Advanced Argillic and Sericitic Alteration in the Subvolcanic Environment of the Yerington Porphyry Copper System, Buckskin Range, Nevada
Joanna L. Lipske, John H. Dilles, 2000. "Advanced Argillic and Sericitic Alteration in the Subvolcanic Environment of the Yerington Porphyry Copper System, Buckskin Range, Nevada", Part I. Contrasting Styles of Intrusion-Associated Hydrothermal Systems: Part II. Geology & Gold Deposits of the Getchell Region, John H. Dilles, Mark D. Barton, David A. Johnson, John M. Proffett, Marco T. Einaudi, Elizabeth Jones Crafford
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The Buckskin Range lies approximately 4 km west of the Yerington porphyry copper district and hosts the Artesia Lake and Fulstone Spring volcanic sequences that structurally overlie the Yerington batholith. Hy-drothermal alteration minerals characteristic of advanced argillic, sericitic, and marginal porphyry copper-type alteration assemblages have been detected via infrared spectrometry, X-ray diffraction, petrography, micro-probe analysis, and hand-lens based-field mapping in the central Buckskin Range.
It is postulated that high-level alteration in the Artesia Lake Volcanics may be contemporaneous with the main event of sericitic alteration and pyrite deposition in the deeper porphyry copper environment. The presence of sericitic alteration underlying or overprinting hypogene advanced argillic assemblages may imply that fluids responsible for porphyry copper mineralization have ascended to epithermal depths.
The spatial relationships of hydrothermal alteration in the Buckskin Range suggest an evolution of low-pH, sulfide-bearing fluids to nearly neutral, oxide-rich hydrothermal fluids. Sulfide-rich, feldspar-destructive advanced argillic and sericitic alteration is crosscut and overlain by feldspar-stable, oxide-rich sericite-hematite-chlorite alteration. Sericite-hematite-chlorite alteration is abruptly overlain by potassium-added, feldspar-stable calcite-chlorite-hematite alteration, produced by late sodic-calcic or potassium-enriched fluids possibly derived from sedimentary or evaporitic brines.