely<br />
avoided for reasons similar to those presented by Gill (1955,<br />
p. 25-29). Wherever possible descriptive terms have been used<br />
for the rocks concerned.
- 14 -<br />
TABLE OF FORMATIONS<br />
CENOZOIC<br />
RECENT<br />
PLEISTOCENE<br />
Beach and river deposits, peat.<br />
Sand, gravel, boulders and pebbles;<br />
silt, varved clay.<br />
Unconformity<br />
PRECAMBRIAN<br />
LATE GRANITIC ROCKS<br />
Biotite-hornblende granite (Little Pic<br />
River Granite)<br />
Intrusive Contact<br />
PORT COLDWELL ALKALIC COMPLEX<br />
Perthosite (dikes)<br />
Lamprophyre (dikes)<br />
Intrusive Contact<br />
Intrusive Contact<br />
1 Secondary 1 Series<br />
Analcite tinguaite (dikes)<br />
Natrolite - perthite rock (dikes)<br />
Nepheline syenites<br />
Nordmarkite<br />
Syenodiorite .<br />
Series: *<br />
Upper Zone:<br />
Laurvikite, massive<br />
Lower Zone:<br />
Layered laurvikite<br />
Predominantly conformable, partly gradational<br />
contact<br />
Inner Border Zone f b f : Layered gabbro<br />
Inner Border Zone f a f : Massive gabbro<br />
Outer Border Zone: Chilled gabbro
- 15 -<br />
Intrusive Contact (Grenville Orogeny)<br />
LATE MAFIC INTRUSIVE ROCKS<br />
Diabase, porphyritic diabase<br />
Intrusive Contact<br />
EARLY GRANITIC ROCKS<br />
Biotite-homblende granite gneiss (Jim Lake<br />
Batholith); trondhjemitic and (or) more<br />
syenitic phases; related lamprophyre dikes.<br />
Intrusive Contact<br />
METAVOLCANIC-METASEDIMENTARY ASSEMBLAGE<br />
(Age relationships between the major rock units are<br />
not definitely known<br />
Metasediments: Bedded metagreywacke; minor argillite;<br />
biotite- (garnet)-quartz-plagioclase schist.<br />
Felsic Metavolcanics: Agglomeratic rhyolite;<br />
rhyolite agglomerate; tuff and banded tuff<br />
agglomerate; porphyritic rhyolite; fine-grained<br />
quartz-sericite schist; some interbedded (?) metasediment*<br />
Mafic to Intermediate Metavolcanics: Pillow lava;<br />
amygdular-lava; diabasic lava; fine-grained and<br />
coarse-grained gneissose garnet amphibolite.
- 16 -<br />
Metavolcanic-Metasedimentary Assemblage<br />
The greater proportion of the map-<strong>area</strong>, marginal to the<br />
<strong>Port</strong> <strong>Coldwell</strong> Alkalic Complex, is underlain by rocks belonging<br />
to the metavolcanic-metasedimentary assemblage. The mafic<br />
metavolcanics to the west outcrop in the vicinity of the Lake<br />
Superior shoreline and in a belt north of the Trans-Canada<br />
Highway 17. These two <strong>area</strong>s of mafic metavolcanics are<br />
separated by a belt of metasediments.<br />
The metasediments to the east are limited to minor<br />
horizons. The mafic metavolcanics to the east outcrop to<br />
the north of an extensive and continuous exposure of felsic<br />
metavolcanics.<br />
For reasons described in the section dealing with structure,<br />
the stratigraphy in the metavolcanic-metasedimentary assemblage<br />
is only imperfectly known.<br />
These rocks are mainly basaltic in composition although<br />
andesitic varieties may be present based on the mineralogy of<br />
some specimens.<br />
The rocks range in colour from dark to pale<br />
green.<br />
recognized.<br />
Porphyritic and non-porphyritic varieties have been
- 17 -<br />
Massive flows may grade from a finer-grained (basal?) phase,<br />
with or without amygdules, to a more centrally located,<br />
medium- to coarse-grained phase which often exhibits ophitic<br />
texture. It is sometimes difficult to impossible to distinguish<br />
these coarser phases from associated basic intrusions but unless<br />
definite evidence of intrusion was found, these diabasic rocks<br />
were mapped as parts of flows.<br />
Pillows are generally well developed and frequently can be<br />
used for f top f determinations.<br />
In thin-section these mafic metavolcanics particularly the<br />
aphanitic varieties, frequently exhibit a relic pilotaxitic<br />
or felted texture. Mineralogically these rocks are composed of<br />
20-25 percent actinolitic amphibole (pseudomorphing diopsidic<br />
augite), up to 35 percent albitic plagioclase, up to 20 percent<br />
chlorite, 1-20 percent epidote (clinozoisite-pistacite), variable<br />
talc, and up to 10 percent fine-grained quartz and feldspar with<br />
minor leucoxene and opaque minerals. Some massive coarser grained<br />
phases occurring in the Coubran Lake roof pendant contain<br />
olivine, variably altered.<br />
The amygdules of the amygdaloidal types are generally<br />
composed of a core of actinolite and epidote or calcite<br />
followed by an outer rim of epidote and chlorite.
- 18 -<br />
Relic ophitic texture is common and its presence and<br />
recognition has proved to be a definite asset for purposes of<br />
identifying (1) the composition and origin of numerous<br />
inclusions within the Complex and (2) rocks derived there<br />
from and which comprise the f secondary 1 series. In thin<br />
section the ophitic-textured phases are composed of 35-45<br />
percent diopsidic augite, variably altered to amphibole *<br />
chlorite * biotite, and labradoritic plagioclase.<br />
Although<br />
not one ophitic-t extured sill was found to be an intrusion,<br />
some maybe.<br />
Other rocks grouped with the mafic to intermediate<br />
metavolcanics are the dark massive, garnet-plagioclaseamphibole<br />
gneisses. Maximum exposure is west of Big Pic<br />
River in vicinity of Jim Lake Granite.<br />
These amphibolites<br />
occur as fine- and coarse-grained varieties.<br />
Hornblende<br />
is readily recognizable in hand specimen and frequently shows<br />
a nematoblastic texture (fibrous schistosity).<br />
Other<br />
mineralogical constituents include plagioclase, sphene,<br />
magnetite, apatite, and sulphides.<br />
Garnet generally exhibits<br />
a well-developed helicitic structure (curved or contorted lines<br />
of inclusions).
- 19 -<br />
FELSIC METAVOLCANICS<br />
Nearly all of the exposures of felsic metavolcanics occur<br />
to the east of the map-<strong>area</strong>. The felsic metavolcanics are<br />
predominantly fine-grained, massive, agglomeratic, and light<br />
grey green in colour. Minor varieties include tuff agglomerates,<br />
rhyolite agglomerate, and porphyritic varieties.<br />
The agglomeratic rhyolites contain variable amounts of<br />
fragments which can vary in size, angularity and composition.<br />
In thin section the rock as a whole is rhyolitic although some<br />
local phases appear dacitic.<br />
A typical specimen is predominantly<br />
composed of quartz, albitic plagioclase and potassic feldspar,<br />
with varying but generally minor amounts of augite, actinolitic<br />
amphibole, chlorite, epidote, biotite, magnetite, and sulphides.<br />
In most samples the potassic feldspar and biotite appeared as<br />
large sieve-like crystals (poikiloblasts) up to 3mm long.<br />
Specimens taken from inclusions and (or) from <strong>area</strong>s<br />
apparently within the contact aureole described by the <strong>Port</strong><br />
<strong>Coldwell</strong> Alkalic Complex are characteristically coarser<br />
grained (up to 2^ mm). In thin section these felsic metavolcanics<br />
were found to contain up to 15 percent potassic feldspar<br />
occurring as poikiloblasts up to 3^ mm long; up to 40 percent<br />
albitic plagioclase; up to 30 percent quartz; up to 10 percent<br />
biotite, commonly occurring as poikiloblasts; and minor
- 20 -<br />
clinopyroxene, magnetite, and sulphides. Hypersthene, up<br />
to 15 percent, is present as discrete grains. Plagioclase and<br />
quartz exhibit a characteristic association and the resultant<br />
texture produced inevitably has small, rectangular and generally<br />
discrete, optically oriented units of plagioclase set in a<br />
matrix composed of a single crystal of quartz. The plagioclasequartz<br />
intergrowths have been found up to 4mm long. There can<br />
be little doubt that the development of this texture is related<br />
to the metamorphism resulting from the emplacement of the <strong>Port</strong><br />
<strong>Coldwell</strong> Alkalic Complex. This metamorphism has also resulted<br />
in the recrystallization and remobilization of potassic feldspar and<br />
quartz so as to produce veins and (or) zones of graphic granite<br />
primarily within the contact gabbros.<br />
Some rocks, within the proposed metamorphic aureole<br />
surrounding the <strong>Port</strong> <strong>Coldwell</strong> Alkalic Complex, are white in<br />
colour and porcellanous in appearance. These rocks fracture<br />
conchoidally.<br />
Minor laminated tuffaceous horizons occur within the<br />
agglomeratic rhyolites.<br />
An exposure of tuffaceous agglomerate was found on the<br />
west shore of Big Pic River at the intersection with the H.E.P.C.<br />
line. The agglomeratic units appeared to be rhyolitic, and on<br />
fresh surface were difficult to distinguish from the slightly<br />
more chloritic matrix.
- 21 -<br />
Several outcrops of banded agglomeratic tuff occur along<br />
Trans-Canada Highway 17, south of Three Finger Lake. Darker<br />
bands appear to alternate with lighter bands which commonly<br />
contain lenticular fragments of quartzite, aphanitic rhyolite,<br />
and schist. The fragments are strongly elliptical and are<br />
elongated parallel to the rock fabric. In thin section the<br />
pale green coloured, schistose matrix is composed of<br />
plagioclase up to 30 percent, augite up to 15 percent,<br />
hypersthene up to 10 percent, and minor accessories including<br />
sulphides and magnetite.<br />
Some aphanitic, massive flows occurring east of the Big<br />
Pic River contain euhedral phenocrysts of potassic feldspar<br />
with or without phenocrysts of quartz.<br />
Other rocks, grouped with the felsic metavolcanics, are<br />
the fine-grained quartz-sericite schists exposed to the east<br />
of Three Finger Lake.<br />
Calcareous-rich rocks, composed of gamet-calcite-pyroxene,<br />
occur near a quartzite outcrop approximately 3/8 mile east of<br />
Mamoos Lake. These rocks may represent minor, intercalated<br />
beds of metasediments within the agglomeratic rhyolite.
- 22 -<br />
METASEDIMENTS<br />
The metasediment s, namely bedded metagreywacke and<br />
argillite have their maximum exposure to the west, near<br />
Middleton. Exposures of massive biotite-quartz-feldspar<br />
schists occur near Wullie Lake and to the southeast of Three<br />
Finger Lake.<br />
Metagreywacke<br />
The metagreywackes near Middleton display graded bedding.<br />
Individual graded beds commonly range from less than one inch<br />
to three inches thick.<br />
A few beds are up to three to four<br />
feet thick.<br />
A typical 3-inch thick bed is composed of a basal, two-inch<br />
thick, sandy to silty unit and a one-inch thick, more argillaceous<br />
to slaty top. A second slaty cleavage, in part attributable<br />
to the emplacement of the <strong>Port</strong> <strong>Coldwell</strong> Alkalic Complex,<br />
intersects the bedding plane, generally at reasonably high<br />
angles. The intersection of these two planes has produced<br />
a prominent lineation.<br />
In <strong>area</strong>s close to the Complex reversed graded bedding<br />
was recognized and attributed to the more marked recrystallization<br />
within the more argillaceous units. Concordant veins of glassy<br />
white quartz are prevalent in these sheared metagreywackes*
- 23 -<br />
The metagreywackes, west of Wullie Lake are massive and<br />
x<br />
do not exhibit bedding. "^<br />
In thin section the metagreywackes appear fine-grained,<br />
average grain size being 1^ mm, and are composed of plagioclase,<br />
potassic feldspar,quartz,with varying proportions of actinolite,<br />
biotite, garnet (variety almandine?), epidote, chlorite,<br />
magnetite and sulphides.<br />
GRANITIC ROCKS<br />
The granitic and more syenitic bodies occur to the north<br />
of the map-<strong>area</strong> and extend, in a more or less uninterrupted<br />
manner, from the Big Pic River to west of Wullie and Martinet<br />
lakes. They make up what the author calls the Jim Lake<br />
batholith. The Jim Lake batholith is principally a biotitehornblende<br />
granite gneiss. The rock weathers a whitish pink<br />
colour and characteristically exhibits 'eyes 1 of quartz.<br />
These quartz f eyes f or rods plunge to the northeast, sub-parallel<br />
to the northeasterly-trending contact with the mafic metavolcanics.<br />
Contact phases with the mafic metavolcanics may exhibit<br />
migmatite development. These peripheral <strong>area</strong>s may be<br />
consistently more syenitic. It is possible that the trondhjemite<br />
body west of Wullie Lake represents a more mafic and syenitic<br />
phase of the Jim Lake granite.
- 24 -<br />
Lamprophyre dikes appear to preferentially, although not<br />
exclusively, cut the granitic intrusions to which they may be<br />
genetically related. All these dikes were seen to occupy<br />
existing joints and to exhibit relations with the predominantly<br />
granitic host rock as to suggest intrusion during a period of<br />
extension. The lamprophyres are represented by porphyritic<br />
and non-porphyritic types. The non-porphyritic dikes apparently<br />
strike northwest, whereas the porphyritic mica lamprophyre dikes<br />
strike N25OE.<br />
LATE MAFIC INTRUSIVE ROCKS<br />
Diabase dikes, porphyritic and non-porphyritic, intrude all<br />
the other pre-existing rocks in the <strong>area</strong>.<br />
The porphyritic diabase dikes are up to sixty feet wide and<br />
strike approximately N40OW (and less commonly N10-15OW) .<br />
The non-porphyritic diabase dikes average three feet in width<br />
and strike predominantly N30OE (and less commonly NIO-IS^).<br />
These two types of diabase appear identical in hand specimen;<br />
the distinction being made on the presence of greenish, plagioclase<br />
phenocrysts in the porphyritic varieties.<br />
With due recognition to the importance of the relative age<br />
assigned to the diabase dikes of the immediate map-<strong>area</strong> it is<br />
important to note that to date diabase dikes have not been found<br />
to cut, unequivocally, the <strong>Port</strong> <strong>Coldwell</strong> Alkalic Complex.<br />
would appear that some earlier observations (Coleman 1900,<br />
It
- 25 -<br />
p. 186-191), at least in part, agree with this relative age<br />
assignment.<br />
Similarly, to the west, it would appear (J.W.R. Walker,<br />
pers. comm.) that the one or two dikes of f diabasic' composition<br />
reported to cut the <strong>Port</strong> <strong>Coldwell</strong> Alkalic Complex could, in<br />
fact, be lamprophyres.<br />
PORT COLDWELL AI^KALIC COMPLEX<br />
Introduction<br />
The <strong>Port</strong> <strong>Coldwell</strong> Alkalic Complex is a lopolith, essentially<br />
circular in plan, which has been emplaced by a process of magma<br />
stoping and assimilation.<br />
At the present level of exposure<br />
roughly 10 percent of the Complex is beneath overlapping or<br />
roof pendants of country rock.<br />
The rocks of the <strong>Port</strong> <strong>Coldwell</strong> Alkalic Complex can be<br />
considered as members of one of two series, namely; a f main f<br />
series, and a 'secondary 1 series. The 'main 1 series include<br />
the gabbros and laurvikites.<br />
The 'secondary' series includes<br />
syenodiorites, nordmarkites and feldspathoidal syenites.<br />
These<br />
rock types are found to be intimately associated with the<br />
inclusions of country rocks, in particular the Coubran Lake<br />
roof pendant.
- 26 -<br />
'Main 1<br />
Series<br />
The 'main 1 series exhibits an overall zonation which is<br />
as follows:<br />
Upper Zone<br />
Laurvikite<br />
Lower Zone<br />
Layered laurvikite<br />
Inner Border Zone 'b' Layered gabbro<br />
Inner Border Zone 'a' Massive gabbro<br />
Outer Border Zone<br />
Chilled gabbro<br />
The gabbros show a maximum thickness equal to approximately<br />
2600 feet and are made up of approximately 80 feet of<br />
marginally located chilled gabbro, followed by approximately<br />
300 feet of massive gabbro which in turn is followed by<br />
approximately 2200 feet of layered gabbro. The gabbros are<br />
conformably overlain by laurvikite, a unit which is<br />
approximately 9,000 feet thick.<br />
The apparent irregularity in gabbro thickness as seen on<br />
surface is in part attributable to the presence of overlapping<br />
and roof pendants of country rock.<br />
Chilled Gabbro<br />
The chilled gabbro is, in general, a massive, fine-grained<br />
(average 1^ mm), magnetic rock restricted to the peripheral <strong>area</strong>s<br />
-<br />
Widths were determined on the basis of lopolith structure and<br />
300 dip of layering.
- 27 -<br />
of the <strong>Port</strong> <strong>Coldwell</strong> Alkalic Complex.<br />
The consistent<br />
peripheral occurrence is not meant to imply that this chilled<br />
gabbro represents a rock which is solely found at the basal<br />
contact with the country rock.<br />
dike-like apophyses of 'chilled 1<br />
Several north-south trending<br />
gabbro have been found up to<br />
800 feet east of the actual Complex-host rock footwall contact.<br />
Veins, veinlets and small dikes of graphic granite,<br />
predominantly joint controlled, may be present.<br />
The veins et<br />
cetera describe a reticulate pattern, of varying intensity,<br />
within the chilled gabbro.<br />
Thin section examination showed that the chilled gabbro is<br />
generally equigranular, massive, and structureless.<br />
But phases<br />
exhibiting phenocrysts of plagioclase and pyroxenes are not<br />
uncommon.<br />
Both an orthopyroxene (variety hypersthene) and a<br />
clinopyroxene (variety diopside) are present in approximately<br />
equal proportions.<br />
Olivine may (up to 10 percent) or may not<br />
be present.<br />
Additional minerals include magnetite and minor<br />
sulphides (pyrrhotite * pyrite) and biotite.<br />
As 1& apparent,<br />
the rock is essentially composed of an anhydrous mineral<br />
assemblage.<br />
Another, apparently higher level, 'chilled 1<br />
gabbro phase<br />
exhibits a characteristic knobby weathered surface.<br />
The knobs<br />
represent poikilitic crystals of olivine and orthopyroxene up to<br />
7mm.<br />
N
- 28 -<br />
In cho f Lold cho actual recognition and identification of<br />
the chilled gabbro is made more difficult by the presence of<br />
overlapping and near-marginal, roof pendants of country rock.<br />
But in general the identification of chilled gabbro can be made<br />
on the basis of the following: Characteristic and essentially<br />
anhydrous mineralogy; high magnetite content; structureless and<br />
massive appearance. Phases exhibiting phenocrysts of plagioclase<br />
or pyroxene have been found south of Bamoos Lake but are minor<br />
in extent.<br />
Massive Gabbro<br />
The massive gabbro is generally coarse-grained, ranging<br />
from 3mm to 8mm, and structurless.<br />
The maximum exposed widths,<br />
where present, appear to range from approximately 2200 feet,<br />
along Trans-Canada Highway 17, to approximately 350 feet,<br />
southeast of Bamoos Lake. Surface continuity for this gabbroic<br />
phase has not been established which may be attributable, in part<br />
only, to the problem presented by irregular contact relationships<br />
with the country rock.<br />
The coarse-grained gabbros, although apparently conformable<br />
to the 'chilled' gabbro in gross aspects, are seen to intrude<br />
and engulf fragments (in part autoliths) of fine-grained gabbro.
- 29 -<br />
Extremely coarse-grained phases, with crystals up to 65mm,<br />
are closely associated with these massive gabbros.<br />
Where<br />
reasonably sharp contacts were observed these very coarse-grained<br />
phases were considered as pegmatitic dikes of a younger gabbro<br />
as opposed to pegmatitic variant of the same gabbro, senso<br />
stricto.<br />
The predominant gabbro framework is composed of the following<br />
silicates, arranged in order of relative abundance; plagioclase;<br />
clinopyroxene, very dark green coloured, generally poikilitic,<br />
augite; olivine, honey yellow coloured, granular although may<br />
occur as poikilitic crystals up to 50mm; and ilmenomagnetite,<br />
variably unmixed up to 35mm.<br />
Other minerals which may be present (in varying relative<br />
proportions) up to as much as 60 percent in extreme cases<br />
include:<br />
Apatite, with phantom structures sometimes present;<br />
sulphides, up to 10 percent; annitic biotite up to 15mm;<br />
potassic feldspar, quartz, actinolite, orthopyroxene, serpentine,<br />
hornblende and chlorite. Generally these minerals are restricted<br />
to the interstitial sites within the existing gabbro framework.<br />
Commonly the intimate association of these interstitial<br />
constituents is reflected by the prevalent intergrowth textures<br />
exhibited by the following mineral pairs; potassic feldspar<br />
and quartz; annitic biotite and sulphides; apatite and sulphides;<br />
serpentine and sulphides; and actinolite and sulphides.
- 30 -<br />
The coarse-grained gabbro appears to grade into a mediumto<br />
cv vi rs o -grained gabbro with poikilitic (up to 25mm) plates of<br />
dark annitic biotite up to 8 volume percent.<br />
Thin section analysis indicated that this biotitic gabbro<br />
has the following composition; plagioclase up to 55 percent;<br />
clinopyroxene (sodic augite) up to 20 percent; orthopyroxene<br />
(variably pseudomorphed by chlorite up to 5 percent).<br />
Accessory<br />
minerals include sodic amphibole, apatite-ilmenomagnetite<br />
intergrowth (up to 10 percent) and trace sulphides.<br />
The exposures of biotite-rich gabbro along Trans-Canada<br />
Highway 17 exhibits plagioclase lamination, dip of 250W and<br />
layering, of a discontinuous and (or) disturbed nature.<br />
The<br />
layering dips 25OW.<br />
In addition these exposures contain<br />
abundant inclusions, varying in size up to 80 feet.<br />
Partial<br />
recrystallization and remobilization has resulted so as to<br />
produce, in effect, a medium-grained hybrid.<br />
Layered Gabbro<br />
The exposures of layered gabbro along Trans-Canada Highway<br />
17 have been examined in some detail. The primary structures<br />
exhibited by these rocks include rhythmic layering with or<br />
without gravity stratification, cryptic layering, inch-scale<br />
layering, and igneous lamination.<br />
Not uncommonly a strong
- 31 -<br />
lineation, in the plane of igneous lamination, is exhibited by<br />
clinopyroxene and (or) plagioclase.<br />
Thin section examination has shown these rocks to be<br />
composed of the following minerals, in varying and sometimes<br />
most discriminating proportions; plagioclase; clinopyroxene;<br />
olivine; ilmenomagnetite; and generally minor amounts of<br />
sulphides, apatite, barkevikitic amphibole, and annitic biotite.<br />
These minerals tend to occur in aggregates separated by small<br />
amounts of interstitial materials.<br />
The interstitial minerals include ilmenomagnetite + apatite<br />
* biotite -H sulphides, (chalcopyrite * pyrrhotite jp bornite)<br />
* trace barkevikitic amphibole. The ilmenomagnetite-apatitesulphide<br />
assemblage can occur with olivine to form a relatively<br />
thin (generally 2 inches thick) but persistent band.<br />
Further<br />
concentration apparently has resulted in the formation of more<br />
massive, but generally less persistent, ilmenomagnetite + apatite<br />
+ olivine bodies. Such bodies occur near Middleton to the west,<br />
near Wullie and Skipper lakes to the north, and near Bamoos<br />
Lake to the northeast.<br />
These ilmenomagnetite bodies are<br />
predominantly concordant with existing structures but some<br />
discordancy has been observed (1000 feet west of Little Pic<br />
River on Trans-Canada Highway 17).
- 32 -<br />
Laurvikites<br />
The laurvikite rocks of the 'main 1<br />
syenite series appear<br />
to represent approximately 65 percent^- of the volume of the<br />
<strong>Port</strong> <strong>Coldwell</strong> Alkalic Complex.<br />
The contact between layered gabbro f below 1<br />
and layered<br />
laurvikite 'above 1 appears gradational. Although textural<br />
features suggestive of laurvikite 'chilling 1<br />
has been seen,<br />
supporting evidence, such as the presence of gabbro autoliths<br />
(cognate inclusions) in laurvikite, necessary to indicate the<br />
former existence of a major hiatus in time and (or) physical-<br />
chemical environment between the two layered rock types has not<br />
been found.<br />
The gradational rock is grey in colour but otherwise resembles<br />
'dark' laurvikte.<br />
of variably exsolved perthite.<br />
Thin section examination indicates the presence<br />
The larger laths reveal included<br />
<strong>area</strong>s that exhibit continuous polysynthetic twinning (i.e.<br />
labradorite).<br />
The ferromagnesian minerals include the following;<br />
olivine, variable serpentinized,up to 8 percent;sodic augite,<br />
fresh, up to 15 percent;and ilmenomagnetite mantled by annitic<br />
biotite, up to 5 percent.<br />
Immediately west of Big Pic River a similar syenite, with<br />
porphyritic texture variably but regularly developed, has been<br />
mapped.<br />
Here the syenite apparently overlies the gabbros of the<br />
Figure derived assuming a limited depth of penetration of the<br />
Coubran Lake metavolcanic roof pendant. (In view of the breaching<br />
of the roof pendant by porphyritic variety of laurvikite, at Gordie<br />
Lake, this assumption would appear justified) and continuity<br />
of structure (as determined on surface) to depth.
- 33 -<br />
'main 1<br />
series.<br />
Layered Laurvikite<br />
The laurvikites exhibit rhythmic and cryptic layering,<br />
although on a less obvious and apparently more restricted scale<br />
than that exhibited by the gabbros.<br />
In general terms, an individual laurvikite layer is comprised<br />
of a f basal 1 lamina of f dark f green laurvikite and an 'upper 1<br />
lamina of pink, hematitized laurvikite.<br />
Characteristically, the<br />
dark 1 green laurvikite is coarse-grained with dark green<br />
laths of perthite (braid perthite visible under hand lens)<br />
up to 12mm (by 5mm by l-4mm).<br />
Carlsbad twins are always present.<br />
The greenish colour is of equal intensity throughout the crystals<br />
of perthite which often exhibit an internal iridescence.<br />
The<br />
mafic minerals present include olivine, aegirine augite,<br />
^<br />
magnetite, primary and secondary barkevikitic amphibole, and<br />
minor zircon, rare earths, apatite, and chlorite.<br />
The hematitized varieties of laurvikite exhibit many of<br />
the same features as the f dark f<br />
green varieties with the<br />
notable differences being, aside from the colour, that the<br />
alkalic feldspars occur as more equant grains, devoid of Carlsbad<br />
twinning.<br />
Perthitic twinning is always clearly identifiable.
- 34 -<br />
The perthitic feldspar grains are not homogeneously coloured<br />
but zoned so as to exhibit a greenish-grey f core f<br />
with a pink<br />
mantle.<br />
Transitional varieties of laurvikite exhibit properties<br />
and textures which represent but variations of the two,<br />
previously mentioned.<br />
Laurvikite, Massive<br />
The layered laurvikites pass insensibly into more massive,<br />
non-lamina ted, hematitized and amphibolitized syenites toward<br />
the geographical centre of the Complex and the Coubran Lake<br />
roof pendant.<br />
Uralitization of aegirine augite to form barkevikitic<br />
amphibole has been found arrested at various stages. Upon<br />
completion the rock has become a f red f amphibole syenite.<br />
Laurvikites, Pegmatites<br />
Numerous dikes of laurvikite pegmatite were encountered in<br />
the course of investigation. In most cases these dikes have<br />
been emplaced along pre-existing ring-like fractures during<br />
periods of local (?) extension.
- 35 -<br />
The time of emplacement, for what would appear to be some<br />
of the earliest pegmatites generated, may be prior to complete<br />
solidification of underlying gabbro.<br />
Exposures along Trans-<br />
Canada Highway 17 show gabbro fragmentation with partial lit-<br />
par-lit type intermixing of laurvikite wich gabbro comprising<br />
the fragment.<br />
But in most examples the laurvikite pegmatite<br />
contacts are sharp, in part chilled with or without the<br />
development of a more magnetite-rich contact aureole in the<br />
gabbros or laurvikite host.<br />
The laurvikite pegmatites frequently exhibit miarolitic<br />
cavities, generally found to be preferentially developed and<br />
(or) concentrated in vicinity of the hanging wall.<br />
These<br />
miarolitic cavities contain, in varying proportions, the<br />
following minerals; crystalline quartz; crystalline amphibole<br />
with or without associated zircon; fluorite; calcite; molybdenite;<br />
and crystalline perthite.<br />
Crystalline graphic intergrowths<br />
between perthite and quartz are not uncommon.<br />
Thin section examination shows that most of the pegmatites<br />
contain the following minerals; perthite, approximately 90<br />
percent; aegirine augite, variably uralitized to barkevikitic<br />
amphibole; quartz, generally about 2 percent; and the<br />
aforementioned accessories.
- 36 -<br />
Laurvikite, Porphyritic Varieties<br />
Porphyritic laurvikites are extensively developed in<br />
vicinity of Gordie Lake, and Penn Lake.<br />
In both occurrences<br />
the porphyritic laurvikite is overlain by metavolcanic rocks.<br />
At Penn Lake the porphyritic varieties can be seen to grade<br />
into more normal and equigranular varieties of laurvikite.<br />
The porphyritic laurvikites appear to represent phases,<br />
near contact with metavolcanics, which have cooled more<br />
rapidly (i.e. chilled).<br />
1 S econdary f S eri es<br />
The rocks comprising the 'secondary 1<br />
series are massive<br />
and essentially structureless, except for the layered nepheline<br />
syenites on Allouez and Pic islands. As previously mentioned<br />
these rocks are seen to be intimately associated with the<br />
metavolcanics belonging to the Coubran Lake metavolcanic<br />
roof pendant.<br />
The syenodiorite-nordmarkite rocks represent a series,<br />
senso stricto, and in all cases are found to grade into one another<br />
and ultimately into the hanging wall metavolcanics.<br />
These<br />
rocks describe a series that is oversaturated with respect to<br />
silica.
- 37 -<br />
The nepheline syenites and related phases outcrop west of<br />
the Redsucker Cove-Mink River lineament. These rocks are a<br />
series that is undersaturated with respect to silica.<br />
Syenodiorite<br />
The rock is somewhat variable in appearance but in general<br />
it is fine- to medium-grained. 'The degree of crystallinity<br />
may be directly related to the degree of crystallinity exhibited<br />
by the nearby metavolcanics.<br />
Coarser grained phases exhibited<br />
a relict diabasic texture.<br />
'Typical 1 syenodiorites are composed of amphibole, biotite,<br />
and plagioclase with variable amounts of quartz and perthite.<br />
Locally the syenodiorites may be cut and brecciated by<br />
numerous dikes of fine- to medium-grained red quartz-hornblende<br />
syenite.<br />
Nordmarkite<br />
The red quartz-bearing hornblende syenites, nordmarkites,<br />
show a grain size variation that is identical to that observed<br />
in the syenodiorites.<br />
Relict diabasic textures have been<br />
observed.<br />
texture.<br />
In many places the nordmarkites have a porphyritic
- 38 -<br />
Thin section examination shows that these rocks are<br />
composed of the following minerals; quartz up to 6 percent;<br />
perthite; minor amounts of riebeckitic amphibole,<br />
clinopyroxene (variety augite), magnetite, apatite and chlorite.<br />
Nepheline Syenites<br />
The field relations of the nepheline syenites, exposed<br />
immediately west of the Redsucker Cove Lineament, may be<br />
considered as representative of the relations exhibited by all<br />
the feldspathoidal syenites of the Complex.<br />
The exposures of the nepheline syenites are topographically<br />
'high 1 and the rocks show a peripheral zoning. The outer<br />
nepheline syenite zone, in contact with the host metavolcanics<br />
belonging to the Coubran Lake metavolcanic roof pendant, is<br />
fine-grained (range from 2mm to 5mm) and meso- to melanocratic.<br />
The nephelinized metavolcanics have a varying nepheline content<br />
which increases towards the nepheline syenites. The crystallization<br />
of nepheline is accompanied by the uralitization of existing<br />
ferromagnesian minerals.<br />
The amphibole in the melanocratic nepheline syenites of the<br />
outer zone is barkevikitic and generally occurs as poikilitic<br />
overgrowths on older clinopyroxenes derived from assimilated<br />
metavolcanics.
- 39 -<br />
Exposures of metavolcanics have been found that appear to<br />
have been nephelinized at two markedly different degrees and<br />
(or) stages.<br />
Generally the less nephelinized parts are included<br />
as angular fragments formed during a period of dilation in the<br />
more nephelinized parts.<br />
The latter can themselves occur as<br />
angular fragments, formed during a second and later period<br />
of dilation, in the more leucocratic nepheline syenite<br />
emplacements.<br />
It would appear therefore that the nephelinization<br />
process was operative over at least two periods of extension.<br />
Nepheline in the outer zone is generally fine-grained and<br />
relatively unaltered.<br />
Much of the nepheline, perthitic and<br />
plagioclase feldspars are poikilitically included in the<br />
barkevikite.<br />
Towards the inner zone, and topographic f high f , the<br />
nepheline syenites become more leucocratic, coarser grained,<br />
and biotite predominates over amphibole.<br />
Relatively unaltered<br />
nepheline is present up to 40 percent.<br />
Later phases exhibit a pink coloured cryptocrystalline<br />
alteration of nepheline.<br />
The alteration product appears to<br />
be a mixture of natrolite and thomsonite.
- 40 -<br />
Natrolite-Perthite Dikes<br />
Natrolite-perthite dikes appear to occupy steeply dipping<br />
cone-sheet fractures. These dikes are characterized by the<br />
complete zeolitization of nepheline which on weathered surface<br />
is indicated by the presence of an orangy pink coloured<br />
natrolite-thomsonite pseudomorphic intermixture. This orangy<br />
pink colouration is characteristically set against a background<br />
of pale grey perthite the combination of which makes a most<br />
attractive rock.<br />
Analcite Tinguaite Dikes<br />
Analcite tinguaite dikes appear to occupy radial fractures<br />
which can extend beyond the confines of the Complex. In<br />
general these dikes are aphanitic to fine-grained and red in<br />
colour. The primary minerals are analcite, perthite and<br />
aegirine augite. Nepheline is not present.<br />
Lamprophyre Dikes<br />
Abundant lamprophyre dikes, generally l foot wide, can be<br />
seen to cut the various phases of f secondary 1 rock types. They<br />
belong to the f secondary 1 series and in part to the f main f series*
- 41 -<br />
These lamprophyre dikes follow in part arcuate cone-shaped<br />
fractures that dip inward towards <strong>Coldwell</strong> at shallow to<br />
moderate dips.<br />
Texturally these lamprophyres are all porphyritic and<br />
include monchiquites and camptonites.<br />
Perthosite Dikes<br />
Several exposures show perthosite dikes cutting lamprophyre<br />
dikes of sodic composition. The perthosite dikes are monomineralic,<br />
and composed of laths of perthite exhibiting a strong foliation<br />
which is parallel to the contacts.<br />
LATE GRANITIC ROCKS<br />
Little Pic River Granite<br />
The Little Pic River granite mainly occupies the northwest<br />
part of the map-<strong>area</strong>.<br />
Here the granite differs from the other<br />
granitic rocks of the <strong>area</strong> in that it exhibits a hypidiomorphic<br />
texture and is essentially structureless. The predominant<br />
ferromagnesian mineral is biotite with lesser proportions of<br />
hornblende.<br />
The northerly extent of this granite is not known although<br />
younger bosses of fresh biotite granite have been reported<br />
(Walker 1961) to the west.
- 42 -<br />
Thin section examination shows the granite (average grain<br />
size 4mm) is composed of the following minerals:<br />
Quartz up to<br />
25 percent; plagioclase, up to 60 percent; alkalic feldspar, up<br />
to 16 percent; actinolite amphibole up to 7 percent; biotite mica<br />
up to 9 percent; minor magnetite and zircon.<br />
The Little Pic River granite intrudes the <strong>Port</strong> <strong>Coldwell</strong><br />
Alkalic Complex.<br />
The intrusion of the granite has brecciated<br />
and variably granitized the rocks comprising the 'main' series<br />
of the Complex.<br />
The zone of granitization and hybridization extends as far<br />
south as the Trans-Canada Highway 17 and eastward to within<br />
2^ miles of Wullie Lake (Walker 1961).<br />
This zone is further<br />
characterized by the predominance of amphibole and the<br />
inhomogeneous distribution of quartz.<br />
PLEISTOCENE AND RECENT<br />
The larger deposits of unconsolidated sand, alluvium, and<br />
clay have been described and are indicated on the accompanying map.<br />
Glacial striae and chatter marks are common and indicate that<br />
the major movement of ice trended approximately 835^. Several<br />
minor lobes were apparently directed along several of the pre<br />
existing lineaments to the east. The valley walls show striae<br />
trending parallel to the east-west strike of the lineaments.
- 43 -<br />
STRUCTURAL GEOLOGY<br />
Introduction<br />
Although the mapping was of a reconnaissance nature, the<br />
structural features defined are believed to represent, fairly<br />
accurately, the salient and some of the more significant minor,<br />
structural features of the <strong>area</strong>, but are not necessarily a final<br />
solution. Despite the fact that most of the country rock is<br />
exposed, particularly along the lake shores, the outcrops are<br />
frequently 'belt-like 1 and because the lithologies of different<br />
sequences of metavolcanics and (or) metasediments are so similar<br />
it is never entirely certain that the same sequence of rocks is<br />
being considered. Fortunately there are a few distinct marker<br />
beds in the <strong>area</strong> and with the aid of these marker beds and inherent<br />
structures, such as: Graded bedding and pillow lavas; local<br />
folds have been proposed within the metavolcanic-metasedimentary<br />
sequences.<br />
The period of maximum deformation, since evidence for more<br />
than one period of folding has not been recognized, was followed<br />
by the intrusion of granitic rocks predominantly into and along<br />
the established folds. This period of intrusion apparently<br />
culminated with the emplacement of granite pegmatite and<br />
lamprophyre dikes. At some later period the <strong>area</strong> was invaded<br />
by near north-south trending diabase dikes. Faulting along
- 44 -<br />
north-south and northeast-southwest trending planes of weakness<br />
followed the diabase intrusion.<br />
The geological history up to<br />
this point is very similar to that given by Pye (1957, p. 46)<br />
for the Manitouwadge <strong>area</strong> (approximately 25 miles northeast of<br />
the <strong>Port</strong> <strong>Coldwell</strong> Alkalic Complex) with an apparent notable<br />
exception being the absence of similar sulphide replacement<br />
deposits.<br />
The period of faulting was followed by the intrusion<br />
of the <strong>Port</strong> <strong>Coldwell</strong> Alkalic Complex.<br />
Structural Elements Within the Metavolcanic-<br />
Metasedimentary Sequences<br />
FOLD STRUCTURES<br />
The metavolcanic-metasedimentary rocks have been deformed<br />
into reasonably tight isoclinal folds.<br />
The strike of these<br />
vertically to steeply dipping structures is N70OE, which<br />
closely parallels that of the Archean rocks from other parts<br />
of the Superior Province.<br />
Deflections to this regional trend<br />
do occur and in the map-<strong>area</strong> the deflections observed are<br />
sharp and help to delimit, more or less, the contact aureole<br />
around the younger, <strong>Port</strong> <strong>Coldwell</strong> Alkalic Complex.<br />
A major fold which has been defined is the Jim Lake anticline,<br />
located immediately to the north of the <strong>Port</strong> <strong>Coldwell</strong> Alkalic<br />
Complex near Skipper Lake.<br />
More will be said regarding the Jim
- 45 -<br />
anticline in the section dealing with structures related to<br />
granitic intrusions.<br />
Other folds, despite the aid of outcrop patterns and top<br />
determinations are less definite.<br />
The axial planes are apparently vertical although folds to<br />
the north may be overturned.<br />
The proposed axial plane belonging<br />
to the Jim Lake anticline is apparently overturned to the south<br />
and apparently plunges to the northeast.<br />
FOLIATION AND LINEATION<br />
Throughout much of the <strong>area</strong> bedding, schistosity (bedding<br />
schistosity?), gneissosity, and flow contacts were found to be<br />
less variable and generally steep or vertical.<br />
Lineation of<br />
amphibole, although variably developed was observed in the<br />
amphibolites (mafic metavolcanics) adjacent to the Jim Lake<br />
granite, a body which itself exhibits northeasterly-plunging<br />
rods of quartz.<br />
A lineation, the product of intersecting cleavage and<br />
bedding planes, is prevalent in the metasediments that are found<br />
within part of the western contact aureole of the <strong>Port</strong> <strong>Coldwell</strong><br />
Alkalic Complex north of Middleton.
- 46 -<br />
FAULTING<br />
It should be made clear at the outset that the steep dips<br />
and lack of a definite stratigraphic column render the<br />
recognition of strike faults regardless of attitude extremely<br />
difficult.<br />
Transverse faults are more easily recognizable, and appear<br />
to be near-vertical and to strike N10OW or N300E. The more<br />
northerly-trending fault cutting the metavolcanics and Jim<br />
Lake granite east of Wullie Lake has sinistral movement as<br />
indicated by the associated drag folding. Gash fractures<br />
filled with quartz are strongly developed on the western<br />
(downthrown) block.<br />
JOINTING<br />
Considering the long and complex history of the <strong>area</strong>, it<br />
is to be expected that all the rocks would be intensely jointed,<br />
more or less. Most outcrops do show at least two distinct<br />
joint sets, and five or more joint sets in a single outcrop<br />
have been observed.<br />
In the course of the field work it became apparent that<br />
several joint sets are related to the folded metavolcanics and<br />
that the various hypabyssal intrusions have been guided during
- 47 -.<br />
intrusion by these pre-existing planes of weakness.<br />
Joint control on the intrusion of various dikes related<br />
to the <strong>Port</strong> <strong>Coldwell</strong> Alkalic Complex was suggested and gave<br />
further impetus to the following study.<br />
Accumulation and Interpretation of the Joint Data<br />
Generally all the visible joints were frequently measured<br />
in an attempt to minimize 'selection-bias 1<br />
and to minimize local<br />
irregularities in the general and (or) regional pattern.<br />
Ideally it was hoped that minor but consistent joint sets<br />
important to the structural interpretation of the <strong>area</strong> would<br />
not be overlooked.<br />
About 6,000 readings of joint attitudes were collected<br />
and plotted on Schmidt equal-<strong>area</strong> nets.<br />
The joint plots were<br />
then counted and contoured using the standard 1-percent <strong>area</strong>counting<br />
device (see Billings, 1942, p. 111-115, for a simple<br />
explanation of the technique).<br />
The interpretations presented are based on the premise<br />
that joints should and can be related to major geologic<br />
events in the <strong>area</strong>.<br />
Persistent joint sets are recognized<br />
on the accompanying joint contour diagrams and their genetic<br />
relations are inferred from their fit with ideal joint sets<br />
that would be related to known folds.
- 48 -<br />
A brief review of joints expected on fold structures may<br />
be warranted.<br />
During plastic or essentially nonplastic<br />
deformation, joints may form parallel to the axial plane.<br />
This set is the "release-tension-joints 11 of de Sitter (1956,<br />
p.131).<br />
The significance in incorporating the aspect of<br />
tension in designating these longitudinal joints stems from<br />
the possibility of tension joints developing in the upper part<br />
of the fold as a result of scretching of the 'cap 1<br />
rocks of the<br />
fold.<br />
A set of joints ("extension joints" of Billings, 1942,<br />
p. 117) may form perpendicular to the fold axis or "release-<br />
tension-joints" resulting from stretching of the beds on the<br />
crest of a doubly plunging fold.<br />
Shear joints (or diagonal<br />
joints) may form in symmetrical positions at angles less than<br />
450 to the principal (greatest) compressive stress, but both<br />
shear directions are not necessarily expressed in the rocks.<br />
Joints in Metavolcanic-Metasedimentary Sequences<br />
The attitudes of 1300 joints in the metavolcanic and<br />
metasedimentary rocks were determined.<br />
The pole intersections,<br />
of perpendiculars to planes representing these joints and the<br />
bottom half of an imaginary sphere, through the centre of which<br />
the planes are assumed to pass, were projected to a horizontal
- 49 - ^<br />
surface to give a point diagram as described by Billings<br />
(1942, p. 114-122). From the point diagram, a contour<br />
diagram, to show the percentage of joints per unit <strong>area</strong> of<br />
projection, was constructed. The contour diagram is<br />
reproduced in Figure 1.<br />
In all there are eight sets of joints recognizable which<br />
describe a pattern symmetrically disposed about the regional<br />
fold axis direction indicated on the plot.<br />
The predominant joint sets labelled 8 and 5 strike parallel<br />
to the regional fold axes and almost always, parallel to the<br />
planes of bedding and (or) parallel to the planes of<br />
schistosity or gneissosity. Joints labelled l and 7 have a<br />
similar strike, parallel to the regional fold axes, but are<br />
horizontal or near horizontal and related to sheeting.<br />
In character the more vertical joints described are<br />
smoother surfaced, straighter and more continuous than any<br />
other joint set observed in the greenstones.<br />
But in company<br />
with the halo of marked deflections in the direction of the<br />
regional fold axes around the <strong>Port</strong> <strong>Coldwell</strong> Alkalic Complex,<br />
the continuity of these joints are solely restricted to the<br />
more competent members.<br />
Instead the prevalent jointing labelled<br />
3 and 4 in Fig. l is parallel to the bedding plane. These<br />
joint surfaces are crenulated due to the intersection with the<br />
axial plane cleavage described.<br />
\
- 50 -<br />
The joint set labelled 2 in Fig. l strikes perpendicular<br />
to the axial plane direction. These joints tend to be<br />
irregularly spaced and terminate against the joints paralleling<br />
the regional fold axis direction.<br />
Structures Related to the Granitic Intrusions<br />
The Jim Lake granite is apparently concordant with the<br />
metavolcanics and metasediments.<br />
The shape of the Jim Lake<br />
granite is known, in part, and may be described as trending<br />
parallel with and into established folds.<br />
The trondhjemite, at Wullie Lake occurs as a more<br />
equidimensional body. Planes of schistosity within the<br />
prevalent metasediments appear to have been deflected around<br />
the western part of the trondhjemite.<br />
JOINTING<br />
As a corollary to the restricted regional study, joint<br />
sets in the granitic rocks were compared. The attitude of the<br />
joints related to the Jim Lake granite is shown in Fig.2 from<br />
which it is readily noticeable that the distribution of the<br />
joints bear a marked similarity to that already described for<br />
the metavolcanics.
- 51 -<br />
Primary joint sets in igneous rocks can be recognized<br />
if dikes related to the igneous body are found to be<br />
intruded along the joints in that body.<br />
On this basis the<br />
joint set striking N20 W and labelled l in Fig.2 which contain<br />
pegmatitic phases of the Jim Lake granite can be considered<br />
as "extension"-type of primary joints.<br />
The granite is also cut by a suite of lamprophyre dikes<br />
which appear to be closely related to the granite in view of<br />
the fact that the dikes have been found restricted in<br />
occurrence to the granite.<br />
These dikes, averaging several<br />
feet in width, exhibit pencil sharp contacts with no chilling<br />
and have attitudes which are joint controlled.<br />
The lamprophyre dikes belonging to the mica-free porphyritic<br />
and non-porphyritic types were intruded along the "extension 11<br />
joints and the intrusion occurred while the intruded portions<br />
of the granite were under tension (See Fig.3).<br />
The structural relationship between the metavolcanics<br />
and granite can best be described by considering the section<br />
centred around Jim Lake.<br />
The pertinent structural features found are as follows:<br />
1. The host rocks containing the granite, so to speak, are<br />
predominantly mafic metavolcanics having a uniform attitude<br />
in schistosity which is identical to that found on a regional scale.
- 52 -<br />
2. The northernmost belt of metavolcanics shows a f oresting 1<br />
in the attitude of the schistosity southward to the granite<br />
contact.<br />
3. The emplacement of the granite has been dominantly of a<br />
concordant nature, paralleling the structures in the<br />
metavolcanics.<br />
Discordant relations are associated with the<br />
granite (were found to be) and were accentuated either by<br />
the presence of aplite apophyses or by the presence of migmatite<br />
zones up to one foot wide and paralleling the granite-metavolcanics<br />
contacts.<br />
4. The quartz rods plunge to the northeast at an angle of<br />
45 0 which is identical to the direction and angle of plunge<br />
obtained from some amphibole lineations in the adjacent<br />
metavolcanics and dragfolds in the metavolcanics comprising<br />
the south-containing limb for the granite.<br />
5. Dragfolds in the metavolcanics involving "off-shoots 11 of<br />
granite indicate a relative movement of the granite to<br />
higher levels.<br />
6. The granite body proper exhibits a barren zone free of<br />
inclusions and a zone highly charged with inclusions of<br />
metavolcanics which is adjacent to the 'cresting 1<br />
portion of<br />
the northernmost limb of the metavolcanics belt.
- 53 -<br />
7. The close similarity in the distribution in the joints<br />
between the granite and metavolcanics would appear to<br />
substantiate the consideration that the granite intrusion<br />
was predominantly of a concordant nature. The lack of<br />
similarity in the relative intensities between the two joint<br />
plots may simply reflect inherent differences in structural<br />
behaviour in a cooling magma.<br />
8. Fig.2 is a composite diagram made up by plotting all the<br />
joints in the granite irrespective of granite character. In<br />
actuality the sub-horizontal joint set, labelled 2 and a product<br />
of sheeting, is predominant in the 'barren 1 zone of the<br />
granite. This would seem to suggest that the major fold axis<br />
should be in close proximity to this zone.<br />
Conclusion<br />
Any one of the eight structural features enumerated cannot<br />
alone reveal the complete structural relationship between the<br />
granite and host rock concerned. But together the evidence<br />
would appear to indicate that the granite is a synorogenic- and<br />
was emplaced into the metavolcanic-metasedimentary sequences<br />
during regional deformation.
- 54 -<br />
Structures Related to <strong>Port</strong> <strong>Coldwell</strong><br />
Alkalic Complex<br />
The <strong>Port</strong> <strong>Coldwell</strong> Alkalic Complex is a lopolith exhibiting<br />
many features common to intrusions classified as laccomorphic<br />
(Benson 1926). The rock types, namely; gabbro and laurvikite,<br />
comprising the 'main 1 series can and have been divided into<br />
conveniently mappable field units. The roof and upper portions<br />
of the Complex is variably hidden beneath overlapping country<br />
rock and roof pendants of country rock. The rock types,<br />
namely; syenodiorite, nordmarkite, various feldspathoids and<br />
zeolitized derivatives, are intimately associated with the<br />
country rocks comprising the roof and upper portions of the<br />
Complex.<br />
Glossary of Terms<br />
Structures within the Complex which have been mapped and<br />
identified include the following, the name of which Is<br />
accompanied by the presently accepted definition (Hess 1960).<br />
Layering:<br />
The arrangement of crystals in layers; analogous to<br />
stratification in sedimentary rocks.<br />
Rhythmic Layering:<br />
Generally refers to layers, <strong>area</strong>lly quite<br />
persistent, which have been repeated rhythmically so as to produce<br />
-<br />
Having the form of a laccolith.
- 55 -<br />
a most conspicuous banded appearance.<br />
Megascopically it<br />
can be seen that this type of layering is due to changes,<br />
commonly a gravity stratification, in the relative proportions<br />
of the minerals concerned.<br />
Cryptic Layering:<br />
Non-megascopic and reflects the upward change<br />
in mineral composition, and not relative proportion, during<br />
cooling.<br />
Phase Layering:<br />
Abrupt mineralogical changes resulting from<br />
the appearance or disappearance of a mineral phase.<br />
Igneous Lamination:<br />
The preferential arrangement of platy<br />
crystals so as to develop a foliated texture.<br />
It is not<br />
uncommon to find that platy crystals exhibit a lineation<br />
in the plane of foliation.<br />
Inch-Scale Layering:<br />
First named by Hess for a type of<br />
layering, whose origin is considered uncertain. Composed<br />
of alterations of pyroxene and plagioclase which are<br />
slightly less than an inch thick.<br />
These structures, although apparently variably developed,<br />
identify the layered gabbros (Inner Border Zone f b ! ) and the<br />
layered laurvikites (Lower Zone).
- 56 -<br />
LAYERING IN THE 'MAIN 1<br />
SERIES<br />
Rhythmic Layering<br />
The rhythmic layering (Skaergaard type) in the layered<br />
gabbros is more or less continuous and regular and has been<br />
traced horizontally, for a distance of 800 feet.<br />
But<br />
continuity in rhythmic layering over such distances does not<br />
preclude the possibility that the development of layering, in<br />
general, in the gabbros may be somewhat discontinuous and<br />
(or) irregular and (or) manifest itself in a somewhat different<br />
texture.<br />
Chilling, commonly of a subtle nature, has been<br />
established petrographically.<br />
Mineralogically the basal portions of the layers are<br />
composed of a greater concentration of anhydrous femic<br />
constituents (with or without a concomitant increase in relative<br />
grain size) .<br />
The ferromagnesian minerals referred to are olivine,<br />
clinopyroxene, ilmenomagnetite with (or) without minor sulphides.<br />
Rhythmic layering is megascopically observable in the<br />
layered laurvikites.<br />
Ferromagnesian minerals are generally<br />
more abundant in the 'dark 1<br />
basal units than in the overlying,<br />
generally more reddish coloured, units.<br />
Determinative work shows that the alkalic feldspar in the<br />
'dark 1 , basal (essentially anhydrous) units is characteristically,<br />
although variably, less unmixed; less potassic; and composed of
- 57 -<br />
higher (intermediate) temperature albite.<br />
In contrast the<br />
alkalic feldspar in the 'reddish 1 , overlying (variably but<br />
generally extensively pseudomorphed by iddingsite, barkevikitic<br />
amphibole, and annitic biotite) units is characteristically,<br />
although variably, more unmixed; more potassic; and composed<br />
of low temperature albite.<br />
Discontinuous and (or) Disturbed Layering<br />
Discontinuous and (or) disturbed layering has been noted<br />
in several <strong>area</strong>s and in all cases the phenomena was restricted<br />
to the basal portion of the layered gabbros.<br />
Whether gabbros<br />
similarly located spatially do exhibit disturbed layering and<br />
therefore contribute to the delimiting, in gross aspects, of a<br />
basal gabbro zone typified by disturbed layering has not been<br />
substantiated nor disproven by the surface mapping to date.<br />
Inch-Scale Layering<br />
Inch-scale layering can be seen in the exposures along<br />
Trans-Canada Highway 17 where it appears restricted to the basal<br />
zone of the rhythmically layered gabbros.<br />
Inch-scale layering<br />
developed to a similar degree or regularity has not been seen<br />
elsewhere.
- 58 -<br />
Cryptic Layering<br />
Cryptic layering is present in the layered gabbros.<br />
Determinative work shows that the olivines range from hortonolite<br />
to chrysolite, plagioclase from calcic labradorite to calcic<br />
albite, and clinopyroxene from diopside to diopside augite.<br />
^-~<br />
Igneous Lamination with (or) without Lineation<br />
CIinopyroxenes, plagioclases , and alkalic feldspars<br />
(perthites) frequently occur as prisms or plates. The feldspar<br />
plates exhibit dimensions which commonly are as follows:<br />
2^ mm wide (i.e. faces describing zone perpendicular to<br />
010 plane) by 3mm to 7mm by 4mm to 9mm. Where lamination is<br />
present the feldspars are oriented so that the (010) plane<br />
is more elongate, the long axis plunges down-dip toward the<br />
geographical centre of the complex. This lineation is strongly<br />
masked in those rocks which appear to contain a bimodal-like<br />
assemblage of feldspars. In an outcrop occurring \ mile east of the<br />
Marathon cut-off on Trans-Canada Highway 17 it was determined<br />
that 55 percent of the larger, more elongate perthites contributed<br />
to the development of a lineation whereas but 30 percent of the<br />
smaller, less elongate perthites exhibited a similar orientation.<br />
The remaining smaller perthites were oriented at varying angles<br />
to the plane of lamination.<br />
4
- 59 -<br />
JOINTING IN THE 'MAIN 1<br />
SERIES<br />
Similar techniques were followed in the accumulation and<br />
presentation of the joint data related to the rocks of the<br />
<strong>Port</strong> <strong>Coldwell</strong> Alkalic Complex (Fig. 4), as described previously.<br />
These joints may be divided into three definite groups:<br />
(1) horizontal and near horizontal joints; and (2) moderately<br />
inclined joints; and (3) vertical or near-vertical joints.<br />
The joints in group (1) include members formed as a<br />
result of a process referred to as sheeting.<br />
Near horizontal joints describe a definite girdle of<br />
concentric fractures which dip outward, toward the margin of<br />
the alkalic syenite complex.<br />
These joint planes have served<br />
as avenues for intrusion of augite syenite pegmatites.<br />
Moderately inclined joints are coincident to 'the primary<br />
flow layering but dip inward, at angles averaging 55O toward<br />
the apex of the alkalic syenite complex.<br />
The joints of groups (1) and (2) may show shearing effects<br />
and may show mineralization including calcite, fluorite and (or)<br />
molybdenite.<br />
The steeply inclined to vertical joints describe a radial<br />
pattern normal to the flow lines.<br />
These joints are frequently<br />
mineralized similar to that reported for joints in groups<br />
(1) and (2); whereas shearing, on the.other hand, is less<br />
prevalent along the joints of near vertical attitude.
- 60 -<br />
LAYERING IN THE 'SECONDARY 1<br />
SERIES<br />
Except for the nepheline syenites occurring on Allouez and<br />
Pic islands, the rocks of the 'secondary 1 series are massive and<br />
essentially structureless.<br />
The nepheline syenites from these locations exhibit rhythmic<br />
layering accompanied by gravity stratification (i.e. mafics,<br />
predominantly sodic amphibole, are more abundant in the basal<br />
units). The layering is generally regular and near-vertical in<br />
attitude. Contortions and folds, steeply plunging, are not<br />
uncommon. In two <strong>area</strong>s the layering was found to describe vortexlike<br />
structures.<br />
JOINTING IN THE 'SECONDARY 1<br />
SERIES<br />
As previously stated the rocks of the 'secondary' syenite _^<br />
series are intimately associated with the country rocks comprising<br />
the roof and upper portions of the Complex. Such a unit of<br />
country rock is referred to as the Coubran Lake metavolcanic<br />
roof pendant.<br />
Poles of 861 joints from the Coubran Lake metavolcanic<br />
roof pendant were plotted and the points contoured (Fig. 5).<br />
Field evidence has shown that the Coubran Lake metavolcanic roof<br />
pendant is overlain by laurvikite along the north exposure three
- 61 -<br />
miles due west from the northwest shoreline of Coubran Lake.<br />
In comparing the plot of the joints from the Coubran Lake<br />
metavolcanic roof pendant to that plot previously presented for<br />
the country rock, the modifications probably imposed on the<br />
existing joint attitudes by the northerly subsidence may<br />
be postulated.<br />
The joint plots for the syenogabbros and nordmarkites<br />
are identical to that obtained from the Coubran Lake metavolcanic<br />
roof pendant.<br />
A contour diagram of 683 joints obtained from the larger<br />
bodies of nepheline syenite is presented in Fig. 6.<br />
These<br />
bodies are generally zoned such that the marginal phases are<br />
finer grained and more mafic.<br />
The peripheral metavolcanics<br />
are variably nephelinized and generally exhibit the presence<br />
of joint controlled dikes of feldspathoidal rocks (Figs. 7 and 8).<br />
The massive exposures of nepheline syenite, particularly<br />
those on Allouez and Pic islands, exhibit a more pinkish alteration<br />
along the joint planes. This pinkish alteration may extend into<br />
the host anywhere from a few inches to several feet and is<br />
attributable to a later period of zeolitization.
- 62 -<br />
LINEAMENTS<br />
Lineaments have been largely deduced from aerial photographs<br />
by commonly accepted methods. The lineaments within the <strong>Port</strong><br />
<strong>Coldwell</strong> Alkalic Complex appear to describe a radial and a<br />
concentric pattern. Movement along many of these lineaments is<br />
strongly suspected in view of many contact relations and outcrop<br />
pattern. Lineaments disposed radially from the Complex<br />
consistently indicate displacement, which is suspected to have<br />
a substantial dip component.<br />
In the map-<strong>area</strong> there are three major north-south trending<br />
lineaments, namely, the Big Pic River, Little Pic River, and<br />
Redsucker Cove.<br />
SUMMARY<br />
The <strong>Port</strong> <strong>Coldwell</strong> Alkalic Complex is a large lopolithic<br />
intrusion. A limited but more or less persistent metamorphic<br />
aureole, characterized by recrystallization and (or)<br />
remobilization, and development of orthopyroxene was developed.<br />
In addition local structures in the country rock were disturbed.<br />
The Complex can be conveniently considered as being composed<br />
of two rock series; namely, a 'main 1 series which includes gabbros<br />
and laurvikites and a f secondary 1 series which includes
- 63 -<br />
syenodiorites, nordmarkites and feldspathoidal rock types.<br />
Within the 'main 1 series a zonation has been recognized<br />
which is as follows:<br />
Upper Zone<br />
Laurvikite<br />
Lower Zone<br />
Layered laurvikite<br />
Inner Border Zone f b f Layered gabbro<br />
Inner Border Zone ! a f Massive gabbro<br />
Outer Border Zone<br />
Chilled gabbro<br />
The massive gabbro does contain significant and perhaps<br />
economic amounts of base metals, largely as chalcopyrite.<br />
The layered structures dip inwards at moderate angles<br />
(range from 70 to 70O ). From field data it would appear that<br />
the dip in layering is small (i.e. 7 O ) near Skipper Lake.<br />
Contact between layered gabbro and layered laurvikite is<br />
variably chilled and appears to be largely conformable.<br />
During cooling of laurvikite, laurvikite pegmatites were<br />
intruded spatially as ring dikes, along pre-existing,<br />
reactivated joints in the basal members of the Complex.<br />
The intrusion of nepheline syenite, largely as domes with<br />
near-vertical sometimes vortex-like layering, has been largely<br />
joint controlled in the peripheral <strong>area</strong>s of these domes.<br />
Late lamprophyre intrusion has occurred along reactivated<br />
joint planes as cone sheets.
- 64 - x-<br />
ECONOMIC GEOLOGY<br />
Introduction<br />
Various parts of the <strong>area</strong> have been staked for building<br />
stone, iron, non-ferrous base metals, and nepheline; and<br />
-^gravel<br />
has been removed locally for road construction.<br />
The early economic interest in the <strong>area</strong> was for the<br />
quarrying of dark (and later red) laurvikite for building<br />
stone.<br />
Mineral prospecting during the early 1930 f s was limited<br />
to the determination of the iron ore potential of the magnetite-<br />
rich bodies within the gabbros of the <strong>Port</strong> <strong>Coldwell</strong> Alkalic<br />
Complex east of Bamoos Lake.<br />
Exploration with similar intent<br />
was continued up to 1960 by which time most of the exposures<br />
of gabbro belonging to the Complex had been variously examined.<br />
During the course of this exploration for iron ore,<br />
extensive copper mineralization within the gabbros was discovered.<br />
The first non-ferrous base metal examination was begun in 1954.<br />
Present investigations appear to indicate the presence of large<br />
tonnages of fairly low-grade copper-nickel mineralization.<br />
The feldspathoidal syenites immediately west of Redsucker<br />
Cove were examined, in 1960, as possible source rocks for the<br />
mineral nepheline.<br />
The results of the exploration were not<br />
encouraging and development has been postponed, apparently, for<br />
an indefinite period.
- 65 -<br />
IRON<br />
The gabbros of the Complex were investigated as a possible<br />
source of iron as early as 1930.<br />
The magnetite-rich bodies<br />
are found to vary from one inch wide to seventy feet wide and<br />
to be present as lenses which generally exhibit similar attitudes<br />
as those of the local gabbro host.<br />
These bodies are found to be mineralogically composed of up<br />
to 80 percent ilmenomagnetite with accessory olivine, apatite<br />
and chalcopyrite.<br />
The chemical composition of the larger, 50 to 70 feet wide,<br />
bodies is as follows: Approximately 40 percent iron, 5 to 8<br />
percent sulphur, 0.3 to l percent phosphorus (^2^5) anc*<br />
approximately 30 percent silica.<br />
All the analyzed and observed bodies of high magnetite<br />
rock, whether conformable or disconformable to the host-rock<br />
layering, contain ilmenomagnetite, variably unmixed.<br />
The<br />
titanium content, under present conditions, does not appear<br />
to make the mineralization attractive either as a source of<br />
iron ore or as an ore of titanium.
- 66 -<br />
Zebe Renshaw<br />
At various times between 1950 and 1954, Zebe Renshaw staked<br />
fifteen claims, ten to cover a zone of high magnetite that was<br />
believed to have possibilities as an ore of iron.<br />
_.<br />
The high magnetite rock is 7/8 of a mile west of the<br />
Little Pic River within the gabbro outcrop on the north side of<br />
Trans-Canada Highway 17.<br />
The rock occurs as a conformable<br />
segregation with a true width of about 50 feet, and dips about<br />
20OE.<br />
This segregation has been traced horizontally for a<br />
distance up to ^ of a mile.<br />
The high magnetite rock is composed of ilmenomagnetite,<br />
60 to 80 percent, and varying amounts of apatite, olivine,<br />
and chalcopyrite.<br />
The host gabbros characteristically contain interstitial<br />
ilmenomagnetite.<br />
In some cases the oxide phases occur as<br />
veins, somewhat irregular in attitude, ranging from 6 inches<br />
to 20 feet wide.<br />
An average of several analyses yielded approximately 37<br />
percent iron, 5 percent titanium,l percent manganese, 30 percent<br />
silica, about l percent phosphorus (^2^5)* anc* aDOUt 0*10 percent<br />
sulphur (Walker 1961, p.5).
- 67 -<br />
George Olson<br />
In 1960 George Olson, proprietor of North Shore Hotel in<br />
Heron Bay, held a group of 71 claims approximately one mile<br />
north of Bamoos Lake and extending westward to Skipper and<br />
Lacobeer lakes. The claim block described a rectangle whose<br />
long dimension, approximately three miles, trended in an<br />
east-west direction.<br />
By 1964 the claims were reduced in number with Olson<br />
retaining 20 claims in partnership with Louis Adams and 18<br />
claims in partnership with Louis Adams and John A. Hamilton.<br />
These 38 claims were optioned by Anaconda American Brass Ltd.<br />
in October, 1964.<br />
The bedrock is predominantly composed of gabbro. Granite,<br />
fine-grained and coarse-grained amphibolite schists occur to<br />
the north and northeast and laurvikites to the southwest.<br />
The gabbro - Jim Lake granite contact is represented by<br />
-an approximately 40-foot wide zone of medium-grained, grey<br />
coloured, hybrid phase of granite.<br />
In thin section this grey<br />
coloured phase of granite is seen to exhibit a characteristic<br />
texture in which the plagioclase appears as rectangular plates<br />
within quartz. The interstitial quartz appears as optically<br />
continuous porphyroblasts up to 8mm. The femic constituents<br />
include serpentine, biotite and penninite.
- 68 -<br />
The gabbros are variably mineralized and may exhibit<br />
folitated and layered structures whose dip component is ^<br />
predominantly shallow, varying from 5 to 40O to the SW.<br />
Numerous layers of ilmenomagnetite are present. One body is<br />
approximately 70 feet wide.<br />
Early geophysical work by Dan Johnson of <strong>Port</strong> <strong>Coldwell</strong>,<br />
which included a dip needle survey, traced the main ilmenomagnetite<br />
body for approximately three quarters of a mile. During these<br />
investigations a sulphide-bearing phase of gabbro was observed<br />
and traced for approximately one mile. The mineralized bodies<br />
were reportedly transected by a northeast-trending fault.<br />
Recent investigations and diamond drilling by Anaconda<br />
American Brass Ltd. have verified the presence of sulphide<br />
mineralization.<br />
Empire Explorations Limited<br />
In 1963 Empire Explorations Ltd. held a group of 9 claims<br />
east of the east end of Bamoos Lake. These claims include<br />
ground formerly staked by H. England of <strong>Port</strong> <strong>Coldwell</strong> (Thomson<br />
1931, p.33). In 1954 they were held by Bamoos Lake Mines Ltd. 1 .<br />
The bedrock is predominantly gabbroic and includes the finemedium-,<br />
and coarse-grained varieties characteristic of the<br />
gabbros belonging to the Complex.<br />
Layering is strongly developed<br />
T The claims were optioned in 1964 to Anaconda American Brass Ltd.<br />
and in 1966 were held by the Keevil Mining Group Ltd.
- 69 -<br />
in the more westerly gabbros.<br />
moderate, approximately 30O ,<br />
The dips are to the west at<br />
angles.<br />
The gabbros contain numerous inclusions of metavolcanics,<br />
generally of felsic composition.<br />
A more mafic inclusion can be<br />
observed along the shorelines at the eastern end of Bamoos Lake.<br />
The gabbros are cut by numerous dikes of laurvikite<br />
pegmatite which generally dip to the east at moderate angles.-<br />
The gabbros contain two pyroxenes, olivine, and plagioclase.<br />
The accessory minerals include ilmenomagnetite, apatite, sulphides<br />
and mica.<br />
The sulphides are predominantly interstitial and<br />
include pyrrhotite, chalcopyrite and pyrite.<br />
Exploration has included trenching, detailed mapping,<br />
various geophysical surveys and diamond drilling.<br />
Bamoos Lake<br />
Mines Ltd. drilled the immediate gabbros in 1954 to test the<br />
-^<br />
copper potential.<br />
Although the presence of mineralized, generally<br />
coarse-grained, gabbros has been substantiated, the grade of<br />
copper and the horizontal and depth continuity have not been<br />
established.<br />
The early investigations were directed toward the<br />
ilmenomagnetite layers.<br />
Analysis of a chip sample, taken along<br />
the total length of a trench on the England claims, contained<br />
40.0 percent iron, 7.35 percent titanium oxide, 0.56 percent<br />
sulphur, and 0.33 percent phosphorous. (Thomson 1931, p.33).
- 70 -<br />
Assessment files show that the iron content in the<br />
ilmenomagnetite bodies was considerably lower and was up<br />
to 27 percent.<br />
Thomson (1931, p.35) referred to the presence of vanadium<br />
from an occurrence of magnetite on the small island in the<br />
lake east of Bamoos Lake as reported by H. England.<br />
A grab<br />
sample of magnetite ore from this outcrop was collected by<br />
Thomson and assayed 0.48 percent vanadium.<br />
The vanadium mineral was not apparently, definitely identified.<br />
Thomson (1931, p.35) reported that Dr. T.L. Walker examined the<br />
specimens and suggested that the sage-green coloured mineral,<br />
occurring as films along joints, may be pintadoite, a hydrous<br />
calcium vanadate*<br />
NON-FERROUS BASE METALS<br />
Early discoveries of copper mineralization of any significance<br />
resulted from the efforts directed toward the exploration for iron<br />
ore.<br />
The base metal potential of the <strong>area</strong>, as related to the<br />
gabbros of the <strong>Port</strong> <strong>Coldwell</strong> Alkalic Complex in particular, was<br />
not given serious consideration until 1954.<br />
Since then<br />
investigations have ultimately become intimately involved with<br />
the coarser-grained gabbro phases generally underlying the layered<br />
and foliated gabbros.<br />
The mineralized gabbros apparently dip
- 71 -<br />
inward, at varying angles, toward the centre of the <strong>Port</strong> <strong>Coldwell</strong><br />
Alkalic Complex.<br />
Results of exploration apparently indicate a general lack of<br />
continuity in grade of mineralization, both horizontally and with<br />
depth.<br />
Assays to date indicate copper values ranging from 0.17 to<br />
approximately l percent.<br />
Nickel values appear to be consistently<br />
low, varying from trace to 0.31 percent.<br />
Moneta Porcupine Mines Limited<br />
In 1954 Moneta Porcupine Mines Ltd. optioned a group of 47<br />
claims from D. Smith and Z. Renshaw both of Marathon, <strong>Ontario</strong>.<br />
This agreement followed the visit and examination in February,<br />
1954, of a showing of copper mineralization by Patrick H. Taylor.<br />
Z. Renshaw had originally staked 15 claims, ten of which<br />
were immediately east of the optioned group.<br />
All of these<br />
claims were staked between 1950 and 1954 initially to include<br />
a zone of high-magnetite rock.<br />
Copper mineralization was<br />
discovered during the performance of assessment work and led to<br />
the subsequent staking of 32 additional claims by a group of<br />
Marathon businessmen which included D. Smith, H. Taylor, G. Ross,<br />
J. Graham, and C. MacMillan.
- 72 -<br />
The claim block is cut by Trans-Canada Highway 17 and is<br />
located approximately 7/8 of a mile west of Little Pic River.<br />
The claims extend westward to Deadhorse Creek, approximately<br />
1/4 of a mile north of the power line, and southward to the<br />
shore of Lake Superior.<br />
The claims are predominantly underlain by rocks belonging<br />
to the metavolcanic-metasedimentary assemblage.<br />
The easternmost<br />
claims include all of the exposed gabbro describing the western<br />
limit of the <strong>Port</strong> <strong>Coldwell</strong> Alkalic Complex.<br />
The metavolcanics are generally very fine-grained, partly<br />
schistose, and mafic in composition.<br />
Pillow structure has been<br />
observed in the vicinity of Middleton station and Trans-Canada<br />
Highway 17.<br />
The metasediments are predominantly argillites and<br />
metagreywackes and outcrop along and to the south of the Highway.<br />
Graded bedding is variably developed.<br />
Tops are to the south.<br />
The metasedimentary-metavolcanic assemblage exhibit structures<br />
which predominantly strike approximately N70OW; and have near-<br />
vertical dips.<br />
The folds are isoclinal.<br />
These structures are strongly flexured and dragfolded within<br />
a ^ mile zone, generally exhibiting a high garnet content, which<br />
lies immediately to the west of the gabbros of the Complex.
- 73 -<br />
The metasedimentary-metavolcanic assemblage approximately<br />
l mile north of the Highway has been cut by a post-deformational,<br />
northwest-trending, diabase dike.<br />
The gabbros of the Complex form a north-trending band<br />
approximately \ mile wide, which is terminated north of the<br />
Highway by the Little Pic River granite and related phases.<br />
These gabbros vary from massive to layered phases to the east.<br />
The layering strikes approximately N10OE and dips approximately<br />
300 to the east (see Fig.9).<br />
Pegmatitic phases of the gabbro cut, in part with a<br />
horizontal attitude, the marginally located metavolcanics and<br />
metasediments.<br />
^ .<br />
The layered gabbros appear to grade into layered laurvikites<br />
to the east. Dikes of laurvikite pegmatite, generally dipping<br />
to the west, cut the basal gabbros.<br />
Ilmenomagnetite segregations occur in the gabbros, and to<br />
a lesser degree in the laurvikites. These segregations generally<br />
exhibit a conformable attitude with respect to the layered host<br />
rocks. The largest body, exposed in the Highway cut located<br />
7/8 mile west of the Little Pic River, is approximately 140 feet<br />
wide. The ilmenomagnetite content varies between 10 to 30<br />
percent.<br />
Some segregations contain up to 80 percent of magnetite.
- 74 -<br />
Red hornblende syenite dikes, with a variable quartz<br />
content up to 10 percent, cut the gabbros, metasediments and<br />
metavolcanics.<br />
These dikes, in part at least, appear to have<br />
been derived from the Little Pic River granite and related phases<br />
to the north.<br />
They strike approximately N10OE and dip steeply,<br />
approximately 70OE.<br />
The gabbros have been cut by nepheline-bearing and zeolitized<br />
nepheline-bearing feldspathoidal pegmatites trending approximately<br />
N50 -10OE and dipping steeply, approximately 70^. The marginal<br />
phases generally include numerous inclusions such as layered<br />
gabbro, ilmenomagnetite segregations, and massive gabbro.<br />
The<br />
gabbros, laurvikites, and feldspathoidal rock types of the<br />
Complex have been cut by various lamprophyric dikes which<br />
^<br />
generally have an east-west strike and dip steeply, approximately<br />
700N.<br />
Mineralogically the gabbros are predominantly composed of<br />
s<br />
two pyroxenes, olivine, and plagioclase with variable amounts of<br />
ilmenomagnetite, sulphides, apatite and biotite.<br />
The sulphides are predominantly chalcopyrite and pyrrhotite<br />
(maximum up to 6 percent) with minor amounts of pyrite and<br />
bornite.<br />
The sulphides generally appear disseminated and occur<br />
interstitially with respect to the silicates comprising the<br />
coarser textured gabbros.<br />
Weathering has resulted in the
- 75 -<br />
development of a little malachite.<br />
Although generally fresh, some outcrops of gabbro containing<br />
sulphides, ilmenomagnetite and apatite may exhibit a characteristic,<br />
knobby weathered surface.<br />
The associated gossan is usually<br />
accompanied by an apatite-rich gravel formed in situ.<br />
Exploration included detailed mapping, and trenching.<br />
Three<br />
gossan <strong>area</strong>s, approximately 700 feet apart and trending parallel<br />
to the strike exhibited by the layering, were observed and<br />
drilled in 1954.<br />
One hole was drilled to test the mineralization<br />
under each gossan.<br />
The best results, 40 feet of 0.46 percent copper, were<br />
obtained from DDK 3.<br />
The mineralized gabbro dips SO0^, an<br />
attitude conformable to that exhibited by the layering (Fig.9).<br />
DDK 2 was collared approximately 100 feet south of the gossan<br />
target.<br />
This hole (and DDH 1) was drilled to test the possible<br />
existence of mineralization having a vertical attitude.<br />
Weak<br />
mineralization, 5 feet of 0.07 percent copper, was intersected.<br />
This may not reflect the true character of the mineralization.<br />
DDH l intersected 5 feet of mineralization with the highest<br />
assay being 0.16 percent copper.<br />
Thirteen analyses were run for nickel, of which twelve<br />
assayed nil and one returned but trace.
- 76 -<br />
In general the drilling results appeared to indicate a<br />
general lack of continuity in grade of mineralization, both<br />
horizontally and with depth.<br />
Lakehead Mines Limited<br />
These holdings include a square of 25 claims centred,<br />
more or less, around Mile Post 8 on the boundary of Township<br />
79. These claims were staked by Head of The Lakes Iron Limited<br />
in 1959.<br />
Exploration, which included electromagnetic and dip<br />
needle surveys, was followed up by diamond drilling in September,<br />
1960. Approximately 17 holes were drilled to an average depth<br />
of 338 feet.<br />
Maximum depth of penetration (DDH 13) was 562 feet.<br />
In 1963 the name of Head of the Lakes Iron Limited was<br />
changed to Lakehead Mines Limited.<br />
Lakehead Mines Limited presently hold approximately 87<br />
claims which describe a rectangular block whose east limit<br />
is represented by the west shore of Wullie Lake.<br />
The west limit<br />
of the claim block is approximately 5,000 feet west of the ^-<br />
boundary of Township 79.<br />
The <strong>area</strong> is predominantly underlain by gabbros and laurvikites<br />
belonging to the <strong>Port</strong> <strong>Coldwell</strong> Alkalic Complex.<br />
To the north the<br />
gabbros intrude the metasediments and older granitic rocks.<br />
l<br />
Effective control belongs to Denison Mines Limited.
- 77 -<br />
The metasediments are predominantly composed of quartz,<br />
feldspar and mica and appear to represent argillites and, in part,<br />
metagreywackes.<br />
Minor massive, aphanitic and amphibolitic units<br />
appear to represent intercalated metavolcanics.<br />
The metavolcanic-metasedimentary assemblage appears to have<br />
been intruded by granitoids of trondjhemitic and apparently earlier<br />
and more syenitic phases.<br />
These intrusions appear to be phases<br />
of the granites comprising the Jim Lake Batholith.<br />
In general the metavolcanic-metasedimentary assemblage<br />
exhibits a strong E-W trending fabric with gentle dips, about<br />
15O to 35OS.<br />
The fabric is somewhat irregular in the vicinity<br />
of the gabbro complex.<br />
The gabbros to the north generally appear fresh whereas to<br />
the south the gabbros are variably weathered to a buff brown<br />
colour so as to appear syenitic.<br />
The gabbros contain two pyroxenes, predominantly clinopyroxene,<br />
and generaly olivine.<br />
Plagioclase is the predominant mineral<br />
component.<br />
Important assessory minerals include biotite, apatite,<br />
ilmenomagnetite and sulphides.<br />
Ilmenomagnetite and apatite are<br />
variable but generally comprise up to 10 percent of many phases.<br />
Ilmenomagnetite segregations, generally conformable in attitude<br />
to the layering have been observed.
- 78 -<br />
The dominant sulphides contained by the mineralized gabbros<br />
are pyrrhotite and chalcopyrite.<br />
The sulphides are intimately<br />
associated with the hydrous silicates and ilmenomagnetite<br />
which occur interstitially with respect to the anhydrous silicate<br />
framework.<br />
"In 1954 Head of The Lakes Iron Limited contracted with<br />
Aeromagnetic Surveys of Toronto for an aeromagnetic survey of the<br />
Wullie Lake property and in 1959 Hunting Technical and<br />
Explorations Limited conducted a helicopter electromagnetic survey<br />
for the company.<br />
A number of electromagnetic anomalies were<br />
subsequently drilled and indicated the presence of magnetite-rich<br />
layers containing minor chalcopyrite and occasional pyrrhotite.<br />
Between 1961 and 1963 parallel line electromagnetic surveys<br />
and a geological survey were completed over parts of the property<br />
under the direction of Denison Mines Limited.<br />
Further drilling<br />
was recommended.<br />
The investigation has indicated a mineralized gabbro apparently<br />
exhibiting some continuity horizontally, and with depth, in grade<br />
of copper. The mineralized gabbros dip about 350S . Assays up to<br />
l percent copper and low nickel have been reported" .<br />
l<br />
V.G. Milne, Geologist, <strong>Ontario</strong> Department of Mines, Toronto
- 79 -<br />
Conwest Exploration Company Limited<br />
Conwest formerly held a group of 5 claims which was cut by<br />
the Trans-Canada Highway 17 approximately 1^ miles east of the<br />
Marathon 'cut-off.<br />
Rock exposures are largely limited to a few road cuts due<br />
to the presence of an approximately 40-foot thick mantle of<br />
sand and gravel.<br />
The property is largely underlain by fine<br />
grained and more mineralized, coarser grained gabbros.<br />
To the<br />
south the gabbros are overlain by metavolcanics, namely,<br />
metarhyolites and banded agglomeratic tuffs.<br />
The contact is<br />
sinuous but generally strikes N60OE and dips to the southwest<br />
at moderate angles.<br />
The contact is not always sharp but rather<br />
characterized by the presence of a hybrid phase.<br />
The contact <strong>area</strong> is further complicated by the presence of<br />
numerous inclusions of metavolcanics in the gabbros.<br />
Although it<br />
is assumed that the metavolcanic contact represents overlapping<br />
(i.e. fixed) portions of the country rock, the numerous<br />
metavolcanic inclusions are interpreted as predominantly non-fixed,<br />
(i.e. free-floating) and suggestive, at best, of near-hanging<br />
wall environments.<br />
The gabbros are cut by dikes of red hornblende syenite<br />
bearing quartz.<br />
These dikes rarely show marginal chill phenomena<br />
and appear to represent remobilized phases of the metavolcanics.
- 80 -<br />
The dikes are somewhat irregular and trend approximately N45O -<br />
700E and dip steeply.<br />
The youngest rock in the <strong>area</strong> is represented by a composite<br />
dike of laurvikite which exhibits two definite sets of chill<br />
surfaces.<br />
The dike strikes N400W and dips about 40OSW.<br />
The metavolcanics exhibit a buff brown weathered surface<br />
and a dark grey fresh surface.<br />
The banded agglomeratic tuffs<br />
contain aphanitic, tuff bands up to approximately 15 feet wide<br />
which alternate with much wider bands containing abundant inclusions<br />
These inclusions or fragments vary in composition but are<br />
predominantly fine-grained quartzites, schists, and massive<br />
metarhyolites.<br />
The fragments generally exhibit a high sphericity<br />
and ellipticity (major axis is six times the minor axis).<br />
The<br />
major axis is contained in a plane which has an attitude identical<br />
to the banding, namely; N20OW strike and 50O to 65O southwesterly<br />
dip.<br />
Thin section examination shows the metavolcanics near the<br />
contacts to be composed of quartz, potassic feldspar, biotite,<br />
hypersthene,clinopyroxene, and sulphides.<br />
Quartz and (or) potassic<br />
feldspar generally occur as megacrysts up to 3mm.<br />
The quartz<br />
megacrysts generally contain disoriented laths of plagioclase.<br />
The structural fabric exhibited by the metavolcanic-<br />
metasedimentary assemblage trends about N25OW and dips 68OSW.
- 81 -<br />
The gabbros may contain abundant, up to 10 percent<br />
biotite megacrysts (up to 30mm), apatite up to 8 percent, and<br />
sulphides.<br />
The mineralized gabbros are generally coarse-grained<br />
with the sulphides, predominantly pyrrhotite and chalcopyrite,<br />
occurring interstially.<br />
Minor amounts of pyrrhotite, pyrite and chalcopyrite are<br />
present in the contact phases of metavolcanics.<br />
"The property has been examined by trenching, diamond<br />
drilling and induced polarization surveys.<br />
Anomalies outlined<br />
by the geophysical survey were investigated by drilling 10<br />
diamond drill holes.<br />
The main mineralization located on the property occurs in<br />
gabbro.<br />
Diamond drill hole No.l intersected a zone of medium- to<br />
coarse-grained mineralized gabbro about 100 feet wide (true<br />
width 80 feet) and dipping about 60^. The mineralization<br />
consists of pyrrhotite and chalcopyrite, with an average grade<br />
of 0.4 percent copper.<br />
Mineralization of a weak and disseminated<br />
nature was reported to a depth of 506 feet (end of hole).<br />
Small<br />
metavolcanic intersections were reported but no large<br />
intersection of footwall volcanics was encountered.<br />
Diamond drillhole No.2 indicates that the main zone of<br />
mineralization thins northwards' to about a 40-foot width with an<br />
average grade of about 0.25 percent copper.<br />
In the north the<br />
mineralized zone dips about 50OW and the main footwall contact<br />
l ~ ~~<br />
Assessment files.
- 82 -<br />
appears co dip about 65OW.<br />
Numerous intersections with metavolcanics were reported and<br />
bands of massive pyrrhotite, sometimes with chalcopyrite, are<br />
o<br />
mentioned as commonly associated with these metavolcanics. 11<br />
Anaconda American Brass Limited<br />
Anaconda began investigations, of a more serious nature,<br />
in the summer of 1963.<br />
A total of approximately 180 claims were<br />
staked.<br />
Presently the Company holds or has options on<br />
approximately 421 claims which extend from the shore of Lake<br />
Superior northward to Bamoos Lake and then northwestward to<br />
beyond the Skipper Lake <strong>area</strong>.<br />
This elongate and curved claim<br />
group covers approximately 15 miles and varies in width from<br />
one to five miles.<br />
The <strong>area</strong> is predominantly underlain by gabbros belonging<br />
to the <strong>Port</strong> <strong>Coldwell</strong> Alkalic Complex.<br />
To the east the gabbros<br />
can be found to intrude the rocks belonging to the metavolcanic-<br />
metasedimentary assemblage.<br />
Inclusions of country rock are<br />
common within these gabbros.<br />
The more westerly occurring gabbros are invariably layered<br />
and (or) foliated.<br />
These gabbros appear to grade westward into<br />
laurvikites which are similarly layered.<br />
The attitude of layering<br />
I<br />
V.G. Milne, Geologist, <strong>Ontario</strong> Department of Mines, Toronto.
- 83 -<br />
in the laurvikites is, more or less, identical to that<br />
exhibited by the underlying gabbros.<br />
These attitudes may show<br />
considerable variation, but in general the average dip is to the<br />
west at moderate (i.e. approximately 30O )<br />
angles.<br />
The gabbros are cut by numerous, generally eastward dipping,<br />
dikes of laurvikite pegmatite.<br />
The youngest rocks in the claim group are represented by<br />
several lamprophyre dikes.<br />
The <strong>area</strong> is transected by numerous linears.<br />
The more<br />
prominent E-W trending linears, in the vicinity of Mile Post<br />
17, appear to represent fault planes the movement along which<br />
appears to have had more of a dip component.<br />
The metavolcanics are predominantly felsic in composition.<br />
Mafic metavolcanics occur to the north, in the vicinity of the<br />
Jim Lake Batholith.<br />
The felsic metavolcanics are predominantly agglomeratic<br />
metarhyolites which normally are composed of quartz, alkali<br />
feldspar, plagioclase, and clinopyroxene.<br />
Accessory minerals<br />
include varying percentages of biotite, chlorite, magnetite,<br />
serpentine, actinolitic amphibole and sulphides.<br />
The sulphides<br />
are predominantly pyrrhotite and pyrite with minor to trace<br />
amounts of chalcopyrite.<br />
The mafic metavolcanics are predominantly<br />
represented by fine- and coarse-grained amphibolitic schists and<br />
gneisses.<br />
Thin section examination shows these rocks to be
- 84 -<br />
composed of plagioclase, actinolitic amphibole, garnet, biotite,<br />
chlorite and magnetite.<br />
The rocks belonging to the metavolcanic-metasedimentary<br />
assemblage exhibit a structural fabric which generally trends<br />
to the northeast. Dips are generally steep. Folds appear to be<br />
isoclinal.<br />
The northeast-trending structural fabric appears to<br />
be more irregular in the vicinity of the <strong>Port</strong> <strong>Coldwell</strong> Alakalic<br />
Complex.<br />
In general the layered and (or) foliated gabbros appear to.<br />
overlie the coarser grained, mineralized phases and the finer<br />
grained, and generally less mineralized, gabbro phases.<br />
The gabbros are composed of varying percentages of the<br />
following minerals; orthopyroxene, clinopyroxene, plagioclase,<br />
olivine, ilmenomagnetite, sulphides, apatite, biotite, actinolite<br />
and serpentine. The sulphides generally occur interstially with<br />
respect to the rock forming silicates. The sulphide minerals<br />
identified include pyrrhotite, chalcopyrite, pyrite and bornite.<br />
"The company began a geological investigation of the <strong>area</strong><br />
in 1962 and this continued through 1964. Trenching and pitting<br />
has been done throughout the claim <strong>area</strong>. An induced potential<br />
geophysical survey was completed in 1963 and drilling started in<br />
late 1964.
- 85 -<br />
Sulphide mineralization is scattered throughout the gabbro<br />
unit but becomes significantly concentrated in some widely "^<br />
separated localities. Assays indicate a variation in copper<br />
from 0.05 percent to about 2 percent. Nickel values are<br />
generally low. The great potential of the <strong>area</strong> is in its possible<br />
development as a low grade, large tonnage open-pit operation 1.1<br />
Falconbridge Nickel Mines Limited<br />
MIn 1963 Falconbridge Nickel Mines Limited held a group of<br />
claims in Township 76 on the west side of the Big Pic River.<br />
The bedrock in the claim <strong>area</strong> consists of dark grey massive<br />
olivine gabbro. The rock is essentially homogeneous but locally<br />
it grades into large, irregular, pink masses consisting mainly of<br />
perthitic feldspar.<br />
Investigation of the claims included diamond drilling. Three<br />
holes were drilled westerly from the same drill location on an<br />
outcrop on the west bank of the Big Pic River. These holes<br />
intersected gabbro and pink perthitic material over their entire<br />
length. One hole was collared within the Big Pic River Lineament<br />
and failed to intersect bedrock at a depth of over three hundred<br />
feet.<br />
No mineralization was encountered."2<br />
1<br />
V.G. Milne, Geologist, <strong>Ontario</strong> Department of Mines, Toronto.<br />
2 V.G. Milne, Geologist, <strong>Ontario</strong> Department of Mines, Toronto.
- 86 -<br />
BUILDING STONE<br />
Laurvikites were first quarried near Marathon about 1880<br />
by tne Canadian Pacific Railway for the construction of bridges<br />
over the Big Pic and Little Pic rivers.<br />
Cold Spring Granite Company<br />
Small scale quarrying, on a commercial basis, was begun in<br />
1927 by Peninsula Granite Quarries, Limited, under the management<br />
of William Morrison. This company was purchased by Cold Spring<br />
Granite Company in 1931 (Hewitt 1964, p.39).<br />
The property consisted of a group of seventeen claims which<br />
extended northward, beginning from the old Peninsula Station,<br />
for approximately 2\ miles. The western limit was the shoreline<br />
of Peninsula Harbour. The claims were cut by the Canadian<br />
Pacific Railway line and quarrying operations were conducted on<br />
both sides of the right-of-way.<br />
The three southernmost quarries were located in the 'dark 1 ,<br />
greenish coloured, laurvikites (so-called black granite); and<br />
the northernmost quarry was located in the reddish coloured<br />
phases of laurvikite (so-called red granite) (see Thomson 1931,<br />
p.34 for location).
- 87 -<br />
The mineralogical and chemical similarities between the<br />
'dark 1 laurvikites from Marathon and the famous laurvikites<br />
from Norway have already been mentioned by Kerr (1910, p.214).<br />
An analysis of 'dark 1 laurvikite from the main southern<br />
quarry, located approximately 18,000 feet west of the old<br />
Peninsula station and 30 feet from the shoreline, is given<br />
by Thomson (1931, p.37).<br />
Mineralogically these 'dark' laurvikites are predominantly<br />
composed of subhedral laths of perthite, which generally measure<br />
12 mm by 8 mm and approximately 4 to 6mm wide. The laths of<br />
perthites characteristically exhibit broad Carlsbad twinning.<br />
In hand specimen the reddish phase appears very similar to<br />
the 'dark'. The predominant mineral is perthite which occurs<br />
as laths slightly smaller in size to that seen in the dark<br />
laurvikites. In addition the Carlsbad twinning is less<br />
prevalent and the iridescence, so spectacular in the perthites<br />
in the darker phases, is more subdued.<br />
Thin section examination shows the perthites to be<br />
extensively stained by hematite. The ferromagnesian minerals<br />
are predominantly hydrous.<br />
Although the quality of the stone is high, apparent failure<br />
to secure and (or) maintain the necessary markets forced the<br />
curtailment of activities in the late 1930's.
- 88 -<br />
Lake Superior Stone Syndicate<br />
This syndicate was formed in April, 1960, by a group of<br />
Toronto mining persons in response to information provided<br />
by C.S. Downey, of North Bay.<br />
The information was concerned<br />
with the quarrying of the laurvikites near Angler.<br />
In May and June of the same year a block of forty-seven<br />
claims were staked which extended southward from Hare Lake to<br />
within half a mile of the Marathon townsite.<br />
These claims<br />
included a block of eleven claims, at Angler, which were<br />
formerly held by H. England, of <strong>Port</strong> <strong>Coldwell</strong>.<br />
The laurvikites in the claim block are generally dark and<br />
of good grade.<br />
Research into the marketing of the laurvikite from these<br />
sites was conducted into late fall.<br />
Although quarrying was<br />
scheduled to begin in the late fall of 1960 the apparent<br />
^.^<br />
failure to secure the necessary markets forced the indefinite<br />
postponement of activity.<br />
NEPHELINE<br />
The first and only attempt to determine the nepheline potential<br />
of the feldspathoidal syenites was made by Denison Mines Limited.
- 89 -<br />
Denison Mines Limited<br />
In early 1960 Denison Mines Limited staked two <strong>area</strong>s of<br />
nepheline syenite immediately west of Redsucker Cove.<br />
The<br />
larger claim block, representing approximately twenty-three<br />
claims, extends northward to the Trans-Canada Highway 17.<br />
The dominant bedrock is composed of feldspathoidal syenites,<br />
of variable femic content, and relatively minor but significant<br />
amounts of variably nephelinized mafic metavolcanics.<br />
These<br />
metavolcanics are considered to belong to the so-called<br />
Coubran Lake roof pendant.<br />
The typical relationships between the feldspathoidal<br />
syenites and mafic metavolcanics are exhibited in the larger<br />
of the two occurrences.<br />
The nephelinized metavolcanics are marginally located with<br />
respect to the topographic 'high 1 .<br />
The nepheline in these older varieties of nepheline syenite<br />
exhibits a greasy lustre and is intimately associated with<br />
and included by the various femagnesian minerals.<br />
The younger phases of feldspathoidal syenite appear more<br />
leucocratic and grade into progressively more zeolitic varieties.<br />
Thin section examination showed the nepheline in these younger"<br />
phases of feldspathoidal syenites to be variably altered to an<br />
aggregate of radiating zeolites which include thomsonite and
- 90 -<br />
natrolite.<br />
This zeolitized nepheline is extensively stained<br />
by hematite and in hand specimen appears as a pale orange<br />
coloured, fine-grained mixture which has been referred to as<br />
hydronepheline, ranite, or suprestein.<br />
Numerous grains<br />
exhibit a deeper orange colour and in these samples the<br />
adjacent perthites are similarly tinted.<br />
Specimens from the various nepheline properties were sent<br />
by Denison to Lakefield Research for routine laboratory magnetic<br />
separation.<br />
For the older, and marginally located nepheline<br />
syenite an initial coarse grind (perhaps to about \ of an inch)<br />
was proposed (W.W. Moorhouse, private report).<br />
This was<br />
intended to separate the more nepheline-rich, leucocratic<br />
portions from the less nephelinized and more mafic-rich<br />
clusters and patches of mafic metavolcanics (Fig.10).<br />
For the<br />
more leucocratic and more centrally located phases of<br />
feldspathoidal syenites, a cleaner separation of dark and light<br />
minerals was achieved.<br />
Unfortunately the later phases,<br />
particularly the associated hypabyssal phases, contained<br />
nepheline which is variably pseudomorphed by a mixture of<br />
thomsonite and natrolite.<br />
Since the iron content was not consistently reduced below<br />
0.08 percent the development of these nepheline occurrences was<br />
discontinued.
- 91 -<br />
SAND AND GKAVEL<br />
Fairly extensive <strong>area</strong>s of sand and gravel occur at<br />
Neys beach, along the Kilalla Lake road, at Angler, and at<br />
Marathon and immediate, vicinity extending eastward to within<br />
\ mile of the Pic River.<br />
A few claims have been staked by Anaconda American Brass<br />
Ltd. with the sand and gravel being used as road fill.<br />
Thomson (1931, p.35) makes mention of the pebble and<br />
cobble stones present in gravels to the south.<br />
Although<br />
described as satisfactory for use in ball mills, no shipments<br />
have been made.
- 92 -<br />
Selected Bibliography<br />
Adams, F.P.<br />
1900: On the probable occurrence of a large <strong>area</strong> of nephelinebearing<br />
rocks on the northeast coast of Lake Superior;<br />
Jour. Geol., Vol. VIII, p. 322-325.<br />
Barlow, A.E.<br />
1913: The nepheline and alkali syenites of the <strong>Port</strong> <strong>Coldwell</strong><br />
<strong>area</strong> in Guide Book No.8, Twelfth Int. Geol. Congress,<br />
Toronto to Victoria and return via Canadian Pacific and<br />
Canadian Northern Railways, Part l, p. 16-24.<br />
Benson, W.N.<br />
1926: The tectonic conditions accompanying the intrusion of<br />
basic and ultrabasic igneous rocks; Mem. Nat. Acad.<br />
Sci. l, Vol. XIX, p. 1-89.<br />
Billings, M.P.<br />
1942: Structural geology, First Edition; Prentice - Hall,<br />
New York.<br />
Coleman, A.P.<br />
1898: <strong>Port</strong> <strong>Coldwell</strong> region in Notes on the petrology of<br />
<strong>Ontario</strong>; <strong>Ontario</strong> Bur. Mines, Vol. VII, pt.2,<br />
p. 146-149.<br />
1899a: Dike rocks near Heron Bay in Notes on petrography in<br />
Copper regions of the Upper Lakes; <strong>Ontario</strong> Bur. Mines,<br />
Vol. VIII, pt.2, p. 172-174.<br />
1899b: A new analcite rock from Lake Superior; Jour. Geol.,<br />
Vol. VII, p. 431-436.<br />
1900: Heronite or analcite-tinguaite in Copper and iron<br />
regions of <strong>Ontario</strong>; <strong>Ontario</strong> Bur. Mines, Vol. IX,<br />
p. 186-191.<br />
1902: Syenites near <strong>Port</strong> <strong>Coldwell</strong>; <strong>Ontario</strong> Bur. Mines,<br />
Vol. XI, p. 208-213.<br />
Farrand, W.R.<br />
1960: Former shorelines in western and northern Lake<br />
Superior basin; unpublished Ph.D. thesis, Dept. of<br />
<strong>Geology</strong>, Univ. of Michigan, Ann Arbor, U.S.A.
- 93 -<br />
Gill, J.E.<br />
1955: Precambrian nomenclature in Canada; Royal Soc.<br />
Canada, Trans., Illrd Series, Vol. 49, Section<br />
IV, p. 25-29.<br />
Hess, H.H.<br />
1960: Stillwater igneous complex, Montana; Geol. Soc.<br />
America, Mem. 80.<br />
Hewitt, D.F.<br />
1964: Building stones of <strong>Ontario</strong>, Part V, Granite and<br />
gneiss; <strong>Ontario</strong> Dept. Mines, Industrial Mineral<br />
Kept. No. 19.<br />
Hough, J.L.<br />
1958: <strong>Geology</strong> of the Great Lakes; University of Illinois<br />
Press, Urbana, Illinois, U.S.A.<br />
Kerr, H.L.<br />
1910: Nepheline syenites of <strong>Port</strong> <strong>Coldwell</strong>; <strong>Ontario</strong> Bur.<br />
Mines, Vol. XIX, pt. l, p. 194-232, accompanied by<br />
map 19b.<br />
Logan, W.E.<br />
1846-7: Report of Progress 1846-7; Geol. Surv. Canada.<br />
(Published 1847).<br />
1863: <strong>Geology</strong> of Canada; Geol. Surv. Canada.<br />
Milne, V.G.<br />
1967: <strong>Geology</strong> of the Cirrus Lake - Bamoos Lake <strong>area</strong>,<br />
District of Thunder Bay; <strong>Ontario</strong> Dept. Mines,<br />
Geol. Rept. No. 43, accompanied by maps 2098 and<br />
2099.<br />
Pye, E.G.<br />
1957: <strong>Geology</strong> of the Manitouwadge <strong>area</strong>; <strong>Ontario</strong> Dept.<br />
Mines, Vol. LXVI, pt. 8, accompanied by map 1957-<br />
8. (Published 1960).<br />
Sitter, L.U.de<br />
1956: Structural geology, First Edition; McGraw-Hill<br />
Book Co., New York. 1
- 94 -<br />
Thomson, J.E.<br />
1931: <strong>Geology</strong> of the Heron Bay <strong>area</strong>, District of Thunder<br />
Bay; <strong>Ontario</strong> Dept. Mines, Vol. XL, pt. 2, p. 21-39,<br />
accompanied by map 40d.<br />
Walker, J.W.R.<br />
1956: Preliminary report on the geology of the Jackfish<br />
- Middleton <strong>area</strong>; <strong>Ontario</strong> Dept. Mines, Geol. Circ.<br />
No. 4.<br />
1961: <strong>Geology</strong> of the Jackfish - Middleton <strong>area</strong>, District<br />
of Thunder Bay, <strong>Ontario</strong>; unpublished Ph.D. thesis,<br />
University of California, Los Angeles, 90024, U.S.A.<br />
Walker, T.L. and Parsons, A.L.<br />
1927: Contact phenomena of the nepheline syenites of<br />
<strong>Port</strong> <strong>Coldwell</strong>, <strong>Ontario</strong>; University of Toronto<br />
Studies, Geol. Series No. 24, p. 28-32.
per on.lt" <strong>area</strong>.<br />
Figure 1<br />
Contour diagram of joints in Precambrian metavolcanicmetasedimentary<br />
sequences in the <strong>Port</strong> <strong>Coldwell</strong> <strong>area</strong><br />
lower hemishpere plot of 1300 poles.<br />
'
,<br />
Figure 2.<br />
Contour diagram of joints in Jim Lake grsr.ite, lower*<br />
hemisphere plot of 700 poles.
L o.mpro pK-j r<br />
Jim L aUa. grarxiie.<br />
Figure 3<br />
Dilation features exhibited by the lamprophyre<br />
dikes emplaced along the extension joints<br />
in the Jim Lake granite.
O<br />
B QMD EH T::]<br />
Figure 4. Contour diagram of joints in the v main s series of rocks<br />
of the <strong>Port</strong> <strong>Coldwell</strong> Alkalic Complex. Lower heinishpere<br />
plot of 1900 poles.
o- 10/;<br />
~<br />
igure J .<br />
roo<br />
2r"a:n of joints in Coubran Lake rae'Gavolcam.<br />
onarG Lcv/er* hemisphere plot of 861 poles.
f<br />
[ mn<br />
..J<br />
Figure 6,<br />
Contour diagram-of joints in the larger bodies iZ<br />
lower hemisphere plot<br />
poles
iigure<br />
syente vens ao<br />
the metavolccinics 5 which have been rea<br />
during emplacement,, From portion c.: C<br />
Li a. K e metavolcaniLC rooi pendant 3 4 n".-.^.e<br />
of <strong>Port</strong> <strong>Coldwell</strong> station, along the Tr<br />
Highway 17.<br />
; ivatea<br />
noraheas<br />
iE# ^-* ill.*"^ *^ ^~^ 1O^
Figure 8<br />
Sketch illustrating the repeated reactivation of jointing<br />
with concomitant intrusion of feldspathoidal syenite dikes
f<br />
Figure 9<br />
Surface Gfolop;ical Plan of Part of the Property of Mon^ta<br />
Porcupine Mines Limited showing the Relative Locations of<br />
Gossan Zones and Diamond Drill Holes (Modified from a<br />
plan by. G. Perrault).
s.^-?ai<br />
"^^T^y 7 J'^:/!''-*' y ''l! ri';^.; VA*<br />
rH D. C -P<br />
rt -H .H C<br />
0) .H .p Qi ,r^<br />
C HO -P .p CO ^- O<br />
O O O JU *0<br />
H<br />
rt 'H P* JO * O)<br />
C<br />
w J-.<br />
W -H * -TJ C o rt<br />
C rH O C F -H<br />
O ^ tr-4 rt C C tt)<br />
C .C rt -P<br />
4-J C, rt C w O .H<br />
O 4) O O^-^ H C<br />
d. C rH -H O Q)<br />
W O -P C > ^.<br />
. . rt o rt w<br />
O rt "-i<br />
T5<br />
O -P O -P fe fe fe<br />
C u, O rt S C rH<br />
E Mv E Q) rH ^H H<br />
,. JH -H ^ H O<br />
O ,Q g jC O. fc<br />
O 'H -H 4-J ^ -P<br />
o<br />
r-4<br />
Q)<br />
V-4<br />
^<br />
W)<br />
iTWivV ''~."/^s*^ ^i" /.w/.'- \v 1<br />
'"tit!<br />
^^Mj
ONTARIO DEPARTMENT OF MINES<br />
PRELIMINARY GEOLOGICAL MAP No. P.114<br />
PORT COLDWELL AREA<br />
DISTRICT OF THUNDER BAY<br />
V'' .S^C. '--'J<br />
Scale l inch to ^ mile<br />
N.T.S. Reference: 42D/9, 42D/10, 42D/15, 42D/16<br />
O.D.M.-G.S.C. Aeromagnetic Maps: 2146G, 2147G, 2156G, 2157G<br />
LEGEND<br />
^<br />
7a<br />
CENOZOIC<br />
RECENT<br />
Beach and river deposits, peat<br />
PLEISTOCENE<br />
Sand. gravel, boulders and pebbles; silt, varved clay<br />
UNCONFORMITY<br />
X3--X<br />
PRECAMBRIAN<br />
LATE GRANITIC ROCKS<br />
15a<br />
15b<br />
15c<br />
15d<br />
15e<br />
15f<br />
Biotite-hornblende granite<br />
Hybrid granite<br />
Hybrid syenite<br />
Hybrid pegmatite<br />
Mylonitized granite<br />
Hybrid porphyritic syenite<br />
INTRUSIVE CONTACT<br />
PORT COLDWELL ALKALIC COMPLEX<br />
14<br />
13<br />
Perthosite (dikes)*<br />
INTRUSIVE CONTACT<br />
A<br />
Lamprophyre (dikes)<br />
INTRUSIVE CONTACT<br />
SECONDARY SERIES<br />
UNSATURATED ROCKS -"<br />
12 Analcite tinguaite (dikes)*<br />
INTRUSIVE CONTACT<br />
k ?v<br />
11 Natrolite-perthite rock (dikes)<br />
INTRUSIVE CONTACT<br />
lOa<br />
lOb<br />
lOc<br />
Leucocratic nepheline syenite<br />
Leucocratic nepheline syenite, trachytic texture<br />
Melanocratic nepheline syenite<br />
INTRUSIVE CONTACT<br />
SATURATED ROCKS<br />
r \\ X<br />
•f \\, 7o<br />
9a<br />
9b<br />
9c<br />
Nordmarkite, undifferentiated<br />
Nordmarkite, aphanitic to fine-grained<br />
Nordmarkite, aphanitic to fine-grained, porphyritic<br />
GRADATIONAL CONTACT<br />
Middleton<br />
jL - H ii'<br />
l 7e /l<br />
\( \C\\ \ \\ 7a<br />
,! Xv\ \ U ' a<br />
8a<br />
8b<br />
8c<br />
8d<br />
8e<br />
8f<br />
Syenodiorite, undifferentiated<br />
Syenodiorite, fine-grained, red amphibole<br />
Syenodiorite, fine- to medium-grained, ophitic texture<br />
Syenodiorite, fine-grained, porphyritic<br />
Syenodiorite, fine-grained, porphyritic with potassic<br />
feldspar alignment<br />
Syenodiorite, fine-grained, plagioclase rimmed by<br />
potassic feldspar<br />
GRADATIONAL CONTACT<br />
MAIN SERIES<br />
PRISONER<br />
COVE<br />
X ^ 7a \ \<br />
' I \<br />
-"- /le/ lOcV<br />
X^\<br />
* l IT^^<br />
7a Laurvikite, undifferentiated<br />
7b Laurvikite pegmatite<br />
7c Laurvikite, fine-grained<br />
7d Laurvikite, fine- to medium-grained, porphyritic<br />
7e Laurvikite, massive, reddish-stained, high<br />
barkevikite content<br />
7f Laurvikite, layered<br />
7g Laurvikite, greyish, highly exsolved, contact phase.<br />
PREDOMINANTLY CONFORMABLE, PARTLY GRADATIONAL CONTACT<br />
6a<br />
6b<br />
6c<br />
6d<br />
6e<br />
6f<br />
Gabbro, undifferentiated<br />
Gabbro, feldspathized<br />
Gabbro, layered<br />
Gabbro, coarse-grained, ophitic textured, pegmatitic<br />
Gabbro, massive, sulphide-bearing<br />
Gabbro, massive, fine- to medium-grained<br />
INTRUSIVE CONTACT (GRENVILLE OROGENT)<br />
LATE MAFIC INTRUSIVE ROCKS<br />
CRADDOCK<br />
COVE<br />
5 Diabase, porphyritic diabase<br />
INTRUSIVE CONTACT<br />
M//V/C HARBOUR<br />
GOOD HOPE^f<br />
ISLAND<br />
MONMOUTH<br />
ISLAND<br />
STURDEE<br />
COVE<br />
\!l \<br />
I/'<br />
6a,6b<br />
EARLY GRANITIC ROCKS<br />
4a Biotite-hornblende granite, undifferentiated ) Jim<br />
Ab Biotite-hornblende granite gneiss ) Lake<br />
4c Biotite-hornblende granite, recrystallized ) Batholith<br />
4d Trondhjemite, grey, massive<br />
INTRUSIVE CONTACT<br />
GUSE<br />
PT<br />
MOSS<br />
THQMPSON<br />
i ^-IW f c^:r-.^<br />
* . * . . f 110 -. y<br />
PENINSULA<br />
DETENTION<br />
ISLAND<br />
PENINSULA BA Y<br />
8c,d<br />
NEUVE'CHAPELLE<br />
POINT<br />
BLONDIN<br />
ISLAND<br />
MANITOBA<br />
SHOAL<br />
PENINSULA HARBOUR<br />
POINT<br />
JOHNSON<br />
SKIN VQ<br />
ISLAND<br />
HARBOUR<br />
METAVOLCANIC-METASEDIMENTARY ASSEMBLAGE**<br />
METASEDIMENT^<br />
3a Bedded metagreywacke, minor argillite<br />
3b Biotite-quartz-plagioclase schist<br />
3c Garnet-biotite-quartz-plagioclase schist<br />
FELSIC METAVOLCANICS<br />
2a Agglomeratic rhyolite<br />
2b Rhyolite agglomerate<br />
2c Tuff, banded tuff, agglomerate<br />
2d Porphyritic rhyolite<br />
2e Fine-grained quartz-sericite schist<br />
MAFIC TO INTERMEDIATE METAVOLCANICS<br />
l<br />
la<br />
Ib<br />
le<br />
Id<br />
Basalt, andesite<br />
Pillow lava<br />
Aphanitic, amygdaloidal basalt, andesite<br />
Diabase (lava)<br />
Game t-plagioclase-amphibole gneiss<br />
NORTHWEST<br />
BAY<br />
SULLIVAN<br />
ISLANDS<br />
9b<br />
(V SLYBOOTS<br />
ROCK<br />
HAWKINS<br />
ISLAND<br />
PEN!NSULA 7<br />
7a<br />
./fZ.Z./^Of<br />
ir^l/f<br />
m<br />
X<br />
Marathon<br />
Brecciated inclusions of gabbro, generally<br />
much altered (unless otherwise coded).<br />
* Not shown.<br />
** Age relationships between the major rock units is not definitely known,<br />
BLACK<br />
ROCK<br />
LXI/CE<br />
SUPERIOR<br />
/3t\ ^ rf<br />
LIST OF PROPERTIES<br />
(circa 1963-64)<br />
1.<br />
2.<br />
Anaconda American Brass Ltd.<br />
Cold Spring Granite Company<br />
3. Conwest Exploration Company Ltd.<br />
4. Denison Mines Ltd.<br />
5. Empire Explorations Ltd.<br />
6. Falconbridge Nickel Mines Ltd.<br />
7. Lakehead Mines Ltd.<br />
8. Lake Superior Stone Syndicate<br />
9. Moneta Porcupine Mines Ltd.<br />
10. Olson, George<br />
11. Renshaw, Zebe<br />
ALLOUEZ<br />
ISLAND<br />
I0c,l<br />
MALE ROCK<br />
SOURCES OF INFORMATION<br />
<strong>Geology</strong> by H.V. Tuominen and assistants, 1958, 1959; F.P. Puskas<br />
1960, 1961.<br />
Additions and correction by F.P. Puskas, 1966.<br />
Base map derived from maps of Forest Resources Inventory, <strong>Ontario</strong><br />
Department of Lands and Forests.<br />
Issued 1961, re-issued 1967.<br />
ODM 4225