Platinum and platinoids in Paleozoic Black shale strata Front ridge (North Caucasus)

Abstract

Relevance. It is determined by the need to generalize the previously obtained data on the contents and mineral forms of platinum and platinoids in the Middle-Upper Devonian black shale strata of the structural-formation zone of the Front Ridge. Aim. To collect, summarize and analyze stock and published data on the presence of mineral forms and the contents of platinum and platinoids in the Middle-Upper Devonian black shale strata of the zone of the Front Ridge and within the areas of their development. Methods. Analysis of the results of previously carried out works and published data, field documentation, sampling, study of cuts and anshlifs, determination of Pt and Pd contents in samples by assay method with ICP-NPP completion. Results. Mineral forms of platinum and platinoids have been established in the alluvium of draining black shale strata of rivers. The contents of native platinum detected at the beginning of the last century in the alluvium of the Vlasinchikha River may correspond to the placer deposit in modern conditions. Analysis of the results of earlier determinations of Pt and Pd contents in the black shale rocks of the Andriuk formation, reaching tenths of a g/t, raise doubts about their reliability, since the publications do not specify methods of sampling and preparation of samples for analysis, nor does the modification of the applied method of atomic absorption spectroscopy. The results obtained by us in a specialized laboratory for the determination of Pt and Pd in the black shale rocks of the Artykchak formation are hundredths of a g/t, confirmed by multifactorial control, and are regarded as elevated (overclark) contents. In isolated cases, the sum of Pt and Pd reached 0.1 g/t, which is a sub-industrial content. Mineralogical studies have made it possible to establish the presence of native platinum secretions directly in the black shale rock. The fact that such secretions are confined to displaced forms of carbonaceous matter and to new formations of chrome mica (fuchsite) of hydrothermal genesis suggests the epigenetic origin of the identified mineral forms of platinum due to metamorphogenic redistribution of ore-forming elements of the ultrabasic petrofund.