登入選單

返回Google圖書搜尋

The Petrology and Geochemistry of the Yerington Batholith and the Ann-Mason Porphyry Copper Deposit, Western Nevada

John Hook Dilles

出版	Stanford University, 1983
URL	http://books.google.com.hk/books?id=kW8SAQAAIAAJ&hl=&source=gbs_api

註釋

Hydrothermal alteration affected 25 km3 of rock at the Ann-Mason porphyry copper deposit. Main stage biotite (potassic) alteration and copper mineralization was contemporaneous with a central QMP dike swarn and was accompanied by flanking/deeper oligoclase-actinolite (sodic-calcic) alteration. Both alterations contain high salinity fluid inclusions trapped at 300-480+C, but field relations, petrology, and stable isotope data suggest that magmatic fluids caused potassic alteration, whereas largely non-magmatic fluids, flowing up a temperature gradient, caused sodic-calcic alteration. Late stage albite-chlorite and lesser sericitic alterations cut main stage alteration, have pyritic mineralization, and contain low salinity fluid inclusions that homogenize at 150-250±°C. Stable isotope data and phase petrology suggest that late stage fluids were either ocean water or isotopicaly heavy meteoric water. I propose that most of the copper in the deposit came from a high silnity, water-rich magmatic fluid that separated from the crystallizing PQM/QMP magma, but that up to 16% may have been derived from leaching during sodic-calcic alteration.