COPPER SULFIDE MINERALIZATION WITHIN GRANODIORITE AND PORPHYRITIC QUARTZ MONZONITE OF THE ANN MASON PORPHYRY DEPOSIT IN THE YERINGTON MINING DISTRICT, NEVADA

The Ann Mason porphyry deposit is located in the Yerington mining district in western Nevada. Containing an estimated 1.4 billion tonnes of copper ore with addition of molybdenum, gold, and silver ores, this site is prospectively an economically viable deposit to mine. My research focuses on the mineralization sequence of copper ores and their associated mineral assemblages. Through transmitted light and reflected light petrographic analyses, I am analyzing the ore mineral and associated alteration mineral assemblages of fifteen granodiorite and porphyritic quartz monzonite samples.

Copper in the Ann Mason porphyry deposit exists as the sulfide minerals bornite and chalcopyrite. In porphyritic quartz monzonite samples bornite is seen as spots within chalcopyrite and on the edges of open spaces in the host rock. At lower depths in granodiorite samples, chalcopyrite dominantly infills open space with occasional bornite spots within it. Pyrite is also observed but fills open space alone.

Relationships between, and mineralization order of, hydrothermal alteration and ore minerals tells us something about conditions during deposition. The focus of my research is to study these relationships in order to develop an understanding of the sequence and conditions of mineralization. This research will contribute to a greater project analyzing the occurrence of gold, silver, and copper distribution in the Ann Mason deposit.