Detailed space-time-level analysis of Miocene hydrothermal zinc-silver-gold mineralization and alteration, Virginia area, Huancavelica, central Peru

The Virginia area is associated with the Mesozoic Condorsinga limestones, upper section of the Pucara Group, which were intruded by different pulses of Miocene dioritic subvolcanic and rhyolitic to dacitic volcanics. The Late Oligocene-Early Miocene microcrystalline dioritic subvolcanic intrusions were emplaced as shallow stocks and dikes, and produced an extensive and apparently barren green garnet skarn alteration. The fluids trapped in garnets show trapping temperatures between 182 +/- 26°C and 234 +/- 48°C, salinity between 13 +/- 9 and 19 +/- 7 eq.wt% NaCl and depths of trapping between 77 and 281 metres. Later Miocene porphyritic rhyolitic to dacitic Caudalosa volcanics were emplaced after and altered the previously formed rocks including the subvolcanic intrusions. The hydrothermal fluids generated during the Caudalosa volcanism produced Zn mineralization hosted by the bottom unit of the volcanics, which comprises carbonate-altered skarn-bearing volcanic breccias; and Au mineralization in a high sulfidation epithermal system hosted by the top units of the volcanics.