At least 40 alteration cells characterized by hydrothermal quartz and alunite occur
in the southern segment of the ancestral Cascades magmatic arc from Portola,CA
to Goldfield, NV. Significant amounts of Au, Ag, Cu and Sº (elemental sulfur) were
produced from 6 cells (Goldfield, Paradise Peak, Borealis, and Ramsey, NV; Masonic
and Monitor, CA), 3 cells contain Au, Ag, and Sº resources (Isabella-Pearl, NV;
Golden Dome and Cinnabar Canyon, CA), and minor amounts of Au, Ag, Cu, and Hg
have been produced from several cells, but no appreciable metal concentrations have
been identified in most cells. Cell exposures vary from ~ 70 km2 (Goldfield) to hundreds
ofm2 (Mystic, CA), and have known vertical dimensions of hundreds of meters.
Cells range in age from about 22 Ma (Goldfield and Pyramid, NV) to 4 Ma (Painted
Rock, CA). Most cells formed in andesite and dacite flows and subvolcanic intrusions
immediately after their eruption and/or emplacement, and are confined to these
slightly older (0 to 2 Ma) volcanic rocks, although several cells (Goldfield; Masonic;
Golden Dome) partly formed in Mesozoic and Paleozoic rocks.