Abstract

The native-silver-bearing deposits of the Great Bear Lake region occur within two separate domains, namely the Echo Bay sector and the Camsell River sector. In all these deposits, native silver occurs in veins, associated with a wide range of Ni-, Co-, and Fe- arsenides, Cu-, Fe-, Ni-, and Co-sulfides, and pitchblende in gangues of quartz, calcite, dolomite, siderite, rhodochrosite, and fluorite. The host rocks of the veins are for the most part Aphebian volcano-sedimentary roof pendants within the Great Bear batholithic complex. The carbonates (calcite, dolomite, siderite, and rhodochrosite) show a wide range of δ18O (6.8 to 22.5‰, SMOW) and δ13C (−2.7 to −13.3‰, PDB) values. A single analysis of quartz gave a δ18O value of 16.54‰ (SMOW). The δD of water in fluid inclusions in quartz, dolomite, and calcite shows a range from −62.2 to −98.5‰ (SMOW). The δD of present-day meteoric waters from the region shows a range of −146.5 to −165.2‰ (SMOW). The δ18O of the hydrothermal fluids (0.47 to 9.12‰, SMOW) was calculated from the δ18O values of the quartz, calcite, and dolomite belonging to different paragenetic sequences. The δ13C of carbon (−2.8 to −8.6‰, PDB) in the hydrothermal fluid was calculated from the δ13C values of the calcites. The oxygen, carbon, and hydrogen isotopic values indicate that in the early stages of mineralization, magmatic water and carbon from a magmatic source were predominant. During the late stages of mineralization, the influence of meteoric water became more pronounced.

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