Genesis of the Gold Deposits: News from Geology, Fluid Inclusions and Isotopes

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

Deadline for manuscript submissions: closed (30 October 2023) | Viewed by 7149

Special Issue Editors


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Guest Editor
State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing 100083, China
Interests: orogenic belt; gold deposits; epithermal transition; polymetallic mineralization; fluid inclusions
College of Earth Sciences, Chengdu University of Technology, Chengdu 610059, China
Interests: gold deposits; porphyry–skarn–epithermal ore system; fluid inclusions
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Special Issue Information

Dear Colleagues,

Gold continues to be a critical commodity with the supply–demand balance and is providing economic stability worldwide. Auriferous deposits have been classified in a number of ways over 40 years. Current genetic types of gold deposits mainly comprise the epithermal, carlin-type, porphyry and skarn, IOCG, and orogenic, with subordinate placer-type, laterite-type, VMS, and magmatic. They are comprehensively constrained by the deposit geology, tectonic setting, ore fluid temperature and salinity, and multiple systems of isotopes. These studies provide a good way of understanding ore-forming process and guiding mineral exploration.

This Special Issue aims at displaying recent achievements in the research of geology, fluid inclusions, isotopic geochemistry, and mineralogy of gold deposits. We welcome studies on the ore genesis of different ore systems, including ore fluids evolution, high-precision dating, ore-forming process, as well as ore-related magmatism, deformation, and related tectonics. We also solicit methodological studies employing in situ analytics that can reflect the ore-forming fluid sources, metallogenic age, and precipitation mechanism.

Dr. Yongmei Zhang
Dr. Yiwei Peng
Guest Editors

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Keywords

  • fluid inclusion
  • isotope geochemistry
  • gold deposit
  • ore genesis
  • mineralization age
  • tectonic evolution
  • ore and gangue minerals

Published Papers (5 papers)

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Research

24 pages, 8308 KiB  
Article
Metallogenic Mechanism of Carlin-Type Gold Deposit in Zhen’an-Xunyang Basin, in the South Qinling of China: Constraints of In Situ Trace Elements and S Isotopes from Newly Discovered Wangzhuang Gold Deposit
by Wuyi Meng, Jiajun Liu, Huanhuan Wu, Zhen Zhang, Weidong Tang, Yongbao Gao, Liyong Wei, Bin Jia, Xin Zheng and Ningbo Liu
Minerals 2023, 13(11), 1459; https://doi.org/10.3390/min13111459 - 20 Nov 2023
Viewed by 824
Abstract
The Zhen’an-Xunyang Basin is a late Paleozoic rifted basin with a series of Au-Hg-Sb deposits that have been found, mostly along the Nanyangshan fault. Recently discovered large- and medium-sized gold deposits such as the Xiaohe and Wangzhuang deposits exhibit typical characteristics of Carlin-type [...] Read more.
The Zhen’an-Xunyang Basin is a late Paleozoic rifted basin with a series of Au-Hg-Sb deposits that have been found, mostly along the Nanyangshan fault. Recently discovered large- and medium-sized gold deposits such as the Xiaohe and Wangzhuang deposits exhibit typical characteristics of Carlin-type gold deposits. Therefore, it is imperative to select a typical deposit for an in-depth study of its metallogenic mechanism to support future prospecting efforts targeting the Carlin-type gold deposits within the area. Based on detailed field investigation and microphotographic observation, four ore-forming stages are identified: I, low-sulfide quartz stage, characterized by euhedral, subhedral pyrite, and fine veins of quartz injected parallel to the strata; II, arsenopyrite–arsenian pyrite–quartz stage, the main mineralization stage characterized by strongly silicified zones of reticulated quartz, disseminated arsenopyrite, fine-grained pyrite; III, low-sulfide quartz stage, characterized by large quartz veins cutting through the ore body or fine veins of quartz; Ⅳ, carbonate–quartz stage, characterized by the appearance of a large number of calcite veins. In situ analysis of trace elements and S isotopes of typical metal sulfides was carried out. The results show significant variations in the trace element compositions of metal sulfides in different stages, among which the main mineralization stage differs notably from those of the Au- and As-low surrounding strata. In situ S isotope analysis reveals δ34S values ranging from 15.78‰ to 28.71‰ for stage I metal sulfides, 5.52‰ to 11.22‰ for stage II, and 0.3‰ to 5.25‰ for stage III, respectively, revealing a gradual decrease in S isotopic values from the pre-mineralization stage to post-mineralization stage, similar to those observed in the Xiaohe gold deposit. These features indicate a distinct injection of relatively low 34S hydrothermal fluids during the mineralization process. The element anomalies of the 1:50,000 stream sediment in the region revealed ore-forming element zonation changing in W→Au (W)→Hg, Sb (Au) anomalies from west to east, manifested by the discovery of tungsten, gold, and mercury–antimony deposits in the area. Moreover, conspicuous Cr-Ni-Ti-Co-Mo anomalies were observed on the western side of the Wangzhuang and Xiaohe gold deposits, indicating a potential concealed pluton related to these deposits. These lines of evidence point to a magmatic–hydrothermal origin for the Carlin-type gold deposits in this area. Furthermore, hydrothermal tungsten deposits, Carlin-type gold deposits, and low-temperature hydrothermal mercury–antimony deposits in this region are probably controlled by the same magma–hydrothermal system. Full article
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33 pages, 40465 KiB  
Article
Ore Mineralogy, Fluid Inclusion Geochemistry, and Zircon U-Pb Geochronology of the Nanmingshui Gold Deposit in East Junggar, Xinjiang, Northwest China: Implications for Ore Genesis
by Zhanlin Ge, Xuexiang Gu, Yongmei Zhang, Cheng Ma, Di Hao, Yanrong Zheng, Xiaoxing Zhang, Luzhi Wang, Ming Liu and Weizhi Chen
Minerals 2023, 13(10), 1296; https://doi.org/10.3390/min13101296 - 06 Oct 2023
Viewed by 1344
Abstract
The Nanmingshui gold deposit, located in the eastern segment of the Kalamaili gold belt (KGB), is hosted by the sub-greenschist facies rocks of the Lower Carboniferous Jiangbasitao Formation. The genesis of this deposit, however, has been debated for decades because of controversial constraints [...] Read more.
The Nanmingshui gold deposit, located in the eastern segment of the Kalamaili gold belt (KGB), is hosted by the sub-greenschist facies rocks of the Lower Carboniferous Jiangbasitao Formation. The genesis of this deposit, however, has been debated for decades because of controversial constraints on the P-T-X conditions and origins of hydrothermal fluid and mineralization age. In this study, we present gold-bearing sulfide compositions, fluid inclusions, H-O isotopes, and the results of hydrothermal zircon U-Pb dating to provide new insights into the genesis of the gold deposit. Three gold mineralization stages are recognized: quartz–pyrite–minor native gold veins (early), quartz–tourmaline–arsenopyrite–pyrite–gold–polymetallic sulfide veins (middle), and quartz–calcite veinlets (late). Gold predominantly occurs as native gold with high fineness ranging from 941 to 944 in sulfides and quartz, and some as solid solutions (Au+) within the lattice of pyrite and arsenopyrite. Three types of primary fluid inclusions are identified in hydrothermal quartz: CO2-H2O (C-type), aqueous (W-type), and pure CO2 (PC-type) inclusions. The early-stage quartz mainly contains C-type and minor W-type inclusions, with total homogenization temperatures (Th) of 220–339 °C, salinities of 0.4–3.7 wt.% NaCl eqv., and bulk densities of 0.66–1.01 g/cm3. All three types of inclusions are observed in the middle-stage quartz, of which the C- and W-type inclusions yield Th values of 190–361 °C, with salinities of 0.4–6.0 wt.% NaCl eqv. and bulk densities of 0.69–0.99 g/cm3. The late-stage quartz contains only W-type inclusions that have lower Th values of 172–287 °C, higher salinities of 1.4–6.9 wt.% NaCl eqv., and bulk densities of 0.79–0.95 g/cm3. Trapping pressures estimated from C-type inclusions in the early and middle stages cluster at 280–340 MPa and 220–310 MPa, respectively, corresponding to metallogenic depths of 10–13 km and 8–11 km. The H-O isotopic compositions (δ18Owater = 1.8–10.9‰, δD = −99 to −62.9‰) and microthermometric data indicate that the ore-forming fluids belong to medium–high-temperature, low-salinity, medium-density, and CO2-rich-H2O-NaCl ± CH4 ± N2 systems, probably originating from metamorphic water. Fluid immiscibility is a crucial mechanism for gold precipitation. Additionally, the U-Pb dating of hydrothermal zircons, from the auriferous quartz–tourmaline vein, yield a weighted mean 206Pb/238U age of 314.6 ± 9.6 Ma. Taking all of the above, the Nanmingshui deposit can be reasonably classed as a typical mesozonal orogenic gold deposit in the KGB, which was formed in a Late Carboniferous tectonic transition from syn-collision between the Jiangjunmiao accretionary complex and Yemaquan arc to post-collision in the East Junggar Orogen. Our results serve to better understand the gold mineralization and genesis of the Late Paleozoic orogenic system in the Kalamaili area, Xinjiang. Full article
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26 pages, 13959 KiB  
Article
Two-Stage Superimposed Gold Mineralization in the Xiejiagou Gold Deposit, Shandong Province: Insights from Fluid Inclusions, H-O-S Isotopes, and Trace Elements
by Ze-Zhong Du, Zhi-Zhong Cheng, Xiao-Feng Yao and Xing-Long Bao
Minerals 2023, 13(9), 1210; https://doi.org/10.3390/min13091210 - 15 Sep 2023
Viewed by 914
Abstract
The Xiejiagou gold deposit located in the Zhaoyuan-Laizhou gold belt is composed of altered-rock-type gold mineralization and superposed auriferous quartz veins, showing unique two-stage gold mineralization. Oxygen and hydrogen isotopic analyses yielded the following results: δ18OH2O = 0.8‰ to 4.4‰ [...] Read more.
The Xiejiagou gold deposit located in the Zhaoyuan-Laizhou gold belt is composed of altered-rock-type gold mineralization and superposed auriferous quartz veins, showing unique two-stage gold mineralization. Oxygen and hydrogen isotopic analyses yielded the following results: δ18OH2O = 0.8‰ to 4.4‰ and δD = −106‰ to −85‰ for altered-rock-type mineralization, and δ18OH2O = 3.6‰ to 5.6‰ and δD = −98‰ to −89‰ for auriferous quartz-veins. Combined studies on Co/Ni, Sb/Bi and As/Ag ratios of pyrites, it can be inferred that the ore-forming fluids were dominated by magmatic water mixed with very little meteoric water. The fractured altered rocks in the ore-hosting fault zones are characterized by mylonitization, cataclastic lithification, and structural lenses, reflecting a compressional (closed) ore-forming system. In contrast, the occurrence of auriferous quartz veins in fissures of altered-rock-type orebodies and the fact that altered-rock-type ores commonly occur as breccias cemented by auriferous quartz veins that reflect an extensional (open) ore-forming system for the vein mineralization. The increase in δ34S values from stage I (5.8‰–7.2‰) to stage II (6.6‰–9.0‰) indicate that the altered-rock-type mineralization was the result of intense water–rock interaction, while the occurrence of immiscible inclusions in auriferous quartz veins demonstrates that fluid immiscibility contributes significantly to gold deposition in the vein-type mineralization. Fluid-inclusion microthermometric data indicate that the fluids for the altered-rock-type mineralization are characterized by moderate-to-high temperature (262–368 °C), and low-to-moderate salinity (4.3–10.8 wt.% NaCl equivalent). In contrast, halite-bearing inclusions are found in auriferous quartz veins, and its fluids are characterized by moderate-to-high temperature (290–376 °C) and moderate-to-high salinity (5.1–41.9 wt.% NaCl equivalent). From early stages (I and II) to the late stage (III), homogenization temperature and high temperature element (W, Sn, and Mo) concentrations in pyrite first decrease and then increase, δ34S values and metallization-related element (Au, Ag, and Bi) concentrations in pyrite first increase and then decrease. Therefore, it can be inferred that the two distinct types of gold mineralization in the Xiejiagou gold deposit may be two separate mineralization events. The presence of magnetite in the auriferous veins suggests an increase in oxidation state during the vein mineralization. Importantly, the Xiejiagou gold deposit preserves two types of mineralization in a single deposit and uniquely records a metallogenic transition from a compressional, reduced environment to an extensional, oxidized environment, as a result of a regional stress field transition that occurred in the Zhaoyuan-Laizhou gold belt at ca. 120 Ma. Full article
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23 pages, 14303 KiB  
Article
Origin and Evolution of Ore-Forming Fluids at the Small-Sized Gold Deposits in the Khudolaz Area, Southern Urals
by Ildar R. Rakhimov, Natalia N. Ankusheva, Aidar A. Samigullin and Svetlana N. Shanina
Minerals 2023, 13(6), 781; https://doi.org/10.3390/min13060781 - 07 Jun 2023
Viewed by 1286
Abstract
Lode gold deposits are widespread in orogenic belts of various ages and are a valuable gold source, but their genesis remains debatable. The close relationship between native gold and quartz was considered a reason to search for acid-magmatic sources of heat and fluids [...] Read more.
Lode gold deposits are widespread in orogenic belts of various ages and are a valuable gold source, but their genesis remains debatable. The close relationship between native gold and quartz was considered a reason to search for acid-magmatic sources of heat and fluids (i.e., granite intrusions), while small gabbro bodies were often ignored. Six minor gold deposits associated with NE-strike faults were studied in the Khudolaz area of the South Urals (Tukan, Bilyan-Tau, Fazly-Tau, Muildy-Tamak, Alasiya-II and Isyanbet-I). It was established, for the first time, that all of the studied deposits are similar geologically but differ in mineralogical diversity of ore-bearing quartz veins, which is due to the different composition of host rocks and ore-bearing intrusions of the Khudolaz (325–329 Ma, U-Pb) and the Ulugurtau (321 ± 15 Ma, Sm-Nd) ultramafic-mafic complexes. Results of the geochemical study of quartz veins (ICP MS) and their fluid inclusions (microthermometry, gas chromatography) showed that native gold was mostly precipitated at temperatures of 230–330 °C from a low- to moderate-saline (8–12 wt.% NaCl-eq.) H2O–CO2–CH4-bearing fluid, when weakly oxidized or near-neutral conditions, were replaced by reducing ones. No significant differences between barren milky white and ore-bearing brownish quartz veins were defined, which indicates their common formation settings and an impulse pattern of vein injection. The stable pattern of the fluid salinity, along with low hydrocarbon and N2 contents, as well as a narrow range of δ18O values, indicate a prevailing magmatogenic source with a certain influence of host rocks but without the influence of meteoric waters. Based on the presented data, the studied deposits were attributed to the epizonal orogenic type. This study shows the formation of lode gold deposits is possible without the participation of granite massifs. Full article
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31 pages, 21611 KiB  
Article
Post-Subduction Granite Magmatism and Gold-Sulfide Mineralization in the Abu Zawal (Fatira) Area, Eastern Desert, Egypt
by Refaey M. El-Wardany, Jiangang Jiao, Basem Zoheir, Mustafa Kumral, Mustafa Kaya and Amr Abdelnasser
Minerals 2023, 13(4), 489; https://doi.org/10.3390/min13040489 - 30 Mar 2023
Viewed by 1740
Abstract
Gold-sulfide mineralization in the Abu Zawal (Fatira) mine area, North Eastern Desert of Egypt, is related to porphyritic felsite dikes and elongate silicification zones in granitic rocks. These felsite dikes and the host granitic rocks exhibit major and trace element geochemical features typical [...] Read more.
Gold-sulfide mineralization in the Abu Zawal (Fatira) mine area, North Eastern Desert of Egypt, is related to porphyritic felsite dikes and elongate silicification zones in granitic rocks. These felsite dikes and the host granitic rocks exhibit major and trace element geochemical features typical of calc-alkaline and metaluminous I-type granites, likely originated in a late-orogenic setting. Their geochemical characteristics along with their fractionated LREE relative to HREE patterns imply either formation in a subduction-related environment or generation from subduction-modified source materials. Partial melting of subduction-metasomatized lower crustal rocks during extension following the lithospheric thickening may account for the production of such fertile, high Sr/Y and La/Yb magmas. In the Abu Zawal (Fatira) area, NE-trending altered felsite dikes, hydrothermal breccias, quartz enclaves, and wall-rock replacements are characterized by disseminations of chalcopyrite, pyrite, and rare gold. Alteration mineralogy, dominated by sericite, drusy quartz, kaolinite, calcite, and specular hematite, combined with the available fluid inclusion data suggests moderate to low temperature and near neutral pH conditions. The geochemical data of the altered wallrocks and mass balance calculations indicate significant mass losses in the altered rocks consistent with fluid/wallrock ratios higher than unity and near neutral pH conditions. Considering that the silica-rich host rocks, hydrothermal alteration, and sulfide-bearing hydrothermal quartz breccia in Fatira mine area were intuitively related to sulfur-saturated, oxidized felsic magmatism and associated hydrothermal systems, they are most likely linked to the post-subduction felsite porphyries (post-Hammamat felsites ~ 607 Ma), or pertaining to the late phases of the subaerial high-K calc-alkaline volcanics (Dokhan Volcanics ≤ 620 Ma). Full article
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