Editorial for the Special Issue “Native Gold as a Specific Indicator Mineral for Gold Deposits, 2nd Edition”

This Special Issue (v.2) [1] is a continuation of “Native Gold as a Specific Indicator Mineral for Gold Deposits” (v.1) [2]. Comprising 14 articles focused on the typomorphic features of native gold and other gold minerals, the genesis of gold mineralization, and sources of ore-forming fluids [1], this Special Issue seeks to explore the reasons behind the variation in the chemical and mineralogical characteristics of native gold and to develop effective criteria for forecasting and searching for gold deposits.

Five papers in this collection examine the typomorphic features of placer gold [Contributions 1–5]. In their work, Chapman et al. [Contribution 1] studied alluvial and in situ gold mineralization from three different localities (Allt Ghamhnain, Eas Anie, and Halliday) and adjacent areas of the Cononish Au–Ag deposit in central Scotland. The genetic relationships between alluvial and in situ occurrences are based on the assumption that the P-T-X conditions at the sites of mineral deposition are reflected in common compositional signatures of gold. Following their analysis, the authors proposed the combination of the alluvial gold signature, a structural model, and (if possible) an in situ gold signature and paragenesis to form a more effective exploration tool.

The work of Nikiforova [Contribution 2] provides new mineralogical and geochemical data on placer gold and the mechanisms of its distribution in the territory east of the Siberian platform. The mineralogical method employed in this study enables the development of criteria for predicting resources and types of gold deposits, and the assessment of the prospects of gold mining potential in platform areas.

Gerasimov and Kondratieva [Contribution 3] present new data on gold mineralization in the Khaptasynnakh ore zone of the Anabar Shield (Far East region, Russia), with the low-temperature gold–telluride paragenesis, as well as mineral inclusions in native gold, suggesting that epithermal Au–Te mineralization and that the gold–sulfide occurrences of the Khaptasynnakh ore zone are sources of the placer deposits.

In their contribution, Drăguşanu and Tămaș [Contribution 4] present new data on the morphology and chemical composition of newly discovered occurrences of native gold from the alluvial placers in the Baia region, Eastern Carpathians, Romania. Gold grains, collected from three different locations in the region, were studied to clarify their morphological characteristics (grain size, shape, sphericity, roundness), chemical composition, and associated minerals. Their morphological characteristics suggest a relatively short distance of transportation of the gold grains (less than 30 km), and based on the chemical composition of the native gold particles (up to 6 wt.% Ag), the authors [Contribution 4] propose an orogenic type of primary gold deposition. While the presence of quartz inclusions within and on the surface of gold grains suggests gold-bearing conglomerates, the presence of ridges on the gold grains indicates the influence of aeolian processes.

The paper by Palyanova et al. [Contribution 5] is devoted to the study of the chemical compositions and relationships of minerals in heterogeneous gold grains collected from a placer locality in Eastern Kamchatka (Russia). They observed the intergrowths of auricupride and tetra-auricupride with earlier-formed and later minerals. These authors assume that the probable source of Au–Ag–Cu mineralization is located in the upper parts of the ultrabasic massif of Mounts Soldatskaya and Golaya (Kamchatka Cape Peninsula).

Prokofiev et al. [Contribution 6] present new data on fluid inclusions composed of dense carbon dioxide in quartz from the depth interval penetrated by an SD-3 Kola Superdeep borehole. The authors propose a new conceptual model of the transport of Au–Ag nanoparticles using high-density carbon dioxide fluid from the Earth’s mantle to its crust.

In their study, Shaparenko et al. [Contribution 7] investigated the composition of volatiles in quartz and pyrite from the Konduyak gold deposit (Yenisei ridge, Russia). The study of volatile compounds in ore formation fluid remains an important clue in elaborating the genesis of deposits, especially hydrothermal deposits. The authors identified a complex composition, including a wide range of hydrocarbons, which suggests a genetic relationship with regional metamorphic processes.

Zhegunov et al. [Contribution 8] present the results of gold mineralization and fluid inclusion study of the Evevpenta Au–Ag epithermal deposit on the Kamchatka Peninsula (Russia). The authors integrate petrographic, microthermometric, and Raman spectroscopic data to constrain the PTX conditions of ore-forming fluids and the paragenesis of quartz generations associated with adularia-quartz veins, providing new data from an area with limited previously published information.

In their study, Li et al. [Contribution 9] explore the source of the ore-forming fluids and ore genesis of the Batailing gold deposit (Central Jilin province, Northeast China). The authors conclude that the origin of the Batailing deposit is of the mesothermal magmatic–hydrothermal lode type. C isotopic data and fluid inclusions indicate an organic carbon source of the fluids, while S-Pb isotopic data show a mainly magmatic source of ore-forming materials. Li et al. [Contribution 9] therefore propose that fluid immiscibility caused by a sudden decrease in pressure may lead to the precipitation of sulfides and Au in the Batailing deposit.

Pyrite is one of the most important Au-bearing minerals in gold deposits, and trace metal contents in this mineral can be used to reconstruct the evolution of ore-forming fluids. In light of this, Liao et al. [Contribution 10] studied the pyrite textures, trace element geochemistry, and Pb Isotopes of the Yanzhupo gold deposit in the Jiangnan Orogen (South China). The chemical compositions of pyrite and galena Pb isotopes suggest that the ore-forming fluids of the Yanzhupo deposit may be from the deep upwelling of granitic magma.

In their work, Rozhdestvina and Palyanova [Contribution 11] studied the morphostructural, chemical, and genetic features of native gold in brown coals from the Yerkovetsky deposit (Far East Russia). They found out that native gold is syngenetic with the formation of the brown coals, and the microphases dispersed in the minerals of loose and sandy-clay sediments were the source of native gold.

Snachev and Rassomakhin [Contribution 12] submitted a review on the occurrence of noble metals related to black shale formations in the Russian Southern Urals. In their paper, they provide a detailed geological description of the studied area and present a reliable genetic model based on the available data. This paper makes a key contribution by highlighting that the structural-formational zones of the Southern Urals appear to provide a natural laboratory for testing this model.

Rozhdestvina and Palyanova [Contribution 13] studied the morphostructural and genetic features of native gold in apocarbonate tremolite–diopside skarns of the Ryabinovoye deposit, located in the southeastern part of the Aldan Shield in the Russian Far East. They found that native gold inherits the morphology of tremolite crystals, aggregates, in intercrystalline spaces, and that in zones with redeposited calcite, it is characterized by irregular lumpy shapes, as well as partially or completely faceted grains with a dense structure. The authors suggest that at many gold-skarn deposits, Au-bearing carbonate rocks may be the source of the gold.

Vikent’eva et al. [Contribution 14] present the results of studies of the montbrayite from the large Svetlinsk gold–telluride deposit (South Urals, Russia). The chemical formula of this mineral was previously given as Au₂Te₃ or (Au, Sb)₂Te₃, and was then revised to (Au, Ag, Sb, Pb, Bi)₂₃(Te, Sb, Pb, Bi)₃₈. The authors show significant variations in Au, Ag, Sb, Bi, Pb, and Te in the composition of the mineral and calculate the empirical formula Au_{16.43–23.28}Sb_1.79–6.09Te_{32.01–38.89}Ag_0–3.69Bi_0–0.14Pb_0–0.90Cu_0–1.96 on the basis of 61 atoms. Studying the decomposition of montbrayite into native gold and Sb-bearing calaverite or tellurantimony with a small amount of altaite, Vikent’eva and coauthors [Contribution 14] propose the substitution mechanisms for Sb with Au and Te in montbrayite.

Given the high standard and broad scope of the research presented here, it is my hope that this Special Issue “Native Gold as a Specific Indicator Mineral for Gold Deposits, v.2” will attract significant attention from authors and assist them in better understanding and predicting how, where, and when gold deposits form and solving the problem of full extraction from ores and tailings after mining.