Ultrabasites and the sources of noble metals (Au, Pt, Pd) in the North Caucasus

Abstract

Relevance. The ultrabasites of the North Caucasus are the oldest igneous rocks, whose age is defined as the Lower Paleozoic (Ordovician-Silurian). These rocks play a key role in the metallogeny of the noble metals of the Caucasus. Huge reserves of metals in the regional carbonaceous Devonian black shale stratum of the North Caucasus are associated with ultrabasites. Permian propylites (Chuchkurskoye deposit) and metal-bearing Jurassic crusts of weathering of ultrabasic massifs are of practical importance. To date, the noble metals of the listvenites of the North Caucasus accompanying ultrabasites have not been evaluated. Aim. Show that ultrabasic rocks are donors of noble metals (Au, Pt, Pd) for the North Caucasus throughout the entire Phanerozoic. Confirm the spatio-temporal relationship of ultrabasic rocks with noble metal mineralization in the black shales of the Caucasus. Prove the presence of an ore-bearing weathering crust on the eroded surface of serpentinites using the example of the Bedensky ultrabasic massif. Methods. A brief historical review of ultrabasite studies with a focus on the genetic relationships of noble metals (Au, Pt, Pd) with ultrabasite magma is made. The analysis of geological materials on the Bedene and Malkin ultrabasite massifs, the largest in the North Caucasus, is carried out - their composition, geochemical features and potential ore content. Results. According to the chemical composition, the ultrabasites of the North Caucasus are attributed to the alpinotype formation type. The ore-forming role of alpinotype ultrabasites for noble metals in sedimentary and metamorphic strata of the Phanerozoic region has been established. Noble metals are actively manifested in the metallogeny of the Phanerozoic Geotectonic epochs: Caledonian, Hercynian, Cimmerian and Alpine, having a single primary ultrabasic source. Fresh, unaltered serpentinites do not currently show anomalous contents of noble metals of industrial interest. The saturation of serpentinite with noble metals is manifested during their exogenous processing in the enriched products of their destruction. Potentially industrial sedimentary complexes consisting of enriched products of destruction of serpentinites are the weathering crusts of serpentinites and sedimentary black-shale strata of the North Caucasus. Ultrabasic magma in the North Caucasus served as the primary deep-seated source of precious metals in sedimentary and metamorphogenic Phanerozoic strata of the Caucasus.