Epithermal gold (± silver) deposits form within active hydrothermal systems associated with volcanic activities. They characteristically form at shallow depths (< 1km) where the heat is supplied by volcanic activities and the fluids discharge as hot springs. They may also be part of a distal porphyry system.
Epithermal deposits are divided into high sulfidation (HS) and low sulfidation (LS) types. The HS deposits occur in leached silicic rocks and are characterized by highly acidic fluids, whereas the LS deposits are characterized by reduced fluids of neural pH.
Common minerals associated with epithermal deposits include microcrystalline, drusy quartz or colloform silica, illite, smectite, and adularia. Specular hematite occurs at some depth and goethite occurs near or at the surface.
Charay property, Sinaloa, Mexico. MUSGROVE MINERALS CORP.