Port Coldwell area - Geology Ontario

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ONTARIO DEPARTMENT OF MINES
GEOLOGICAL BRANCH .
OPEN FILE REPORT
No. SOU
GEOLOGY OF
PORT COLDWELL AREA
DISTRICT OF THUNDER BAY
ONTARIO
DEC. 4, 1967

DEP/vrrv.- M T "; VMM FS
Open-file Reports
Open-file reports are made available to the
public subject to certain conditions. Anyone using them
shall be deemed to have agreed to these conditions which
are as follows:
This report is unedited. Discrepancies may
occur for which the Department does not
assume liability.
Open-file copies may be read at the following
places:
The Library (Room 1433, Whitney
Block), Department of Mines,
Parliament Buildings, Toronto.
The office of the Resident Geologist in
whose district the area covered by this
report is located.
A report cannot be taken out of these offices.
Handwritten notes and sketches may be made
from it. This particular report is on file in
the Resident Geologist's office located at:
179 South Algoma St. ,
Port Arthur
Open-file reports cannot be handed out for
office reading until a card, giving the name
and address of the applicant, is filed with the
Resident Geologist or Librarian.
A copy of this report is available for interlibrary
loan.
The Department cannot supply photocopies.
Arrangements may be made for photocopying
by an outside firm at the user l s expense. The
Librarian or Resident Geologist will supply
information about these arrangements.
The right to reproduce this report is reserved
by the Ontario Department of Mines. Permis
sion for other reproduction must be obtained in
writing from the Director, Geological di ranch.
J, E. Thomson,
Director, Geological Branch.

ONTARIO
DEPARTMENT OF MINES
GEOLOGY OF
PORT COLDWELL AREA
DISTRICT OF THUNDER BAY
ONTARIO
by
Frank P. Puskas

Table of Contents
Page
Abstract .......................... *...... *............. v
Introduction ........................................... l
Mapping Methods ..................................... 2
Acknowledgments ..................................... 3
ireviou- Geological Investigation ................... 4
To -jogra^ay ... ....... ...... .... . ... . . .. .............. 5
Ncrural Resources ................................... 8
General Geology ........................................ 9
Table of formations .............................. 14
Metavolcanic-Metasedimentary Assemblage ............. 16
Mafic to Intermediate Metavolcanics .............. 16
Felsic Metavolcanics ............................. 19
Metasediments .................................... 22
Mecagreywacke ................................. 22
Early Granitic Rocks ................................ 23
Late Mafic Intrusive Rocks .......................... 24
Port Coldwell Alkalic Complex ....................... 25
Introduction ..................................... 25
f Main f Series ................................. 26
"Chilled 1 Gabbro ........................ 26
Massive Gabbro .......................... 28
Layered Gabbro .......................... 30
Laurvikites ............................. 32
Layered Laurvikite ................... 33
Laurvikite, massive .................. 34
Laurvikite, pegmatites ............... 34
Laurvikite, porphyritic varieties .... 36
'Secondary* Series ............................ 36
Syenodiorite ............................ 37
Nordmarkite . .. ..... .... ................. 37
Nepheline Syenites ...................... 38
Natrolite-Perthite Dikes ................ 40
Analcite Tinguaite Dikes ................ 40
Lamprophyre Dikes ............................. 40
Perthosite Dikes .............................. 41
Late Granitic Rocks ................................. 41
Little Pic River Granite ......................... 41
Pleistocene and Recent ................................. 42
Structural Geology ..................................... 43
Introduction ........................................ 43
Structural Elements within the Metavolcanic-
Metasedimentary Sequences ....... 44
Fold Structures .................................. 44

Page
Foliation and Lineation ............................ 45
Faulting ........................................... 46
Jointing ........................................... 46
Accumulation and Interpretation of Joint data ... 47
Joints in Metavolcanic-Metasedimentary Sequences. 48
Structures Related to the Granitic Intrusions ......... 50
Jointing ........................................... 50
Conclusion ...................................... 53
Structures Related to Port Coldwell Alkalic Complex ... 54
Glossary of Terms .................................. 54
Layering in the 'Main 1 Series ...................... 56
Rhythmic Layering ............................... 56
Discontinuous and/or Disturbed Layering ......... 57
Inch-Scale Layering ............................. 57
Cryptic Layering ......................,......... 58
Igneous Lamination in the 'Main 1 Series ............ 58
Jointing in the 'Main 1 Series ...................... 59
Layering in the 'Secondary' Series ................. 60
Jointing in the 'Secondary' Series .........ooo..... 60
Lineaments ......................................... 62
Summary ............................................ 62
Economic Geology ..................................o...... 64
Introduction ...........*.............................. 64
Iron ....................o.............**..*..........* 65
Zebe Renshaw ............o. 0 ............*.....o..... 66
George Olson ......................o................ 67
Empire Explorations Ltd. ..........................o 68
Non-Ferrous Base Metals ............................... 70
Moneta Porcupine Mines Limited ..................... 71
Lakehead Mines Limited ............................. 76
Conwest Exploration Company Limited ................ 79
Anaconda American Brass Limited .................... 82
Falconbridge Nickel Mines Limited .................. 85
Building Stone ........................................ 86
Cold Spring Granite Company ......................*. 86
Lake Superior Stone Syndicate ...................... 88
Nepheline ............................................. 88
Denison Mines Limited .............................. 89
Sand and Gravel ....................................... 91
Selected Bibliography ...................................o 92
- iii -

Figures*
1. Contour diagram of joints in Precambrian metavolcanicmetasedimentary
sequences in the Port Coldwell area,
lower hemisphere plot of 1300 poles.
2. Contour diagram of joints in Jim Lake granite, lower
hemisphere plot of 700 poles.
3. Dilation features exhibited by the lamprophyre dikes
emplaced along the extension joints in the Jim Lake
granite.
4. Contour diagram of joints in the 'main 1 series of rocks
of the Port Coldwell Alkalic Complex. Lower hemisphere
plot of 1900 poles.
5. Contour diagram of joints in Coubran Lake metavolcanic
roof pendant, lower hemisphere plot of 861 poles.
6. Contour diagram of joints in the larger bodies of
nepheline syenite, lower hemisphere plot of 683 poles.
7. Sketch illustrating the presence of nepheline syenite
veins along pre-existing joints, in the metavolcanics,
which have been reactivated during emplacement. From
portion of Coubran Lake metavolcanic roof pendant, 4
miles northeast of Port Coldwell station, along the
Trans Canada Highway 17.
8. Sketch illustrating the repeated reactivation of jointing
with concomitant intrusion of feldspathoidal syenite
dikes.
9. Surface geological plan of part of the property of Moneta
Porcupine Mines Limited showing the relative locations
of gossan zones and diamond drill holes (modified from
a plan by G. Perrault).
10. Diagram of sections along a specimen of nephelinized
mafic metavolcanic. Note the brecciation and partial
assimilation (shown by stippling) of the metavolcanics.
Veinlets of nepheline syenite are joint controlled.
* These figures follow page 94, at the back of this report.
- iv -

Preliminary Map*
(Back pocket)
P.114 Port Coldwell Area, Scale l inch to \ mile
* Preliminary maps may be purchased at Publications Office, Ontario
Department of Mines, Whitney Block, Parliament Buildings, Toronto.

ABSTRACT
The map-area, in the District of Thunder Bay, is dominated
by the Port Coldwell Alkalic Complex.
The Complex is Precambrian
(1000+ m.y.), approximately 580 square kilometres in area,
more or less circular in outline, and lies within a metavolcanicmetasedimentary
belt which extends westward from White Lake
along the northern shore of Lake Superior.
The Port Coldwell Alkalic Complex is composed of two
series of rocks: A 'main 1 series which includes gabbros and
laurvikites, and a 'secondary 1
series which includes syenodiorites,
nordmarkites and feldspathoidal rock types.
Within the 'main* series a zonation has been recognized
which is as follows:
Upper Zone:
Lower Zone:
Inner Border Zone f b f
Inner Border Zone 'a 1
Outer Border Zone:
Laurvikite
Layered laurvikite
Layered gabbro
Massive gabbro
Chilled gabbro
The rhythmic layering (Skaergaard type) in the gabbro and
laurvikite dips inwards at moderate angles.
Lensoid bodies
of titanomagnetite-apatite up to 50 feet wide are generally
concordant with the attitude of layering.
The Little Pic River granite has intruded the northwestern
part of the Port Coldwell Complex.
Inclusions of gabbro,
laurvikite and mafic metavolcanics are abundant within the

granite or hybrid phases thereof.
The area has been investigated for iron and non-ferrous
base metals, but there has been no production to date.
Analyses to date indicate a fairly large concentration of
titanium in the ilmenomagnetite bands. Base metal mineralization
is predominantly restricted to the massive gabbros, a zone
approximately 300 metres wide. Detailed drilling of the
sulphide-bearing gabbro, by various companies, more or less
including all portions of the zone exposed, has indicated a
limited or large tonnage of fairly low-grade copper ore.
Continued exploration in the area and changing market demands
may eventually lead to the development of an ore deposit.
- vi -

- l -
Geology of the Port Coldwell Area
District of Thunder Bay
By F. P. Puskas 1
INTRODUCTION
The Port Coldwell area is between approximate longitudes
860 17 f and 86O40'W and latitudes 48o41 f and 48O54 f N and comprises
all or parts of the following townships: Pic, 76, 77, 78,
79, and 80, in the District of Thunder Bay, Port Arthur Mining
Division.
The area lies on the north shore of Lake Superior
which in most cases is rocky and precipitous and generally
offers but limited opportunity for safe disembarkation.
Protected harbours can be found at Port Monroe, Port Coldwell
and Marathon.
The south part of the area is traversed by the Canadian
Pacific Railway line and Trans-Canada Highway 17 with both
right-of-ways running very close to the shoreline. The
panoramic view along this stretch of the coast is almost
unrivalled for scenic beauty.
The northwest parts of the area were reached by vehicle
by way of Killala Lake road which has a reasonably good gravel
surface up to the Little Pic River bridge.
Maintenance costs
I
Postgraduate student, Department of Geology, Lehigh University,
Allentown, Penna., Manuscript received by the Chief Geologist,
6 Jan. 1967.

- 2 -
were formerly met by revenue received from tolls but with
discontinuance (in 1958) of tolling the various bridges,
including the Little Pic River bridge, have been closed to
vehicle traffic.
The north parts of the map-area are
accessible by means of the Gordie Lake-Coubran Lake-Wullie
Lake waterway system and by means of the Pic and Little Pic
rivers which can be navigated by canoe from their mouths
northward for distances up to 50 miles.
A few short portages
are necessary during low-water season.
The airstrip, belonging to Marathon Pulp and Paper
Company, is located near the Highway 17 turnoff to the Marathon
townsite and is adequate for medium-range, twin-engine aircraft,
Mapping Methods
The present geological survey was carried out during the
summers of 1958 and 1959 by a field party consisting of two
senior geologists, and two assistants, and during the summer of
1960 by a two-man party.
The geology was plotted on perfatrace overlays on aerial
photographs at a scale of l inch to 1/4 mile.
All exposures
along the shorelines, power lines, railway and highway were
examined and plotted; intervening forest-covered country was
mapped by running pace-and-compass surveys generally at 1/4

- 3 -
mile intervals. Data from the overlays were transferred to a
base map prepared by the Cartography Unit of the Ontario
Department of Mines. In transferring data to the base map
care was taken to minimize marginal distortions by recording
only that data centrally located in each respective overlay.
A preliminary geological map (P.114) on the scale of l inch
to % mile was issued in 1961. A revised edition shows the
outcrop areas.
Acknowledgments
Much of the early mapping was done by H. V. Tuominen and
N. T. Irvine in 1958 and 1959. In 1960 the author and
H. V. Tuominen were assisted by T. Wade and W. Shorten; in
1961 the author was assisted by T. Wade.
The author received all possible assistance from the
mining companies that own properties in the area and his
indebtedness to them is hereby acknowledged. As well it is an
equal pleasure to record the assistance given by various
residents of the Marathon area, and various members of the
Ontario Department of Mines, in particular; E.G. Pye, resident
geologist at Port Arthur; and J.E. Thomson, Chief Geologist;
and M.E. Hurst, Director.

- 4 -
Previous Geological Investigation
As early as 1846 the presence of syenite had been
reported (Logan 1846-7, p.29-30) and mention of nepheline
syenite was made by 1863 (Logan 1863,p.80-81, 480, 647).
A brief account of the early investigations up to 1910 has
been given by Kerr (1910, p. 194-232) to which the reader
is referred.
The first reconnaissance investigation of the region
was carried out by Kerr (1910) during the fall of 1906 and
1907. In all a period in the order of ten weeks was spent
in the mapping of the geology along the shore line, along
the Canadian Pacific Railway, and along five north-south
traverses. The high standard of Kerr 1 s investigation cannot
be denied regardless of the early date at which the work was
done, and despite the obvious retarding factors, such as the
adverse weather conditions encountered, the limited field time
available, and the absence of modern mapping aids and highway
cuts.
The west limit of the map-area was mapped by Walker
(1956) and the east limit of the area was examined by Thomson
(1931) and Milne (1964).

- 5 -
Topography
The highest hills in the area are found within the Port
Coldwell Complex and are generally capped by volcanic flows
and (or) their metamorphic equivalents.
These hills can be
considered as belonging to one of two categories; namely,
hills f peripheral 1
to, and those hills associated with, the
more extensive and centrally located metavolcanic roof pendant
(presently named the Coubran Lake roof pendant).
The
1 peripheral 1 hills have elevations in the order of 900 to 1300
feet above mean sea level.
The centrally located hills have
elevations which are 1300 to 1500 feet and in places nearly
1600 feet above mean sea level.
The relative differences in elevation of the rocks within
the Port Coldwell Complex are distinctive and appear significant
in that the feldspathoidal syenites, which characteristically
occur associated with the Coubran Lake roof pendant, consistently
exhibit the highest elevations.
Most hills in the Port Coldwell area have a north-south
profile represented by a moderately gentle dipping north slope
and a more or less rounded top, followed by a precipitous slope
to the south.

- 6 -
Since the mean water level of Lake Superior is 602 feet
above mean sea level, the available relief in the area is
considerably higher than the general elevation of the
surrounding Shield areas.
The high relief in the area may be
attributed to rapid post-glacial uplift and older (i.e. pre-
Pleistocene) downfaulting associated with and (or) related to
the formation of the Lake Superior basin.
The area is dissected by numerous lineaments and valleys,
the more prominent of which are:
(1) south-trending valleys of the Pic and
Little Pic River, Redsucker Cove lineament, east
Wullie Lake lineament, Jim Lake lineament;
(2) northwest-trending valleys of Bamoos Lake, Knob lake,
Coubran Lake;
(3) northeast-trending valleys of Seeley and Lacobeer lakes
and Pic Island;
(4) east-west trending valleys.
Many valleys, but mainly those which trend to the south, were enlarged
during Pleistocene time.
Ice moving southwestward, as indicated
by the direction of glacial striae was partly channelled along
the relatively straight courses of many of these valleys.
The
valley floors are relatively flat and generally occupied by
lake(s), rivers and (or) streams, and (or) alluvium.

- 7 -
A broad clay terrace generally flanks and trends parallel
to the present course of the Pic River for a distance of more
than 50 miles (Farrand 1960). Varved clay banks are approximately
60 feet in height.
Extensive sand and gravel deposits occur near the mouths
of the Pic and Little Pic rivers. Within the vicinity of the
Pic, southwest of Trans-Canada Highway 17, there are numerous
depressions up to 400 feet in diameter. This pitted outwash
plain merges into the coastal beach deposits which extend
westward, discontinuously, beyond Middleton station.
The beach deposits are predominantly gravels with minor
pebbles and cobbles. The deposits have been built on
dissected topography, but are themselves undissected and
remarkably fresh. Hough (1958, chap.11) considers these
beaches to be Nipissing and not Algonquin in age.
The elevation
of the beach at Marathon is given by Hough (1958, Table 16,
p. 257) as 710 feet above mean sea level, or 108 feet above
the present surface of Lake Superior. This beach extends
northward for a distance of approximately 2% miles and
represents a fairly large sand and gravel deposit.
There are at least six beach levels at Marathon (see also
Thomson 1931). The vertical interval between the terraces is
5 to 45 feet. Walker (1961) states that the vertical interval

- 8 -
between terraces occurring 20 or more miles to the west is
5 to 10 feet. This relationship may indicate a substantial
increase in the rate of post-glacial isostatic adjustment
in the Marathon area than that to the west.
It is interesting to note that in 1884, at a site 600 feet
east of Pic River along the Canadian Pacific Railroad track,
a copper hook, or gaff, and some charcoal were found in the
bottom of a rock cavity under 18 feet of clay topped with
gravel. Hough (1958, p. 258) states that:
"The most reasonable interpretation of this information is that
the archeological material was emplaced sometime during a
pre-Nipissing low-water stage and that the site was flooded
by water rising to the Nipissing level." In the past years
archeological investigations in-the area have been carried
out by parties organized and directed by various staff members
from the University of Toronto.
Natural Resources
The entire area is forest-covered and timber of commercial
value is obtained from large stands approximately 40 miles north
from the mouth of the Pic River.
The stands are generally mixed
soft and hardwood and include spruce, black spruce, balsam,
jackpine, balsam fir, balsam poplar, tamarack, white birch and

- 9 -
cedar.
Most of the trees are less than 12 inches in diameter
at the base.
Pulp drives which were so common along the Pic
River in the past may eventually be supplanted by the direct
pipelining of chips to the mill site.
Moose, black bear, fox, rabbit, beaver, and skunk are
common in the area.
Moose were observed during most of the
summer along the edge of lakes and rivers.
Numerous beaver
dams occur in the streams, and generally made travel difficult
owing to flooding.
Because of poor fur prices trapping in
the area has fallen off considerably.
Whitefish, pickerel, pike, and lake trout can be caught
in Lake Superior; and many areas, such as Mink Creek and
Gordie Lake contain speckled trout.
In the past commercial
fishing was carried out from Port Coldwell.
GENERAL GEOLOGY
Although this report deals mainly with the larger unit
comprising the entire map-area, namely the Port Coldwell Complex,
it cannot neglect the granitic-metavolcanic country rocks,
expecially when the overall geological history is being considered*
All the bedrock in the map-area is Precambrian in age and
includes intrusions, extrusive rocks with minor amounts of
associated tuffaceous pyroclastic rocks and metasediments.

- 10 -
The metavolcanic-metasedimentary sequences comprise the
oldest formations.
The metavolcanics are composed primarily
of mafic lavas, porphyritic varieties of intermediate to
felsic composition, and non-porphyritic felsic varieties
comprising rhyolite agglomerate, tuff and banded tuff agglomerate,
The metasediments, predominantly laminated argillites and
metagreywackes, are intercalated with the extrusive rocks and
characteristically the contact between the magmatic rocks and
metasediments is sharp.
The metasediments predominate in the north part of the
map-area and consistently occur as the younger member in
synclinal structures.
The metavolcanics predominate in the
south part of the map-area.
Outcrops of the more mafic lavas
generally exhibit pillow structures in varying degrees of
development.
The metavolcanic-metasedimentary sequences have been
intruded, apparently to a minor degree by dikes, sills and
irregular bodies of diorite.
Upon deformation the rocks were
isoclinally folded to a near-vertical attitude.
The folds
strike approximately N70OE and plunge gently eastward.
This
major period of deformation was closely followed by the
emplacement of a biotite-homblende-quartz f eye f
granite into
and along the crestal region of an anticlinal fold.
This

- 11 -
granite, hereafter called the Jim Lake granite, resembles the
Owl Lake - Cairngorm Lake granite described by Walker (1961).
A body of trondhjemite, exhibiting earlier more-syenitic phases,
has intruded the metasediments at Wullie Lake. It is possible
itthat these rocks represent more mafic and syenitic phases of
the Jim Lake granite. This granite is cut by two sets of
lamprophyric dikes striking approximately NIO 0^ and N30OE.
These dikes are predominantly contained within the trondhjemitegranite
bodies to which they are believed to be genetically
related.
The folded metavolcanics-trondhjemite-granite association
has been cut by porphyritic and non-porphyritic diabase dikes.
Diabase dikes exhibiting a porphyritic texture trend
approximately N400W, whereas more predominant non-porphyritic
diabase dikes trend approximately N30OE.
Intersections were
not found but in nearby areas where the diabase dikes exhibit
the same general trends and textures the porphyritic variety
is older.
All the aforementioned rock types comprise the host rock
for the Port Coldwell Complex which is a circular body,
approximately 580 square kilometres in size. The host rocks
have undergone various metamorphic and (or) assimilative
phenomena related to the emplacement of the Complex. Part
of the Complex is overlain by a volcanic roof pendant,

- 12 -
predominantly of mafic composition, to which the name Coubran
Lake roof pendant has been given.
The rocks of the Port Coldwell Complex can be considered
as members of one of two series, namely; a f main f series and
a f secondary 1 series generally found associated with the
inclusions, in particular the Coubran Lake roof pendant.
The rocks of the f main t series include the gabbros and
laurvikites and their respective differentiated and layered
phases. Mineralogically, these rocks are predominantly
composed of olivine, pyroxene, feldspar, amphibole,
titanomagnetite, apatite and sulphides.
The rocks of the f secondary 1 series include a mediumgrained
red hornblende syenite (syenodiorite) - red quartz
syenite (nordmarkite), and feldspathoidal syenites.
The
metavolcanic-syenodiorite-nordmarkite suite exhibit gradational
and (or) diffuse contacts whereas the metavolcanic-feldspathoidal
syenites suite exhibit sharp intrusive contacts and (or)
gradational contacts or both.
Mineralogically these rocks are
predominantly composed of alkalic feldspar, nepheline or
natrolite or analcite, amphibole and (or) biotite and quartz
in the syenodiorites-nordmarkites.
The youngest rock in the complex is a set of perthosite
pegmatite dikes that radiate from the Coubran Lake roof pendant.

- 13 -
These dikes transect the suite of lamprophyre dikes associated
with the alkalic complex.
The youngest rock in the map-area is an undelimited granite
body given the name Little Pic River granite.
This granite has
invaded the Complex, more or less solely within the northwest
quadrant.
The rocks belonging to the Complex have been
variably granitized and brecciated.
The accompanying table outlines the general sequence of
formations in the area, from youngest to oldest* Terms, such
as Keewatin, Timiskaming etc., for rocks pre-dating the
Grenville orogeny (i.e. 1,000 + m.y.) have been purposely
avoided for reasons similar to those presented by Gill (1955,
p. 25-29). Wherever possible descriptive terms have been used
for the rocks concerned.

- 14 -
TABLE OF FORMATIONS
CENOZOIC
RECENT
PLEISTOCENE
Beach and river deposits, peat.
Sand, gravel, boulders and pebbles;
silt, varved clay.
Unconformity
PRECAMBRIAN
LATE GRANITIC ROCKS
Biotite-hornblende granite (Little Pic
River Granite)
Intrusive Contact
PORT COLDWELL ALKALIC COMPLEX
Perthosite (dikes)
Lamprophyre (dikes)
Intrusive Contact
Intrusive Contact
1 Secondary 1 Series
Analcite tinguaite (dikes)
Natrolite - perthite rock (dikes)
Nepheline syenites
Nordmarkite
Syenodiorite .
Series: *
Upper Zone:
Laurvikite, massive
Lower Zone:
Layered laurvikite
Predominantly conformable, partly gradational
contact
Inner Border Zone f b f : Layered gabbro
Inner Border Zone f a f : Massive gabbro
Outer Border Zone: Chilled gabbro

- 15 -
Intrusive Contact (Grenville Orogeny)
LATE MAFIC INTRUSIVE ROCKS
Diabase, porphyritic diabase
Intrusive Contact
EARLY GRANITIC ROCKS
Biotite-homblende granite gneiss (Jim Lake
Batholith); trondhjemitic and (or) more
syenitic phases; related lamprophyre dikes.
Intrusive Contact
METAVOLCANIC-METASEDIMENTARY ASSEMBLAGE
(Age relationships between the major rock units are
not definitely known
Metasediments: Bedded metagreywacke; minor argillite;
biotite- (garnet)-quartz-plagioclase schist.
Felsic Metavolcanics: Agglomeratic rhyolite;
rhyolite agglomerate; tuff and banded tuff
agglomerate; porphyritic rhyolite; fine-grained
quartz-sericite schist; some interbedded (?) metasediment*
Mafic to Intermediate Metavolcanics: Pillow lava;
amygdular-lava; diabasic lava; fine-grained and
coarse-grained gneissose garnet amphibolite.

- 16 -
Metavolcanic-Metasedimentary Assemblage
The greater proportion of the map-area, marginal to the
Port Coldwell Alkalic Complex, is underlain by rocks belonging
to the metavolcanic-metasedimentary assemblage. The mafic
metavolcanics to the west outcrop in the vicinity of the Lake
Superior shoreline and in a belt north of the Trans-Canada
Highway 17. These two areas of mafic metavolcanics are
separated by a belt of metasediments.
The metasediments to the east are limited to minor
horizons. The mafic metavolcanics to the east outcrop to
the north of an extensive and continuous exposure of felsic
metavolcanics.
For reasons described in the section dealing with structure,
the stratigraphy in the metavolcanic-metasedimentary assemblage
is only imperfectly known.
These rocks are mainly basaltic in composition although
andesitic varieties may be present based on the mineralogy of
some specimens.
The rocks range in colour from dark to pale
green.
recognized.
Porphyritic and non-porphyritic varieties have been

- 17 -
Massive flows may grade from a finer-grained (basal?) phase,
with or without amygdules, to a more centrally located,
medium- to coarse-grained phase which often exhibits ophitic
texture. It is sometimes difficult to impossible to distinguish
these coarser phases from associated basic intrusions but unless
definite evidence of intrusion was found, these diabasic rocks
were mapped as parts of flows.
Pillows are generally well developed and frequently can be
used for f top f determinations.
In thin-section these mafic metavolcanics particularly the
aphanitic varieties, frequently exhibit a relic pilotaxitic
or felted texture. Mineralogically these rocks are composed of
20-25 percent actinolitic amphibole (pseudomorphing diopsidic
augite), up to 35 percent albitic plagioclase, up to 20 percent
chlorite, 1-20 percent epidote (clinozoisite-pistacite), variable
talc, and up to 10 percent fine-grained quartz and feldspar with
minor leucoxene and opaque minerals. Some massive coarser grained
phases occurring in the Coubran Lake roof pendant contain
olivine, variably altered.
The amygdules of the amygdaloidal types are generally
composed of a core of actinolite and epidote or calcite
followed by an outer rim of epidote and chlorite.

- 18 -
Relic ophitic texture is common and its presence and
recognition has proved to be a definite asset for purposes of
identifying (1) the composition and origin of numerous
inclusions within the Complex and (2) rocks derived there
from and which comprise the f secondary 1 series. In thin
section the ophitic-textured phases are composed of 35-45
percent diopsidic augite, variably altered to amphibole *
chlorite * biotite, and labradoritic plagioclase.
Although
not one ophitic-t extured sill was found to be an intrusion,
some maybe.
Other rocks grouped with the mafic to intermediate
metavolcanics are the dark massive, garnet-plagioclaseamphibole
gneisses. Maximum exposure is west of Big Pic
River in vicinity of Jim Lake Granite.
These amphibolites
occur as fine- and coarse-grained varieties.
Hornblende
is readily recognizable in hand specimen and frequently shows
a nematoblastic texture (fibrous schistosity).
Other
mineralogical constituents include plagioclase, sphene,
magnetite, apatite, and sulphides.
Garnet generally exhibits
a well-developed helicitic structure (curved or contorted lines
of inclusions).

- 19 -
FELSIC METAVOLCANICS
Nearly all of the exposures of felsic metavolcanics occur
to the east of the map-area. The felsic metavolcanics are
predominantly fine-grained, massive, agglomeratic, and light
grey green in colour. Minor varieties include tuff agglomerates,
rhyolite agglomerate, and porphyritic varieties.
The agglomeratic rhyolites contain variable amounts of
fragments which can vary in size, angularity and composition.
In thin section the rock as a whole is rhyolitic although some
local phases appear dacitic.
A typical specimen is predominantly
composed of quartz, albitic plagioclase and potassic feldspar,
with varying but generally minor amounts of augite, actinolitic
amphibole, chlorite, epidote, biotite, magnetite, and sulphides.
In most samples the potassic feldspar and biotite appeared as
large sieve-like crystals (poikiloblasts) up to 3mm long.
Specimens taken from inclusions and (or) from areas
apparently within the contact aureole described by the Port
Coldwell Alkalic Complex are characteristically coarser
grained (up to 2^ mm). In thin section these felsic metavolcanics
were found to contain up to 15 percent potassic feldspar
occurring as poikiloblasts up to 3^ mm long; up to 40 percent
albitic plagioclase; up to 30 percent quartz; up to 10 percent
biotite, commonly occurring as poikiloblasts; and minor

- 20 -
clinopyroxene, magnetite, and sulphides. Hypersthene, up
to 15 percent, is present as discrete grains. Plagioclase and
quartz exhibit a characteristic association and the resultant
texture produced inevitably has small, rectangular and generally
discrete, optically oriented units of plagioclase set in a
matrix composed of a single crystal of quartz. The plagioclasequartz
intergrowths have been found up to 4mm long. There can
be little doubt that the development of this texture is related
to the metamorphism resulting from the emplacement of the Port
Coldwell Alkalic Complex. This metamorphism has also resulted
in the recrystallization and remobilization of potassic feldspar and
quartz so as to produce veins and (or) zones of graphic granite
primarily within the contact gabbros.
Some rocks, within the proposed metamorphic aureole
surrounding the Port Coldwell Alkalic Complex, are white in
colour and porcellanous in appearance. These rocks fracture
conchoidally.
Minor laminated tuffaceous horizons occur within the
agglomeratic rhyolites.
An exposure of tuffaceous agglomerate was found on the
west shore of Big Pic River at the intersection with the H.E.P.C.
line. The agglomeratic units appeared to be rhyolitic, and on
fresh surface were difficult to distinguish from the slightly
more chloritic matrix.

- 21 -
Several outcrops of banded agglomeratic tuff occur along
Trans-Canada Highway 17, south of Three Finger Lake. Darker
bands appear to alternate with lighter bands which commonly
contain lenticular fragments of quartzite, aphanitic rhyolite,
and schist. The fragments are strongly elliptical and are
elongated parallel to the rock fabric. In thin section the
pale green coloured, schistose matrix is composed of
plagioclase up to 30 percent, augite up to 15 percent,
hypersthene up to 10 percent, and minor accessories including
sulphides and magnetite.
Some aphanitic, massive flows occurring east of the Big
Pic River contain euhedral phenocrysts of potassic feldspar
with or without phenocrysts of quartz.
Other rocks, grouped with the felsic metavolcanics, are
the fine-grained quartz-sericite schists exposed to the east
of Three Finger Lake.
Calcareous-rich rocks, composed of gamet-calcite-pyroxene,
occur near a quartzite outcrop approximately 3/8 mile east of
Mamoos Lake. These rocks may represent minor, intercalated
beds of metasediments within the agglomeratic rhyolite.

- 22 -
METASEDIMENTS
The metasediment s, namely bedded metagreywacke and
argillite have their maximum exposure to the west, near
Middleton. Exposures of massive biotite-quartz-feldspar
schists occur near Wullie Lake and to the southeast of Three
Finger Lake.
Metagreywacke
The metagreywackes near Middleton display graded bedding.
Individual graded beds commonly range from less than one inch
to three inches thick.
A few beds are up to three to four
feet thick.
A typical 3-inch thick bed is composed of a basal, two-inch
thick, sandy to silty unit and a one-inch thick, more argillaceous
to slaty top. A second slaty cleavage, in part attributable
to the emplacement of the Port Coldwell Alkalic Complex,
intersects the bedding plane, generally at reasonably high
angles. The intersection of these two planes has produced
a prominent lineation.
In areas close to the Complex reversed graded bedding
was recognized and attributed to the more marked recrystallization
within the more argillaceous units. Concordant veins of glassy
white quartz are prevalent in these sheared metagreywackes*

- 23 -
The metagreywackes, west of Wullie Lake are massive and
x
do not exhibit bedding. "^
In thin section the metagreywackes appear fine-grained,
average grain size being 1^ mm, and are composed of plagioclase,
potassic feldspar,quartz,with varying proportions of actinolite,
biotite, garnet (variety almandine?), epidote, chlorite,
magnetite and sulphides.
GRANITIC ROCKS
The granitic and more syenitic bodies occur to the north
of the map-area and extend, in a more or less uninterrupted
manner, from the Big Pic River to west of Wullie and Martinet
lakes. They make up what the author calls the Jim Lake
batholith. The Jim Lake batholith is principally a biotitehornblende
granite gneiss. The rock weathers a whitish pink
colour and characteristically exhibits 'eyes 1 of quartz.
These quartz f eyes f or rods plunge to the northeast, sub-parallel
to the northeasterly-trending contact with the mafic metavolcanics.
Contact phases with the mafic metavolcanics may exhibit
migmatite development. These peripheral areas may be
consistently more syenitic. It is possible that the trondhjemite
body west of Wullie Lake represents a more mafic and syenitic
phase of the Jim Lake granite.

- 24 -
Lamprophyre dikes appear to preferentially, although not
exclusively, cut the granitic intrusions to which they may be
genetically related. All these dikes were seen to occupy
existing joints and to exhibit relations with the predominantly
granitic host rock as to suggest intrusion during a period of
extension. The lamprophyres are represented by porphyritic
and non-porphyritic types. The non-porphyritic dikes apparently
strike northwest, whereas the porphyritic mica lamprophyre dikes
strike N25OE.
LATE MAFIC INTRUSIVE ROCKS
Diabase dikes, porphyritic and non-porphyritic, intrude all
the other pre-existing rocks in the area.
The porphyritic diabase dikes are up to sixty feet wide and
strike approximately N40OW (and less commonly N10-15OW) .
The non-porphyritic diabase dikes average three feet in width
and strike predominantly N30OE (and less commonly NIO-IS^).
These two types of diabase appear identical in hand specimen;
the distinction being made on the presence of greenish, plagioclase
phenocrysts in the porphyritic varieties.
With due recognition to the importance of the relative age
assigned to the diabase dikes of the immediate map-area it is
important to note that to date diabase dikes have not been found
to cut, unequivocally, the Port Coldwell Alkalic Complex.
would appear that some earlier observations (Coleman 1900,
It

- 25 -
p. 186-191), at least in part, agree with this relative age
assignment.
Similarly, to the west, it would appear (J.W.R. Walker,
pers. comm.) that the one or two dikes of f diabasic' composition
reported to cut the Port Coldwell Alkalic Complex could, in
fact, be lamprophyres.
PORT COLDWELL AI^KALIC COMPLEX
Introduction
The Port Coldwell Alkalic Complex is a lopolith, essentially
circular in plan, which has been emplaced by a process of magma
stoping and assimilation.
At the present level of exposure
roughly 10 percent of the Complex is beneath overlapping or
roof pendants of country rock.
The rocks of the Port Coldwell Alkalic Complex can be
considered as members of one of two series, namely; a f main f
series, and a 'secondary 1 series. The 'main 1 series include
the gabbros and laurvikites.
The 'secondary' series includes
syenodiorites, nordmarkites and feldspathoidal syenites.
These
rock types are found to be intimately associated with the
inclusions of country rocks, in particular the Coubran Lake
roof pendant.

- 26 -
'Main 1
Series
The 'main 1 series exhibits an overall zonation which is
as follows:
Upper Zone
Laurvikite
Lower Zone
Layered laurvikite
Inner Border Zone 'b' Layered gabbro
Inner Border Zone 'a' Massive gabbro
Outer Border Zone
Chilled gabbro
The gabbros show a maximum thickness equal to approximately
2600 feet and are made up of approximately 80 feet of
marginally located chilled gabbro, followed by approximately
300 feet of massive gabbro which in turn is followed by
approximately 2200 feet of layered gabbro. The gabbros are
conformably overlain by laurvikite, a unit which is
approximately 9,000 feet thick.
The apparent irregularity in gabbro thickness as seen on
surface is in part attributable to the presence of overlapping
and roof pendants of country rock.
Chilled Gabbro
The chilled gabbro is, in general, a massive, fine-grained
(average 1^ mm), magnetic rock restricted to the peripheral areas
-
Widths were determined on the basis of lopolith structure and
300 dip of layering.

- 27 -
of the Port Coldwell Alkalic Complex.
The consistent
peripheral occurrence is not meant to imply that this chilled
gabbro represents a rock which is solely found at the basal
contact with the country rock.
dike-like apophyses of 'chilled 1
Several north-south trending
gabbro have been found up to
800 feet east of the actual Complex-host rock footwall contact.
Veins, veinlets and small dikes of graphic granite,
predominantly joint controlled, may be present.
The veins et
cetera describe a reticulate pattern, of varying intensity,
within the chilled gabbro.
Thin section examination showed that the chilled gabbro is
generally equigranular, massive, and structureless.
But phases
exhibiting phenocrysts of plagioclase and pyroxenes are not
uncommon.
Both an orthopyroxene (variety hypersthene) and a
clinopyroxene (variety diopside) are present in approximately
equal proportions.
Olivine may (up to 10 percent) or may not
be present.
Additional minerals include magnetite and minor
sulphides (pyrrhotite * pyrite) and biotite.
As 1& apparent,
the rock is essentially composed of an anhydrous mineral
assemblage.
Another, apparently higher level, 'chilled 1
gabbro phase
exhibits a characteristic knobby weathered surface.
The knobs
represent poikilitic crystals of olivine and orthopyroxene up to
7mm.
N

- 28 -
In cho f Lold cho actual recognition and identification of
the chilled gabbro is made more difficult by the presence of
overlapping and near-marginal, roof pendants of country rock.
But in general the identification of chilled gabbro can be made
on the basis of the following: Characteristic and essentially
anhydrous mineralogy; high magnetite content; structureless and
massive appearance. Phases exhibiting phenocrysts of plagioclase
or pyroxene have been found south of Bamoos Lake but are minor
in extent.
Massive Gabbro
The massive gabbro is generally coarse-grained, ranging
from 3mm to 8mm, and structurless.
The maximum exposed widths,
where present, appear to range from approximately 2200 feet,
along Trans-Canada Highway 17, to approximately 350 feet,
southeast of Bamoos Lake. Surface continuity for this gabbroic
phase has not been established which may be attributable, in part
only, to the problem presented by irregular contact relationships
with the country rock.
The coarse-grained gabbros, although apparently conformable
to the 'chilled' gabbro in gross aspects, are seen to intrude
and engulf fragments (in part autoliths) of fine-grained gabbro.

- 29 -
Extremely coarse-grained phases, with crystals up to 65mm,
are closely associated with these massive gabbros.
Where
reasonably sharp contacts were observed these very coarse-grained
phases were considered as pegmatitic dikes of a younger gabbro
as opposed to pegmatitic variant of the same gabbro, senso
stricto.
The predominant gabbro framework is composed of the following
silicates, arranged in order of relative abundance; plagioclase;
clinopyroxene, very dark green coloured, generally poikilitic,
augite; olivine, honey yellow coloured, granular although may
occur as poikilitic crystals up to 50mm; and ilmenomagnetite,
variably unmixed up to 35mm.
Other minerals which may be present (in varying relative
proportions) up to as much as 60 percent in extreme cases
include:
Apatite, with phantom structures sometimes present;
sulphides, up to 10 percent; annitic biotite up to 15mm;
potassic feldspar, quartz, actinolite, orthopyroxene, serpentine,
hornblende and chlorite. Generally these minerals are restricted
to the interstitial sites within the existing gabbro framework.
Commonly the intimate association of these interstitial
constituents is reflected by the prevalent intergrowth textures
exhibited by the following mineral pairs; potassic feldspar
and quartz; annitic biotite and sulphides; apatite and sulphides;
serpentine and sulphides; and actinolite and sulphides.

- 30 -
The coarse-grained gabbro appears to grade into a mediumto
cv vi rs o -grained gabbro with poikilitic (up to 25mm) plates of
dark annitic biotite up to 8 volume percent.
Thin section analysis indicated that this biotitic gabbro
has the following composition; plagioclase up to 55 percent;
clinopyroxene (sodic augite) up to 20 percent; orthopyroxene
(variably pseudomorphed by chlorite up to 5 percent).
Accessory
minerals include sodic amphibole, apatite-ilmenomagnetite
intergrowth (up to 10 percent) and trace sulphides.
The exposures of biotite-rich gabbro along Trans-Canada
Highway 17 exhibits plagioclase lamination, dip of 250W and
layering, of a discontinuous and (or) disturbed nature.
The
layering dips 25OW.
In addition these exposures contain
abundant inclusions, varying in size up to 80 feet.
Partial
recrystallization and remobilization has resulted so as to
produce, in effect, a medium-grained hybrid.
Layered Gabbro
The exposures of layered gabbro along Trans-Canada Highway
17 have been examined in some detail. The primary structures
exhibited by these rocks include rhythmic layering with or
without gravity stratification, cryptic layering, inch-scale
layering, and igneous lamination.
Not uncommonly a strong

- 31 -
lineation, in the plane of igneous lamination, is exhibited by
clinopyroxene and (or) plagioclase.
Thin section examination has shown these rocks to be
composed of the following minerals, in varying and sometimes
most discriminating proportions; plagioclase; clinopyroxene;
olivine; ilmenomagnetite; and generally minor amounts of
sulphides, apatite, barkevikitic amphibole, and annitic biotite.
These minerals tend to occur in aggregates separated by small
amounts of interstitial materials.
The interstitial minerals include ilmenomagnetite + apatite
* biotite -H sulphides, (chalcopyrite * pyrrhotite jp bornite)
* trace barkevikitic amphibole. The ilmenomagnetite-apatitesulphide
assemblage can occur with olivine to form a relatively
thin (generally 2 inches thick) but persistent band.
Further
concentration apparently has resulted in the formation of more
massive, but generally less persistent, ilmenomagnetite + apatite
+ olivine bodies. Such bodies occur near Middleton to the west,
near Wullie and Skipper lakes to the north, and near Bamoos
Lake to the northeast.
These ilmenomagnetite bodies are
predominantly concordant with existing structures but some
discordancy has been observed (1000 feet west of Little Pic
River on Trans-Canada Highway 17).

- 32 -
Laurvikites
The laurvikite rocks of the 'main 1
syenite series appear
to represent approximately 65 percent^- of the volume of the
Port Coldwell Alkalic Complex.
The contact between layered gabbro f below 1
and layered
laurvikite 'above 1 appears gradational. Although textural
features suggestive of laurvikite 'chilling 1
has been seen,
supporting evidence, such as the presence of gabbro autoliths
(cognate inclusions) in laurvikite, necessary to indicate the
former existence of a major hiatus in time and (or) physical-
chemical environment between the two layered rock types has not
been found.
The gradational rock is grey in colour but otherwise resembles
'dark' laurvikte.
of variably exsolved perthite.
Thin section examination indicates the presence
The larger laths reveal included
areas that exhibit continuous polysynthetic twinning (i.e.
labradorite).
The ferromagnesian minerals include the following;
olivine, variable serpentinized,up to 8 percent;sodic augite,
fresh, up to 15 percent;and ilmenomagnetite mantled by annitic
biotite, up to 5 percent.
Immediately west of Big Pic River a similar syenite, with
porphyritic texture variably but regularly developed, has been
mapped.
Here the syenite apparently overlies the gabbros of the
Figure derived assuming a limited depth of penetration of the
Coubran Lake metavolcanic roof pendant. (In view of the breaching
of the roof pendant by porphyritic variety of laurvikite, at Gordie
Lake, this assumption would appear justified) and continuity
of structure (as determined on surface) to depth.

- 33 -
'main 1
series.
Layered Laurvikite
The laurvikites exhibit rhythmic and cryptic layering,
although on a less obvious and apparently more restricted scale
than that exhibited by the gabbros.
In general terms, an individual laurvikite layer is comprised
of a f basal 1 lamina of f dark f green laurvikite and an 'upper 1
lamina of pink, hematitized laurvikite.
Characteristically, the
dark 1 green laurvikite is coarse-grained with dark green
laths of perthite (braid perthite visible under hand lens)
up to 12mm (by 5mm by l-4mm).
Carlsbad twins are always present.
The greenish colour is of equal intensity throughout the crystals
of perthite which often exhibit an internal iridescence.
The
mafic minerals present include olivine, aegirine augite,
^
magnetite, primary and secondary barkevikitic amphibole, and
minor zircon, rare earths, apatite, and chlorite.
The hematitized varieties of laurvikite exhibit many of
the same features as the f dark f
green varieties with the
notable differences being, aside from the colour, that the
alkalic feldspars occur as more equant grains, devoid of Carlsbad
twinning.
Perthitic twinning is always clearly identifiable.

- 34 -
The perthitic feldspar grains are not homogeneously coloured
but zoned so as to exhibit a greenish-grey f core f
with a pink
mantle.
Transitional varieties of laurvikite exhibit properties
and textures which represent but variations of the two,
previously mentioned.
Laurvikite, Massive
The layered laurvikites pass insensibly into more massive,
non-lamina ted, hematitized and amphibolitized syenites toward
the geographical centre of the Complex and the Coubran Lake
roof pendant.
Uralitization of aegirine augite to form barkevikitic
amphibole has been found arrested at various stages. Upon
completion the rock has become a f red f amphibole syenite.
Laurvikites, Pegmatites
Numerous dikes of laurvikite pegmatite were encountered in
the course of investigation. In most cases these dikes have
been emplaced along pre-existing ring-like fractures during
periods of local (?) extension.

- 35 -
The time of emplacement, for what would appear to be some
of the earliest pegmatites generated, may be prior to complete
solidification of underlying gabbro.
Exposures along Trans-
Canada Highway 17 show gabbro fragmentation with partial lit-
par-lit type intermixing of laurvikite wich gabbro comprising
the fragment.
But in most examples the laurvikite pegmatite
contacts are sharp, in part chilled with or without the
development of a more magnetite-rich contact aureole in the
gabbros or laurvikite host.
The laurvikite pegmatites frequently exhibit miarolitic
cavities, generally found to be preferentially developed and
(or) concentrated in vicinity of the hanging wall.
These
miarolitic cavities contain, in varying proportions, the
following minerals; crystalline quartz; crystalline amphibole
with or without associated zircon; fluorite; calcite; molybdenite;
and crystalline perthite.
Crystalline graphic intergrowths
between perthite and quartz are not uncommon.
Thin section examination shows that most of the pegmatites
contain the following minerals; perthite, approximately 90
percent; aegirine augite, variably uralitized to barkevikitic
amphibole; quartz, generally about 2 percent; and the
aforementioned accessories.

- 36 -
Laurvikite, Porphyritic Varieties
Porphyritic laurvikites are extensively developed in
vicinity of Gordie Lake, and Penn Lake.
In both occurrences
the porphyritic laurvikite is overlain by metavolcanic rocks.
At Penn Lake the porphyritic varieties can be seen to grade
into more normal and equigranular varieties of laurvikite.
The porphyritic laurvikites appear to represent phases,
near contact with metavolcanics, which have cooled more
rapidly (i.e. chilled).
1 S econdary f S eri es
The rocks comprising the 'secondary 1
series are massive
and essentially structureless, except for the layered nepheline
syenites on Allouez and Pic islands. As previously mentioned
these rocks are seen to be intimately associated with the
metavolcanics belonging to the Coubran Lake metavolcanic
roof pendant.
The syenodiorite-nordmarkite rocks represent a series,
senso stricto, and in all cases are found to grade into one another
and ultimately into the hanging wall metavolcanics.
These
rocks describe a series that is oversaturated with respect to
silica.

- 37 -
The nepheline syenites and related phases outcrop west of
the Redsucker Cove-Mink River lineament. These rocks are a
series that is undersaturated with respect to silica.
Syenodiorite
The rock is somewhat variable in appearance but in general
it is fine- to medium-grained. 'The degree of crystallinity
may be directly related to the degree of crystallinity exhibited
by the nearby metavolcanics.
Coarser grained phases exhibited
a relict diabasic texture.
'Typical 1 syenodiorites are composed of amphibole, biotite,
and plagioclase with variable amounts of quartz and perthite.
Locally the syenodiorites may be cut and brecciated by
numerous dikes of fine- to medium-grained red quartz-hornblende
syenite.
Nordmarkite
The red quartz-bearing hornblende syenites, nordmarkites,
show a grain size variation that is identical to that observed
in the syenodiorites.
Relict diabasic textures have been
observed.
texture.
In many places the nordmarkites have a porphyritic

- 38 -
Thin section examination shows that these rocks are
composed of the following minerals; quartz up to 6 percent;
perthite; minor amounts of riebeckitic amphibole,
clinopyroxene (variety augite), magnetite, apatite and chlorite.
Nepheline Syenites
The field relations of the nepheline syenites, exposed
immediately west of the Redsucker Cove Lineament, may be
considered as representative of the relations exhibited by all
the feldspathoidal syenites of the Complex.
The exposures of the nepheline syenites are topographically
'high 1 and the rocks show a peripheral zoning. The outer
nepheline syenite zone, in contact with the host metavolcanics
belonging to the Coubran Lake metavolcanic roof pendant, is
fine-grained (range from 2mm to 5mm) and meso- to melanocratic.
The nephelinized metavolcanics have a varying nepheline content
which increases towards the nepheline syenites. The crystallization
of nepheline is accompanied by the uralitization of existing
ferromagnesian minerals.
The amphibole in the melanocratic nepheline syenites of the
outer zone is barkevikitic and generally occurs as poikilitic
overgrowths on older clinopyroxenes derived from assimilated
metavolcanics.

- 39 -
Exposures of metavolcanics have been found that appear to
have been nephelinized at two markedly different degrees and
(or) stages.
Generally the less nephelinized parts are included
as angular fragments formed during a period of dilation in the
more nephelinized parts.
The latter can themselves occur as
angular fragments, formed during a second and later period
of dilation, in the more leucocratic nepheline syenite
emplacements.
It would appear therefore that the nephelinization
process was operative over at least two periods of extension.
Nepheline in the outer zone is generally fine-grained and
relatively unaltered.
Much of the nepheline, perthitic and
plagioclase feldspars are poikilitically included in the
barkevikite.
Towards the inner zone, and topographic f high f , the
nepheline syenites become more leucocratic, coarser grained,
and biotite predominates over amphibole.
Relatively unaltered
nepheline is present up to 40 percent.
Later phases exhibit a pink coloured cryptocrystalline
alteration of nepheline.
The alteration product appears to
be a mixture of natrolite and thomsonite.

- 40 -
Natrolite-Perthite Dikes
Natrolite-perthite dikes appear to occupy steeply dipping
cone-sheet fractures. These dikes are characterized by the
complete zeolitization of nepheline which on weathered surface
is indicated by the presence of an orangy pink coloured
natrolite-thomsonite pseudomorphic intermixture. This orangy
pink colouration is characteristically set against a background
of pale grey perthite the combination of which makes a most
attractive rock.
Analcite Tinguaite Dikes
Analcite tinguaite dikes appear to occupy radial fractures
which can extend beyond the confines of the Complex. In
general these dikes are aphanitic to fine-grained and red in
colour. The primary minerals are analcite, perthite and
aegirine augite. Nepheline is not present.
Lamprophyre Dikes
Abundant lamprophyre dikes, generally l foot wide, can be
seen to cut the various phases of f secondary 1 rock types. They
belong to the f secondary 1 series and in part to the f main f series*

- 41 -
These lamprophyre dikes follow in part arcuate cone-shaped
fractures that dip inward towards Coldwell at shallow to
moderate dips.
Texturally these lamprophyres are all porphyritic and
include monchiquites and camptonites.
Perthosite Dikes
Several exposures show perthosite dikes cutting lamprophyre
dikes of sodic composition. The perthosite dikes are monomineralic,
and composed of laths of perthite exhibiting a strong foliation
which is parallel to the contacts.
LATE GRANITIC ROCKS
Little Pic River Granite
The Little Pic River granite mainly occupies the northwest
part of the map-area.
Here the granite differs from the other
granitic rocks of the area in that it exhibits a hypidiomorphic
texture and is essentially structureless. The predominant
ferromagnesian mineral is biotite with lesser proportions of
hornblende.
The northerly extent of this granite is not known although
younger bosses of fresh biotite granite have been reported
(Walker 1961) to the west.

- 42 -
Thin section examination shows the granite (average grain
size 4mm) is composed of the following minerals:
Quartz up to
25 percent; plagioclase, up to 60 percent; alkalic feldspar, up
to 16 percent; actinolite amphibole up to 7 percent; biotite mica
up to 9 percent; minor magnetite and zircon.
The Little Pic River granite intrudes the Port Coldwell
Alkalic Complex.
The intrusion of the granite has brecciated
and variably granitized the rocks comprising the 'main' series
of the Complex.
The zone of granitization and hybridization extends as far
south as the Trans-Canada Highway 17 and eastward to within
2^ miles of Wullie Lake (Walker 1961).
This zone is further
characterized by the predominance of amphibole and the
inhomogeneous distribution of quartz.
PLEISTOCENE AND RECENT
The larger deposits of unconsolidated sand, alluvium, and
clay have been described and are indicated on the accompanying map.
Glacial striae and chatter marks are common and indicate that
the major movement of ice trended approximately 835^. Several
minor lobes were apparently directed along several of the pre
existing lineaments to the east. The valley walls show striae
trending parallel to the east-west strike of the lineaments.

- 43 -
STRUCTURAL GEOLOGY
Introduction
Although the mapping was of a reconnaissance nature, the
structural features defined are believed to represent, fairly
accurately, the salient and some of the more significant minor,
structural features of the area, but are not necessarily a final
solution. Despite the fact that most of the country rock is
exposed, particularly along the lake shores, the outcrops are
frequently 'belt-like 1 and because the lithologies of different
sequences of metavolcanics and (or) metasediments are so similar
it is never entirely certain that the same sequence of rocks is
being considered. Fortunately there are a few distinct marker
beds in the area and with the aid of these marker beds and inherent
structures, such as: Graded bedding and pillow lavas; local
folds have been proposed within the metavolcanic-metasedimentary
sequences.
The period of maximum deformation, since evidence for more
than one period of folding has not been recognized, was followed
by the intrusion of granitic rocks predominantly into and along
the established folds. This period of intrusion apparently
culminated with the emplacement of granite pegmatite and
lamprophyre dikes. At some later period the area was invaded
by near north-south trending diabase dikes. Faulting along

- 44 -
north-south and northeast-southwest trending planes of weakness
followed the diabase intrusion.
The geological history up to
this point is very similar to that given by Pye (1957, p. 46)
for the Manitouwadge area (approximately 25 miles northeast of
the Port Coldwell Alkalic Complex) with an apparent notable
exception being the absence of similar sulphide replacement
deposits.
The period of faulting was followed by the intrusion
of the Port Coldwell Alkalic Complex.
Structural Elements Within the Metavolcanic-
Metasedimentary Sequences
FOLD STRUCTURES
The metavolcanic-metasedimentary rocks have been deformed
into reasonably tight isoclinal folds.
The strike of these
vertically to steeply dipping structures is N70OE, which
closely parallels that of the Archean rocks from other parts
of the Superior Province.
Deflections to this regional trend
do occur and in the map-area the deflections observed are
sharp and help to delimit, more or less, the contact aureole
around the younger, Port Coldwell Alkalic Complex.
A major fold which has been defined is the Jim Lake anticline,
located immediately to the north of the Port Coldwell Alkalic
Complex near Skipper Lake.
More will be said regarding the Jim

- 45 -
anticline in the section dealing with structures related to
granitic intrusions.
Other folds, despite the aid of outcrop patterns and top
determinations are less definite.
The axial planes are apparently vertical although folds to
the north may be overturned.
The proposed axial plane belonging
to the Jim Lake anticline is apparently overturned to the south
and apparently plunges to the northeast.
FOLIATION AND LINEATION
Throughout much of the area bedding, schistosity (bedding
schistosity?), gneissosity, and flow contacts were found to be
less variable and generally steep or vertical.
Lineation of
amphibole, although variably developed was observed in the
amphibolites (mafic metavolcanics) adjacent to the Jim Lake
granite, a body which itself exhibits northeasterly-plunging
rods of quartz.
A lineation, the product of intersecting cleavage and
bedding planes, is prevalent in the metasediments that are found
within part of the western contact aureole of the Port Coldwell
Alkalic Complex north of Middleton.

- 46 -
FAULTING
It should be made clear at the outset that the steep dips
and lack of a definite stratigraphic column render the
recognition of strike faults regardless of attitude extremely
difficult.
Transverse faults are more easily recognizable, and appear
to be near-vertical and to strike N10OW or N300E. The more
northerly-trending fault cutting the metavolcanics and Jim
Lake granite east of Wullie Lake has sinistral movement as
indicated by the associated drag folding. Gash fractures
filled with quartz are strongly developed on the western
(downthrown) block.
JOINTING
Considering the long and complex history of the area, it
is to be expected that all the rocks would be intensely jointed,
more or less. Most outcrops do show at least two distinct
joint sets, and five or more joint sets in a single outcrop
have been observed.
In the course of the field work it became apparent that
several joint sets are related to the folded metavolcanics and
that the various hypabyssal intrusions have been guided during

- 47 -.
intrusion by these pre-existing planes of weakness.
Joint control on the intrusion of various dikes related
to the Port Coldwell Alkalic Complex was suggested and gave
further impetus to the following study.
Accumulation and Interpretation of the Joint Data
Generally all the visible joints were frequently measured
in an attempt to minimize 'selection-bias 1
and to minimize local
irregularities in the general and (or) regional pattern.
Ideally it was hoped that minor but consistent joint sets
important to the structural interpretation of the area would
not be overlooked.
About 6,000 readings of joint attitudes were collected
and plotted on Schmidt equal-area nets.
The joint plots were
then counted and contoured using the standard 1-percent areacounting
device (see Billings, 1942, p. 111-115, for a simple
explanation of the technique).
The interpretations presented are based on the premise
that joints should and can be related to major geologic
events in the area.
Persistent joint sets are recognized
on the accompanying joint contour diagrams and their genetic
relations are inferred from their fit with ideal joint sets
that would be related to known folds.

- 48 -
A brief review of joints expected on fold structures may
be warranted.
During plastic or essentially nonplastic
deformation, joints may form parallel to the axial plane.
This set is the "release-tension-joints 11 of de Sitter (1956,
p.131).
The significance in incorporating the aspect of
tension in designating these longitudinal joints stems from
the possibility of tension joints developing in the upper part
of the fold as a result of scretching of the 'cap 1
rocks of the
fold.
A set of joints ("extension joints" of Billings, 1942,
p. 117) may form perpendicular to the fold axis or "release-
tension-joints" resulting from stretching of the beds on the
crest of a doubly plunging fold.
Shear joints (or diagonal
joints) may form in symmetrical positions at angles less than
450 to the principal (greatest) compressive stress, but both
shear directions are not necessarily expressed in the rocks.
Joints in Metavolcanic-Metasedimentary Sequences
The attitudes of 1300 joints in the metavolcanic and
metasedimentary rocks were determined.
The pole intersections,
of perpendiculars to planes representing these joints and the
bottom half of an imaginary sphere, through the centre of which
the planes are assumed to pass, were projected to a horizontal

- 49 - ^
surface to give a point diagram as described by Billings
(1942, p. 114-122). From the point diagram, a contour
diagram, to show the percentage of joints per unit area of
projection, was constructed. The contour diagram is
reproduced in Figure 1.
In all there are eight sets of joints recognizable which
describe a pattern symmetrically disposed about the regional
fold axis direction indicated on the plot.
The predominant joint sets labelled 8 and 5 strike parallel
to the regional fold axes and almost always, parallel to the
planes of bedding and (or) parallel to the planes of
schistosity or gneissosity. Joints labelled l and 7 have a
similar strike, parallel to the regional fold axes, but are
horizontal or near horizontal and related to sheeting.
In character the more vertical joints described are
smoother surfaced, straighter and more continuous than any
other joint set observed in the greenstones.
But in company
with the halo of marked deflections in the direction of the
regional fold axes around the Port Coldwell Alkalic Complex,
the continuity of these joints are solely restricted to the
more competent members.
Instead the prevalent jointing labelled
3 and 4 in Fig. l is parallel to the bedding plane. These
joint surfaces are crenulated due to the intersection with the
axial plane cleavage described.
\

- 50 -
The joint set labelled 2 in Fig. l strikes perpendicular
to the axial plane direction. These joints tend to be
irregularly spaced and terminate against the joints paralleling
the regional fold axis direction.
Structures Related to the Granitic Intrusions
The Jim Lake granite is apparently concordant with the
metavolcanics and metasediments.
The shape of the Jim Lake
granite is known, in part, and may be described as trending
parallel with and into established folds.
The trondhjemite, at Wullie Lake occurs as a more
equidimensional body. Planes of schistosity within the
prevalent metasediments appear to have been deflected around
the western part of the trondhjemite.
JOINTING
As a corollary to the restricted regional study, joint
sets in the granitic rocks were compared. The attitude of the
joints related to the Jim Lake granite is shown in Fig.2 from
which it is readily noticeable that the distribution of the
joints bear a marked similarity to that already described for
the metavolcanics.

- 51 -
Primary joint sets in igneous rocks can be recognized
if dikes related to the igneous body are found to be
intruded along the joints in that body.
On this basis the
joint set striking N20 W and labelled l in Fig.2 which contain
pegmatitic phases of the Jim Lake granite can be considered
as "extension"-type of primary joints.
The granite is also cut by a suite of lamprophyre dikes
which appear to be closely related to the granite in view of
the fact that the dikes have been found restricted in
occurrence to the granite.
These dikes, averaging several
feet in width, exhibit pencil sharp contacts with no chilling
and have attitudes which are joint controlled.
The lamprophyre dikes belonging to the mica-free porphyritic
and non-porphyritic types were intruded along the "extension 11
joints and the intrusion occurred while the intruded portions
of the granite were under tension (See Fig.3).
The structural relationship between the metavolcanics
and granite can best be described by considering the section
centred around Jim Lake.
The pertinent structural features found are as follows:
1. The host rocks containing the granite, so to speak, are
predominantly mafic metavolcanics having a uniform attitude
in schistosity which is identical to that found on a regional scale.

- 52 -
2. The northernmost belt of metavolcanics shows a f oresting 1
in the attitude of the schistosity southward to the granite
contact.
3. The emplacement of the granite has been dominantly of a
concordant nature, paralleling the structures in the
metavolcanics.
Discordant relations are associated with the
granite (were found to be) and were accentuated either by
the presence of aplite apophyses or by the presence of migmatite
zones up to one foot wide and paralleling the granite-metavolcanics
contacts.
4. The quartz rods plunge to the northeast at an angle of
45 0 which is identical to the direction and angle of plunge
obtained from some amphibole lineations in the adjacent
metavolcanics and dragfolds in the metavolcanics comprising
the south-containing limb for the granite.
5. Dragfolds in the metavolcanics involving "off-shoots 11 of
granite indicate a relative movement of the granite to
higher levels.
6. The granite body proper exhibits a barren zone free of
inclusions and a zone highly charged with inclusions of
metavolcanics which is adjacent to the 'cresting 1
portion of
the northernmost limb of the metavolcanics belt.

- 53 -
7. The close similarity in the distribution in the joints
between the granite and metavolcanics would appear to
substantiate the consideration that the granite intrusion
was predominantly of a concordant nature. The lack of
similarity in the relative intensities between the two joint
plots may simply reflect inherent differences in structural
behaviour in a cooling magma.
8. Fig.2 is a composite diagram made up by plotting all the
joints in the granite irrespective of granite character. In
actuality the sub-horizontal joint set, labelled 2 and a product
of sheeting, is predominant in the 'barren 1 zone of the
granite. This would seem to suggest that the major fold axis
should be in close proximity to this zone.
Conclusion
Any one of the eight structural features enumerated cannot
alone reveal the complete structural relationship between the
granite and host rock concerned. But together the evidence
would appear to indicate that the granite is a synorogenic- and
was emplaced into the metavolcanic-metasedimentary sequences
during regional deformation.

- 54 -
Structures Related to Port Coldwell
Alkalic Complex
The Port Coldwell Alkalic Complex is a lopolith exhibiting
many features common to intrusions classified as laccomorphic
(Benson 1926). The rock types, namely; gabbro and laurvikite,
comprising the 'main 1 series can and have been divided into
conveniently mappable field units. The roof and upper portions
of the Complex is variably hidden beneath overlapping country
rock and roof pendants of country rock. The rock types,
namely; syenodiorite, nordmarkite, various feldspathoids and
zeolitized derivatives, are intimately associated with the
country rocks comprising the roof and upper portions of the
Complex.
Glossary of Terms
Structures within the Complex which have been mapped and
identified include the following, the name of which Is
accompanied by the presently accepted definition (Hess 1960).
Layering:
The arrangement of crystals in layers; analogous to
stratification in sedimentary rocks.
Rhythmic Layering:
Generally refers to layers, areally quite
persistent, which have been repeated rhythmically so as to produce
-
Having the form of a laccolith.

- 55 -
a most conspicuous banded appearance.
Megascopically it
can be seen that this type of layering is due to changes,
commonly a gravity stratification, in the relative proportions
of the minerals concerned.
Cryptic Layering:
Non-megascopic and reflects the upward change
in mineral composition, and not relative proportion, during
cooling.
Phase Layering:
Abrupt mineralogical changes resulting from
the appearance or disappearance of a mineral phase.
Igneous Lamination:
The preferential arrangement of platy
crystals so as to develop a foliated texture.
It is not
uncommon to find that platy crystals exhibit a lineation
in the plane of foliation.
Inch-Scale Layering:
First named by Hess for a type of
layering, whose origin is considered uncertain. Composed
of alterations of pyroxene and plagioclase which are
slightly less than an inch thick.
These structures, although apparently variably developed,
identify the layered gabbros (Inner Border Zone f b ! ) and the
layered laurvikites (Lower Zone).

- 56 -
LAYERING IN THE 'MAIN 1
SERIES
Rhythmic Layering
The rhythmic layering (Skaergaard type) in the layered
gabbros is more or less continuous and regular and has been
traced horizontally, for a distance of 800 feet.
But
continuity in rhythmic layering over such distances does not
preclude the possibility that the development of layering, in
general, in the gabbros may be somewhat discontinuous and
(or) irregular and (or) manifest itself in a somewhat different
texture.
Chilling, commonly of a subtle nature, has been
established petrographically.
Mineralogically the basal portions of the layers are
composed of a greater concentration of anhydrous femic
constituents (with or without a concomitant increase in relative
grain size) .
The ferromagnesian minerals referred to are olivine,
clinopyroxene, ilmenomagnetite with (or) without minor sulphides.
Rhythmic layering is megascopically observable in the
layered laurvikites.
Ferromagnesian minerals are generally
more abundant in the 'dark 1
basal units than in the overlying,
generally more reddish coloured, units.
Determinative work shows that the alkalic feldspar in the
'dark 1 , basal (essentially anhydrous) units is characteristically,
although variably, less unmixed; less potassic; and composed of

- 57 -
higher (intermediate) temperature albite.
In contrast the
alkalic feldspar in the 'reddish 1 , overlying (variably but
generally extensively pseudomorphed by iddingsite, barkevikitic
amphibole, and annitic biotite) units is characteristically,
although variably, more unmixed; more potassic; and composed
of low temperature albite.
Discontinuous and (or) Disturbed Layering
Discontinuous and (or) disturbed layering has been noted
in several areas and in all cases the phenomena was restricted
to the basal portion of the layered gabbros.
Whether gabbros
similarly located spatially do exhibit disturbed layering and
therefore contribute to the delimiting, in gross aspects, of a
basal gabbro zone typified by disturbed layering has not been
substantiated nor disproven by the surface mapping to date.
Inch-Scale Layering
Inch-scale layering can be seen in the exposures along
Trans-Canada Highway 17 where it appears restricted to the basal
zone of the rhythmically layered gabbros.
Inch-scale layering
developed to a similar degree or regularity has not been seen
elsewhere.

- 58 -
Cryptic Layering
Cryptic layering is present in the layered gabbros.
Determinative work shows that the olivines range from hortonolite
to chrysolite, plagioclase from calcic labradorite to calcic
albite, and clinopyroxene from diopside to diopside augite.
^-~
Igneous Lamination with (or) without Lineation
CIinopyroxenes, plagioclases , and alkalic feldspars
(perthites) frequently occur as prisms or plates. The feldspar
plates exhibit dimensions which commonly are as follows:
2^ mm wide (i.e. faces describing zone perpendicular to
010 plane) by 3mm to 7mm by 4mm to 9mm. Where lamination is
present the feldspars are oriented so that the (010) plane
is more elongate, the long axis plunges down-dip toward the
geographical centre of the complex. This lineation is strongly
masked in those rocks which appear to contain a bimodal-like
assemblage of feldspars. In an outcrop occurring \ mile east of the
Marathon cut-off on Trans-Canada Highway 17 it was determined
that 55 percent of the larger, more elongate perthites contributed
to the development of a lineation whereas but 30 percent of the
smaller, less elongate perthites exhibited a similar orientation.
The remaining smaller perthites were oriented at varying angles
to the plane of lamination.
4

- 59 -
JOINTING IN THE 'MAIN 1
SERIES
Similar techniques were followed in the accumulation and
presentation of the joint data related to the rocks of the
Port Coldwell Alkalic Complex (Fig. 4), as described previously.
These joints may be divided into three definite groups:
(1) horizontal and near horizontal joints; and (2) moderately
inclined joints; and (3) vertical or near-vertical joints.
The joints in group (1) include members formed as a
result of a process referred to as sheeting.
Near horizontal joints describe a definite girdle of
concentric fractures which dip outward, toward the margin of
the alkalic syenite complex.
These joint planes have served
as avenues for intrusion of augite syenite pegmatites.
Moderately inclined joints are coincident to 'the primary
flow layering but dip inward, at angles averaging 55O toward
the apex of the alkalic syenite complex.
The joints of groups (1) and (2) may show shearing effects
and may show mineralization including calcite, fluorite and (or)
molybdenite.
The steeply inclined to vertical joints describe a radial
pattern normal to the flow lines.
These joints are frequently
mineralized similar to that reported for joints in groups
(1) and (2); whereas shearing, on the.other hand, is less
prevalent along the joints of near vertical attitude.

- 60 -
LAYERING IN THE 'SECONDARY 1
SERIES
Except for the nepheline syenites occurring on Allouez and
Pic islands, the rocks of the 'secondary 1 series are massive and
essentially structureless.
The nepheline syenites from these locations exhibit rhythmic
layering accompanied by gravity stratification (i.e. mafics,
predominantly sodic amphibole, are more abundant in the basal
units). The layering is generally regular and near-vertical in
attitude. Contortions and folds, steeply plunging, are not
uncommon. In two areas the layering was found to describe vortexlike
structures.
JOINTING IN THE 'SECONDARY 1
SERIES
As previously stated the rocks of the 'secondary' syenite _^
series are intimately associated with the country rocks comprising
the roof and upper portions of the Complex. Such a unit of
country rock is referred to as the Coubran Lake metavolcanic
roof pendant.
Poles of 861 joints from the Coubran Lake metavolcanic
roof pendant were plotted and the points contoured (Fig. 5).
Field evidence has shown that the Coubran Lake metavolcanic roof
pendant is overlain by laurvikite along the north exposure three

- 61 -
miles due west from the northwest shoreline of Coubran Lake.
In comparing the plot of the joints from the Coubran Lake
metavolcanic roof pendant to that plot previously presented for
the country rock, the modifications probably imposed on the
existing joint attitudes by the northerly subsidence may
be postulated.
The joint plots for the syenogabbros and nordmarkites
are identical to that obtained from the Coubran Lake metavolcanic
roof pendant.
A contour diagram of 683 joints obtained from the larger
bodies of nepheline syenite is presented in Fig. 6.
These
bodies are generally zoned such that the marginal phases are
finer grained and more mafic.
The peripheral metavolcanics
are variably nephelinized and generally exhibit the presence
of joint controlled dikes of feldspathoidal rocks (Figs. 7 and 8).
The massive exposures of nepheline syenite, particularly
those on Allouez and Pic islands, exhibit a more pinkish alteration
along the joint planes. This pinkish alteration may extend into
the host anywhere from a few inches to several feet and is
attributable to a later period of zeolitization.

- 62 -
LINEAMENTS
Lineaments have been largely deduced from aerial photographs
by commonly accepted methods. The lineaments within the Port
Coldwell Alkalic Complex appear to describe a radial and a
concentric pattern. Movement along many of these lineaments is
strongly suspected in view of many contact relations and outcrop
pattern. Lineaments disposed radially from the Complex
consistently indicate displacement, which is suspected to have
a substantial dip component.
In the map-area there are three major north-south trending
lineaments, namely, the Big Pic River, Little Pic River, and
Redsucker Cove.
SUMMARY
The Port Coldwell Alkalic Complex is a large lopolithic
intrusion. A limited but more or less persistent metamorphic
aureole, characterized by recrystallization and (or)
remobilization, and development of orthopyroxene was developed.
In addition local structures in the country rock were disturbed.
The Complex can be conveniently considered as being composed
of two rock series; namely, a 'main 1 series which includes gabbros
and laurvikites and a f secondary 1 series which includes

- 63 -
syenodiorites, nordmarkites and feldspathoidal rock types.
Within the 'main 1 series a zonation has been recognized
which is as follows:
Upper Zone
Laurvikite
Lower Zone
Layered laurvikite
Inner Border Zone f b f Layered gabbro
Inner Border Zone ! a f Massive gabbro
Outer Border Zone
Chilled gabbro
The massive gabbro does contain significant and perhaps
economic amounts of base metals, largely as chalcopyrite.
The layered structures dip inwards at moderate angles
(range from 70 to 70O ). From field data it would appear that
the dip in layering is small (i.e. 7 O ) near Skipper Lake.
Contact between layered gabbro and layered laurvikite is
variably chilled and appears to be largely conformable.
During cooling of laurvikite, laurvikite pegmatites were
intruded spatially as ring dikes, along pre-existing,
reactivated joints in the basal members of the Complex.
The intrusion of nepheline syenite, largely as domes with
near-vertical sometimes vortex-like layering, has been largely
joint controlled in the peripheral areas of these domes.
Late lamprophyre intrusion has occurred along reactivated
joint planes as cone sheets.

- 64 - x-
ECONOMIC GEOLOGY
Introduction
Various parts of the area have been staked for building
stone, iron, non-ferrous base metals, and nepheline; and
-^gravel
has been removed locally for road construction.
The early economic interest in the area was for the
quarrying of dark (and later red) laurvikite for building
stone.
Mineral prospecting during the early 1930 f s was limited
to the determination of the iron ore potential of the magnetite-
rich bodies within the gabbros of the Port Coldwell Alkalic
Complex east of Bamoos Lake.
Exploration with similar intent
was continued up to 1960 by which time most of the exposures
of gabbro belonging to the Complex had been variously examined.
During the course of this exploration for iron ore,
extensive copper mineralization within the gabbros was discovered.
The first non-ferrous base metal examination was begun in 1954.
Present investigations appear to indicate the presence of large
tonnages of fairly low-grade copper-nickel mineralization.
The feldspathoidal syenites immediately west of Redsucker
Cove were examined, in 1960, as possible source rocks for the
mineral nepheline.
The results of the exploration were not
encouraging and development has been postponed, apparently, for
an indefinite period.

- 65 -
IRON
The gabbros of the Complex were investigated as a possible
source of iron as early as 1930.
The magnetite-rich bodies
are found to vary from one inch wide to seventy feet wide and
to be present as lenses which generally exhibit similar attitudes
as those of the local gabbro host.
These bodies are found to be mineralogically composed of up
to 80 percent ilmenomagnetite with accessory olivine, apatite
and chalcopyrite.
The chemical composition of the larger, 50 to 70 feet wide,
bodies is as follows: Approximately 40 percent iron, 5 to 8
percent sulphur, 0.3 to l percent phosphorus (^2^5) anc*
approximately 30 percent silica.
All the analyzed and observed bodies of high magnetite
rock, whether conformable or disconformable to the host-rock
layering, contain ilmenomagnetite, variably unmixed.
The
titanium content, under present conditions, does not appear
to make the mineralization attractive either as a source of
iron ore or as an ore of titanium.

- 66 -
Zebe Renshaw
At various times between 1950 and 1954, Zebe Renshaw staked
fifteen claims, ten to cover a zone of high magnetite that was
believed to have possibilities as an ore of iron.
_.
The high magnetite rock is 7/8 of a mile west of the
Little Pic River within the gabbro outcrop on the north side of
Trans-Canada Highway 17.
The rock occurs as a conformable
segregation with a true width of about 50 feet, and dips about
20OE.
This segregation has been traced horizontally for a
distance up to ^ of a mile.
The high magnetite rock is composed of ilmenomagnetite,
60 to 80 percent, and varying amounts of apatite, olivine,
and chalcopyrite.
The host gabbros characteristically contain interstitial
ilmenomagnetite.
In some cases the oxide phases occur as
veins, somewhat irregular in attitude, ranging from 6 inches
to 20 feet wide.
An average of several analyses yielded approximately 37
percent iron, 5 percent titanium,l percent manganese, 30 percent
silica, about l percent phosphorus (^2^5)* anc* aDOUt 0*10 percent
sulphur (Walker 1961, p.5).

- 67 -
George Olson
In 1960 George Olson, proprietor of North Shore Hotel in
Heron Bay, held a group of 71 claims approximately one mile
north of Bamoos Lake and extending westward to Skipper and
Lacobeer lakes. The claim block described a rectangle whose
long dimension, approximately three miles, trended in an
east-west direction.
By 1964 the claims were reduced in number with Olson
retaining 20 claims in partnership with Louis Adams and 18
claims in partnership with Louis Adams and John A. Hamilton.
These 38 claims were optioned by Anaconda American Brass Ltd.
in October, 1964.
The bedrock is predominantly composed of gabbro. Granite,
fine-grained and coarse-grained amphibolite schists occur to
the north and northeast and laurvikites to the southwest.
The gabbro - Jim Lake granite contact is represented by
-an approximately 40-foot wide zone of medium-grained, grey
coloured, hybrid phase of granite.
In thin section this grey
coloured phase of granite is seen to exhibit a characteristic
texture in which the plagioclase appears as rectangular plates
within quartz. The interstitial quartz appears as optically
continuous porphyroblasts up to 8mm. The femic constituents
include serpentine, biotite and penninite.

- 68 -
The gabbros are variably mineralized and may exhibit
folitated and layered structures whose dip component is ^
predominantly shallow, varying from 5 to 40O to the SW.
Numerous layers of ilmenomagnetite are present. One body is
approximately 70 feet wide.
Early geophysical work by Dan Johnson of Port Coldwell,
which included a dip needle survey, traced the main ilmenomagnetite
body for approximately three quarters of a mile. During these
investigations a sulphide-bearing phase of gabbro was observed
and traced for approximately one mile. The mineralized bodies
were reportedly transected by a northeast-trending fault.
Recent investigations and diamond drilling by Anaconda
American Brass Ltd. have verified the presence of sulphide
mineralization.
Empire Explorations Limited
In 1963 Empire Explorations Ltd. held a group of 9 claims
east of the east end of Bamoos Lake. These claims include
ground formerly staked by H. England of Port Coldwell (Thomson
1931, p.33). In 1954 they were held by Bamoos Lake Mines Ltd. 1 .
The bedrock is predominantly gabbroic and includes the finemedium-,
and coarse-grained varieties characteristic of the
gabbros belonging to the Complex.
Layering is strongly developed
T The claims were optioned in 1964 to Anaconda American Brass Ltd.
and in 1966 were held by the Keevil Mining Group Ltd.

- 69 -
in the more westerly gabbros.
moderate, approximately 30O ,
The dips are to the west at
angles.
The gabbros contain numerous inclusions of metavolcanics,
generally of felsic composition.
A more mafic inclusion can be
observed along the shorelines at the eastern end of Bamoos Lake.
The gabbros are cut by numerous dikes of laurvikite
pegmatite which generally dip to the east at moderate angles.-
The gabbros contain two pyroxenes, olivine, and plagioclase.
The accessory minerals include ilmenomagnetite, apatite, sulphides
and mica.
The sulphides are predominantly interstitial and
include pyrrhotite, chalcopyrite and pyrite.
Exploration has included trenching, detailed mapping,
various geophysical surveys and diamond drilling.
Bamoos Lake
Mines Ltd. drilled the immediate gabbros in 1954 to test the
-^
copper potential.
Although the presence of mineralized, generally
coarse-grained, gabbros has been substantiated, the grade of
copper and the horizontal and depth continuity have not been
established.
The early investigations were directed toward the
ilmenomagnetite layers.
Analysis of a chip sample, taken along
the total length of a trench on the England claims, contained
40.0 percent iron, 7.35 percent titanium oxide, 0.56 percent
sulphur, and 0.33 percent phosphorous. (Thomson 1931, p.33).

- 70 -
Assessment files show that the iron content in the
ilmenomagnetite bodies was considerably lower and was up
to 27 percent.
Thomson (1931, p.35) referred to the presence of vanadium
from an occurrence of magnetite on the small island in the
lake east of Bamoos Lake as reported by H. England.
A grab
sample of magnetite ore from this outcrop was collected by
Thomson and assayed 0.48 percent vanadium.
The vanadium mineral was not apparently, definitely identified.
Thomson (1931, p.35) reported that Dr. T.L. Walker examined the
specimens and suggested that the sage-green coloured mineral,
occurring as films along joints, may be pintadoite, a hydrous
calcium vanadate*
NON-FERROUS BASE METALS
Early discoveries of copper mineralization of any significance
resulted from the efforts directed toward the exploration for iron
ore.
The base metal potential of the area, as related to the
gabbros of the Port Coldwell Alkalic Complex in particular, was
not given serious consideration until 1954.
Since then
investigations have ultimately become intimately involved with
the coarser-grained gabbro phases generally underlying the layered
and foliated gabbros.
The mineralized gabbros apparently dip

- 71 -
inward, at varying angles, toward the centre of the Port Coldwell
Alkalic Complex.
Results of exploration apparently indicate a general lack of
continuity in grade of mineralization, both horizontally and with
depth.
Assays to date indicate copper values ranging from 0.17 to
approximately l percent.
Nickel values appear to be consistently
low, varying from trace to 0.31 percent.
Moneta Porcupine Mines Limited
In 1954 Moneta Porcupine Mines Ltd. optioned a group of 47
claims from D. Smith and Z. Renshaw both of Marathon, Ontario.
This agreement followed the visit and examination in February,
1954, of a showing of copper mineralization by Patrick H. Taylor.
Z. Renshaw had originally staked 15 claims, ten of which
were immediately east of the optioned group.
All of these
claims were staked between 1950 and 1954 initially to include
a zone of high-magnetite rock.
Copper mineralization was
discovered during the performance of assessment work and led to
the subsequent staking of 32 additional claims by a group of
Marathon businessmen which included D. Smith, H. Taylor, G. Ross,
J. Graham, and C. MacMillan.

- 72 -
The claim block is cut by Trans-Canada Highway 17 and is
located approximately 7/8 of a mile west of Little Pic River.
The claims extend westward to Deadhorse Creek, approximately
1/4 of a mile north of the power line, and southward to the
shore of Lake Superior.
The claims are predominantly underlain by rocks belonging
to the metavolcanic-metasedimentary assemblage.
The easternmost
claims include all of the exposed gabbro describing the western
limit of the Port Coldwell Alkalic Complex.
The metavolcanics are generally very fine-grained, partly
schistose, and mafic in composition.
Pillow structure has been
observed in the vicinity of Middleton station and Trans-Canada
Highway 17.
The metasediments are predominantly argillites and
metagreywackes and outcrop along and to the south of the Highway.
Graded bedding is variably developed.
Tops are to the south.
The metasedimentary-metavolcanic assemblage exhibit structures
which predominantly strike approximately N70OW; and have near-
vertical dips.
The folds are isoclinal.
These structures are strongly flexured and dragfolded within
a ^ mile zone, generally exhibiting a high garnet content, which
lies immediately to the west of the gabbros of the Complex.

- 73 -
The metasedimentary-metavolcanic assemblage approximately
l mile north of the Highway has been cut by a post-deformational,
northwest-trending, diabase dike.
The gabbros of the Complex form a north-trending band
approximately \ mile wide, which is terminated north of the
Highway by the Little Pic River granite and related phases.
These gabbros vary from massive to layered phases to the east.
The layering strikes approximately N10OE and dips approximately
300 to the east (see Fig.9).
Pegmatitic phases of the gabbro cut, in part with a
horizontal attitude, the marginally located metavolcanics and
metasediments.
^ .
The layered gabbros appear to grade into layered laurvikites
to the east. Dikes of laurvikite pegmatite, generally dipping
to the west, cut the basal gabbros.
Ilmenomagnetite segregations occur in the gabbros, and to
a lesser degree in the laurvikites. These segregations generally
exhibit a conformable attitude with respect to the layered host
rocks. The largest body, exposed in the Highway cut located
7/8 mile west of the Little Pic River, is approximately 140 feet
wide. The ilmenomagnetite content varies between 10 to 30
percent.
Some segregations contain up to 80 percent of magnetite.

- 74 -
Red hornblende syenite dikes, with a variable quartz
content up to 10 percent, cut the gabbros, metasediments and
metavolcanics.
These dikes, in part at least, appear to have
been derived from the Little Pic River granite and related phases
to the north.
They strike approximately N10OE and dip steeply,
approximately 70OE.
The gabbros have been cut by nepheline-bearing and zeolitized
nepheline-bearing feldspathoidal pegmatites trending approximately
N50 -10OE and dipping steeply, approximately 70^. The marginal
phases generally include numerous inclusions such as layered
gabbro, ilmenomagnetite segregations, and massive gabbro.
The
gabbros, laurvikites, and feldspathoidal rock types of the
Complex have been cut by various lamprophyric dikes which
^
generally have an east-west strike and dip steeply, approximately
700N.
Mineralogically the gabbros are predominantly composed of
s
two pyroxenes, olivine, and plagioclase with variable amounts of
ilmenomagnetite, sulphides, apatite and biotite.
The sulphides are predominantly chalcopyrite and pyrrhotite
(maximum up to 6 percent) with minor amounts of pyrite and
bornite.
The sulphides generally appear disseminated and occur
interstitially with respect to the silicates comprising the
coarser textured gabbros.
Weathering has resulted in the

- 75 -
development of a little malachite.
Although generally fresh, some outcrops of gabbro containing
sulphides, ilmenomagnetite and apatite may exhibit a characteristic,
knobby weathered surface.
The associated gossan is usually
accompanied by an apatite-rich gravel formed in situ.
Exploration included detailed mapping, and trenching.
Three
gossan areas, approximately 700 feet apart and trending parallel
to the strike exhibited by the layering, were observed and
drilled in 1954.
One hole was drilled to test the mineralization
under each gossan.
The best results, 40 feet of 0.46 percent copper, were
obtained from DDK 3.
The mineralized gabbro dips SO0^, an
attitude conformable to that exhibited by the layering (Fig.9).
DDK 2 was collared approximately 100 feet south of the gossan
target.
This hole (and DDH 1) was drilled to test the possible
existence of mineralization having a vertical attitude.
Weak
mineralization, 5 feet of 0.07 percent copper, was intersected.
This may not reflect the true character of the mineralization.
DDH l intersected 5 feet of mineralization with the highest
assay being 0.16 percent copper.
Thirteen analyses were run for nickel, of which twelve
assayed nil and one returned but trace.

- 76 -
In general the drilling results appeared to indicate a
general lack of continuity in grade of mineralization, both
horizontally and with depth.
Lakehead Mines Limited
These holdings include a square of 25 claims centred,
more or less, around Mile Post 8 on the boundary of Township
79. These claims were staked by Head of The Lakes Iron Limited
in 1959.
Exploration, which included electromagnetic and dip
needle surveys, was followed up by diamond drilling in September,
1960. Approximately 17 holes were drilled to an average depth
of 338 feet.
Maximum depth of penetration (DDH 13) was 562 feet.
In 1963 the name of Head of the Lakes Iron Limited was
changed to Lakehead Mines Limited.
Lakehead Mines Limited presently hold approximately 87
claims which describe a rectangular block whose east limit
is represented by the west shore of Wullie Lake.
The west limit
of the claim block is approximately 5,000 feet west of the ^-
boundary of Township 79.
The area is predominantly underlain by gabbros and laurvikites
belonging to the Port Coldwell Alkalic Complex.
To the north the
gabbros intrude the metasediments and older granitic rocks.
l
Effective control belongs to Denison Mines Limited.

- 77 -
The metasediments are predominantly composed of quartz,
feldspar and mica and appear to represent argillites and, in part,
metagreywackes.
Minor massive, aphanitic and amphibolitic units
appear to represent intercalated metavolcanics.
The metavolcanic-metasedimentary assemblage appears to have
been intruded by granitoids of trondjhemitic and apparently earlier
and more syenitic phases.
These intrusions appear to be phases
of the granites comprising the Jim Lake Batholith.
In general the metavolcanic-metasedimentary assemblage
exhibits a strong E-W trending fabric with gentle dips, about
15O to 35OS.
The fabric is somewhat irregular in the vicinity
of the gabbro complex.
The gabbros to the north generally appear fresh whereas to
the south the gabbros are variably weathered to a buff brown
colour so as to appear syenitic.
The gabbros contain two pyroxenes, predominantly clinopyroxene,
and generaly olivine.
Plagioclase is the predominant mineral
component.
Important assessory minerals include biotite, apatite,
ilmenomagnetite and sulphides.
Ilmenomagnetite and apatite are
variable but generally comprise up to 10 percent of many phases.
Ilmenomagnetite segregations, generally conformable in attitude
to the layering have been observed.

- 78 -
The dominant sulphides contained by the mineralized gabbros
are pyrrhotite and chalcopyrite.
The sulphides are intimately
associated with the hydrous silicates and ilmenomagnetite
which occur interstitially with respect to the anhydrous silicate
framework.
"In 1954 Head of The Lakes Iron Limited contracted with
Aeromagnetic Surveys of Toronto for an aeromagnetic survey of the
Wullie Lake property and in 1959 Hunting Technical and
Explorations Limited conducted a helicopter electromagnetic survey
for the company.
A number of electromagnetic anomalies were
subsequently drilled and indicated the presence of magnetite-rich
layers containing minor chalcopyrite and occasional pyrrhotite.
Between 1961 and 1963 parallel line electromagnetic surveys
and a geological survey were completed over parts of the property
under the direction of Denison Mines Limited.
Further drilling
was recommended.
The investigation has indicated a mineralized gabbro apparently
exhibiting some continuity horizontally, and with depth, in grade
of copper. The mineralized gabbros dip about 350S . Assays up to
l percent copper and low nickel have been reported" .
l
V.G. Milne, Geologist, Ontario Department of Mines, Toronto

- 79 -
Conwest Exploration Company Limited
Conwest formerly held a group of 5 claims which was cut by
the Trans-Canada Highway 17 approximately 1^ miles east of the
Marathon 'cut-off.
Rock exposures are largely limited to a few road cuts due
to the presence of an approximately 40-foot thick mantle of
sand and gravel.
The property is largely underlain by fine
grained and more mineralized, coarser grained gabbros.
To the
south the gabbros are overlain by metavolcanics, namely,
metarhyolites and banded agglomeratic tuffs.
The contact is
sinuous but generally strikes N60OE and dips to the southwest
at moderate angles.
The contact is not always sharp but rather
characterized by the presence of a hybrid phase.
The contact area is further complicated by the presence of
numerous inclusions of metavolcanics in the gabbros.
Although it
is assumed that the metavolcanic contact represents overlapping
(i.e. fixed) portions of the country rock, the numerous
metavolcanic inclusions are interpreted as predominantly non-fixed,
(i.e. free-floating) and suggestive, at best, of near-hanging
wall environments.
The gabbros are cut by dikes of red hornblende syenite
bearing quartz.
These dikes rarely show marginal chill phenomena
and appear to represent remobilized phases of the metavolcanics.

- 80 -
The dikes are somewhat irregular and trend approximately N45O -
700E and dip steeply.
The youngest rock in the area is represented by a composite
dike of laurvikite which exhibits two definite sets of chill
surfaces.
The dike strikes N400W and dips about 40OSW.
The metavolcanics exhibit a buff brown weathered surface
and a dark grey fresh surface.
The banded agglomeratic tuffs
contain aphanitic, tuff bands up to approximately 15 feet wide
which alternate with much wider bands containing abundant inclusions
These inclusions or fragments vary in composition but are
predominantly fine-grained quartzites, schists, and massive
metarhyolites.
The fragments generally exhibit a high sphericity
and ellipticity (major axis is six times the minor axis).
The
major axis is contained in a plane which has an attitude identical
to the banding, namely; N20OW strike and 50O to 65O southwesterly
dip.
Thin section examination shows the metavolcanics near the
contacts to be composed of quartz, potassic feldspar, biotite,
hypersthene,clinopyroxene, and sulphides.
Quartz and (or) potassic
feldspar generally occur as megacrysts up to 3mm.
The quartz
megacrysts generally contain disoriented laths of plagioclase.
The structural fabric exhibited by the metavolcanic-
metasedimentary assemblage trends about N25OW and dips 68OSW.

- 81 -
The gabbros may contain abundant, up to 10 percent
biotite megacrysts (up to 30mm), apatite up to 8 percent, and
sulphides.
The mineralized gabbros are generally coarse-grained
with the sulphides, predominantly pyrrhotite and chalcopyrite,
occurring interstially.
Minor amounts of pyrrhotite, pyrite and chalcopyrite are
present in the contact phases of metavolcanics.
"The property has been examined by trenching, diamond
drilling and induced polarization surveys.
Anomalies outlined
by the geophysical survey were investigated by drilling 10
diamond drill holes.
The main mineralization located on the property occurs in
gabbro.
Diamond drill hole No.l intersected a zone of medium- to
coarse-grained mineralized gabbro about 100 feet wide (true
width 80 feet) and dipping about 60^. The mineralization
consists of pyrrhotite and chalcopyrite, with an average grade
of 0.4 percent copper.
Mineralization of a weak and disseminated
nature was reported to a depth of 506 feet (end of hole).
Small
metavolcanic intersections were reported but no large
intersection of footwall volcanics was encountered.
Diamond drillhole No.2 indicates that the main zone of
mineralization thins northwards' to about a 40-foot width with an
average grade of about 0.25 percent copper.
In the north the
mineralized zone dips about 50OW and the main footwall contact
l ~ ~~
Assessment files.

- 82 -
appears co dip about 65OW.
Numerous intersections with metavolcanics were reported and
bands of massive pyrrhotite, sometimes with chalcopyrite, are
o
mentioned as commonly associated with these metavolcanics. 11
Anaconda American Brass Limited
Anaconda began investigations, of a more serious nature,
in the summer of 1963.
A total of approximately 180 claims were
staked.
Presently the Company holds or has options on
approximately 421 claims which extend from the shore of Lake
Superior northward to Bamoos Lake and then northwestward to
beyond the Skipper Lake area.
This elongate and curved claim
group covers approximately 15 miles and varies in width from
one to five miles.
The area is predominantly underlain by gabbros belonging
to the Port Coldwell Alkalic Complex.
To the east the gabbros
can be found to intrude the rocks belonging to the metavolcanic-
metasedimentary assemblage.
Inclusions of country rock are
common within these gabbros.
The more westerly occurring gabbros are invariably layered
and (or) foliated.
These gabbros appear to grade westward into
laurvikites which are similarly layered.
The attitude of layering
I
V.G. Milne, Geologist, Ontario Department of Mines, Toronto.

- 83 -
in the laurvikites is, more or less, identical to that
exhibited by the underlying gabbros.
These attitudes may show
considerable variation, but in general the average dip is to the
west at moderate (i.e. approximately 30O )
angles.
The gabbros are cut by numerous, generally eastward dipping,
dikes of laurvikite pegmatite.
The youngest rocks in the claim group are represented by
several lamprophyre dikes.
The area is transected by numerous linears.
The more
prominent E-W trending linears, in the vicinity of Mile Post
17, appear to represent fault planes the movement along which
appears to have had more of a dip component.
The metavolcanics are predominantly felsic in composition.
Mafic metavolcanics occur to the north, in the vicinity of the
Jim Lake Batholith.
The felsic metavolcanics are predominantly agglomeratic
metarhyolites which normally are composed of quartz, alkali
feldspar, plagioclase, and clinopyroxene.
Accessory minerals
include varying percentages of biotite, chlorite, magnetite,
serpentine, actinolitic amphibole and sulphides.
The sulphides
are predominantly pyrrhotite and pyrite with minor to trace
amounts of chalcopyrite.
The mafic metavolcanics are predominantly
represented by fine- and coarse-grained amphibolitic schists and
gneisses.
Thin section examination shows these rocks to be

- 84 -
composed of plagioclase, actinolitic amphibole, garnet, biotite,
chlorite and magnetite.
The rocks belonging to the metavolcanic-metasedimentary
assemblage exhibit a structural fabric which generally trends
to the northeast. Dips are generally steep. Folds appear to be
isoclinal.
The northeast-trending structural fabric appears to
be more irregular in the vicinity of the Port Coldwell Alakalic
Complex.
In general the layered and (or) foliated gabbros appear to.
overlie the coarser grained, mineralized phases and the finer
grained, and generally less mineralized, gabbro phases.
The gabbros are composed of varying percentages of the
following minerals; orthopyroxene, clinopyroxene, plagioclase,
olivine, ilmenomagnetite, sulphides, apatite, biotite, actinolite
and serpentine. The sulphides generally occur interstially with
respect to the rock forming silicates. The sulphide minerals
identified include pyrrhotite, chalcopyrite, pyrite and bornite.
"The company began a geological investigation of the area
in 1962 and this continued through 1964. Trenching and pitting
has been done throughout the claim area. An induced potential
geophysical survey was completed in 1963 and drilling started in
late 1964.

- 85 -
Sulphide mineralization is scattered throughout the gabbro
unit but becomes significantly concentrated in some widely "^
separated localities. Assays indicate a variation in copper
from 0.05 percent to about 2 percent. Nickel values are
generally low. The great potential of the area is in its possible
development as a low grade, large tonnage open-pit operation 1.1
Falconbridge Nickel Mines Limited
MIn 1963 Falconbridge Nickel Mines Limited held a group of
claims in Township 76 on the west side of the Big Pic River.
The bedrock in the claim area consists of dark grey massive
olivine gabbro. The rock is essentially homogeneous but locally
it grades into large, irregular, pink masses consisting mainly of
perthitic feldspar.
Investigation of the claims included diamond drilling. Three
holes were drilled westerly from the same drill location on an
outcrop on the west bank of the Big Pic River. These holes
intersected gabbro and pink perthitic material over their entire
length. One hole was collared within the Big Pic River Lineament
and failed to intersect bedrock at a depth of over three hundred
feet.
No mineralization was encountered."2
1
V.G. Milne, Geologist, Ontario Department of Mines, Toronto.
2 V.G. Milne, Geologist, Ontario Department of Mines, Toronto.

- 86 -
BUILDING STONE
Laurvikites were first quarried near Marathon about 1880
by tne Canadian Pacific Railway for the construction of bridges
over the Big Pic and Little Pic rivers.
Cold Spring Granite Company
Small scale quarrying, on a commercial basis, was begun in
1927 by Peninsula Granite Quarries, Limited, under the management
of William Morrison. This company was purchased by Cold Spring
Granite Company in 1931 (Hewitt 1964, p.39).
The property consisted of a group of seventeen claims which
extended northward, beginning from the old Peninsula Station,
for approximately 2\ miles. The western limit was the shoreline
of Peninsula Harbour. The claims were cut by the Canadian
Pacific Railway line and quarrying operations were conducted on
both sides of the right-of-way.
The three southernmost quarries were located in the 'dark 1 ,
greenish coloured, laurvikites (so-called black granite); and
the northernmost quarry was located in the reddish coloured
phases of laurvikite (so-called red granite) (see Thomson 1931,
p.34 for location).

- 87 -
The mineralogical and chemical similarities between the
'dark 1 laurvikites from Marathon and the famous laurvikites
from Norway have already been mentioned by Kerr (1910, p.214).
An analysis of 'dark 1 laurvikite from the main southern
quarry, located approximately 18,000 feet west of the old
Peninsula station and 30 feet from the shoreline, is given
by Thomson (1931, p.37).
Mineralogically these 'dark' laurvikites are predominantly
composed of subhedral laths of perthite, which generally measure
12 mm by 8 mm and approximately 4 to 6mm wide. The laths of
perthites characteristically exhibit broad Carlsbad twinning.
In hand specimen the reddish phase appears very similar to
the 'dark'. The predominant mineral is perthite which occurs
as laths slightly smaller in size to that seen in the dark
laurvikites. In addition the Carlsbad twinning is less
prevalent and the iridescence, so spectacular in the perthites
in the darker phases, is more subdued.
Thin section examination shows the perthites to be
extensively stained by hematite. The ferromagnesian minerals
are predominantly hydrous.
Although the quality of the stone is high, apparent failure
to secure and (or) maintain the necessary markets forced the
curtailment of activities in the late 1930's.

- 88 -
Lake Superior Stone Syndicate
This syndicate was formed in April, 1960, by a group of
Toronto mining persons in response to information provided
by C.S. Downey, of North Bay.
The information was concerned
with the quarrying of the laurvikites near Angler.
In May and June of the same year a block of forty-seven
claims were staked which extended southward from Hare Lake to
within half a mile of the Marathon townsite.
These claims
included a block of eleven claims, at Angler, which were
formerly held by H. England, of Port Coldwell.
The laurvikites in the claim block are generally dark and
of good grade.
Research into the marketing of the laurvikite from these
sites was conducted into late fall.
Although quarrying was
scheduled to begin in the late fall of 1960 the apparent
^.^
failure to secure the necessary markets forced the indefinite
postponement of activity.
NEPHELINE
The first and only attempt to determine the nepheline potential
of the feldspathoidal syenites was made by Denison Mines Limited.

- 89 -
Denison Mines Limited
In early 1960 Denison Mines Limited staked two areas of
nepheline syenite immediately west of Redsucker Cove.
The
larger claim block, representing approximately twenty-three
claims, extends northward to the Trans-Canada Highway 17.
The dominant bedrock is composed of feldspathoidal syenites,
of variable femic content, and relatively minor but significant
amounts of variably nephelinized mafic metavolcanics.
These
metavolcanics are considered to belong to the so-called
Coubran Lake roof pendant.
The typical relationships between the feldspathoidal
syenites and mafic metavolcanics are exhibited in the larger
of the two occurrences.
The nephelinized metavolcanics are marginally located with
respect to the topographic 'high 1 .
The nepheline in these older varieties of nepheline syenite
exhibits a greasy lustre and is intimately associated with
and included by the various femagnesian minerals.
The younger phases of feldspathoidal syenite appear more
leucocratic and grade into progressively more zeolitic varieties.
Thin section examination showed the nepheline in these younger"
phases of feldspathoidal syenites to be variably altered to an
aggregate of radiating zeolites which include thomsonite and

- 90 -
natrolite.
This zeolitized nepheline is extensively stained
by hematite and in hand specimen appears as a pale orange
coloured, fine-grained mixture which has been referred to as
hydronepheline, ranite, or suprestein.
Numerous grains
exhibit a deeper orange colour and in these samples the
adjacent perthites are similarly tinted.
Specimens from the various nepheline properties were sent
by Denison to Lakefield Research for routine laboratory magnetic
separation.
For the older, and marginally located nepheline
syenite an initial coarse grind (perhaps to about \ of an inch)
was proposed (W.W. Moorhouse, private report).
This was
intended to separate the more nepheline-rich, leucocratic
portions from the less nephelinized and more mafic-rich
clusters and patches of mafic metavolcanics (Fig.10).
For the
more leucocratic and more centrally located phases of
feldspathoidal syenites, a cleaner separation of dark and light
minerals was achieved.
Unfortunately the later phases,
particularly the associated hypabyssal phases, contained
nepheline which is variably pseudomorphed by a mixture of
thomsonite and natrolite.
Since the iron content was not consistently reduced below
0.08 percent the development of these nepheline occurrences was
discontinued.

- 91 -
SAND AND GKAVEL
Fairly extensive areas of sand and gravel occur at
Neys beach, along the Kilalla Lake road, at Angler, and at
Marathon and immediate, vicinity extending eastward to within
\ mile of the Pic River.
A few claims have been staked by Anaconda American Brass
Ltd. with the sand and gravel being used as road fill.
Thomson (1931, p.35) makes mention of the pebble and
cobble stones present in gravels to the south.
Although
described as satisfactory for use in ball mills, no shipments
have been made.

- 92 -
Selected Bibliography
Adams, F.P.
1900: On the probable occurrence of a large area of nephelinebearing
rocks on the northeast coast of Lake Superior;
Jour. Geol., Vol. VIII, p. 322-325.
Barlow, A.E.
1913: The nepheline and alkali syenites of the Port Coldwell
area in Guide Book No.8, Twelfth Int. Geol. Congress,
Toronto to Victoria and return via Canadian Pacific and
Canadian Northern Railways, Part l, p. 16-24.
Benson, W.N.
1926: The tectonic conditions accompanying the intrusion of
basic and ultrabasic igneous rocks; Mem. Nat. Acad.
Sci. l, Vol. XIX, p. 1-89.
Billings, M.P.
1942: Structural geology, First Edition; Prentice - Hall,
New York.
Coleman, A.P.
1898: Port Coldwell region in Notes on the petrology of
Ontario; Ontario Bur. Mines, Vol. VII, pt.2,
p. 146-149.
1899a: Dike rocks near Heron Bay in Notes on petrography in
Copper regions of the Upper Lakes; Ontario Bur. Mines,
Vol. VIII, pt.2, p. 172-174.
1899b: A new analcite rock from Lake Superior; Jour. Geol.,
Vol. VII, p. 431-436.
1900: Heronite or analcite-tinguaite in Copper and iron
regions of Ontario; Ontario Bur. Mines, Vol. IX,
p. 186-191.
1902: Syenites near Port Coldwell; Ontario Bur. Mines,
Vol. XI, p. 208-213.
Farrand, W.R.
1960: Former shorelines in western and northern Lake
Superior basin; unpublished Ph.D. thesis, Dept. of
Geology, Univ. of Michigan, Ann Arbor, U.S.A.

- 93 -
Gill, J.E.
1955: Precambrian nomenclature in Canada; Royal Soc.
Canada, Trans., Illrd Series, Vol. 49, Section
IV, p. 25-29.
Hess, H.H.
1960: Stillwater igneous complex, Montana; Geol. Soc.
America, Mem. 80.
Hewitt, D.F.
1964: Building stones of Ontario, Part V, Granite and
gneiss; Ontario Dept. Mines, Industrial Mineral
Kept. No. 19.
Hough, J.L.
1958: Geology of the Great Lakes; University of Illinois
Press, Urbana, Illinois, U.S.A.
Kerr, H.L.
1910: Nepheline syenites of Port Coldwell; Ontario Bur.
Mines, Vol. XIX, pt. l, p. 194-232, accompanied by
map 19b.
Logan, W.E.
1846-7: Report of Progress 1846-7; Geol. Surv. Canada.
(Published 1847).
1863: Geology of Canada; Geol. Surv. Canada.
Milne, V.G.
1967: Geology of the Cirrus Lake - Bamoos Lake area,
District of Thunder Bay; Ontario Dept. Mines,
Geol. Rept. No. 43, accompanied by maps 2098 and
2099.
Pye, E.G.
1957: Geology of the Manitouwadge area; Ontario Dept.
Mines, Vol. LXVI, pt. 8, accompanied by map 1957-
8. (Published 1960).
Sitter, L.U.de
1956: Structural geology, First Edition; McGraw-Hill
Book Co., New York. 1

- 94 -
Thomson, J.E.
1931: Geology of the Heron Bay area, District of Thunder
Bay; Ontario Dept. Mines, Vol. XL, pt. 2, p. 21-39,
accompanied by map 40d.
Walker, J.W.R.
1956: Preliminary report on the geology of the Jackfish
- Middleton area; Ontario Dept. Mines, Geol. Circ.
No. 4.
1961: Geology of the Jackfish - Middleton area, District
of Thunder Bay, Ontario; unpublished Ph.D. thesis,
University of California, Los Angeles, 90024, U.S.A.
Walker, T.L. and Parsons, A.L.
1927: Contact phenomena of the nepheline syenites of
Port Coldwell, Ontario; University of Toronto
Studies, Geol. Series No. 24, p. 28-32.

per on.lt" area.
Figure 1
Contour diagram of joints in Precambrian metavolcanicmetasedimentary
sequences in the Port Coldwell area
lower hemishpere plot of 1300 poles.
'

,
Figure 2.
Contour diagram of joints in Jim Lake grsr.ite, lower*
hemisphere plot of 700 poles.

L o.mpro pK-j r
Jim L aUa. grarxiie.
Figure 3
Dilation features exhibited by the lamprophyre
dikes emplaced along the extension joints
in the Jim Lake granite.

O
B QMD EH T::]
Figure 4. Contour diagram of joints in the v main s series of rocks
of the Port Coldwell Alkalic Complex. Lower heinishpere
plot of 1900 poles.

o- 10/;
~
igure J .
roo
2r"a:n of joints in Coubran Lake rae'Gavolcam.
onarG Lcv/er* hemisphere plot of 861 poles.

f
[ mn
..J
Figure 6,
Contour diagram-of joints in the larger bodies iZ
lower hemisphere plot
poles

iigure
syente vens ao
the metavolccinics 5 which have been rea
during emplacement,, From portion c.: C
Li a. K e metavolcaniLC rooi pendant 3 4 n".-.^.e
of Port Coldwell station, along the Tr
Highway 17.
; ivatea
noraheas
iE# ^-* ill.*"^ *^ ^~^ 1O^

Figure 8
Sketch illustrating the repeated reactivation of jointing
with concomitant intrusion of feldspathoidal syenite dikes

f
Figure 9
Surface Gfolop;ical Plan of Part of the Property of Mon^ta
Porcupine Mines Limited showing the Relative Locations of
Gossan Zones and Diamond Drill Holes (Modified from a
plan by. G. Perrault).

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ONTARIO DEPARTMENT OF MINES
PRELIMINARY GEOLOGICAL MAP No. P.114
PORT COLDWELL AREA
DISTRICT OF THUNDER BAY
V'' .S^C. '--'J
Scale l inch to ^ mile
N.T.S. Reference: 42D/9, 42D/10, 42D/15, 42D/16
O.D.M.-G.S.C. Aeromagnetic Maps: 2146G, 2147G, 2156G, 2157G
LEGEND
^
7a
CENOZOIC
RECENT
Beach and river deposits, peat
PLEISTOCENE
Sand. gravel, boulders and pebbles; silt, varved clay
UNCONFORMITY
X3--X
PRECAMBRIAN
LATE GRANITIC ROCKS
15a
15b
15c
15d
15e
15f
Biotite-hornblende granite
Hybrid granite
Hybrid syenite
Hybrid pegmatite
Mylonitized granite
Hybrid porphyritic syenite
INTRUSIVE CONTACT
PORT COLDWELL ALKALIC COMPLEX
14
13
Perthosite (dikes)*
INTRUSIVE CONTACT
A
Lamprophyre (dikes)
INTRUSIVE CONTACT
SECONDARY SERIES
UNSATURATED ROCKS -"
12 Analcite tinguaite (dikes)*
INTRUSIVE CONTACT
k ?v
11 Natrolite-perthite rock (dikes)
INTRUSIVE CONTACT
lOa
lOb
lOc
Leucocratic nepheline syenite
Leucocratic nepheline syenite, trachytic texture
Melanocratic nepheline syenite
INTRUSIVE CONTACT
SATURATED ROCKS
r \\ X
•f \\, 7o
9a
9b
9c
Nordmarkite, undifferentiated
Nordmarkite, aphanitic to fine-grained
Nordmarkite, aphanitic to fine-grained, porphyritic
GRADATIONAL CONTACT
Middleton
jL - H ii'
l 7e /l
\( \C\\ \ \\ 7a
,! Xv\ \ U ' a
8a
8b
8c
8d
8e
8f
Syenodiorite, undifferentiated
Syenodiorite, fine-grained, red amphibole
Syenodiorite, fine- to medium-grained, ophitic texture
Syenodiorite, fine-grained, porphyritic
Syenodiorite, fine-grained, porphyritic with potassic
feldspar alignment
Syenodiorite, fine-grained, plagioclase rimmed by
potassic feldspar
GRADATIONAL CONTACT
MAIN SERIES
PRISONER
COVE
X ^ 7a \ \
' I \
-"- /le/ lOcV
X^\
* l IT^^
7a Laurvikite, undifferentiated
7b Laurvikite pegmatite
7c Laurvikite, fine-grained
7d Laurvikite, fine- to medium-grained, porphyritic
7e Laurvikite, massive, reddish-stained, high
barkevikite content
7f Laurvikite, layered
7g Laurvikite, greyish, highly exsolved, contact phase.
PREDOMINANTLY CONFORMABLE, PARTLY GRADATIONAL CONTACT
6a
6b
6c
6d
6e
6f
Gabbro, undifferentiated
Gabbro, feldspathized
Gabbro, layered
Gabbro, coarse-grained, ophitic textured, pegmatitic
Gabbro, massive, sulphide-bearing
Gabbro, massive, fine- to medium-grained
INTRUSIVE CONTACT (GRENVILLE OROGENT)
LATE MAFIC INTRUSIVE ROCKS
CRADDOCK
COVE
5 Diabase, porphyritic diabase
INTRUSIVE CONTACT
M//V/C HARBOUR
GOOD HOPE^f
ISLAND
MONMOUTH
ISLAND
STURDEE
COVE
\!l \
I/'
6a,6b
EARLY GRANITIC ROCKS
4a Biotite-hornblende granite, undifferentiated ) Jim
Ab Biotite-hornblende granite gneiss ) Lake
4c Biotite-hornblende granite, recrystallized ) Batholith
4d Trondhjemite, grey, massive
INTRUSIVE CONTACT
GUSE
PT
MOSS
THQMPSON
i ^-IW f c^:r-.^
* . * . . f 110 -. y
PENINSULA
DETENTION
ISLAND
PENINSULA BA Y
8c,d
NEUVE'CHAPELLE
POINT
BLONDIN
ISLAND
MANITOBA
SHOAL
PENINSULA HARBOUR
POINT
JOHNSON
SKIN VQ
ISLAND
HARBOUR
METAVOLCANIC-METASEDIMENTARY ASSEMBLAGE**
METASEDIMENT^
3a Bedded metagreywacke, minor argillite
3b Biotite-quartz-plagioclase schist
3c Garnet-biotite-quartz-plagioclase schist
FELSIC METAVOLCANICS
2a Agglomeratic rhyolite
2b Rhyolite agglomerate
2c Tuff, banded tuff, agglomerate
2d Porphyritic rhyolite
2e Fine-grained quartz-sericite schist
MAFIC TO INTERMEDIATE METAVOLCANICS
l
la
Ib
le
Id
Basalt, andesite
Pillow lava
Aphanitic, amygdaloidal basalt, andesite
Diabase (lava)
Game t-plagioclase-amphibole gneiss
NORTHWEST
BAY
SULLIVAN
ISLANDS
9b
(V SLYBOOTS
ROCK
HAWKINS
ISLAND
PEN!NSULA 7
7a
./fZ.Z./^Of
ir^l/f
m
X
Marathon
Brecciated inclusions of gabbro, generally
much altered (unless otherwise coded).
* Not shown.
** Age relationships between the major rock units is not definitely known,
BLACK
ROCK
LXI/CE
SUPERIOR
/3t\ ^ rf
LIST OF PROPERTIES
(circa 1963-64)
1.
2.
Anaconda American Brass Ltd.
Cold Spring Granite Company
3. Conwest Exploration Company Ltd.
4. Denison Mines Ltd.
5. Empire Explorations Ltd.
6. Falconbridge Nickel Mines Ltd.
7. Lakehead Mines Ltd.
8. Lake Superior Stone Syndicate
9. Moneta Porcupine Mines Ltd.
10. Olson, George
11. Renshaw, Zebe
ALLOUEZ
ISLAND
I0c,l
MALE ROCK
SOURCES OF INFORMATION
Geology by H.V. Tuominen and assistants, 1958, 1959; F.P. Puskas
1960, 1961.
Additions and correction by F.P. Puskas, 1966.
Base map derived from maps of Forest Resources Inventory, Ontario
Department of Lands and Forests.
Issued 1961, re-issued 1967.
ODM 4225