Epithermal Deposits: Origin of Fluids, Mineralization and Geochemistry

A special issue of Minerals (ISSN 2075-163X). This special issue belongs to the section "Mineral Deposits".

Deadline for manuscript submissions: closed (31 December 2023) | Viewed by 8184

Special Issue Editors


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Guest Editor
Department of Geological Engineering, Pamukkale University, Denizli 20070, Turkey
Interests: hydrothermal mineral deposits; fluid inclusions; geochemistry

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Guest Editor
School of Earth and Environment, University of Leeds, Woodhouse Lane, Leeds LS2 9JT, UK
Interests: geochemistry of crustal fluids; metallic mineralization; gold

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Guest Editor
Central Research Institute of Geological Prospecting for Base and Precious Metals, Moscow 117545, Russia
Interests: gold deposits; geology of ore deposits; mineralogy; metallogeny

Special Issue Information

Dear Colleagues,

We cordially invite you to submit contributions to the Special Issue on ‘Epithermal Deposits: Origin of Fluids, Mineralization and Geochemistry’.

Epithermal, from the Greek meaning nearby heat, are a class of mineral deposits whose exploited resources are gold, silver, mercury, and base-metals. Deposits can be classified as low-, intermediate-, and high-sulfidation that are found close to the surface, largely above igneous intrusions, and show characteristic alteration and ore mineral assemblages. Hot-spring deposits and both liquid- and vapor-dominated geothermal systems are also commonly associated with epithermal deposits. In epithermal mineralized systems, low-density magmatic vapor or low-salinity liquids ascend to within circa 1 km of the surface, whereby through a number of processes, gold and other precious metals may precipitate in vein systems. As epithermal deposits have been the source of a significant portion of the world’s gold and silver supply, understanding key processes that transport and precipitate metals is very important. Advances in technology have led to new ideas of how metals might be transported and in what concentrations. Knowledge of how structure and alteration results in favorable fluid conduits and sites where the greatest mineralization occurs. These and other factors have improved our understanding of epithermal mineralization.

The main objective of this Special Issue of Minerals is to publish the latest research on ore-forming fluids, mineralization, and geochemistry in epithermal deposits.

We look forward to receiving your contributions.

Prof. Dr. Gülcan Bozkaya
Dr. David Banks
Dr. Evgeniy Naumov
Guest Editors

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Keywords

  • epithermal
  • fluid inclusions
  • geochemistry
  • mineralizations
  • gold

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Published Papers (3 papers)

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Research

24 pages, 6179 KiB  
Article
The Devonian Kalarskoe Epithermal Occurrence of the Kaburchak Au-Ag Cluster in the Altai-Sayan Folded Area, Russia: Geological Setting; Mineralogical, Geochemical, and Geochronological Features
by Alexander I. Chernykh, Polina N. Leibham, Lidia A. Sokolova, Olga V. Yakubovich, Maria O. Anosova and Evgeny A. Naumov
Minerals 2024, 14(7), 708; https://doi.org/10.3390/min14070708 - 12 Jul 2024
Cited by 1 | Viewed by 1139
Abstract
Prospecting efforts to located Au mineralization within the Altai-Sayan fold area (ASFA) over previous decades have revealed that Devonian epithermal Au-Ag mineralization is more widespread than previously recognized. The preservation of this type of mineralization in Paleozoic rocks offers new prospects for the [...] Read more.
Prospecting efforts to located Au mineralization within the Altai-Sayan fold area (ASFA) over previous decades have revealed that Devonian epithermal Au-Ag mineralization is more widespread than previously recognized. The preservation of this type of mineralization in Paleozoic rocks offers new prospects for the exploration of Au-Ag deposits in the underexplored region of Gornaya Shoria. The Kalarskoe epithermal Au-Ag occurrence represents Devonian epithermal mineralization within the Kaburchak cluster, Gornaya Shoria, Russia. This occurrence is confined to zones of argillic alteration that were superimposed on previously formed propylites. The argillic-altered rocks host quartz-sulfide veinlet zones. The mineralization of the Kalarskoe site is characterized by a high abundance of sulfide minerals: commonly, 5%–10%; often, up to 20%; and in some cases, up to 60%–70%. The ore minerals are represented by pyrite, arsenopyrite, sphalerite, galena, chalcopyrite, fahlores, native Au, and electrum, as well as by the sulfosalts Pb, Bi, Ag, Cu, and the tellurides of Au, Ag, and Pb. Based on mineralogical observations, at least four generations of sulfide mineral formations are distinguished within the ore occurrence. The mineralization of the Kalarskoe ore occurrence may be assigned to the intermediate sulfidation (IS) type. The results of the (U,Th)-He dating of pyrite from the pyrite-arsenopyrite massive body (pyr-3 and 4) revealed the protracted history of the mineralization in the intervals from ~399 to ~371 Ma. The obtained results substantially enhance the prospecting models for the exploration of epithermal Au-Ag deposits in the western part of the Altai-Sayan fold area (ASFA). Full article
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17 pages, 4915 KiB  
Article
Precious-Metal Mineralization and Formation Conditions of the Biche-Kadyr-Oos Epithermal Au-Ag Ore Occurrence (Eastern Sayan, Russia)
by Renat V. Kuzhuget, Natalia N. Ankusheva, Ailai K. Hertek, Yuri A. Kalinin, Bulat B. Damdinov, Franco Pirajno, Yuri V. Butanaev, Nadezhda V. Suge-Maadyr and Sholban N. Soldup
Minerals 2023, 13(12), 1529; https://doi.org/10.3390/min13121529 - 8 Dec 2023
Cited by 1 | Viewed by 1590
Abstract
The Biche-Kadyr-Oos epithermal Au-Ag ore occurrence is a prospective object in the Ak-Sug porphyry copper ore cluster (Eastern Sayan) in the northern part of the Central Asian orogenic belt (CAOB). The mineralization consists of gold-sulfide-quartz and gold-polysulfide-carbonate-quartz veins with argillic zones in the [...] Read more.
The Biche-Kadyr-Oos epithermal Au-Ag ore occurrence is a prospective object in the Ak-Sug porphyry copper ore cluster (Eastern Sayan) in the northern part of the Central Asian orogenic belt (CAOB). The mineralization consists of gold-sulfide-quartz and gold-polysulfide-carbonate-quartz veins with argillic zones in the Lower Cambrian volcanic-sedimentary rocks. The origin of the Au-Ag ore occurrence is still debatable. To determine the origin, we examined the mineralogical and geochemical features, conditions of formation, and fluid sources of the Biche-Kadyr-Oos ore. A mineralogical and geochemical investigation outlines three stages of mineral formation: early argillic stage; gold-sulfide-quartz stage with pyrite, marcasite, pyrrhotite, arsenopyrite, chalcopyrite, less frequently sphalerite, hessite, gold, and electrum; and late gold-polysulfide-carbonate-quartz stage with gold, electrum, Hg-electrum, Se-acanthite, Se-galena, bornite, tennantite, tetrahedrite, hessite, tellurobismuthite, bismuthinite, matildite, jamesonite, ourayite, native Bi, and barite. Fluid inclusion study (thermometry, Raman spectroscopy) in quartz and mineral thermometry (electrum and sphalerite paragenesis) determined that ore veins were formed at P~0.5 kbar from CO2-water Na-K-chloride fluid (4.9–9.6 wt % NaCl eqv) and temperatures from 300 to 200 °C (early gold-sulfide-quartz veins at 300–230 °C, and late gold-polysulfide-carbonate-quartz veins at 290–200 °C) and variations in fO2, fS2, fSe2 and fTe2. The S isotopic composition in sulfides and δ34SH2S values of the fluid are +1.3‰ and +4.7‰, respectively, (T = 300–275 °C) indicating magmatic S in ore formation. The oxygen isotope data indicate that during the formation of veins, the magmatic fluid mixed with meteoric water (δ18Ofluid is from +3.4 to +6.4‰). The isotopic data that were obtained combined with mineralogical and geochemical features and conditions of ore formation indicate the similarity of Biche-Kadyr-Oos ore occurrence with epithermal Au-Ag deposits of intermediate sulfidation (IS) type. The presence of epithermal Au-Ag mineralization of the Biche-Kadyr-Oos IS type in ore cluster of the Ak-Sug Cu-Au-Mo porphyry deposit indicates the existence of a single porphyry-epithermal ore-magmatic system. Full article
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38 pages, 9948 KiB  
Article
Trace Element Characteristics of Pyrite and Arsenopyrite from the Golden Ridge Gold Deposit, New Brunswick, Canada: Implications for Ore Genesis
by Alan Cardenas-Vera, Moya MacDonald, David R. Lentz and Kathleen G. Thorne
Minerals 2023, 13(7), 954; https://doi.org/10.3390/min13070954 - 17 Jul 2023
Cited by 1 | Viewed by 3414
Abstract
The Golden Ridge gold deposit is located in southwestern New Brunswick, in the Canadian Appalachians. Gold mineralization is consistently associated with acicular arsenopyrite, and to a lesser degree with pyrite, disseminated in host rocks, sulphide veinlets, quartz-carbonate veins, and the breccia matrix. According [...] Read more.
The Golden Ridge gold deposit is located in southwestern New Brunswick, in the Canadian Appalachians. Gold mineralization is consistently associated with acicular arsenopyrite, and to a lesser degree with pyrite, disseminated in host rocks, sulphide veinlets, quartz-carbonate veins, and the breccia matrix. According to petrographic-based textural differences, four types of pyrite and two types of arsenopyrite are recognized with associated assemblages. Based on SEM-BSE imaging and LA-ICP-MS spot analyses of the different types of pyrites and arsenopyrites, “invisible gold” (solid solution in the crystal lattice of pyrite and arsenopyrite or <100 nm nanoparticles) and micrometer-size inclusions were identified as the main forms of Au. Four syn-gold mineralization pulses of fluid are suggested. The initial hydrothermal fluid, which generated low-grade pyrite (Py-I) enriched in Sb, Pb, Cu, Co, Ni, and Bi, was followed by a second pulse of fluid enriched in arsenic and gold, generating coprecipitated Py-II and Asp-I. The third and fourth pulses were enriched in both arsenic and gold and precipitated Py-III, then coprecipitated Py-IV and Asp-II, which constitute the most important Au depositional episodes. The repeated occurrence of growth zones with Au enrichment in the arsenian pyrites (Py-II, Py-III, and Py-IV) indicate surface growth during metal deposition and disequilibrium crystallization processes. Full article
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