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Ore Mineralogy and Geochemistry of Rare Metal Deposits

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

Deadline for manuscript submissions: closed (25 May 2021) | Viewed by 38458

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Special Issue Editors

Prof. Dr. Vasilios Melfos

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Department of Mineralogy, Petrology and Economic Geology, Faculty of Geology, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece
Interests: ore deposits; porphyry-epithermal mineralization; mineralogy; geochemistry; fluid inclusions
Special Issues, Collections and Topics in MDPI journals

Prof. Dr. Panagiotis Voudouris

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Faculty of Geology and Geoenvironment, National and Kapodistrian University of Athens, University Campus-Zografou, 15784 Athens, Greece
Interests: ore minerals; critical metals; magmatic-hydrothermal ore deposits; mineralogy of hydrothermal alterations in porphyry-epithermal systems; mineralogy and genesis of gemstones
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Rare metals occur in diverse deposit types and are mined in substantial quantities that meet the world demands. By definition, rare-metal deposits hardly occur in technically and economically exploitable, worthy concentrations and have high monetary acquisition costs. In some cases, rare metals occur in the form of independent rare-element minerals; in other cases, they are present as impurities in carrier minerals, which constitute the ore of non-rare metals, while more rarely, the rare elements are dispersed in nonmetalliferous rock-forming minerals. Many factors crucial for the formation of rare-metal deposits control their mineral paragenesis, textures, and mineral chemistry. These features affect the exploration projects and the mining and metallurgical processes of the companies, which invest a considerable amount of capital to extract these metals from deep in the Earth’s crust.

This Special Issue welcomes contributions on original research which presents new data from rare-metal deposits, focusing mainly on mineralogy and mineral chemistry studied with several techniques, e.g., optical microscopy, Raman, SEM, EPMA, LA-ICP-MS, SIMS, TIMS, PIXE, PGNAA, QEMSCAN, and others. We focus on the mineralogy of Bi, Ta, Co, V, Te, W, Se, Re, Ga, Ge, In, Cd, Hg, Li, Rb, Sr, Be, Y, Ce, Nd, Sc, Au, Ag, U, Th, the REE-Lanthanides, and the Platinum Group Elements (PGE). These data will contribute significantly to the knowledge about the distribution of rare metals in specific minerals for a possible future exploration and exploitation.

Prof. Dr. Vasilios Melfos
Prof. Dr. Panagiotis Voudouris
Guest Editors

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Keywords

Rare metals
Mineralogy
Mineral chemistry
Ore deposits
LA-ICP-MS
SIMS
PIXE
QEMSCAN
Lithium
Neodymium

Published Papers (10 papers)

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Research

21 pages, 18453 KiB

Open AccessEditor’s ChoiceArticle

Automated Quantitative Characterization REE Ore Mineralogy from the Giant Bayan Obo Deposit, Inner Mongolia, China

by Taotao Liu, Wenlei Song, Jindrich Kynicky, Jinkun Yang, Qian Chen and Haiyan Tang

Minerals 2022, 12(4), 426; https://doi.org/10.3390/min12040426 - 30 Mar 2022

Cited by 6 | Viewed by 3018

Abstract

Rare earth elements (REEs) are considered critical elements in modern society due to their irreplaceable role in new innovative and energy technologies. The giant carbonatite-related Bayan Obo deposit contributes most REE resources in the world’s market, while its origin is still unclear because of the complicated and diverse REE ore mineralogy and texture. Thescanning electron mircroscopy SEM)-based automated mineralogy allows for the numeric assessment of rocks and ores’ compositional and textural properties. Here, we use TIMA (TESCAN Integrated Mineral Analyzer) to quantitatively characterize REE ore mineralogy from the deep drill core within the H8 unit (“dolomite marble”) to better understand the deposit. The mineral composition, occurrence, and Ce elemental deportment of the borehole ores at different depths (i.e., 1107 m, 1246 m, 1406 m, 1546 m, and 1682 m) were obtained. The results show that the main types of ores in the investigated samples can be divided into banded REE-Fe ores, banded REE ores, disseminated REE-Fe ores, and veined REE ores. REE and gangue minerals vary significantly in abundance and occurrence. Monazite-(Ce) and bastnäsite-(Ce) are the primary REE host minerals, and both contribute the most to the REE budget. Other REE minerals, such as parisite-(Ce)/synchysite-(Ce), cerite-(Ce), huanghoite-(Ce)/cebaite-(Ce), and aeschynite-(Ce), are significant contributors. The gangue minerals generally include fluorite, barite, magnetite, pyrite, quartz, magnesio-arfvedsonite, and minerals of the biotite and apatite groups, among others. Combined with the newly published mineral-scale chronological and isotopic geochemical analyses, it is reasonable to conclude that the later hydrothermal fluids remobilized and redistributed the original Mesoproterozoic carbonatitic REE minerals and formed a high variable ore mineral assemblage. Furthermore, it is demonstrated that the mineralogical study using TIMA can provide accurate and reliable mineralogy data for the comprehensive interpretation of the complex REE ores, and extend our understanding of the deposit. Full article

(This article belongs to the Special Issue Ore Mineralogy and Geochemistry of Rare Metal Deposits)

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10 pages, 1302 KiB

Open AccessArticle

Iron Isotope Constraints on the Mineralization Process of Shazi Sc-Rich Laterite Deposit in Qinglong County, China

by Jun Sun, Yunlong Liu and Xiqiang Liu

Minerals 2021, 11(7), 737; https://doi.org/10.3390/min11070737 - 07 Jul 2021

Cited by 2 | Viewed by 1866

Abstract

The Shazi deposit is a newly discovered, potential large-scale scandium deposit located in Qinglong, southwestern Guizhou Province, China. The iron isotopic composition of magnetite in fresh basalt, weathered basalt, and mineralized laterite was investigated. The Fe content of fresh basalt and of weathered basalt vary from 15.41 wt.% to 15.51 wt.% and from 14.60 wt.% to 15.12 wt.%, respectively, while the δ⁵⁶Fe of magnetite varies from 0.23‰ to 0.29‰ and from 0.02‰ to 0.07‰. Laterite has the highest Fe content, in the range of 23.53%~28.95%, but δ⁵⁶Fe is similar to weathered basalt, and the range of variation is −0.09‰–0.03‰. The change in iron isotope composition in weathered basalt and laterite is related to the hydrolysis of clinopyroxene. Combined with the existing research results, the genesis of scandium deposit is considered to be related to in situ hydrolysis in deep and surface weathering leaching of Emeishan basalt. Full article

(This article belongs to the Special Issue Ore Mineralogy and Geochemistry of Rare Metal Deposits)

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28 pages, 5861 KiB

Open AccessArticle

Rare and Critical Metals in Pyrite, Chalcopyrite, Magnetite, and Titanite from the Vathi Porphyry Cu-Au±Mo Deposit, Northern Greece

by Christos L. Stergiou, Vasilios Melfos, Panagiotis Voudouris, Lambrini Papadopoulou, Paul G. Spry, Irena Peytcheva, Dimitrina Dimitrova, Elitsa Stefanova and Katerina Giouri

Minerals 2021, 11(6), 630; https://doi.org/10.3390/min11060630 - 14 Jun 2021

Cited by 10 | Viewed by 4739

Abstract

The Vathi porphyry Cu-Au±Mo deposit is located in the Kilkis ore district, northern Greece. Hydrothermally altered and mineralized samples of latite and quartz monzonite are enriched with numerous rare and critical metals. The present study focuses on the bulk geochemistry and the mineral chemistry of pyrite, chalcopyrite, magnetite, and titanite. Pyrite and chalcopyrite are the most abundant ore minerals at Vathi and are related to potassic, propylitic, and sericitic hydrothermal alterations (A- and D-veins), as well as to the late-stage epithermal overprint (E-veins). Magnetite and titanite are found mainly in M-type veins and as disseminations in the potassic-calcic alteration of quartz monzonite. Disseminated magnetite is also present in the potassic alteration in latite, which is overprinted by sericitic alteration. Scanning electron microscopy and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analyses of pyrite and chalcopyrite reveal the presence of pyrrhotite, galena, and Bi-telluride inclusions in pyrite and enrichments of Ag, Co, Sb, Se, and Ti. Chalcopyrite hosts bornite, sphalerite, galena, and Bi-sulfosalt inclusions and is enriched with Ag, In, and Ti. Inclusions of wittichenite, tetradymite, and cuprobismutite reflect enrichments of Te and Bi in the mineralizing fluids. Native gold is related to A- and D-type veins and is found as nano-inclusions in pyrite. Titanite inclusions characterize magnetite, whereas titanite is a major host of Ce, Gd, La, Nd, Sm, Th, and W. Full article

(This article belongs to the Special Issue Ore Mineralogy and Geochemistry of Rare Metal Deposits)

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21 pages, 19756 KiB

Open AccessFeature PaperArticle

Tellurium and Selenium Mineralogy of Gold Deposits in Northern Fennoscandia

by Arkadii A. Kalinin

Minerals 2021, 11(6), 574; https://doi.org/10.3390/min11060574 - 27 May 2021

Cited by 4 | Viewed by 3690

Abstract

Mineralization of Te and Se was found in gold deposits and uranium occurrences, located in the Paleoproterozoic greenstone belts in Northern Fennoscandia. These deposits are of different genesis, but all of them formed at the late stages of the Svecofennian orogeny, and they have common geochemical association of metals Au, Cu, Co, U, Bi, Te, and Se. The prevalent Te minerals are Ni and Fe tellurides melonite and frohbergite, and Pb telluride altaite. Bismuth tellurides were detected in many deposits in the region, but usually not more than in two–three grains. The main selenide in the studied deposits is clausthalite. The most diversified selenium mineralization (clausthalite, klockmannite, kawazulite, skippenite, poubaite) was discovered in the deposits, located in the Russian part of the Salla-Kuolajarvi belt. Consecutive change of sulfides by tellurides, then by selenotellurides and later by selenides, indicates increase of selenium fugacity, fSe₂, in relation to fTe₂ and to fS₂in the mineralizing fluids. Gold-, selenium-, and tellutium-rich fluids are potentially linked with the post-Svecofennian thermal event and intrusion of post-orogenic granites (1.79–1.75 Ga) in the Salla-Kuolajarvi and Perapohja belts. Study of fluid inclusions in quartz from the deposits in the Salla-Kuolajarvi belt showed that the fluids were high-temperature (240–300 °C) with high salinity (up to 26% NaCl-eq.). Composition of all studied selenotellurides, kawazulite-skippenite, and poubaite varies significantly in Se/Te ratio and in Pb content. Skippenite and kawazulite show the full range of Se-Te isomorphism. Ni-Co and Co-Fe substitution plays an important role in melonite and mattagamite: high cobalt was detected in nickel telluride in the Juomasuo and Konttiaho, and mattagamites from Ozernoe and Juomasuo contain significant Fe. In the Ozernoe uranium occurrence, the main mineral-concentrator of selenium is molybdenite, which contains up to 16 wt.% of Se in the marginal parts of the grains. The molybdenite is rich in Re (up to 1.2 wt.%), and the impurity of Re is irregularly distributed in molybdenite flakes and spherulites. Full article

(This article belongs to the Special Issue Ore Mineralogy and Geochemistry of Rare Metal Deposits)

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19 pages, 20760 KiB

Open AccessArticle

Metallogenic Characteristics and Formation Mechanism of Naomugeng Clay-Type Lithium Deposit in Central Inner Mongolia, China

by Chuan Li, Zilong Li, Tao Wu, Yaqin Luo, Jun Zhao, Xinren Li, Wencai Yang and Xuegang Chen

Minerals 2021, 11(3), 238; https://doi.org/10.3390/min11030238 - 25 Feb 2021

Cited by 8 | Viewed by 3491

Abstract

A newly discovered Naomugeng lithium mineralization area is located to the east of the Central Asian Orogenic Belt (CAOB). The lithium is hosted in the volcanic rocks of the Manketou’ebo Formation. The altered volcanic rocks mainly consist of quartz, orthoclase, chlorite, montmorillonite, calcite, and dolomite. Here, we present integrated studies of petrography, mineralogy, and geochemistry of the altered volcanic rocks (with an average Li₂O content of 0.43 wt.%) collected from the drilling hole and trail trench to systematically investigate the occurrence of lithium, the mineralizing processes, and the metallogenic mechanisms. The secondary minerals of the core samples are montmorillonite, chlorite calcite, and dolomite, while the secondary minerals from the earth surface ones are montmorillonite, chlorite, and calcite. The mass change calculation and isocon analysis show that the rocks received MnO, P₂O₅, Co, Ni, Cu, and Li and lost Na₂O, K₂O, MgO, rare earth elements (REE), and Rb in the alteration process. However, other elements such as Fe, V, Co, and Ca of the core samples increased while those of the earth surface ones did not change by much. Hence, there are two zones of alterations, i.e., the montmorillonization-chloritization zone and the montmorillonization-chloritization-carbonatization zone. Lithium enrichment occurs in the zone where montmorillonization and chloritization occur. The lithium is probably enriched in altered minerals such as montmorillonite and chlorite in the forms of interlayered or adsorbed ions. The slightly negative to positive Eu anomalies of the rocks can be explained by the metasomatism of hydrothermal fluid that enriched Eu. We suggest that the Naomugeng deposit is a clay-type lithium deposit and formed under a caldera setting. The meteoric and hydrothermal fluids leach the lithium from the volcanic materials and then alter the host rocks (e.g., tuff or sediments) in the caldera basin, which forms the type of lithium clay deposit. This study analyzed the migration behavior of elements in the Naomugeng lithium deposit during a hydrothermal process, which shows that the mass balance calculation has good application in reflecting the mineralization process of clay type deposit. This study also reveals the great exploration potential of the Naomugeng deposit and has important significance for further prospecting of clay-type lithium deposits in central Inner Mongolia. Full article

(This article belongs to the Special Issue Ore Mineralogy and Geochemistry of Rare Metal Deposits)

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28 pages, 11013 KiB

Open AccessEditor’s ChoiceArticle

Rare-Metal (In, Bi, Te, Se, Be) Mineralization of Skarn Ores in the Pitkäranta Mining District, Ladoga Karelia, Russia

by Vasily I. Ivashchenko

Minerals 2021, 11(2), 124; https://doi.org/10.3390/min11020124 - 27 Jan 2021

Cited by 12 | Viewed by 3556

Abstract

The results of the study of rare-metal (Bi, Te, Se. Be, In) mineralization of skarn deposits (Sn, Zn) in the Pitkäranta Mining District, genetically related to the Salmi anorthosite-rapakivi granite batholiths of Early Riphean age are reported. Minerals and their chemical composition were identified on the base of optical microscopy as well as electron microanalysis. The diversity of rare-metal ore mineralization (native metals, oxides, and hydroxides, carbonates, tellurides, selenides, sulfides, sulphosalts, borates, and silicates) in Pitkäranta Mining District ores is indicative of considerable variations in the physicochemical conditions of their formation controlled by the discrete-pulse-like supply of fluids. Bismuth, wittichenite, and matildite are the most common rare-metal minerals. Sulfosalts of the bismuthinite-aikinite series are represented only by its end-members. The absence of solid solution exsolution structures in sulfobismuthides suggests that they crystallized from hydrothermal solutions at low temperatures. Be (>10 minerals) and In (roquesite) minerals occur mainly in aposkarn greisens. Roquesite in Pitkäranta Mining District ores formed upon greisen alteration of skarns with In released upon the alteration of In-bearing solid sphalerite (Cu¹⁺ In³⁺) ↔ (Zn²⁺, Fe²⁺) and chalcopyrite In³⁺ ↔ Fe³⁺ and 2Fe³⁺ ↔ (Fe²⁺, Zn²⁺) Sn⁴⁺ solutions. Sphalerite with an average In concentration of 2001 ppm, is a major In-bearing mineral in the ores. Full article

(This article belongs to the Special Issue Ore Mineralogy and Geochemistry of Rare Metal Deposits)

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16 pages, 8949 KiB

Open AccessArticle

Tennantite–Tetrahedrite-Series Minerals and Related Pyrite in the Nibao Carlin-Type Gold Deposit, Guizhou, SW China

by Dongtian Wei, Yong Xia, Jeffrey A. Steadman, Zhuojun Xie, Xijun Liu, Qinping Tan and Ling’an Bai

Minerals 2021, 11(1), 2; https://doi.org/10.3390/min11010002 - 22 Dec 2020

Cited by 6 | Viewed by 2923

Abstract

A number of sediment-hosted, Carlin-type/-like gold deposits are distributed in the Youjiang basin of SW China. The gold ores are characterized by high As, Hg, and Sb contents but with low base metal contents (Cu+Pb+Zn < 500–1000 ppm). The Nibao deposit is unique among these gold deposits by having tennantite–tetrahedrite-series minerals in its ores. The deposit is also unique in being primarily hosted in the relatively unreactive siliceous pyroclastic rocks, unlike classic Carlin-type gold deposits that are hosted in carbonates or calcareous clastic rocks. In this study, we have identified tennantite-(Zn), tennantite-(Hg), and tetrahedrite-(Zn) from the tennantite–tetrahedrite-series mineral assemblage. The tennantite-(Zn) can be further divided into two sub-types of Tn-(Zn)-I; and Tn-(Zn)-II;. Tn-(Zn)-I; usually occurs in the core of a Tennantite–tetrahedrite composite and appears the darkest under the SEM image, whereas Tn-(Zn)-II overgrows on Tn-(Zn)-I and is overgrown by tetrahedrite-(Zn). Tennantite-(Hg) occasionally occurs as inclusions near the uneven boundary between Tn-(Zn)-I and Tn-(Zn)-II. An appreciable amount of Au (up to 3540 ppm) resides in the tennantite–tetrahedrite-series minerals, indicating that the latter is a major Au host at Nibao. The coexistence of tennantite–tetrahedrite-series minerals and Au-bearing pyrite indicates the Nibao ore fluids were more oxidized than the Carlin-type ore fluids. The tennantite–tetrahedrite series at Nibao evolved from Tn-(Zn)-I through Tn-(Zn)-II to tetrahedrite-(Zn), which is likely caused by Sb accumulation in the ore fluids. This indicates that the Nibao ore fluids may have become more reduced and less acidic during Au precipitation. Full article

(This article belongs to the Special Issue Ore Mineralogy and Geochemistry of Rare Metal Deposits)

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20 pages, 15405 KiB

Open AccessArticle

Post-Magmatic Fluids Dominate the Mineralization of Dolomite Carbonatitic Dykes Next to the Giant Bayan Obo REE Deposit, Northern China

by Le Hu, Yike Li, Maoshan Chuan, Ruiping Li, Changhui Ke and Zhongjian Wu

Minerals 2020, 10(12), 1117; https://doi.org/10.3390/min10121117 - 12 Dec 2020

Cited by 2 | Viewed by 2748

Abstract

The Bayan Obo rare earth element (REE) deposit in Inner Mongolia, northern China, is the largest REE deposit in the world, whose mineralization process remains controversial. There are dozens of carbonatite dykes that are tightly related to the deposit. Here we report the petrological and mineralogical characteristics of a typical dolomite carbonatite dyke near the deposit. The dolomite within the dyke experienced intense post-emplacement fluids metasomatism as evidenced by the widespread hydrothermal REE-bearing minerals occurring along the carbonate mineral grains. REE contents of bulk rocks and constituent dolomite minerals (>90 vol.%) are 1407–4184 ppm and 63–152 ppm, respectively, indicating that dolomite is not the dominant mineral controlling the REE budgets of the dyke. There are three types of apatite in the dyke: Type 1 apatite is the primary apatite and contains REE₂O₃ at 2.35–4.20 wt.% and SrO at 1.75–2.19 wt.%; Type 2 and Type 3 apatites are the products of replacement of primary apatite. The REE₂O₃ (6.10–8.21 wt.%) and SrO (2.83–3.63 wt.%) contents of Type 2 apatite are significantly elevated for overprinting of REE and Sr-rich fluids derived from the carbonatite. Conversely, Type 3 apatite has decreased REE₂O₃ (1.17–2.35 wt.%) and SrO (1.51–1.99 wt.%) contents, resulting from infiltration of fluids with low REE and Na concentrations. Our results on the dyke suggest that post-magmatic fluids expelled from the carbonatitic melts dominated the REE mineralization of the Bayan Obo deposit, and a significant fluid disturbance occurred but probably provided no extra REEs to the deposit. Full article

(This article belongs to the Special Issue Ore Mineralogy and Geochemistry of Rare Metal Deposits)

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15 pages, 6782 KiB

Open AccessArticle

Rare-Metal Pegmatite Deposits of the Kalba Region, Eastern Kazakhstan: Age, Composition and Petrogenetic Implications

by Sergey V. Khromykh, Tatiana A. Oitseva, Pavel D. Kotler, Boris A. D’yachkov, Sergey Z. Smirnov, Alexey V. Travin, Alexander G. Vladimirov, Ekaterina N. Sokolova, Oxana N. Kuzmina, Marina A. Mizernaya and Bakytgul’ B. Agaliyeva

Minerals 2020, 10(11), 1017; https://doi.org/10.3390/min10111017 - 16 Nov 2020

Cited by 15 | Viewed by 6440

Abstract

The paper presents new geological, mineralogical, and isotope geochronological data for rare-metal pegmatites in the Kalba granitic batholith (Eastern Kazakhstan). Mineralization is especially abundant in the Central-Kalba ore district, where pegmatite bodies occur at the top of large granite plutons and at intersections of deep faults. The pegmatites contain several successive mineral assemblages from barren quartz-microcline and quartz-microcline-albite to Li-Cs-Ta-Nb-Be-Sn-bearing cleavelandite-lepidolite-spodumene. Ar-Ar muscovite and lepidolite ages bracket the metallogenic event between 291 and 286 Ma. The pegmatite mineral deposits formed synchronously with the emplacement of the phase 1 Kalba granites during the evolution of hydrous silicate rare-metal magmas that are produced by the differentiation of granite magma at large sources with possible inputs of F and rare metals with fluids. Full article

(This article belongs to the Special Issue Ore Mineralogy and Geochemistry of Rare Metal Deposits)

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23 pages, 5069 KiB

Open AccessEditor’s ChoiceArticle

Mineralogical Setting of Precious Metals at the Assarel Porphyry Copper-Gold Deposit, Bulgaria, as Supporting Information for the Development of New Drill Core 3D XCT-XRF Scanning Technology

by Mihaela-Elena Cioacă, Marian Munteanu, Edward P. Lynch, Nikolaos Arvanitidis, Mikael Bergqvist, Gelu Costin, Desislav Ivanov, Viorica Milu, Ronald Arvidsson, Adina Iorga-Pavel, Karin Högdahl and Ventsislav Stoilov

Minerals 2020, 10(11), 946; https://doi.org/10.3390/min10110946 - 24 Oct 2020

Cited by 5 | Viewed by 3577

Abstract

A petrographic investigation of ore samples from the Assarel porphyry copper deposit in the Srednogorie metallogenic zone (Bulgaria) constrains the setting and character of precious metals (Au, Ag, PGE) and related minerals within the deposit. This work supports renewed interest in understanding the deportment of precious metals and provides mineralogical knowledge during the testing and validation of novel drill core 3D X-ray computed tomography–X-ray fluorescence (XCT-XRF) scanning technology being developed as part of the X-MINE project. Scanning electron microscopy–energy dispersive spectrometry (SEM-EDS) results indicate precious metals occur in their native state (Au, Ag), as sulfides (Ag), sulfosalts (Au), tellurides (Ag, Pd), and selenides (Ag), and typically form micron-sized inclusions in pyrite and chalcopyrite or are disseminated in the groundmass of the rock. Preservation of early Fe oxide–chalcopyrite ± bornite assemblage as relics in the more dominant pyrite-chalcopyrite mineralization assemblage supports mineral disequilibrium relationships and multi-stage mineralization events. Several rare minerals (e.g., merenskyite, acanthite, sorosite, tetra-auricupride, auricupride, greenokite, bismuthinite, nagyagite, native Ni) are reported for the first time at Assarel and highlight the mineralogical diversity of the ore. The occurrence of precious metals and related minerals at Assarel attest to a complex hydrothermal system that underwent progressive physicochemical changes during the evolution of the mineralizing system (e.g., redox conditions, fluid chemistry). Full article

(This article belongs to the Special Issue Ore Mineralogy and Geochemistry of Rare Metal Deposits)

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