Gold-bearing reefs of the Witwatersrand Basin: A model of synsedimentation hydrothermal formation

Abstract

The current concepts concerning the genesis of the unique ore-bearing reefs of the Witwatersrand Basin and its gold resource potential are considered. The results of microscopic examination of ore from the Black, Ventersdorp Contact, Carbon Leader, and Vaal reefs, as well as of thermobarometric study of quartz, are presented. A model of synsedimentation hydrothermal origin of the reefs in the process of evolution of primary colloidal-disperse systems is substantiated on the basis of these results and the data published by other authors. The formation of these systems is related to the periodic gain of deep ore-bearing gas-saturated fluids. The gold mineralization was formed under conditions of partially closed systems, where various mineral-forming processes developed (metasomatism, crystallization of true solutions and gels, gel metasomatism, dispersion of crystalline phases, segregation of mineral particles, formation of early minerals, etc.). New data on REE specialization of ore-bearing fluids are discussed. The specific features of the gold, carbonic, and uranium mineralization of the intracratonic basin are emphasized.

Structure of ore fields and deposits: Current status and outlook for further development

“…Recent data on the formation conditions of gold mineralization in the Witwatersrand Basin, together with results of some previous investigations, allow us to consider gold-bearing conglomerates as polygenetic synsedimentation hydrothermal ore related to a deep source of main ore components (Safonov and Prokof'ev, 2006). These conclusions are important for a critical analysis of the nature of ore mineralization in sedimentary basins and return us to the problem of stratiform deposits of Au, Cu, Pb, Zn, U, Ni, Mo, REE, and other metals and some industrial minerals.…”

Ore–Bearing Fluids of the Blagodatnoye Gold Deposit (Yenisei Ridge, Russia): Results of Fluid Inclusion and Isotopic Analyses

“…Homogenization in these inclusions occurs to vapor, suggesting a gaseous state of the fluid. Data from [5][6][7][8][9]43,44] show that the CO 2 /CH 4 value is an indicator of redox conditions of hydrothermal systems. Based on this fact, the fluid trapped in the inclusions in which CO 2 > CH 4 (CO 2 /CH 4 value ranges from 15.4 to 93.0, Table 2) is attributed to the oxidized type.…”

“…There are a number of works in international and Russian journals devoted to the study of gold deposits by fluid inclusions analysis. In these works, data on the temperatures, pressures and salinity of fluids are reported [5][6][7][8][9][10]. Development of Raman spectroscopy and its application to individual fluid inclusions resulted in an increased number of works in which fluid composition is discussed [6,[10][11][12][13][14][15][16][17][18][19].…”

Typomorphic Features and Source of Native Gold from the Sykhoi Log Area Placer Deposits, Bodaibo Gold-Bearing District, Siberia, Russia

“…The sulphide-poor quartz-gold-bearing lodes favourable for the formation of placers are of subordinate importance in the territory of the Bodaibo District. We can only assume that the placers were formed due to giant primary, mainly quartz-gold lode deposits, which are now completely eroded [7][8][9][10].…”