Abstract

The Elder deposit is located on the southeast border of the Flavrian Batholith, which intrudes the Blake River Group of archean volcanic rocks. The ore zone is composed of veins 1, 3, 5, and 4. The first three veins are a series of brecciated quartz veins having mean strike and dip of N72°E and 28°SE. Least important is vein 4, striking N20°W and dipping 28°NE. A reverse fault and a mafic dike are associated with the main vein 1, which occurs within trondhjemite in contact with hybrid rocks. The mafic dike represents an important metallotect. The ore zone is marked by abundant carbonates and pyrite, is slightly enriched in hematite and rutile, and is lightly depleted in sericite and chlorite. The mineralogical variation depends on CaO, MgO, CO2, S, TiO2, Fe2O3, MnO, and P2O5 enrichments and SiO2, Na2O, Al2O3, and H2Odepletions. A gold-bearing halo 8 m wide surrounds the ore zone. Seventy-nine per cent of the gold grains are associated with pyrite; otherwise gold occurs mostly as inclusions in the plagioclase matrix. Gold enrichment and rare-earth-element (REE) losses in the ore zone are similar to those observed in other Abitibi gold mines. In veins 1, 3, and 5, divergences in Ag and As enrichments, gold content, and REE concentrations suggest different ore-forming solutions.[Journal Translation]

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