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Geochemistry and Genesis of Hydrothermal Ore Deposits

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

Deadline for manuscript submissions: 30 June 2024 | Viewed by 14346

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Prof. Dr. Yuichi Morishita

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Guest Editor

Center for Integrated Research and Education of Natural Hazards, Shizuoka University, 836 Ohya, Shizuoka 422-8529, Japan
Interests: genesis of ore deposits deposits; source and evolution of hydrothermal fluids; carbon and oxygen isotopes systematics; secondary ion mass spectrometry (SIMS)

Prof. Dr. Napoleon Q. Hammond

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Guest Editor

Department of Geology and Mining, University of Limpopo, Polokwane 0727, South Africa
Interests: genesis of ore deposits; gold mineralization in greenstone belts; fluid evolution in hydrothermal systems; geometallurgy

Special Issue Information

Dear Colleagues,

Hydrothermal ore deposits are formed via the circulation of ore-forming hydrothermal fluids from a variety of sources within the crust, including fluids of mixed origin. The formation of these deposits has been associated with different tectonic processes and geodynamic settings, and is hosted in a wide variety of lithologies. These deposits may form near the surface, such as in epithermal deposits, or at deeper levels, such as in porphyry deposits. Their formation is engendered by the various physico-chemical conditions encountered by these fluids along their flow paths.

Several research studies, for example, in seismology and volcanology, have clearly evidenced the role of these fluids in a variety of hydrothermal deposits. The involvement of mixed hydrothermal fluids in other types of ore deposits has been established. For example, magmatic fluids have been found to potentially evolve into hydrothermal fluid that is mixed with meteoric water in many geological studies. The involvement of hydrothermal fluids in non-hydrothermal-related deposits has been established worldwide; this includes, for example, paleo-placer sedimentary ore deposits such as the uranium-gold deposits found in the vast Witwatersrand goldfields in South Africa

In recent years, significant strides have been made regarding the application of modern analytical techniques to advance the understanding of these deposits. This Special Issue aims to elucidate the role and importance of hydrothermal fluid in the formation of hydrothermal ore deposits in a broad sense. In this Special Issue, we welcome the submission of review and research papers that apply analytical techniques, including geothermometry (oxygen isotope equilibrium temperature) and geobarometry based on the chemical and isotopic composition of related minerals, geochemical and geophysical techniques, and geological observations to address the source and evolution of hydrothermal fluid. With this, we may be able to disclose the genesis of ore deposits, as well as their relevance to the exploration of these deposits.

Prof. Dr. Yuichi Morishita
Prof. Dr. Napoleon Q. Hammond
Guest Editors

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Keywords

hydrothermal ore deposits
source of hydrothermal fluid
fluid evolution
genesis of ore deposit
metallic mineral deposits
geochemistry
stable isotopes
mineral exploration

Published Papers (9 papers)

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Research

33 pages, 5620 KiB

Open AccessArticle

Cu and Au Mineralization of the Tolparovo Ore Occurrence: Evidence for the Formation of Redbed Copper Occurrences in Neoproterozoic Deposits of the Southern Urals

by Sergey Vasilievich Michurin and Gulfiya Mavletovna Kazbulatova

Minerals 2024, 14(2), 148; https://doi.org/10.3390/min14020148 - 29 Jan 2024

Cited by 1 | Viewed by 762

Abstract

The mineralization and geochemical features of the Tolparovo ore occurrence are studied to reveal the contribution of diagenetic and epigenetic processes in the formation of copper mineralization in redbed deposits. The methods of electron microscopy, ICP MS, X-ray fluorescence, X-ray phase, atomic absorption, thermogravimetric analyses, and C and O isotopic composition were used. The ore is confined to the fault zone and feathering dolomite–calcite veins, having formed at temperatures of ~330–200 °C and pressures of 0.8–0.2 kbar. Similar to other copper redbed occurrences of the Bashkirian uplift, the Tolparovo copper ore occurrence is confined to basal Neoproterozoic deposits. Siliciclastic and carbonate deposits of this level were accumulated at low paleoequator latitudes in arid climates of continental and coastal–marine environments close to evaporite ones. Rocks of this stratigraphic interval demonstrate increased background concentrations of copper (~2–5 times exceeding the clark), which explains the stratification of redbed copper ore occurrences, indicating a predominantly sedimentary copper source. However, most of the redbed copper ore occurrences of the Bashkirian uplift are located in tectonic zones and are associated with the dikes of the Inzer gabbrodolerite complex. This connects the generation of ore occurrences with the formation of the Southern Urals Arsha Large Igneous Province (707–732 Ma) and the activity of postmagmatic fluids. Magmatic processes were presumably activated due to the collapse of the Rodinia supercontinent. It is shown that copper mineralization in stratiform deposits may result from a joint manifestation of dia- and epigenesis processes. Full article

(This article belongs to the Special Issue Geochemistry and Genesis of Hydrothermal Ore Deposits)

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13 pages, 2283 KiB

Open AccessArticle

The Solubility of Antimony (Sb) in Liquid Hydrocarbons and Its Implication for the Ore-Forming Process of Orogenic Antimony-Gold Deposits in Southern Tibet

by Yue Su, Xiaoming Sun and Zhengpeng Ding

Minerals 2024, 14(2), 141; https://doi.org/10.3390/min14020141 - 27 Jan 2024

Viewed by 1049

Abstract

Orogenic antimony-gold deposits contribute significantly to the global antimony resource base. China’s orogenic antimony-gold deposits are primarily in southern Tibet. Investigations indicate that antimony combines and migrates with sulfur hydroxides in ore-forming fluids. Previous research on fluid inclusions in orogenic antimony-gold ores with sedimentary rock accommodation revealed the presence of organic inclusions, including liquid hydrocarbons, alongside common components such as CO₂, H₂O, CH₄, and NaCl. However, the impact of liquid hydrocarbons on antimony migration and mineralization is still debatable. To investigate the transportability of antimony by liquid hydrocarbons in orogenic antimony ores, we selected n-dodecanethiol and n-dodecane as the subjects. We measured the solubility and occurrence form of antimony in these compounds at various temperatures and durations. The results indicate that after 5 and 10 days of reaction at 100 °C, the antimony concentrations in the n-dodecanethiol and n-dodecane groups were 67.44 ± 7.62 ppm, 75.15 ± 16.74 ppm, 1.40 ± 1.02 ppm, and 3.02 ± 3.09 ppm, respectively. At 150 °C for 5 and 10 days, the respective concentrations were 50.58 ± 5.39 ppm, 77.26 ± 45.20 ppm, 2.66 ± 3.08 ppm, and 2.41 ± 2.03 ppm. At 200 °C for 5 and 10 days, the corresponding concentrations were 339.76 ± 71.94 ppm, 218.97 ± 25.03 ppm and 6.53 ± 7.17 ppm, 2.27 ± 0.82 ppm (n = 3). The measured solubility of antimony in the n-dodecanethiol group increased gradually with rising temperature. The solubility of antimony in the n-dodecane group was low and notably inferior to that observed in the n-dodecanethiol group. X-ray photoelectron spectroscopy (XPS) analysis demonstrated a distinct thiol (R-SH) peak at 163.31 eV and compound peaks of antimony reacting with thiols at 162.06 and 160.87 eV. This suggests that antimony predominantly forms complexes with thiols for migration. Our findings suggest that specific liquid hydrocarbon components, predominantly thiols, can interact with antimony at metallogenic temperatures and persist in ore-forming fluids, facilitating migration and mineral enrichment. Earlier experimental studies on gold and crude oil have indicated that liquid hydrocarbons also play an essential role in the transportation and enrichment of gold during the formation of gold deposits, thus indicating that liquid hydrocarbons possess the considerable potential to act as an ore-forming fluid during orogenic antimony-gold deposit formation in southern Tibet. Full article

(This article belongs to the Special Issue Geochemistry and Genesis of Hydrothermal Ore Deposits)

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30 pages, 14011 KiB

Open AccessArticle

Fluid Evolution of Greisens from Krupka Sn-W Ore District, Bohemian Massif (Czech Republic)

by Michaela Krejčí Kotlánová, Zdeněk Dolníček, Miloš René, Walter Prochaska, Jana Ulmanová, Jaroslav Kapusta, Vlastimil Mašek and Kamil Kropáč

Minerals 2024, 14(1), 86; https://doi.org/10.3390/min14010086 - 11 Jan 2024

Viewed by 1135

Abstract

The Sn-W ore deposits in the Krupka surroundings are associated with greisens, which occur in the upper parts of Late Variscan granitoid intrusions. Fluid inclusions were studied in samples of quartz, cassiterite, apatite, fluorite, and topaz in greisenized granites, greisens, and hydrothermal veins with Sn-W mineralization. The greisenization process took place at temperatures 370–490 °C and pressures 155–371 bars, and associated fluids had predominantly low salinity and a low gas (CO₂, N₂ and CH₄) content. The post-greisenization stage was connected with the formation of (i) low-salinity (0–8 wt. % NaCl eq.) fluid inclusions with homogenization temperatures <120–295 °C and (ii) high-salinity (18 to >35 wt. % NaCl eq.) fluid inclusions with homogenization temperatures 140–370 °C, often containing trapped crystals of quartz, topaz, and sulfides, or daughter crystals of salts and carbonates, which were identified by microthermometric measurements, electron microprobe analysis, and Raman spectroscopy. Analyses of fluid inclusion leachates have shown that Na and Ca chlorides predominate in fluids. According to hydrogen stable isotopes, the source of greisenizing and post-greisenizing fluids was not only magmatogenic but also meteoric water or fluids derived from sedimentary rocks. Full article

(This article belongs to the Special Issue Geochemistry and Genesis of Hydrothermal Ore Deposits)

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32 pages, 19786 KiB

Open AccessArticle

Sulfur and Carbon–Oxygen Isotopic Geochemistry and Fluid Inclusion Characteristics of the Yolindi Cu-Fe Skarn Mineralization, Biga Peninsula, NW Turkey: Implications for the Source and Evolution of Hydrothermal Fluids

by Mustafa Kaya, Mustafa Kumral, Cihan Yalçın and Amr Abdelnasser

Minerals 2023, 13(12), 1542; https://doi.org/10.3390/min13121542 - 14 Dec 2023

Viewed by 917

Abstract

The current study sought to investigate the physiochemical conditions and fluid evolution within the Yolindi Cu-Fe skarn mineralization located in the Biga Peninsula, NW Turkey. This was accomplished through a comprehensive investigation of geological and mineralogical data, along with isotopic analyses of sulfur (δ³⁴S), carbon (δ¹³C), and oxygen (δ¹⁸O) of sulfide and calcite minerals, respectively, as well as fluid inclusion data pertaining to various minerals (e.g., andradite, quartz, and calcite). The Yolindi area features a complex geological framework, including the Paleozoic Kalabak Group (which includes the Torasan, Yolindi, and Sazak formations) and the Triassic Karakaya Complex. These formations were subsequently intruded via Early Miocene Şaroluk granitoids and Hallaçlar volcanics. Skarn formation is zoned into endoskarn and exoskarn types (being categorized into proximal, intermediate, and distal zones), with distinct mineral assemblages indicating concentric and contact metamorphic alteration patterns around the western part of Şaroluk granitoid intrusion in contact with the Torasan formation. The ore mineralogy and paragenesis suggest three distinct stages of evolution: an initial phase of prograde metasomatism characterized by the formation of magnetite and pyrite alongside anhydrous calc-silicate minerals; a subsequent phase of retrograde alteration marked by the formation of epidote, actinolite, and scapolite, accompanied by the occurrence of chalcopyrite and specular hematite; and finally, a post-metasomatic stage involving oxidation processes that led to the development of secondary mineral assemblages containing cerussite, covellite, and malachite. Sulfur isotopes (δ³⁴S) of sulfides from endoskarn (from +0.27 to +0.57‰_VCDT) to intermediate exoskarn (from −9.44 to −5.46‰_VCDT) zones indicate a diverse sulfur source, including magmatic, sedimentary, and possibly organic matter. δ³⁴S values in hydrothermal fluids suggest a magmatic–hydrothermal origin, with endoskarn and proximal zone fluids showing a slight negative signature and intermediate zone fluids indicating a strong influence from organic-rich or metamorphic sulfur reservoirs. Carbon and oxygen isotopic compositions (δ¹³C and δ¹⁸O) of calcite revealed a progression from marine carbonate signatures in marble samples (from +1.89 to +2.23‰_VPDB; from +21.61 to +21.73‰_VSMOW) to depleted values in prograde (from −6.0 to +0.09‰_VPDB; from +6.22 to +18.14‰_VSMOW) and retrograde skarns (from −3.8 to −2.25‰_VPDB; from +0.94 to +3.62‰_VSMOW), reflecting interactions with high-temperature magmatic fluids and meteoric water mixing. The fluid inclusions in prograde minerals generated under the conditions of fluid boiling exhibited high temperatures, reaching up to 412 °C, and salinities up to 26 wt.% NaCl equivalent. Conversely, the fluid inclusions in retrograde minerals, which were generated due to fluid mixing, exhibited lower temperatures (with an average of 318 °C) and salinities with an average of 4.9 wt.% NaCl equivalent. This indicated that the cooler and more diluted fluids mix with meteoric waters and interact with organic materials in the host rocks. This suggests a multifaceted origin involving various sources and processes. Therefore, this study concluded that the skarn mineralization in the Yolindi area resulted from complex interactions between magmatic, metamorphic, and meteoric fluids, reflecting a dynamic ore-forming environment with implications for the regional metallogeny of Cu-Fe skarn deposits. Full article

(This article belongs to the Special Issue Geochemistry and Genesis of Hydrothermal Ore Deposits)

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26 pages, 14601 KiB

Open AccessArticle

Isotope Geochemistry of the Heihaibei Gold Deposit within the Kunlun River Area in the Eastern Kunlun Orogen in Northwest China and Its Metallogenic Implications

by Hai-Feng Lu, Tong Pan, He Jiao, Qing-Feng Ding, Xuan Zhou and Rui-Zhe Wu

Minerals 2023, 13(2), 274; https://doi.org/10.3390/min13020274 - 15 Feb 2023

Viewed by 1117

Abstract

The Heihaibei gold deposit is located in the Eastern Kunlun Orogen in Northwest China. The gold mineralization here occurs predominantly in quartz veins within faulted granite zones. The sulfide mineral assemblage is dominated by pyrite and arsenopyrite, with minor chalcopyrite, galena, sphalerite, tetrahedrite, and micro-native gold. Weak alterations in Heihaibei granites include silicification and sericitization, with minor chloritization and carbonatization. The measured δD_H2O and δ¹⁸O_quartz values of quartz in auriferous quartz veins range from −104.2‰ to −81.1‰ and +9.2‰ to +13.9‰, respectively. The δ³⁴S values of sulfides in auriferous quartz veins range from +7.60‰ to +8.65‰, and the lead isotope compositions of sulfides in ores range from 18.7219 to 19.0007 for ²⁰⁶Pb/²⁰⁴Pb, 15.6959 to 15.7062 for ²⁰⁷Pb/²⁰⁴Pb, and 37.7359 to 38.8055 for ²⁰⁸Pb/²⁰⁴Pb. The Pb isotope compositions of potassic feldspars from Heihaibei granites vary from 18.3532 to 19.4864 for ²⁰⁶Pb/²⁰⁴Pb, 15.6475 to 15.6812 for ²⁰⁷Pb/²⁰⁴Pb, and 37.1750 to 38.4598 for ²⁰⁸Pb/²⁰⁴Pb. Collectively, the isotope (H, O, S, and Pb) geochemistry suggests that the ore-forming fluid was a special metamorphic water evolved from the deep slab-derived fluids, and the sulfur and lead were predominantly sourced from such metamorphic fluids, and from the deep parts of the Heihaibei granites. Therefore, the Heihaibei gold deposit can be classified as an orogenic gold deposit, which is closely associated with the subduction of the Paleo-Tethys oceanic plate, and even the final closure of this ocean by the Later Triassic. Full article

(This article belongs to the Special Issue Geochemistry and Genesis of Hydrothermal Ore Deposits)

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20 pages, 6872 KiB

Open AccessArticle

Genesis and Evolution of Hydrothermal Fluids in the Formation of the High-Grade Hishikari Gold Deposit: Carbon, Oxygen, and Sulfur Isotopic Evidence

by Yuichi Morishita and Yoriko Yabe

Minerals 2022, 12(12), 1595; https://doi.org/10.3390/min12121595 - 12 Dec 2022

Cited by 3 | Viewed by 1555

Abstract

The Hishikari low-sulfidation epithermal gold (Au) deposit in Kyushu, Japan, is world-famous for its premium ore. It has been hypothesized that magmatic contributions to the hydrothermal fluid during early stages of mineralization is possible, even if the hydrothermal fluids for many Au occurrences near the Hishikari deposit are of meteoric origin and are influenced by basement sedimentary rocks. The purpose of this study is to obtain constraints on the genesis and evolution of hydrothermal fluids in the formation of the high-grade Hishikari Au deposit by carbon and oxygen isotope ratios of calcite-bearing samples. Since the microanalysis of carbon and oxygen isotope ratios in every 12 μm of the calcite-bearing sample along the growth direction (corresponding to 10 years of the Hishikari mineralization) scatter in a particular range, the fluid evolution might not be a gradual change from a magmatic to a meteoric origin. Alternatively, a rapid turnover of two fluids might be happening locally. The average sulfur isotope ratio of hydrothermal pyrite is similar to that of the adjacent magma. However, according to the secondary ion mass spectrometry (SIMS) microanalysis, local pyrite with extremely low sulfur isotope ratios may interact with basement sedimentary rocks. Unlike other epithermal Au deposits in the vicinity, rapid local mixing of the magmatic-origin deep fluid and meteoric-origin fluid reacted with organic matter containing basement sedimentary rocks might cause gold precipitation at the Hishikari deposit. Full article

(This article belongs to the Special Issue Geochemistry and Genesis of Hydrothermal Ore Deposits)

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38 pages, 13674 KiB

Open AccessFeature PaperArticle

Mineralogical and Fluid Inclusion Evidence for Reworking of Au Mineralization by Ag-Sb-Base Metal-Rich Fluids from the Bytíz Deposit, Příbram Uranium and Base-Metal Ore District, Czech Republic

by Jiří Sejkora, Zdeněk Dolníček, Jiří Zachariáš, Jana Ulmanová, Vladimír Šrein and Pavel Škácha

Minerals 2022, 12(12), 1539; https://doi.org/10.3390/min12121539 - 29 Nov 2022

Cited by 3 | Viewed by 1742

Abstract

This mineralogical and fluid inclusion study was conducted on an Au-bearing quartz–sulfide vein encountered in the deep parts of the Bytíz deposit in the Příbram uranium and base-metal district, Bohemian Massif, Czech Republic. The samples were taken where the Au-bearing vein is crosscut by the common base-metal Zn-Pb ore vein Bt23C. The early mineralization of the Au-bearing vein is composed mainly of quartz (Q-1 to Q-3), illite–muscovite, Fe-Mg chlorite, arsenopyrite, and Au-Ag alloys, showing a wide range of compositions (4–69 at. % Ag) and a decrease in Au/(Au + Ag) ratios during vein evolution. Younger hydrothermal processes led to the crystallization of nests and veinlets composed of late quartz (Q-4), carbonates (siderite, dolomite–ankerite and calcite), base-metal sulfides (galena, sphalerite, chalcopyrite, and tetrahedrite), a suite of Ag and Bi-tellurides, and acanthite. The input of Sb is manifested by the partial to complete replacement of some gold grains by aurostibite and an unnamed (Ag,Au)-Sb oxide with a composition close to AuSbO₃. The fluid inclusion study, combined with chlorite thermometry and arsenopyrite thermometry, showed that the early mineralization crystallized from progressively cooled (from 300 to 400 °C down to ca. 180 °C), diluted (1.2–7.0 wt. % NaCl eq.) aqueous solutions. The late portion of the mineralization formed from aqueous fluids with highly variable salinity (0.2–23.4 wt. % NaCl eq.) and homogenization temperatures decreasing from ca. 250 °C to < 50 °C, which compare well with the base-metal mineralization of the vein Bt23C and other base-metal veins of the Příbram ore area. Our study illustrates the nature and intensity of the processes of the reworking of the early gold mineralization mediated by the younger Ag,Sb-rich base-metal fluids, giving rise to Příbram’s typical late-Variscan vein Zn-Pb mineralization. Full article

(This article belongs to the Special Issue Geochemistry and Genesis of Hydrothermal Ore Deposits)

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28 pages, 8898 KiB

Open AccessArticle

Genesis of the Halılar Metasediment-Hosted Cu-Pb (±Zn) Mineralization, NW Turkey: Evidence from Mineralogy, Alteration, and Sulfur Isotope Geochemistry

by Demet Kiran Yildirim

Minerals 2022, 12(8), 991; https://doi.org/10.3390/min12080991 - 04 Aug 2022

Cited by 2 | Viewed by 1814

Abstract

This study contributes to our understanding of the evolution of Halılar Cu-Pb (±Zn) mineralization (NW Turkey) based on mineralogical and geochemical results and sulfur isotope data. The study area represents local Cu-Pb with some Zn brecciated-stockwork vein type mineralization along the NE–SW fault gouge zone at the lower boundary of the Sakarkaya and Düztarla granitoid rocks. Two main zones, consisting of sericite–quartz–chlorite ± kaolinite ± pyrite (i.e., zone-1) and calcite–epidote–albite ± chlorite ± sericite (i.e., zone-2), were observed within the central ore mineral zone at the mining site. Different mineralization assemblages were recorded; the main ore mineral contains chalcopyrite, galena, pyrite, and sphalerite within alteration zone-1, and the oxidation/supergene mineralization includes covellite and goethite. The mass balance calculations show that the samples of zone-1 show an increase in SiO₂, Fe₂O₃, K₂O, and LOI along with Ag, As, Cu, Mo, Pb, S, Sb, and Zn, reflecting high pyritization with sericitization and silicification. On the other hand, the samples from zone-2 are rich in CaO; Na₂O; P₂O₅; TiO₂; LOI; and carbon-reflecting calcite, epidote, and albite alterations. A uniform magmatic sulfur source of Halılar sulfides is suggested by their mean δ³⁴S value of −1.62‰. Furthermore, the primary metal source is metasediments and intrusive Düztarla granitoid magmatism. These observations suggest that the Halılar metasediment-hosted Cu-Pb (±Zn) mineralization was formed by epigenetic hydrothermal processes after sedimentation/diagenesis and metamorphism. Full article

(This article belongs to the Special Issue Geochemistry and Genesis of Hydrothermal Ore Deposits)

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19 pages, 5903 KiB

Open AccessArticle

The Magmatic-Hydrothermal Ore-Forming Processes of the Tonggou Cu-Zn Deposit, NW China: Constraints from Magnetite Chemistry and Fluid Inclusions

by Chang-Cheng Han, Xue-Bing Zhang, Shi-Shan Wu and Ying-Ting Liu

Minerals 2022, 12(4), 485; https://doi.org/10.3390/min12040485 - 15 Apr 2022

Cited by 2 | Viewed by 2100

Abstract

The Tonggou deposit is a porphyry Cu and vein-type Cu-Zn mineralization system located in the Bogda Orogenic Belt, north of Eastern Tianshan. Systematic fluid inclusion analyses were performed on granular quartz from the magnetite–quartz stage and pyrite–chalcopyrite–quartz stage from the porphyry Cu mineralization. During the early stage of porphyry Cu mineralization, the ore-forming fluids were at high temperatures (450–501 °C) and high salinity (51.2–55.2 wt.% NaCl equiv.) H₂O-NaCl hydrothermal fluids with fluid boiling. These fluids evolved to high temperature (412–450 °C) and intermediate to low salinity (8.3–14.2 wt.% NaCl equiv.) H₂O-NaCl hydrothermal fluids during the pyrite–chalcopyrite–quartz stage. In addition, magnetite from the Tonggou deposit was studied as a marker for the ore-forming process evolution of porphyry and vein-type mineralization. Sampled magnetite can be divided into Mag_I (allotriomorphic magnetite from altered granodiorite), Mag_II (magnetite from altered granodiorite found in veinlets or as granular aggregates), Mag_III (from the magnetite–quartz stage of porphyry mineralization), and Mag_IV (from the polymetallic sulfide–epidote–quartz stage of vein-type mineralization). Magnetite LA-ICP-MS data indicate a hydrothermal origin. The contents of Ti, Si, Al, and Ta are controlled by temperature, and these elements gradually decrease from Mag_I to Mag_IV. Moreover, fO₂ has considerable influence on the substitution of Sn, V, and Mn in magnetite, and the contents of these elements generally decrease from Mag_I to Mag_III—increasing only in Mag_IV. Indeed, high fO₂ in the polymetallic sulfide–epidote–quartz stage (Mag_IV) of vein-type mineralization is shown by the presence of a replacement texture in ilmenite grains within hydrothermal magnetite. On the other hand, magnetite samples from the Tonggou deposit have relatively low Ti + V contents compared to other porphyry Cu deposits—plotting in the skarn field of the (Ti + V) vs. (Ca + Al + Mn) diagram—and shows negative correlations in the (Ti + V) vs. Sn diagram. These data indicate that the porphyry Cu mineralization at Tonggou formed at relatively lower fO₂ conditions than the Tonggou vein-type mineralization and other typical porphyry Cu deposits. Finally, porphyry and vein-type mineralization at Tonggou are both sourced from the porphyry system, as a result of ore-forming fluid transfer to a different location. Full article

(This article belongs to the Special Issue Geochemistry and Genesis of Hydrothermal Ore Deposits)

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