Causes and Factors in the Genesis of Bonanza Orebodies in the Bakhmut Zone of the Pioner Stockwork Gold Deposit in Piamurye

Abstract

When studying an ore shoot in the Bakhmut ore zone of the Pioner mesothermal stockwork gold deposit (Priamurye, Russia) of vein and disseminated gold-quartz ores at its different levels, the authors identified discrete anomalously gold-rich areas (bonanzas). The objective of the research was to investigate the causes and conditions for bonanza formation and the facilitating factors. In addition to the analysis of the general distribution of gold in orebodies, a detailed macro- and microscopic study was carried out on the distribution of native gold in samples of ore and the nature of native gold. Gold particles are found to be hypogene, including those at the surface. In the zones of brecciated rocks, a distinct spatial displacement of native gold accumulations upwards relative to a dense network of veinlets and nests of quartz and their almost complete absence in the quartz bodies indicate telescoping of high-grade gold accumulations formed in a single productive gold-quartz stage. At the same time, spatial proximity is established between fields of gold particle accumulations and quartz-filled fracture cavities that show dominance in size and zones where swellings of quartz-filled fractures tend to thin and pinch out. Our findings and laboratory experiments yielded the information for a scientifically sound model of natural gas flotation of native gold nanoparticles as part of the «Aucr + gas» associates with the formation of bonanzas under the above favorable conditions at higher levels of the deposit in the presence of different low permeability screens.