Moose River Basin: geology and mineral potential - Geology Ontario

Lignite and Industrial Mineral Resources
shown in Figure 2.11.
Examination of outcrops in Adam Creek, east of the Mattagami River in
Kipling Township, established the occurrence of quartz sand-kaolinitic clay
and fireclay deposits in this area (Telford et al. 1975). Drillhole samples were
analysed by staff of the Geoservices Section, Ontario Geological Survey. Com
posite samples of quartz sand and associated clays, representing drillhole sec
tions shown in Figures 5.5 to 5.8 were described and tested for size distribution,
mineralogy, chemical composition, and physical characteristics.
The presence of kaolinitic clay in quartz sand was qualitatively established
in samples of water flushing the drill chips to surface in reverse circulation
drilling. Otherwise the -325 mesh fraction in all but one composite sample of
sand was found to be fine quartz silt. The exception was sand 4 (Figure 5.5) in
which an appreciable amount of chlorite, illite and expanding clay occurred.
Geology
Little is known about the disposition of the pre-Mesozoic erosion surface in
the Moose River Basin. The underlying Paleozoic strata generally dip from 30
to 50 towards the centre of the basin but changes due to local folding are com
mon. In the Coral Rapids area, local folding is probably associated with intru
sion of post-Middle Devonian lamprophyre and kimberlitic dikes and sills
(Bennet et al. 1967, p. 31). The Grand Rapids area, on the Mattagami River, has
reversed dips ascribed by Martison (1953, p. 54) to a gently undulating base
ment floor. Sections obtained by drilling and geophysical surveys, done during
the winter of 1975, showed a generally flat, near-horizontal Paleozoic surface.
In detail, this surface is dissected by occasional faults with a vertical displace
ment of up to 40 m. The faults were detected in seismic and resistivity profiles
and are postulated to intersect both the Paleozoic and Precambrian surfaces.
Their strike was not determined.
To the south, the Paleozoic surface dips downward towards the Precam
brian escarpment. The escarpment is the topographic expression of an older,
east-trending fault zone which controlled deposition of Paleozoic and younger
rocks in the southern part of the basin (Bennet et al. 1967, p. 31). It occurs at an
elevation of approximately 155 m above sea level, and its location is marked by
falls and rapids in the river courses.
The present surface of the Moose River Basin slopes gently towards James
Bay. Near the Precambrian escarpment which occurs approximately at 155 m
a.s.I., river valleys approach elevations of 91 m. A gradual decrease of elevation
occurs between here and the coast. In a distance of approximately 240 km the
decrease amounts to an average of 0.4 m per km for the large rivers, and ap
proximately 0.6 m per km for the land in between. Under these conditions
drainage is so incomplete that most of the area consists of muskeg, bog and
swamp, with islands of wooded terrain in between.
Major deposits of quartz sand and vari-coloured fireclays are found in the
Mattagami and Missinaibi River area immediately north of the Precambrian
escarpment (see Figure 5.4); other deposits underlie a smaller basin at Onaka
wana. The Onakawana basin is limited by the Grand Rapids Arch to the south-
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