Myauchan Ore Field (Northeastern Asia), an Example of Weakly Eroded Ag-Pb-Zn Volcanoplutonic Mineralization
A.N. Glukhov, E.E. Kolova, A.V. Sobolev
N.A. Shilo Northeastern Interdisciplinary Research Institute, Far Eastern Branch of the Russian Academy of Sciences, Magadan, Russia
Keywords: Ag-Pb-Zn mineralization, rhyolite, Ag-tetrahedrite, fluid inclusions, epithermal, gradient
Abstract
The Myauchan ore field located in the Omsukchan zone of the Okhotsk-Chukotka Volcanic Belt is described. The Korennoe and Malyutka Ag-Pb-Zn ore occurrences forming this field are localized at the center of anticlinal fold of NW strike made up of Upper Triassic carbonate-terrigenous deposits intruded by stock-like bodies and dikes of Upper Cretaceous andesite, monzodiorite, granite-porphyry, and rhyolite-porphyry. Sulfide-carbonate-fluorite-quartz veins and vein-veinlet zones with arsenopyrite, pyrite, sphalerite, galena, chalcopyrite, and Ag-tetrahedrite are localized both in intrusions and in terrigenous strata. The field bears As-Sb-Ag-Pb-Au-Bi-Cu-Zn-W mineralization. Study of fluid inclusions and REE and ore element patterns show that the field ores formed from chloride solutions with the participation of surface waters in hydrothermal-magmatic system under epithermal conditions. The ores were deposited from solutions with TDS = 0.5-9.0 wt.% NaCl equiv. in the temperature range 106-287 ºC. The ores containing ca. 70 ppm Ag and up to 1.2% Pb formed through boiling-off of solutions enriched in iron salts. The ores with Ag < 7 ppm and Pb ≤ 25 ppm were generated from diluted hydrothermal solutions with predominant sodium salts and potassium admixture. Mineralization of the Myauchan ore field marks the upper level of the Ag-Pb-Zn ore system similar to the Gol’tsovoe deposit.
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