UBC Theses and Dissertations
Structural, mineralogical and fluid evolution of the Shahumyan intermediate sulphidation vein deposit, Kapan district, Armenia Yarra, Dharani Raja
The Kapan District located in the Syunik province of SE Armenia is part of the Lesser Caucasus. The district consists of multiple vein type deposits that were emplaced in the Middle-Upper Jurassic. The Shahumyan deposit is the only actively producing deposit within the district. Understanding vein geometry, and hydrothermal fluid evolution is fundamental in establishing the genesis and exploration significance within an epithermal vein district, providing both near mine and district scale targets. Over 120 veins of varying thicknesses (20cm to 3 m) are identified at the Shahumyan deposit. The veins are sub-vertical, south-dipping and trend east to northeast. Veins comprise of small bends, extensional jogs, soft and hard linked step-overs, pinch and swell structures and cymoid loops. These features are observed along both strike and down-dip of individual veins and contain higher metal grades relative to the rest of the vein. Along strike and down-dip connectivity of these structural features define high-grade ore-shoots within mineralized veins. Three main hydrothermal stages associated with mineralization are defined: Stage 1, pyrite, fine grained quartz ±chlorite; Stage 2a & b, pyrite, chalcopyrite, sphalerite, galena, sulfosalts, Au-Ag tellurides, fine and coarse white quartz, ±calcite; Stage 3; calcite, quartz, pyrite. Au-Ag-Pb tellurides are associated with localized brecciation. Tellurides are predominantly present in fractured sphalerite, pyrite, chalcopyrite and galena. Based on textures and fluid inclusion studies, Au-Ag-Pb tellurides are linked to boiling mechanisms. The epithermal event at The Shahumyan deposit is characterised by punctuated periods of hydrothermal brecciation interspersed with more quiescent periods when coarsely banded vein material was precipitated. Localized brecciation provide increased fluid permeability and ideal fluid pathways for mineralizing fluids. Localized brecciation corresponds with continued propagation or re-opening of the fracture-vein system. Localized boiling is interpreted to be the primarily driver for Au-Ag telluride precipitation.
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