Abstract
Microthermometry study of fluid inclusions in quartz veins of the Maletoyvayam deposit (Koryak Highland, Russia) was carried out. This epithermal gold deposit contains unique Au compounds including maletoyvayamite, which has not been reported anywhere else. Two paragenetic mineral associations (pyrite-quartz and maletoyvayamite-quartz) with quartz of different generations corresponding to different pulses were also described. Only early generations of quartz (Q1) include ore minerals: pyrite for the first mineral assemblage, and in Au-bearing minerals, sulfosalts, bismuthinite, and others—for the second assemblage. A study on fluid inclusions in quartz showed a salinity (mainly NaCl + KCl) range from 0.2 to 4.3 wt.% NaCl eq., increasing from the first mineral association to the second due to boiling fluids. The obtained temperature variations for quartz crystallization were 295–135 °C, the fluid pressure ranged from 79 to 4 bar. On the other hand, the range of conditions obtained for the gold productive ore association is more narrow: salinity of the fluid inclusions is 4.3 wt.% NaCl eq., the temperatures vary from 255 °C to 245 °C, and the pressure from 39 to 32 bar. These physicochemical characteristics of the Maletoyvayam ore deposit greatly coincide with other HS-type epithermal deposits; however, within the Central Kamchatka Volcanic Belt it is so far the only deposit of this type reported.
Highlights
The term “epithermal” was defined by W
Hedenquist and coauthors [3,4] consider that an epithermal Au deposit consists of three subtypes: high sulfidation (HS), intermediate sulfidation (IS), and low sulfidation (LS), each represented by characteristic alteration mineral assemblages, occurrences, textures, and characteristic suites of Minerals 2020, 10, 1093; doi:10.3390/min10121093
The results obtained from fluid inclusions microthermometry in vein quartz of the The results obtained from fluidarea) inclusions microthermometry veinformed quartz of Maletoyvayam deposit (Gaching indicate that the quartzinwas inthe a wide range of deposit (Gaching area) indicate that the quartz was formed in a wide range of temperatures temperatures from nearly 300 to 180 °C and even below
Summary
The term “epithermal” was defined by W. Lindgren [1] to include a broad range of tellurides, antimonides or selenides of Au, Ag and base metals deposits which he estimated to be formed from aqueous fluids at low temperatures (less than 200 ◦ C) and moderate pressures. It is, generally accepted that mainly magmatic fluids at slightly higher temperatures (200–300 ◦ C). HS deposits are associated with some types of hydrothermal systems due to influence of a deep magma chamber [13] and with andesitic volcanoes in which surface manifestations include high-temperature fumaroles and acid sulfate-chloride hot springs. LS deposits of reduced (H2 S-rich) hydrothermal fluids with neutral pH are similar to those found in geothermal systems [13], that exhibit in the surface: sinter-terraces of silica, hot springs and steam-heated acid-sulfate alterations [14]
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