Contrasting Surficial Composition of Native Gold from Two Different Types of Gold Ore Deposits

Minerals

Vladimir L. Tauson¹  Artem S. Makshakov¹  Sergey V. Lipko¹  Raisa G. Kravtsova¹  Kirill Yu. Arsent’ev² 

[1] A.P. Vinogradov Institute of Geochemistry, Siberian Branch of Russian Academy of Sciences, Irkutsk 664033, Russia;Limnological Institute, Siberian Branch of Russian Academy of Sciences, Irkutsk 664033, Russia;

关键词: native gold;    surface;    chemical composition;    electrum;    sulfidation;    oxidation;    XPS;    AES;    SEM-EDX;    EMPA;   

DOI  :  10.3390/min7080142

来源: DOAJ

【 摘 要 】

Native gold grains sampled at two different gold ore deposits in Eastern Russia have been studied by the techniques of electron spectroscopy (X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES)), electron microprobe analysis (EMPA), and scanning electron microscopy with energy dispersive X-ray spectrometry (SEM-EDX). The high-fineness gold of the deposit hosted by relatively high temperature gold-quartz-sulfide mesothermal ore formation contains no oxidized Au constituents on grain surfaces, whereas the less fine gold of the epithermal Au-Ag deposit contains gold oxidized to the Au (I) state, or higher, in half of the cases. At this deposit the surface of native Au consists of a thin layer (~15 nm) with elevated Ag and S contents and an underlying SiO2–containing layer ~30–60 nm thick. Such a composite coating can perform a protective function and prevent the gold-silver sulfides in surficial parts of AuAg grains from oxidation. The sulfur-enriched marginal parts of native gold particles do not always correlate with the stoichiometry of well-known binary AuAg-sulfides and have a variable composition. This may be due to the existence of solid solutions, Ag2−xAuxS, if there is enough S or S adsorption-stabilized cluster agglomerates, AgnAumS, under sulfur deficit. The effect of the formation of nano-scale surficial zonality on the surface of native gold is quite common in nature and applicable to geological exploration and technology of gold-ore processing. It can facilitate establishing the geochemical environment and genetic type of Au mineralization.

【 授权许可】

Unknown