MINERALOGY OF ORES AND CONDITIONS OF FORMATION OF THE KUMROCH GOLD DEPOSIT (KAMCHATKA, RUSSIA)
Y.A. Kalinin1, E.D. Greku1, V.P. Petrochenko2, A.A. Tomilenko1, V.A. Yakovlev1, S.S. Nikitin1, F.I. Zhimulev1, K.I. Zatolokina1, A.Sh. Shavekina1, R.A. Shelepaev1, M.L. Kuibida1, A.A. Milskaya3, M.O. Shapovalova1, I.V. Vikentiev4
1 V.S. Sobolev Institute of Geology and Mineralogy SB RAS, Novosibirsk, Russia
2 JSC Bystrinskaya Mining Company 683001, Petropavlovsk-Kamchatsky, Russia
3 Lomonosov Moscow State University, Faculty of Geology, Moscow, Russia
4 Institute of Geology of Ore Deposits, Petrography, Mineralogy and Geochemistry of the Russian Academy of Sciences, Moscow, Russia
Keywords: Kumroch ore field; mineralogical and geochemical features of ores; fluid inclusions; porphyry and epithermal types of mineralization.
Abstract
The Kumroch deposit, located in the middle part of the East Kamchatka tectonic zone, is one of the most significant gold mining sites in Kamchatka. It is characterized by a combination of signs of Au-Cu-porphyry and Au-Ag vein ore genesis. The hydrothermal ore-magmatic system is represented by intrusions of dioritic porphyrites containing interspersed quark copper mineralization, as well as zones of volumetric hydrothermal mining of host volcanites with large gold ore polysulfide quartz veins. The spatial and genetic relationship between the gold-copper-porphyry and vein subepithermal stages of the ore-bearing system activity in the Miocene-Pliocene time is shown. Lateral zonation was revealed, expressed in a change from the southwest to the northeast of mineral associations: chalcopyrite-magnetite and pyrite-chalcopyrite (early), manifested in the centers of Cu-Au porphyry mineralization, gold-polysulfide and gold-pale ore-telluride (transitional), forming an intermediate part with Au-polymetallic subepithermal tools, and As-pyrite-antimonite (late) epithermal, in the peripheral part. The coexistence of two types of hydrothermal fluids has been established: 1) high-temperature (Thom
= 515–330 °C) and highly salted (>50 wt. % NaCl-eq.), responsible for the formation of Au-Cu porphyry mineralization, and 2) medium-temperature (Thom
= 350–160 ° C), with increased salinity (up to 11 wt. % NaCl-eq.), with signs of boiling and heterogenization of mineral-forming solutions, which deposited vein Au mineralization.
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