Cargill Township carbonatite complex, District of ... - Geology Ontario

CARBONATITE - ALKALIC ROCK COMPLEXES: CARGILL TOWNSHIP
At the southwest end of the south subcomplex, kaolinite at least 22 m in
thickness occurs beneath the quartz sand at one location (Sandvik and Erdosh
1977, p.92). The sand-clay unit is variable in thickness but reaches 130 m in
thickness in one of the preglacial troughs (Sandvik and Erdosh 1977, p.92).
Overlying the preglacial overburden are stiff, varved, tan to grey lake clays
(Sandvik and Erdosh 1977, p.92). Sandvik and Erdosh (1977, p.92) reported
that these clays range from 1.5 to 10 m in thickness and average between 6 and 8
m. Erdosh (1979) correlated these clays with glacial Lake Barlow-Ojibway.
A sample of organic material recovered from drill hole B1-1A at a depth of
345 to 350 feet was donated to the Ministry by the International Minerals and
Chemical Corporation and examined by G. Norris of the University of Toronto.
Norris reported that the sample is tentatively Campanian (Late Cretaceous) to
Paleocene (Early Tertiary) in age. The organic material contains pollen not previ
ously reported in North America and which has been previously considered to be
indicative of arid warm climates (G. Norris, personal communication). The unit is
not correlative to units presently known in the Moose River basin where Upper
Cretaceous is absent (G. Norris, personal communication). One of the fluids used
for drilling contained Quik-Gel, a Baroid of Canada Limited product, which is a
bentonite of Cretaceous age mined in Wyoming (G. Erdosh, written communica
tion). Contamination by drilling mud is unlikely since Cretaceous floras of the
western interior are distinctly different from eastern floras (G. Norris, personal
communication, 1977).
Len Kelley (geologist, Sherritt Gordon Mines Limited, personal communica
tion, 1981) reported that in the centre of the complex a north-south trough
300-400 m in length and less than 100 m in width is present. This trough consists
of stacked layers of sand, clay, peat, organic sand and clean sand. The individual
layers are reported by Kelley to vary between 3 and 8 m in thickness. Sides of the
trough are steep and locally the trough exceeds 75 m in depth. The trough ap
pears to have formed by progressive collapse concomittant with deposition of the
sediments, and leaching of the underlying carbonate (L. Kelley, personal commu
nication, 1981). The trough filling is Cretaceous sediments and visual examina
tion of the sand and clay by the author suggested that it may have too many
impurities to be of economic interest.
In 1981, the author visited the site of stripping operations being undertaken
by Sherritt Gordon Mines Limited to uncover the apatite-bearing residuum. On
the basis of this stripping and a sonic drilling program undertaken by the company
to futher evaluate the results obtained by the International Minerals and Chemi
cal Corporation (Canada) Limited, a consistent pattern of stratigraphy of the
overburden has been established. Len Kelley (personal communication) has pro
posed the stratigraphic column shown in Table 2 for the overburden lying above
the Cargill residual apatite deposits.
The glacial and preglacial deposits were described by Kelley (1984a) as fol
lows. The stiff, tan-coloured clay of glacial Lake Barlow-Ojibway consists of
varves l to 10 cm thick. The glaciolacustrine clay averages 2 m thick and overlies
an average of 15 m of grey-green glacial till composed of clay, sand, silt, cobbles
and boulders. The glacial sediments overlie brown-black organic rich quartz sand
with numerous layers of peat, kaolinite and clean, white, well sorted sand l to 4
m thick. These late Cretaceous to Paleocene sediments may locally total approxi
mately 80 m in thickness. The white quartz and the kaolinite are nearly pure.
Kelley (1984a) proposed that a coal swamp depositional environment existed
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