MERN - Québec Mines Diamonds in the Apple Formation?

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June 2004

Diamonds in the Apple Formation?

Claude Dion and Jean Goutier
Direction de Géologie Québec


The Apple Formation (Goutier et al., 1998, 1999, 2000; Paquette and Gauthier, 1997) in the Lac Yasinski area (NTS sheet 33F), Baie James region, is a quartz-rich sedimentary unit composed of quartz arenite and pyritic and uraniferous conglomerate. This unit (PDF Format, 411 Kb) unconformably overlies the Archean basement, which consists of tonalitic gneiss of the Langelier Complex (2.78 to 3.6 Ga). The Apple deposit (map sheet 33F/02) is a uraniferous conglomerate-type deposit (Goutier et al., 1999) with a geological resource of 8.5 Mt at 0.052% U3O8 (Robertson et al., 1986). This deposit, discovered by Canico in the early 1970s, bears some resemblance to paleoplacer-type gold or uranium deposits found in the Witwatersrand Basin in South Africa and at Elliot Lake in Ontario (Gauthier et al., 1997). However, gold grades at Apple are low (below 100 ppb Au; Paquette and Gauthier, 1997).

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Apple Deposit

Heavy mineral accumulations encountered in placer-type deposits constitute important resources for several mineral substances such as precious metals (gold, platinum group elements), oxides (cassiterite, rutile, magnetite, ilmenite), industrial and high-technology minerals (garnet, zircon, monazite), and gemstones (diamond, ruby, sapphire). In Québec, these types of deposits are known to occur in the Beauce region (gold placers) and in the Côte-Nord region (heavy mineral deposit at the mouth of the Rivière Natashquan). Paleoplacers are similar deposits that were subsequently modified to various degrees by metamorphism and hydrothermal fluid circulation, and that have been preserved through geological time. The Apple deposit is a rare example of this type of mineralization in Québec.

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