ARESENOPYRITE-PYRITE PARAGENESIS IN GOLD DEPOSITS (thermodynamic modeling)
N.V. Vilor1, L.A. Kaz’min2, L.A. Pavlova1
1A.P. Vinogradov Institute of Geochemistry, Siberian Branch of the Russian Academy of Sciences, ul. Favorskogo 1A, Irkutsk, 664033, Russia
2Research Geotechnological Center, Far Eastern Branch of the Russian Academy of Sciences, Severo-Vostochnoe shosse 30, Petropavlovsk-Kamchatskii, 683002, Russia
Keywords: As–pyrite, arsenopyrite, paragenesis, hydrothermal solution, physicochemical modeling, acidity–alkalinity, redox potential
Abstract
The compositions of parageneses including arsenopyrite (Asp), pyrite (Py), and As–pyrite (As–Py) have been calculated by the solution of primal physicochemical modeling problems. The numerical models for the interaction of Py matrix with hydrothermal solution saturated with Asp are considered for three variants of the solution penetration into the Py matrix: percolation, spreading, and tightening at 100–300 ºC and 300 bars. It is shown that Asp forms in the zone of an ore column where fluid (solution) is predominant, with the Py matrix being replaced independently of the type of solution transfer. Prevailing As and Fe complexes are considered. The calculated models for the three types of interaction show that the redox potential in the solution varies fr om –0.055 V at the ends of the Asp-containing ore column to –0.55 V in its central zone. This difference makes an electrochemical geochemical barrier at the interface, wh ere metallic gold is deposited in Asp–Py ores.
DOI: http://dx.doi.org/10.1016/j.rgg.2014.06.003
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