The Asachinskoe epithermal Au-Ag deposit in southern Kamchatka: physicochemical conditions of formation

Abstract

The Asachinskoe epithermal Au-Ag deposit (southern Kamchatka) is referred to as low-sulfidation in quartz-adularia-sericite in Corbett’s classification. Research into fluid inclusions of its minerals gave an insight into the PT-conditions of formation and gas composition of ore-forming fluids as well as the vertical variations in these parameters to a depth of more than 200 m within a 2 km long horizontal site of the deposit ore zone. It is shown that mineral assemblages formed at 320 to <100 °C. Ore-forming hydrothermal solutions were poor in salts (3–9.2 wt.% NaCl equiv.), with NaCl being the main component. Mineral assemblages with high contents of Au crystallized at 250–175 °C. Ore-free quartz-carbonate veins formed at 80–120 °C. High-temperature (300–320 °C) veins also lack ores. Rich gold ores were deposited in the environments where ore-bearing fluids boiled, mixing with meteoric waters.

The Gold Mineralization of the Baranyevskoe Au-Ag Epithermal Deposit in Central Kamchatka

“…The microthermometry study on fluid inclusions in quartz with the most abundant dissemination of chalcopyrite and sulfosalts grains (gold-sulfosalts-quartz association) revealed in the quartz aggregate, temperatures corresponding to a range of 299-226 • C. Similar temperatures of homogenization of primary inclusions were reported for the quartz of the Aginskoe deposit (LS type) 230-280 • C [9], and were also established for the Rodnikovoe and Asachinskoe deposits in South Kamchatka [6,49,50]. In addition, at the IS type field (Cesme Hafez, Iran) [51], homogenization temperatures of primary inclusions are within the same range (140-280 • C).…”

“…These deposits are located in volcanic belts extending along the subduction zone [1,2], and occur in a geodynamic setting of island arc [3]. Among the aforementioned deposits stand out Asachinskoe, Ametistovoe, Ozernovskoe, Aginskoe, Rodnikovoe, Mutnovskoe, Maletoyvayam and others [4][5][6][7][8][9][10][11].…”

Gold Mineralization at the Maletoyvayam Deposit (Koryak Highland, Russia) and Physicochemical Conditions of Its Formation

“…For example, the homogenization temperatures of primary inclusions in quartz from the Aginskoye deposit (LS type) were 230-280 • C, with the ore phase being in the range of 250-260 • C [59]. Similar temperature ranges have been established both for the LS type deposits (Rodnikovoye and Asachinskoye in South Kamchatka, Russia) [19,21,60] and in regard to the IS type deposit (Cheshmeh Hafez, Iran) [61], the homogenization temperatures of the primary inclusions are in the range of 140-280 • C with peaks at around 180-250 • C. This is also compatible with all HS type deposits, and with the obtained formation parameters of the Maletoyvayam deposit (Table 5).…”

“…In late veinlets, crustified, microdruse, cockade and, less often, collomorphic textures can be observed (Figure 8a). These textures are also representative of mineral associations in other gold-bearing low sulfidation epithermal deposits in the Kamchatka Peninsula [19]. Late quartz veins also contain sporadic pyrite, but very rarely.…”

“…Within the Kamchatka Peninsula, Au-Ag epithermal deposits are localized in volcanic belts of different ages (Eocene-Oligocene Koryak-West Kamchatka, Oligocene-Quaternary Central Kamchatka, and Pliocene-Quaternary East Kamchatka), extending along the modern subduction trend [15][16][17][18][19]. All of the Au-Ag mines located there (Aginskoe, Asacha, Ametistovoe, Zolotoe, Baran'evskoe, Kungurtsevskoe, Oganchinskoe, Ozernovskoe), as well as most of the known Au-Ag deposits and prospects, fit into the LS epithermal type [19][20][21][22][23]. These deposits are characterized by the presence of quartz, adularia, illite and calcite in Au-Ag-bearing veins.…”