Mustard Gold of the Gaching Ore Deposit (Maletoyvayam Ore Field, Kamchatka, Russia)

Tolstykh Tolstykh,Sidorov Sidorov,Bobrova Bobrova,Palyanova Palyanova

doi:10.3390/min9080489

Abstract

The Gaching high-sulfidation (HS) epithermal Au–Ag deposits, part of the Maletoyvayam ore field, which is located in the volcanic belts of the Kamchatka Peninsula (Russia). The main ore components are native gold, tellurides, selenides, and sulphoselenotellurides of Au and oxidation products of Au-tellurides. This study examines the different types of native gold in this ore deposit and the mechanisms and sequential transformation of calaverite (AuTe2) into mustard gold. The primary high fineness gold (964‰–978‰) intergrown with maletoyvayamite Au3Te6Se4 and other unnamed phases (AuSe, Au(Te,Se)) differ from the secondary (mustard) gold in terms of fineness (1000‰) and texture. Primary gold is homogeneous, whereas mustard is spongy. Two types of mustard gold were identified: a) Mixtures of Fe-Sb(Te,Se,S) oxides and fine gold particles, which formed during the hypogenic transformation stage of calaverite due to the impact of hydrothermal fluids, and b) spotted and colloform gold consisting of aggregates of gold particles in a goethite/hydrogoethite matrix. This formed during the hypergenic transformation stage. Selenides and sulphoselenotellurides of gold did not undergo oxidation. Pseudomorphic replacement of calaverite by Au-Sb(Te,Se,S,As) oxides was also observed.

Highlights

One of the fundamental tasks in the study of the epithermal deposits is identifying the mechanisms of gold formation
The high concentrations of Au in the hypergenesis zones of epithermal deposits is due to the presence of so-called mustard gold, which is difficult to detect
Our research shows a sequential transformation of the primary mineralization, which is represented by calaverite to mustard gold

Summary

Introduction

One of the fundamental tasks in the study of the epithermal deposits is identifying the mechanisms of gold formation. Sample analyses show high concentrations of Au, while the presence of visible gold is absent or is only represented by single grains where the amount of Au is not capable the providing such high concentrations. It appears that the finest fraction (

Methods

Results

Discussion

Conclusion