Geochemical and Isotopic Characteristics of Disseminated Sulfide Mineralization of Orogenic Gold Deposits of the Yana-Kolyma Metallogenic Belt, Northeast Russia

The results of study of the chemical and S isotopic composition of disseminated pyrite and arsenopyrite from metasomatites of the orogenic Mal.-Taryn, Badran, Khangalas, V'yun, and Shumniy gold deposits of the Yana-Kolyma metallogenic belt are presented. Pyrite and arsenopyrite are characterized by a nonstoichiometric composition. Arsenopyrite is enriched in S (an As/S ratio of 0.77-0.99) and contains Sb, Co, Ni, and Cu, the total amount of which is <0.15 wt %. Pyrite contains the same elements (up to 3.71 wt % in total), as well as rare Pb, is depleted in S, and is enriched in As (up to 3.16 wt %). The Ni/Co ratio of pyrite (10.0 > Ni/Co > 0.1) is typical of hydrothermal negatively charged pyrite with high conductivity (p-type). It is suggested that the mode of occurrence of invisible Au+ in disseminated pyrite and arsenopyrite is mostly isomorphic structurally bounded. The delta S-34 values of sulfides of the studied deposits range from -6.4 to +5.6%, which is characteristic of juvenile/magmatic S sources.