Silver-gold and polymetallic mineralization in the banded iron formations deposit in Kryvyi Rih, Ukraine

Abstract

Since the beginning of iron mining in Kryvyi Rih in 1881, gold was a target of interest. Exploration for gold began in 1936. As a result, many gold occurrences were discovered. In this paper, regional geology of the gold mineralization and the iron deposit details are also described for better understanding of the position of hydrothermal mineral association. Gold - silver and polymetallic mineralization was found in the iron ore horizon in the Ingulets operating iron open pit. A new association of gold and Sb-bearing sulfosalts is described. Gold occurs in an association with arsenopyrite, pyrite, and pyrrhotite in quartz-arsenopyrite veins type mineralization discovered in the Ingulets quarry. Gold was found as minute inclusions in arsenopyrite and as inclusions in Ag-Sb-, Pb-Sb-, Ag-Pb-Sb- sulfosalts. Based on both ore microscope and EMP measurements, the following minerals have been identified: arsenopyrite, pyrite, pyrrhotite, tetrahedrite, freibergite, sphalerite, chalcopyrite, galena, stibnite, plagonite, zinkenite, fuloppite, miargyrite, chalcostibite, andorite, and native Sb and electrum. It is the first discovery of Ag-Sb-Cu-Pb mineral association in the whole Kryvyi Rich structure. In this paper quantitative EMP measurements of all new minerals of the newly discovered association are presented. The baroacoustic decrepitation analyses of the massive arsenopyrite and pyrite showed temperature formation ranging between 450 ◦C and 650 ◦C with an average of T ~ 585 ◦C. Based on mineralogical investigations, ore occurrences are considered as the product of high and middle temperature hydrothermal processes.