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Critical Metal Minerals, 2nd Edition

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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: 31 May 2025 | Viewed by 5172

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Special Issue Editors

Prof. Dr. Pei Ni

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1. State Key Laboratory for Mineral Deposits Research, Institute of Geofluids, Frontiers Science Center for Critical Earth Material Cycling, School of Earth Sciences and Engineering, Nanjing University, Nanjing 210023, China
2. Joint Research Center for Circum-Pacific Strategic Mineral Resources, Nanjing 210000, China
Interests: hydrothermal ore deposits; mineral, fluid and melt inclusion; mineral resource prospecting and exploration; tectonics and metallogeny
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Prof. Ruoshi Jin

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1. Tianjin Center, China Geological Survey (North China Center for Geoscience Innovation), Tianjin 300170, China
2. Key Laboratory of Uranium Geology, China Geological Survey, Tianjin 300170, China
Interests: sandstone-type uranium deposits; mineral resource prospecting and exploration

Prof. Mincheng Xu

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Guest Editor

1. Joint Research Center for Circum-Pacific Strategic Mineral Resources, Nanjing 210000, China
2. Nanjing Center, China Geological Survey, Nanjing 210016, China
Interests: regional metallogenesis; mineral resources prospecting and exploration
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Dr. Tiangang Wang

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Guest Editor

1. Joint Research Center for Circum-Pacific Strategic Mineral Resources, Nanjing 210000, China
2. Nanjing Center, China Geological Survey, Nanjing 210016, China
Interests: hydrothermal ore deposits; ore-forming fluids; regional metallogenesis; mineral resources prospecting
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Dr. Yinhang Cheng

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Guest Editor

1. Tianjin Center, China Geological Survey (North China Center for Geoscience Innovation), Tianjin 300170, China
2. Key Laboratory of Uranium Geology, China Geological Survey, Tianjin 300170, China
Interests: uranium deposits; tectonics and metallogeny; mineral resource prospecting and exploration

Dr. Junyi Pan

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Guest Editor

1. State Key Laboratory for Mineral Deposits Research, Frontiers Science Center for Critical Earth Material Cycling, School of Earth Sciences and Engineering, Nanjing University, Nanjing 210023, China
2. Joint Research Center for Circum-Pacific Strategic Mineral Resources, Nanjing 210000, China
Interests: granite-related W-Sn deposits; porphyry-epithermal ore deposits; fluid and melt inclusion; LA-ICP-MS analytical techniques
Special Issues, Collections and Topics in MDPI journals

Dr. Yitao Cai

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Guest Editor

School of Materials Engineering, Jinling Institute of Technology, Nanjing 211169, China
Interests: mineralogy; petrology; magmatic ore deposits; mineral resources evaluation

Special Issue Information

Dear Colleagues,

An increasingly wide range of mineral materials are used to enable the technologies that sustain our living standard in modern society. In particular, “Critical Metals” or “Critical Minerals” have been regarded as crucial strategic resources for global high-technology applications. In 2021–2022, we announced the Special Issue "Critical Metal Minerals" (https://www.mdpi.com/journal/minerals/special_issues/Critical_Metal_Minerals), and subsequently multiple contributions were published. We are now launching the 2nd Edition of the Special Issue, and we invite the latest research on critical metals to be published in this new Special Issue.

The critical metals generally consist of four major elemental groups: rare metals (e.g., Li, Be, Rb, Cs, W, Sn, Nb, Ta, Zr, Hf, U, and Th), rare earth elements (REEs, e.g., La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Sc, and Y), rare dispersed elements (e.g., Ga, Ge, Se, Cd, In, Te, Re, and Tl), and other precious metals (e.g., PGE, Cr, and Co). Most of these elements are present at very low abundances in the Earth’s upper crust and/or are difficult to efficiently extract and utilize. The rapidly growing demand for critical mineral resources worldwide requires new understandings of the characterization of metal-host minerals, the geochemistry and ore genesis of critical metal deposits, and exploration advances aiding in the discovery of new economic targets. In this regard, the present Special Issue is focused on relevant topics, including, but not limited to (1) geochemical exploration, data handling, and statistical analysis for critical minerals of economic and/or environmental importance; (2) mineralogy, geochemistry, geochronology, fluid evolution, and isotopic constraints on the genesis of critical mineral deposits; (3) experimental advances in critical metal behavior during metallogenic processes; (4) geological controls of the global or regional distribution of critical mineral deposits; (5) 3D modeling of critical metal deposits; and (6) the resource assessment of critical minerals and developments in metal extraction and recovery.

We look forward to high quality submissions that complement contributions published as part of the 1st Edition.

Prof. Dr. Pei Ni
Prof. Ruoshi Jin
Prof. Mincheng Xu
Dr. Tiangang Wang
Dr. Yinhang Cheng
Dr. Junyi Pan
Dr. Yitao Cai
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Minerals is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

critical metals
geologic characteristics and setting
geochemical exploration
statistical data analysis
mineral geochemistry
petrogenesis and ore genesis
3D modeling
resource assessment
mineral processing

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Related Special Issue

Critical Metal Minerals in Minerals (15 articles)

Published Papers (6 papers)

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Research

53 pages, 7077 KiB

Open AccessArticle

The Diversity of Rare-Metal Pegmatites Associated with Albite-Enriched Granite in the World-Class Madeira Sn-Nb-Ta-Cryolite Deposit, Amazonas, Brazil: A Complex Magmatic-Hydrothermal Transition

by Ingrid W. Hadlich, Artur C. Bastos Neto, Vitor P. Pereira, Harald G. Dill and Nilson F. Botelho

Minerals 2025, 15(6), 559; https://doi.org/10.3390/min15060559 - 23 May 2025

Abstract

This study investigates pegmatites with exceptionally rare mineralogical and chemical signatures, hosted by the 1.8 Ga peralkaline albite-enriched granite, which corresponds to the renowned Madeira Sn-Nb-Ta-F (REE, Th, U) deposit in Pitinga, Brazil. Four distinct pegmatite types are identified: border pegmatites, pegmatitic albite-enriched granite, miarolitic pegmatite, and pegmatite veins. The host rock itself has served as the source for the fluids that gave rise to all these pegmatites. Their mineral assemblages mirror the rare-metal-rich paragenesis of the host rock, including pyrochlore, cassiterite, riebeckite, polylithionite, zircon, thorite, xenotime, gagarinite-(Y), genthelvite, and cryolite. These pegmatites formed at the same crustal level as the host granite and record a progressive magmatic–hydrothermal evolution driven by various physicochemical processes, including tectonic decompressing, extreme fractionation, melt–melt immiscibility, and internal fluid exsolution. Border pegmatites crystallized early from a F-poor, K-Ca-Sr-Zr-Y-HREE-rich fluid exsolved during solidification of the pluton’s border and were emplaced in contraction fractures between the pluton and country rocks. Continued crystallization toward the pluton’s core produced a highly fractionated melt enriched in Sn, Nb, Ta, Rb, HREE, U, Th, and other HFSE, forming pegmatitic albite-enriched granite within centimetric fractures. A subsequent pressure quench—likely induced by reverse faulting—triggered the separation of a supercritical melt, further enriched in rare metals, which migrated into fractures and cavities to form amphibole-rich pegmatite veins and miarolitic pegmatites. A key process in this evolution was melt–melt immiscibility, which led to the partitioning of alkalis between two phases: a K-F-rich aluminosilicate melt (low in H₂O), enriched in Y, Li, Be, and Zn; and a Na-F-rich aqueous melt (low in SiO₂). These immiscible melts crystallized polylithionite-rich and cryolite-rich pegmatite veins, respectively. The magmatic–hydrothermal transition occurred independently in each pegmatite body upon H₂O saturation, with the hydrothermal fluid composition controlled by the local degree of melt fractionation. These highly F-rich exsolved fluids caused intense autometasomatic alteration and secondary mineralization. The exceptional F content (up to 35 wt.% F in pegmatite veins), played a central role in concentrating strategic and critical metals such as Nb, Ta, REEs (notably HREE), Li, and Be. These findings establish the Madeira system as a reference for rare-metal magmatic–hydrothermal evolution in peralkaline granites. Full article

(This article belongs to the Special Issue Critical Metal Minerals, 2nd Edition)

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50 pages, 21988 KiB

Open AccessEditor’s ChoiceArticle

Transforming LCT Pegmatite Targeting Models into AI-Powered Predictive Maps of Lithium Potential for Western Australia and Ontario: Approach, Results and Implications

by Oliver P. Kreuzer and Bijan Roshanravan

Minerals 2025, 15(4), 397; https://doi.org/10.3390/min15040397 - 9 Apr 2025

Viewed by 1223

Abstract

Here, we present holistic targeting models for lithium–cesium–tantalum (LCT) pegmatites in Western Australia, the world’s largest supplier of hardrock lithium ores, and Ontario, an emerging hardrock lithium mining jurisdiction. In this study, the LCT pegmatite targeting models, informed by a review of this deposit type and framed in the context of a mineral system approach, served to identify a set of targeting criteria that are mappable in the publicly available exploration data for Western Australia and Ontario. This approach, which formed the basis for artificial intelligence (AI)-powered mineral potential modeling (MPM), using multiple, complimentary modeling techniques, not only delivered the first published regional-scale views of lithium potential across the Archean to Proterozoic terrains of Western Australia and Ontario, but it also delivered an effective framework for exploration and revealed hidden trends. For example, we identified a statistically verifiable proximity relationship between lithium, gold, and nickel occurrences and confirmed a significant size differential between LCT pegmatites in Western Australia and Ontario, with the former typically containing much larger resources than the latter. Overall, this regional-scale targeting study served to demonstrate the power of precompetitive, high-quality geoscience data, not only for regional-scale targeting but also for the development of camp-scale targets that have the resolution to be investigated using conventional prospecting techniques. Importantly, MPM does not generate ‘treasure maps’. Rather, MPM provides another tool in the ‘exploration toolbox’, and its output should be taken as the starting point for further investigations. Full article

(This article belongs to the Special Issue Critical Metal Minerals, 2nd Edition)

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23 pages, 16611 KiB

Open AccessArticle

Study on the Occurrence States and Enrichment Mechanisms of the Dispersed Elements Ga, Ge, and In in the Chipu Pb-Zn Deposit, Sichuan Province, China

by Tian Tan, Huijuan Peng, En Qin, Ziyue Wang and Xingxing Mao

Minerals 2025, 15(4), 341; https://doi.org/10.3390/min15040341 - 26 Mar 2025

Viewed by 326

Abstract

The dispersed elements Ga, Ge, and In are crucial strategic mineral resources often enriched in Pb-Zn deposits. The Chipu Pb-Zn deposit, located on the western edge of the Yangtze Block, lies to the north of the Sichuan-Yunnan-Guizhou (SYG) Pb-Zn metallogenic province with large amounts of Emeishan basalt. Based on trace element and in situ sulfur isotope analyses by (LA)-ICP-MS, sphalerite is the main carrier mineral for Ga (17~420 ppm), Ge (3.87~444 ppm), and In (31~720 ppm). Ga or Ge correlate significantly with Cu, while In substitutes for Zn in sphalerite alongside Fe. Key substitution reactions include Ga³⁺ + Cu⁺ ↔ 2Zn²⁺, Ge⁴⁺ + 2Cu⁺ ↔ 3Zn²⁺, and 2In³⁺ + Fe²⁺ ↔ 4Zn²⁺. Sphalerite crystallized at medium to low temperatures (114–195 °C). Sulfide δ³⁴S values (+3.48 to +24.74‰) suggest sulfur mainly originated from Dengying Formation marine sulfates via thermochemical sulfate reduction (TSR). Metal-bearing fluid release at 30 Ma post-Emeishan mantle plume activity (261–257 Ma) coincides with the Chipu deposit’s mineralization period (230–200 Ma), suggesting the Chipu deposit is associated with Emeishan plume activity. The magmatic activity drove basinal brine circulation, extracting In from intermediate-felsic igneous rocks and metamorphic basement. Elevated temperatures promoted the coupling of Fe and In into sphalerite, causing anomalous In enrichment. Full article

(This article belongs to the Special Issue Critical Metal Minerals, 2nd Edition)

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20 pages, 2493 KiB

Open AccessArticle

Evaluation and Classification of Uranium Prospective Areas in Madagascar: A Geochemical Block-Based Approach

by Datian Wu, Jun’an Liu, Mirana Razoeliarimalala, Tiangang Wang, Rachel Razafimbelo, Fengming Xu, Wei Sun, Bruno Ralison, Zhuo Wang, Yongheng Zhou, Yuandong Zhao and Jun Zhao

Minerals 2025, 15(3), 280; https://doi.org/10.3390/min15030280 - 10 Mar 2025

Viewed by 590

Abstract

The Precambrian crystalline basement of Madagascar, shaped by its diverse geological history of magmatic activity, sedimentation, and metamorphism, is divided into six distinct geological units. Within this intricate geological framework, five primary types of uranium deposits are present. Despite the presence of these deposits, their resource potential remains largely unquantified. To address this, a comprehensive study was conducted on Madagascar’s uranium geochemical blocks. This study processed the original data of uranium elements across the region, following the “Theoretical Model Pedigree of Geochemical Block Mineralization” proposed by Xie Xuejin. The analysis is based on the geochemical mapping data of Madagascar at a scale of 1:100,000, which was jointly completed by the China–Madagascar team and involved the delineation of geochemical blocks and the division of their internal structures using the 15 km × 15 km window data. The study used an isoline with a uranium content greater than 3.2 × 10⁻⁶ as a boundary and considered five key factors for the classification of prospective areas. These factors included uranium bulk density, anomaly intensity, block structure, prospective area, and the tracing of uranium enrichment trajectories through the pedigree chart of 5-level geochemical blocks. By integrating these factors with potential resource assessment, uranium mining economics, and conditions for uranium mining and utilization, the study successfully classified and evaluated uranium resources in Madagascar. As a result, 10 uranium prospective areas were identified, ranging from Level I to IV, with 3 being Level I areas deemed highly promising for exploration and investment. For the first time, the study predicted a resource potential of 72,600 t of uranium resources, marking a significant step towards understanding Madagascar’s uranium endowment. Full article

(This article belongs to the Special Issue Critical Metal Minerals, 2nd Edition)

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20 pages, 6276 KiB

Open AccessArticle

Critical Minerals in Tibetan Geothermal Systems: Their Distribution, Flux, Reserves, and Resource Effects

by Di Wang, Fei Xue, Lijian Ren, Xin Li, Songtao Wang and Xie Qibei Er

Minerals 2025, 15(1), 93; https://doi.org/10.3390/min15010093 - 20 Jan 2025

Viewed by 1073

Abstract

Critical mineral resources (CMRs) are essential for emerging high-tech industries and are geopolitically significant, prompting countries to pursue resource exploration and development. Tibetan geothermal systems, recognized for their CMR potential, have not yet been systematically evaluated. This study presents a comprehensive investigation of the spatial distributions, resource flux, reserves, and resource effects of CMRs, integrating and analyzing hydrochemical and discharge flow rate data. Geochemical findings reveal significant enrichment of lithium (Li), rubidium (Rb), cesium (Cs), and boron (B) in the spring waters and sediments, primarily located along the Yarlung Zangbo suture and north–south rift zones. Resource flux estimates include approximately 246 tons of Li, 54 tons of Rb, 233 tons of Cs, and 2747 tons of B per year, underscoring the mineral potential of the geothermal spring waters. Additionally, over 40,000 tons of Cs reserves are preserved in siliceous sinters in Tagejia, Gulu, and Semi. The Tibetan geothermal systems thus demonstrate considerable potential for CMRs, especially Cs, through stable discharge and widespread distribution, also serving as indicators for endogenous mineral exploration and providing potential sources for lithium in exogenous salt lakes. This study evaluates the CMR potential of the Tibetan geothermal systems, advancing CMR exploration while contributing to the future security of CMR supplies. Full article

(This article belongs to the Special Issue Critical Metal Minerals, 2nd Edition)

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18 pages, 5748 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Investigating Physicochemical Methods to Recover Rare-Earth Elements from Appalachian Coals

by Rachel Yesenchak, Scott Montross and Shikha Sharma

Minerals 2024, 14(11), 1106; https://doi.org/10.3390/min14111106 - 30 Oct 2024

Viewed by 1251

Abstract

The demand for rare-earth elements is expected to grow due to their use in critical technologies, including those used for clean energy generation. There is growing interest in developing unconventional rare-earth element resources, such as coal and coal byproducts, to help secure domestic supplies of these elements. Within the U.S., Appalachian Basin coals are particularly enriched in rare-earth elements, but recovery of the elements is often impeded by a resistant aluminosilicate matrix. This study explores the use of calcination and sodium carbonate roasting pre-treatments combined with dilute acid leaching to recover rare-earth elements from Appalachian Basin coals and underclay. The results suggest that rare-earth element recovery after calcination is dependent on the original mineralogy of samples and that light rare-earth minerals may be more easily decomposed than heavy rare-earth minerals. Sodium carbonate roasting can enhance the recovery of both light and heavy rare-earth elements. Maximum recovery in this study, ranging from 70% to 84% of total rare-earth elements, was achieved using a combination of calcination and sodium carbonate roasting, followed by 0.25 M citric acid leaching. Full article

(This article belongs to the Special Issue Critical Metal Minerals, 2nd Edition)

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