NATURE OF CARBONACEOUS ROCKS IN SHEAR ZONES IN THE DAL'NEGORSK DISTRICT, PRIMORYE: BLACK SHALES OR MANTLE-RELATED ILMENITE-GRAPHITE METASOMATITES?

Abstract

Carbonaceous mineralization with associated metals in the sulfide or native form has been reported from various geological settings. However, the source of metals remains an open issue. The superimposed character of mineralization is evident in areas with the deposition of carbon in contrasting environments, such as fissures, cavities, exfoliation zones in granites, granitic pegmatites, and marbles. In such cases, the carbon isotopic composition also matches the endogenic composition. It is more difficult to elucidate the nature of carbon-bearing rocks in crush zones if the rocks are similar to carbonaceous units in sedimentary sections of the region in terms of age and composition. The problem is complicated by the fact that the carbon isotopic composition also matches the sedimentary type in all cases. Elaboration of criteria of the endogenic carbonization in sedimentary rocks (siltstones, mudstones, and siliceous shales) is a pressing issue.