MINERALOGY, GEOCHEMISTRY AND GENESIS OF THE BAZILEVO COPPER OCCURRENCE (SOUTHERN PRE-URALS)

Abstract

The relevance of the research results from the discovery of new copper ore occurrences and the need to clarify the conditions of their formation in the Permian deposits of the Southern Pre-Urals against the background of poor lithological, mineralogical and geochemical studies of the latter. The genesis of copper sandstones of the Pre-Ural belt is still a matter of debate. The emergence of Cu mineralization is associated with both syn- and epigenetic processes, while infiltration or exfiltration mechanism of Cu-bearing fluid migration is assumed for the latter. The work is aimed at the mineralogical and geochemical study of the ores of the Bazilevo copper occurrence and clarification of conditions of its formation. Methods of research include field geological work, optical and scanning electron microscopy with X-ray spectral microanalysis, X-ray diffraction, X-ray fluorescence spectrometry, as well as mass spectrometric and atomic emission analysis with inductively coupled plasma. Results. The mineralogical and geochemical characteristics of the ores of the Bazilevo copper occurrence in the Southern Pre-Urals were completed; the conditions for the formation of host rocks and ore bodies were studied. Their association with tree fossils with inheritance of general morphology is established. Ores (0,2–18,8 wt. % Cu, Ag up to 150 ppm, Pb up to 270 ppm) are localized in gray-colored sandy deposits of the Kazanian Stage, which are alluvial sediments. The area of ore occurrence is ≥1200 m2, two ore-bearing beds were identified in the section. Three types of ore bodies were identified according to their internal structure. The main ore minerals are hydrocarbonates (azurite, malachite) and Cu sulfides (chalcocite, bornite, chalcopyrite, etc.). On the whole, the mineralogical and geochemical features of ores are consistent with the polygenic hydrogenic-sedimentary model of their formation with the participation of biogenic processes. The underlying terrigenous rocks (especially red-colored ones) served as the source of ore elements, and the ascending migration of mineral-forming fluids occurred along faults.

Keywords

• southern pre-urals
• kazanian stage
• copper sandstones
• mineralized trees
• mineralogy
• geochemistry