Moose River Basin: geology and mineral potential - Geology Ontario

Lignite Potential of Moose River Basin
Lignite and Industrial Mineral Resources
In an evaluation of lignite potential of the Moose River Basin it is neces
sary to consider various parameters. Beginning with the overall size of the area
underlain, or rather, expected to be underlain by Mesozoic sediments, an upper
limit is immediately imposed. This area is presently considered to be of the or
der of 7000 km2 . The particular basin configuration required to allow protected
growth and accumulation of vegetative matter protected from erosion, dilution
with inorganic matter, or introduction of oxidising fresh water currents, fur
ther limits the scope for significant lignite deposits. Assuming that major river
courses of the pre-Pleistocene period were comparable in number and size to
the present ones the area favourable for lignite deposition remaining is about
2,000 km 2 .
The chance of lignite accumulation actually having occurred in favourable
areas must be estimated conservatively in view of the failure, thus far, to detect
any significant deposits outside Onakawana. If estimated to be limited to 10
percent then a mere 200 km2 remain.
The effect of fossil river courses is twofold. At the time of accumulation,
major rivers would have impeded continuous accumulation in their immediate
environment. Subsequent to their period of accumulation lignite deposits be
came subject to erosion, particularly when in the path of major streams. Such
streams may have altered their courses frequently in the areas underlain by
unconsolidated Mesozoic sediments. The aggregate effect reduces the lignite
potential of the Moose River Basin, bringing the area in which significant lig
nite deposits are estimated to occur to below 200 km2 . The possibility that ero
sion of deposits has caused potentially economic accumulation of lignite else
where, as lignite gravel, is remote since existing lignite gravels show a high
ash content due to admixed mineral matter.
The Onakawana deposits occur in two to three separate layers with an ag
gregate average thickness of 10 m. The geological parameters determining ac
cumulation, whether linked to basin subsidence or sea level rises, are not suffi
ciently well known to speculate on the possible thickness of deposits elsewhere.
It is prudent to consider thicknesses encountered at Onakawana as maximum
for the Moose River Basin as a whole. In view of the marginal economic feasi
bility of developing the Onakawana deposits which occur adjacent to an estab
lished railway line it may be reasoned that the area required for deposits else
where, in order to be economic, needs to be much larger. This condition applied
to a potential total area of 200 km2 reduces the estimated maximum number of
significant lignite deposits to:
200
——————————————— =
200
——— =4.8
2 x area Onakawana deposits 2x21
The possibility of finding a deposit of the size of Onakawana by drilling has
been estimated to have 90 percent chance of success when about 400 holes are
drilled over the entire basin. (T. Pauk, Ontario Geological Survey, personal
communication). In view of the ^3 reduction in basin area since 1974, the equiv
alent number of required holes is now 266. It is obvious that at this stage much
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