The origin of base metal indicator minerals from till and stream sediment samples: constraints from mineral chemical and S-Pb isotope geochemistry

King, Robert (2022) The origin of base metal indicator minerals from till and stream sediment samples: constraints from mineral chemical and S-Pb isotope geochemistry. Masters thesis, Memorial University of Newfoundland.

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Abstract

Base metal indicator minerals recovered from till and stream sediment samples in the southern Northwest Territories were studied to determine their potential origins. Major and trace element geochemistry and S- and Pb-isotopes were used to determine whether these indicator minerals were derived from known mineralised bedrock sources or if they were from undiscovered mineral occurrences within the southwestern Northwest Territories, a region with very little previous mineral exploration and thick Quaternary cover. The geochemical and isotopic composition of sphalerite grains indicates derivation from low-temperature (T<250°C) sources consistent with Mississippi Valley-style mineralisation, yet distinct from known nearby mineral occurrences. Galena grains also have geochemical signatures indicative of derivation from low-temperature mineralisation; however, Pb-isotopic data, and previous provenance studies, indicate they were not from the Pine Point deposit or other known mineral occurrences and together with sphalerite represent potentially undiscovered Zn-Pb mineralisation in this area. The geochemical and δ³⁴S compositions of chalcopyrite grains suggest that they were likely derived from low-temperature sources, such as sediment-hosted Cu, and/or kipushi-type deposits. Arsenopyrite grains have δ³⁴S signatures similar to that of igneous sources (i.e., δ³⁴S = ±3‰), the only source of which would be fluids from Canadian Shield basement rocks, remobilized along basement faults in the region.

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