Geological structure and gold prospectivity of the Shamansky ore cluster of the Altai-Sayan folded region (Republic of Khakassia)

Abstract

In this work, we consider the geological settings, mineralogical composition and age of rocks and ores, as well as regularities in the formation of gold mineralization of the Shamansky ore cluster, which is one of the most prospective ore clusters in the Altai-Sayan mineragenic province. It is shown that the cluster has a complex fold-block structure. The rocks are characterized by intense folded and discontinuous dislocations. We identified the area of the reatest deformations, where the known prospective signs of gold mineralization are concentrated. Two morphological types of gold-sulfidequartz ores have been distinguished: veins and pyritequartz-sericite-ankerite metasomatite. We characterized the composition of gold and its morphological features. Sulfur isotope data of sulfides from gold-bearing quartz veins predominantly have values of δ34S from +3.7 to+6.5 ‰ that indicate their hydrothermal-sedimentary origin. 40Ar/39Ar isotope-geochronological data on sericite from gold-bearing quartz shows the age of 359.5 ± 5.5 Ma testifying to the Late Devonian-Early Carboniferous stage of the formation of gold-sulfide-quartz veins. A comparison of geological, metallogenic, mineralogical-geochemical and isotope-geochronological data allowed us to conclude that the gold mineralization of the Shamansky cluster belongs to the orogenic type. According to the model of formation, gold mineralization occurred in three stages: ore-preparation islandarc (540-520 Ma), main ore orogenic-1 accretion-collisional (510-450 Ma), and additional ore orogenic-2 transpressional-collisional (380-345 Ma).