Ni-Co-ARSENIDES AND SULPHOARSENIDES FROM GOLD-RARE-METAL DEPOSITS OF EASTERN YAKUTIA

摘要

Gold-rare metal deposits of Eastern Yakutia are closely associated with granitoids and are localized in a zone of their exo-, endocontact. Despite a low-sulphide (1-3 percent) content of ores and subcrustal abundances of Co and Ni in the igneous and sedimentary rocks, the abundance of Ni-Co-arsenides and sulphoarsenides in ore bodies is typical of these deposits. In addition to typomorphic compositionally stable nickeline, ore minerals are represented by rammelsbergite with components insignificantly varying in composition and safflorite-lollingite-series minerals. In some deposits, lollingite contains Ni and Co widely ranging (to 12 percent) in composition. The most variable composition is typical of sulphoarsenides. Almost the whole series of minerals from gersdorffite to cobaltite with relatively insignificant variations of Fe concentrations (4-10 is observed. The diagram of sulphoarsenide contents shows that the field of Ni-Co-bearing arsenopyrites is significantly widens. The findings of Ni-Co-arsenides and sulphoarsenides with the above-mentioned variations of the component compositions in the low-sulphide gold4are metal deposits are described for the first time. Province differences in composition of these minerals are distinguished. The formation of Ni-Co-arsenide and sulphoarsenide associations in these deposits can be explained in the light of ore formation under shallow-depth conditions.