Gold in the Oxidized Ores of the Olympiada Deposit (Eastern Siberia, Russia)

Sergey A Silyanov,Yelena A Zvyagina,Boris M Lobastov,Anatoly M Sazonov,Andrey A Savichev

doi:10.3390/min11020190

Abstract

Native gold and its satellite minerals were studied throughout the 300 m section of oxidized ores of the Olympiada deposit (Eastern Siberia, Russia). Three zones are identified in the studied section: Upper Zone ~60 g/t Au; Middle Zone ~3 g/t Au; Lower Zone ~20 g/t Au. Supergene and hypogene native gold have been found in these zones. Supergene gold crystals (~1 μm), their aggregates and their globules (100 nm to 1 μm) predominate in the Upper and less in Middle Zone. Relic hypogene gold particles (flattened, fracture and irregular morphology) are sporadically distributed throughout the section. Spongiform gold occurs in the Lower Zone at the boundary with the bedrock, as well as in the bedrock. This gold formed in the process of oxidation of aurostibite, leaching of impurities and its further dissolution. Hypogene gold is commonly isolated but for supergene gold typically associated with ferric (hydr)oxides. New formation of gold occurred due to oxidation of sulfide ores and release of “invisible” gold, as well as dissolution, mobilization and re-deposition of metallic hypogene gold. A model for the formation of oxidized ores with the participation of meteoric and low-temperature hydrothermal waters has been proposed.

Highlights

We provided a general review of geology and primary sulfides ore of the Olympiada gold deposit [26]
The middle part of the section (Middle Zone) from a depth of ~135 to ~213 m has a graybrown color with a yellowish tint in the roof, which changes to light gray-brown and dark raspberry-red towards the bottom
The Lower Zone is distinguished by a significant accumulation of Au, usually in the form of spongiform gold, which appeared during the destruction of hypogene aurostibite, as well as wide development of supergene antimony and mercury minerals

Summary

Introduction

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Oxidized ores of gold deposits are important formations for the mining and metallurgical industry, as the weathering process leads to their partial enrichment and increased content of the noble metal. Oxidized ores do not require complex processing technologies and are profitable even at low grades. Valuable oxidation zones of gold ores are known in Russia, Kazakhstan, Australia, Brazil and other countries [1,2,3,4,5]

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