Extrusive subvolcanic rhyodacites of pyrite-bearing formations

Stable spatial and temporal relationships of pyrite mineralization with aci d volcanism make it possible to characterize rhyodacites of producing forma tions, no matter to which differentiates, or tholeiitic or calc-alkalic mag mas, they belong. The rhyodacites of pyrite-bearing formations are distingu ished by higher, as compared with average types, contents of iron (FeO* - 3 .5-4% and more versus 2-2.5%), high temperatures of homogenization of melt inclusions, and contrasting hematite-pyrite zoning of extrusive subvolcanic massifs. The massifs confined to deposit structures are distinguished by a wide deve lopment of the phenomena of perlite disintegration, liquation layering, and autobrecciation conjugate with autometamorphism implicately coming to hydr othermal changes of the stage of ore deposition. The extrusive subvolcanic massiv that lie far from ore fields have no such indications of fluid enric hment. In ore fields, the replacement of small-porphyry rhyodacites by larg e-porphyry ones and change of perlite decomposition by liquation phenomena are evident of active separation of fluids in connection with the origin of peripheral chambers at interparoxismal stages of ore deposition.