Date of Award
Doctor of Philosophy
Pyrite associated with gold deposits has been characterized on the basis of morphology, optical and chemical microstructures, and minor and trace element geochemistry. Gold deposits studied include: Agnico-Eagle mine (Quebec), Fairview mine (South Africa), Bousquet mine (Quebec), Williams mine (Ontario), Dome mine (Ontario), Pistol Lake prospect (Northwest Territories), Freddies Consolidated mine (South Africa), Pilgrim's Rest Gold Field (South Africa), and Clontibret prospect (Ireland). Pyrite from Buchans (Newfoundland), Kosaka (Japan), Axial Seamount and Explorer Ridge volcanogenic massive sulphide bodies are included in the study. Colour-staining of polished surfaces of pyrite with a potassium permanganate solution enhances internal microstructures and facilitates detailed examination of pyrite morphologies. The minor element content of gold-bearing arsenian pyrite was determined by electron microprobe, and trace gold distributions were determined by ion-mapping by SIMS.;Pyrite from strata-bound-stratiform gold deposits and massive sulphide deposits contains up to 8 wt. % arsenic in oscillatory growth zones. The amount of arsenic varies from zone to zone and this correlates well with the colour variations of stained polished sections. White-blue zones are enriched in arsenic, brown-yellow zones contain negligible amounts of arsenic. Oscillatory growth zones enriched in arsenic indicate a complex crystallization history of episodic flow of hydrothermal fluids. Arsenic substitutes for sulphur in the pyrite structure. Gold is concentrated in the arsenic-rich growth zones and absent from the arsenic-poor zones. Cobalt, copper, and nickel are present in trace amounts only. Pyrite from the Bousquet and Williams mines and Pistol Lake prospect contains no arsenic and negligible cobalt, copper and nickel. Pyrite from modern massive sulphide deposits also contains negligible arsenic, cobalt, copper, and nickel.;The typical microstructure of arsenian pyrite with a framboidal and/or sector-zoned core surrounded by oscillatory growth zones is similar to oscillatory-zoned sphalerite from epithermal Pb-Zn deposits and to pyrite from diagenetic base metal ores. Furthermore, arsenian pyrite is associated with geothermal systems and Carlin-type epithermal gold deposits. These textural and compositional similarities suggest that gold deposits dominated by arsenian pyrite may have formed by rock fluid-processes during diagenesis and burial metamorphism.
MacLean, Peter John, "Characterization Of Pyrite From Gold Deposits" (1991). Digitized Theses. 1938.