First findings of palladium-gold-REE ore mineralization in precambrian carbonaceous shales on the western slope of the Southern Urals

Abstract

866 During the last 20 years, a new type of veindissem� inated goldsulfide ore mineralization with dispersed gold and platinum group minerals has been identified. These deposits are located within rift structures in areas of weakly manifested magmatism and localized in ancient rocks enriched in organic carbon matter. Black shale sequences form extended regional zones, but the deposits within them are associated with local fields, where dynamothermal processes and certain types of metasomatic alterations are manifested. On the western slope of the Southern Urals, Riphean black shale deposits are widespread. Testing of these mineralized black shale deposits showed the presence of abnormally high (up to industrial) gold content. Scientific and research works carried out by the authors in 2005-2009 within the northern area of the anticlinoriums of Mayardak and Yamantau (Fig. 1) made it possible to study the Precambrian carbon� aceous deposits on noble metals, tungsten, molybde� num, and vanadium (Table 1). The most interesting results were obtained as a result of study of carbon� aceous shales of the ZigazinoKomarovskaya suite. The geological traverses carried out in the area of this suite showed that it is composed of chlorite, sericite, quartz, mica-quartz, mica-feldspar-quartz shales, quartz siltstones, and sandstones in various propor� tions, enriched to varying degrees in carbon matter. In shales sulfidization (from single disseminated grains of pyrite to sulfide veinlets up to 1 cm) at a sulfide con� tent in the rocks of up to 25-30% is very often observed. Most outcrops and eluvial-deluvial placers are presented by more or less weathered rocks in which, instead of the primary sulfides, one can observe cavities of cubic habit or intensively ferruginous zones with cavernous textures. During further weathering, brown ironstones formed instead of these rocks. All this, in our opinion, indicates that this stratigraphic level is potentially a noble metalbearing area. This horizon has to be taken into account as the main object for organization in this area searching works for Au and PGE. The contents of Au, Pt, Rh, and Ir were determined in the chemical laboratory of the Institute