Mineralogy, paragenesis, and fluid inclusion relationships of the hydrothermal ore deposits at Florida Mountain, Carson mining district, Owyhee County, Idaho

Exploration on Florida Mountain in southwestern Owyhee County, Idaho has defined four separate Au-Ag-Se orebodies. These deposits differ greatly in size, shape, grade, and metal ratios. However, all four are related to the same episode of epithermal vein mineralization. Ore deposition was associated with an active geothermal field related to a series of Mid-Miocene (15.2 to 16.6 m.y.a.) silicic domes and flows. Hydrothermal fluids of meteoric origin were localized along NW-trending faults and leached their constituents from the surrounding rocks. Metals were transported as complexes of sulfur and selenium in a 1% NaCl equivalent solution at 260{dollar}spcirc{dollar}C. Ore deposition occurred some 400m below the paleo-surface as the result of boiling and fluid mixing. The major ore minerals are aguilarite, acanthite, and electrum. The gangue is predominantly quartz and adularia. Hydrothermal alteration includes propylitic, sericitic, kaolinitic, and potassic assemblages. Supergene effects in the deposits are minimal.