<strong>Moose</strong> <strong>River</strong> <strong>Basin</strong> blue-green hornblende, altered pyroxene <strong>and</strong> hypersthene, medium pink gar net, some orange garnet, <strong>and</strong> low magnetite <strong>and</strong> ilmenite, pyrite, siderite <strong>and</strong> staurolite twins. The "upper" Mattagami Formation s<strong>and</strong>s of 75-05 <strong>and</strong> 75-06 are poorly calcareous (with dolomite dominating calcite), white, well sorted, angular, low sphericity, very pure, fine silica s<strong>and</strong> containing much kaolinitic clay matrix, some brown <strong>and</strong> black organics, <strong>and</strong> quartz <strong>and</strong> Precambrian granules. They have a low heavy <strong>mineral</strong> content of relatively high magnetite <strong>and</strong> ilmenite, siderite, pyrite, twinned staurolite, rutile, biotite, dolomite <strong>and</strong> spinel, medium high blue-green hornblende <strong>and</strong> pink garnet, <strong>and</strong> somewhat lower pyroxenes. The "lower" s<strong>and</strong>s of drillhole 75-06 are calcareous (with equal dolomite <strong>and</strong> calcite), white, moderately sorted, angular, high sphericity, fairly pure, medium to coarse silica s<strong>and</strong> containing little matrix, abundant black lignite in places <strong>and</strong> equal proportions of limestone, quartz <strong>and</strong> Precambrian pebbles <strong>and</strong> granules. Compared to overlying s<strong>and</strong>s they have a relatively higher green-brown hornblende, pyrite <strong>and</strong> topaz, <strong>and</strong> lower blue-green hornblende, altered pyroxene, enstatite <strong>and</strong> rutile percentages. Several samples contain traces of indicolite, <strong>and</strong> pyrite is very abundant, occurring as authigenic framboids, euhedral cubes <strong>and</strong> organic pseudomorphs. This unit is tentatively sepa rated as a deposit of slightly different age, character <strong>and</strong> possibly derivation, although it is assumed to be still within the Lower Cretaceous. It differs from the overlying more typical Mattagami Formation s<strong>and</strong>s in having slightly coarser grain size, higher sphericity, higher carbonate,lignite, <strong>and</strong> limestone contents, but slightly lower sorting, purity <strong>and</strong> matrix content, <strong>and</strong> contains several characteristic pegmatite <strong>and</strong> igneous <strong>mineral</strong>s (topaz, indicolite, com mon hornblende). SYNTHESIS OF DATA A simplified cross-section through the <strong>Moose</strong> <strong>River</strong> <strong>Basin</strong> using informa tion from the six winter 1975 drillholes is shown in Figure 3.6. The Middle Ju rassic Mistuskwia Beds are restricted to the central part of the basin, pinching out between drillholes 75-02 <strong>and</strong> 75-04. The older phase of Lower Cretaceous deposition, which is lignite-bearing, is probably confined to the south <strong>and</strong> southeastern parts of the basin. The younger Lower Cretaceous phase extends over most of the basin but eventually pinches out in the northwest near drill hole 75-02. Petrographic <strong>and</strong> heavy <strong>mineral</strong> characteristics for the units described in this study are listed in Table 3.2. The Middle Jurassic deposit is particularly characterized by s<strong>and</strong>s with high rounding <strong>and</strong> sphericity, containing lime stone (Paleozoic) <strong>and</strong> Precambrian granules, <strong>and</strong> a very restricted detrital heavy <strong>mineral</strong> assemblage. These qualities indicate a dominantly sedimentary source with minor input from metamorphosed igneous rocks. The deposit ap pears to be deltaic, in a general sense, <strong>and</strong> likely built out from the northwest. The older Cretaceous phase contains high sphericity s<strong>and</strong>s with a high or ganic content <strong>and</strong> a heavy <strong>mineral</strong> assemblage which suggests a dominantly unmetamorphosed igneous provenance (mafic <strong>and</strong> granitic/pegmatitic rocks). 70
Petrography of Mesozoic <strong>and</strong> Pleistocene S<strong>and</strong>s 180-1 75-03 75-02 75-04 150- 120- 90- 75-01 PI 75-05 . PI * 60- "v Z C 2 \ . PI PI C2 0- J\ \ Ci Pi-Pleistocene C2"Maltagami PhaseE Ci- Mattagami Phase I 30- -30- -60- J - Jurassic P- Paleozoic -90 J Figure 3.6-<strong>Basin</strong>al Cross Section from drillhole information. 71