Genesis of barite associated with the Lemarchant Zn-Pb-Cu-Ag-Au-rich volcanogenic massive sulfide (VMS) deposit: implications for the genesis of VMS-related barite, Cambrian seawater chemistry, and the origin of barite-rich VMS deposits

Lajoie, Marie-Ève (2017) Genesis of barite associated with the Lemarchant Zn-Pb-Cu-Ag-Au-rich volcanogenic massive sulfide (VMS) deposit: implications for the genesis of VMS-related barite, Cambrian seawater chemistry, and the origin of barite-rich VMS deposits. Masters thesis, Memorial University of Newfoundland.

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Abstract

The Cambrian Tally Pond group hosts the Zn-Pb-Cu-Ag-Au-Ba Lemarchant VMS deposit. Despite the presence of barite in the deposit, the detailed relationships to mineralization, textural variations, and genesis are not well understood. Barite in the Lemarchant deposit is generally massive and locally bladed. Trace element as well as stable and radiogenic isotopic signatures of barite crystals are remarkably homogeneous regardless of texture. The results presented herein reveal a complex origin for the barite indicating input from Cambrian seawater and mixing with VMS-related hydrothermal fluids. Fluid inclusion studies of bladed barite show three types of fluid inclusions. Low-salinity carbonic-rich inclusions are the most abundant, but these inclusions are interpreted to be secondary in origin. These results illustrate that barite in VMS deposits is useful for recording physical and chemical processes associated with the formation of VMS deposits. In addition, the study of barite is useful for identifying potential sources of hydrothermal fluids responsible for the formation of barite and associated mineralization in the Lemarchant deposit and in other barite-rich VMS globally.

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