Characteristics of Supergene Gold of Karst Cavities of the Khokhoy Gold Ore Field (Aldan Shield, East Russia)

Galina S Anisimova,Larisa A Kondratieva,Veronika N Kardashevskaia

doi:10.3390/min10020139

Abstract

Typomorphic features of supergene gold in karst cavities were studied in the recently discovered Au–Te–Sb–Tl deposit within the Khokhoy gold ore field of the Aldan-Stanovoy auriferous province (Aldan shield, East Russia). Two morphological types of supergene gold, massive and porous, are recognized there. The first type is represented by gold crystals and irregular mass, with the fineness ranging from 835 to 1000‰. They are closely associated with goethite, siderite, unnamed Fe, Te, and Tl carbonates, Tl tellurites/tellurates and antimonates, as well as avicennite with a Te impurity. The second type is represented by mustard gold of two types with different internal structure: microporous and dendritic. The supergene gold is characterized by persistently high fineness. Along with Ag, it invariably contains Hg (up to 5.78 wt%) and Bi, and, rarely, Pb, Cu, and Fe. The supergene gold is chemically homogeneous, and its particles are all marked by high fineness, without any rims or margins. The obtained characteristics made it possible to prove the existence of two genetic types of supergene gold. Mustard microporous gold is the result of the decomposition of the associated minerals—goethite, Tl oxides, tellurium, Fe, Mn and Tl carbonates and antimonates, containing microinclusions of gold. Massive gold and dendrites are newly formed. The decomposition, remobilization, and reprecipitation of residual gold nanoparticles and their aggregation led to the formation of dendrites, and with further crystal growth and filling of pores, to gold of massive morphology. In terms of morphology, internal structure, fineness, and trace element composition, supergene gold of the Khokhoy gold ore field is comparable to gold from the Kuranakh deposit (Russia) and the Carlin-type gold deposits. It also is similar to spungy and mustard gold from Au–Te and Au–Sb deposits, weathering crusts, and placers. Its main characteristic feature is a close paragenesis with Tl minerals.

Highlights

The importance of gold-bearing supergene zones increased significantly in relation to the discovery and commercial exploitation of the Carlin-type gold deposits (USA) [1,2,3,4,5]
In Russia, assigned to this type are deposits localized in karst cavities such as the Kuranakh deposit within the Central Aldan district of Yakutia and the Vorontsovskoe deposit in the Urals [6,7,8,9]
Supergene gold in karst cavities has specific features, exhibits various textural and chemical characteristics that can help in elucidating the process of formation of supergenic gold

Summary

Introduction

The importance of gold-bearing supergene zones increased significantly in relation to the discovery and commercial exploitation of the Carlin-type gold deposits (USA) [1,2,3,4,5]. In Russia, assigned to this type are deposits localized in karst cavities such as the Kuranakh deposit within the Central Aldan district of Yakutia and the Vorontsovskoe deposit in the Urals [6,7,8,9]. The question of native gold formation in supergene conditions, including in karst cavities, remains are as yet poorly investigated. Supergene gold in karst cavities has specific features, exhibits various textural and chemical characteristics that can help in elucidating the process of formation of supergenic gold. That’s why studies on the typomorphic features of the recently discovered supergene gold from the Khokhoy gold ore field within the Aldan-Stanovoy auriferous province are quite topical now.

Methods

Results

Conclusion