Rare Metal Deposits Research Articles

The formation and recycling of Neoproterozoic granitoids in the Jiangnan Orogen, South China: Implications for Mesozoic rare metal mineralization

In the era of energy transition on the Earth, rare metal mineralization has attained increased significance for various energy sectors and understanding their formation and evolution in various tectonic settings is of great importance for formulating exploration strategies. The Neoproterozoic Jiangnan Orogen in South China marks the assembly zone of the Yangtze and Cathaysia blocks and carries numerous rare metal deposits. In this contribution, we investigate the Neoproterozoic Jiuling composite batholith to understand the formation of rare metal mineralization. We present new in-situ zircon U–Pb ages and Lu–Hf isotopes, and whole-rock geochemistry and Sm–Nd isotopes of the Banbei biotite granodiorite and the associated rare metal-mineralized Baishawo granite in the western portion of the Jiuling batholith suite. Zircon U–Pb dating indicates that the Banbei biotite granodiorite, and the Baishawo two-mica granite and muscovite granite formed at ca. 820 Ma, 153 Ma, and 142 Ma, respectively. The εHf(t) values of the biotite granodiorite, two-mica granite and muscovite granite are –4.4 to +5.8, –11.8 to –7.0, and –10.5 to –7.3, respectively. The εNd(t) values of the biotite granodiorite, two-mica granite and muscovite granite are –3.88 to –2.73, –10.6 to –10.2, and –9.23 to –9.16, respectively. Zircon Hf isotopes and whole-rock Sm–Nd isotopes suggest that the granite suite was sourced from the Mesoproterozoic crust. Geochemical modeling suggests that the Banbei biotite granodiorite was derived from partial melting of Meso- to Neoproterozoic metasedimentary rocks, whereas the Baishawo two-mica granite and muscovite granite were derived from assimilation–fractional crystallization of the Neoproterozoic Banbei biotite granodiorite and Mesozoic magma with low degrees of differentiation. Combined with previous studies on the granite suites in the Jiangnan Orogen, we suggest that collision between the Yangtze and Cathaysia blocks ceased at least 820 Ma, and that Precambrian rocks might have contributed significantly to the enrichment of rare metal mineralization in Mesozoic granite through reworking.

Role of metasomatism in formation of the Yichun rare-metal deposit, China

What role post-magmatic processes have played in the development and mineralization of rare-metal peraluminous granites and how important that role can be, are questions that researchers have been wrestling with for decades. The Yichun Li-Ta-Nb deposit is an example that has been the subject of such a debate. The granitic appearance of rocks, the inert nature of tantalum, and the scarcity of mineralization in country rocks have been taken to suggest that fluid overprints were limited to within the granites and were unimportant in rock- and ore-forming processes. In this study, the identification of two types of abundant Li- and Cs-rich pseudomorphs in both the topaz-lepidolite granite and overlying pegmatite, the only two mineralized units at Yichun, suggests that extensive metasomatism was involved in rock and ore formation. The textural and chemical similarities of lepidolite in comparable mineral assemblages from a variety of occurrences, including lepidolite in pseudomorphs, veins, and miarolitic cavities from both the topaz-lepidolite granite and pegmatite, suggest that all lepidolite at Yichun is metasomatic and largely inherited its chemical signatures from a magmatic-hydrothermal transitional fluid, rich in Li, Cs, and Ta, derived possibly from the Li-muscovite granite that lies beneath the topaz-lepidolite granite. We propose that this transitional liquid, composition of which lies between a silicate melt and aqueous fluid, was not in equilibrium with the original igneous mineralogy, thus bringing about significant metasomatism along its infiltration and evolution upwards. Variations in the trace-element composition of lepidolite likely reflect the influence on mineral compositions by precursor minerals. The ambiguous boundary between the topaz-lepidolite and Li-muscovite granites, combined with the intensely metasomatized nature of the former, is most consistent with the topaz-lepidolite granite being the extensively altered upper portion of the Li-muscovite granite, which is itself somewhat metasomatized. Although magmatic fractionation played a key role in the initial concentration of Nb, Li, and Ta in both granite and pegmatite formation, the Li-Ta-Nb-Cs mineralization and its host rocks were largely formed through magmatic-hydrothermal rejuvenation and re-enrichment.

Petrogenesis and tectonic setting of granitic pegmatites in the Beishan orogenic Belt, Northwest China: Evidence from geology, geochronology and geochemistry

The Weiboshan (Li-, Cs- and Ta-enriched) LCT-type Nb–Ta deposit located in Ejin Banner, Inner Mongolia, represents a newly discovered pegmatite-type rare metal deposit of significant interest. In this paper, we describe the petrography and present new mineralogical and whole-rock geochemical data and zircon U–Pb ages of ore-related granitic pegmatites in this deposit. Pegmatite dikes can be divided into three distinct zones on the basis of their contents: the K-feldspar graphic granite pegmatite zone (Kf), microcline graphic granite pegmatite zone (Mic), and albite–muscovite granite pegmatite zone (Ab). The pegmatite dikes and associated mineralization formed during the Mesozoic. Granite pegmatites in various zones display distinctive geochemical features characterized by high silicon contents, substantial alkali enrichment, and relatively low iron, calcium, and magnesium levels. These pegmatites are classified as peraluminous or quasialuminous and exhibit low total rare earth element concentrations. Notably, these pegmatites are enriched in large ion lithophile elements (LILEs), such as Rb, K, and U, but depleted in high field strength elements (HFSEs), such as P and Ti. The progression from the Kf to Mic to Ab zones signifies the thorough evolution of the granitic magma, where the late-stage near-hydrothermal system assumed a crucial role in the mineralization of rare metals during magma differentiation. The Weiboshan pegmatites, which exhibit syncollisional attributes, are A-type granites formed through crustal partial melting induced by decompression. This process occurred against the background of postorogenic extension driven by asthenospheric mantle upwelling resulting from lithospheric delamination due to crustal collision and thickening.

New insights on the petrogenesis of the Koktokay No.3 pegmatitic dyke: Petrological and zirconological evidence from the Aral granitic complex (Xinjiang, China)

The Koktokay No.3 pegmatite dyke (KPD), containing numerous Li–Be–Nb–Ta–Cs mineral resources, is among the world’s most famous rare-metal deposits, and attracted much attention. Up to now, over thirty geochronological data have been reported ranging from 332 Ma to 120 Ma for the KPD, which causes uncertainty about the origin and petrogenesis of the pegmatite. In this contribution, whole-rock geochemistry and zircon geochronology have been conducted on the Aral biotite monzogranite (BMG), the Koktokay muscovite alkali-feldspar granite (MAG), and the KPD. Petrological and whole-rock geochemistry results reveal that the BMG is normal granite with medium SiO2 (mean of 67.23 %), enriched in compatible trace elements such as Ba, Sr and Zr, and slight negative Eu anomalies, while the MAG belongs to highly-fractionated granite with high SiO2 (mean of 73.92 %) and extensive negative Eu anomalies, and enriched in incompatible trace elements such as Rb, Ta, and U. Zircon morphology and LA–ICPMS analysis reveal that magmatic zircons from the BMG, hydrothermal zircons from the MAG and KPD yield lower intercept ages at 217.3 ± 2.4 Ma, 197.8 ± 4.7 Ma, and 195.4 ± 2.0 Ma, respectively. Combining with tectonic information and geochronological data of granitic activity and its mineralization in the Altay, this study explains the petrogenetic mechanism of the KPD after Wang et al. (2021)‘s metallogenic model: (1) In late stage of Middle Triassic, the collision between the Siberian plate and the Kazakhstan–Junggar plate caused a large number of thrust nappe faults and crust thickening in the Altay orogenic belt; At ∼217 Ma, the compression reached its peak, the crustal anatexis produced syn-collisional BMG (i.e., the Aral BMG); After the compressive peak, huge amount of granitic magma in deep-seated magma chamber underwent over 20 Myr of fractional crystallization, and the residual magma enriched in ore-forming materials (rare metal elements, volatile components, and aqueous fluids) occurred at the top of the magma chamber; (2) When the regional stress converted from compression to extension, the highly-fractionated residual magma ascended rapidly from the long-lived magma chamber along extensional faults at ∼195 Ma; The huge amount of melt-bearing fluids were exsolved from the residual magma in the course of its emplacement due to sharply decreasing pressure, and intruded into a large cavity generated by extensional fault; Along with slowly decreasing temperature, the melt-enriched fluids crystallized outside-in as (quasi-) concentric pegmatitic zones (i.e., KPD); (3) The residual magma which lost huge amount of fluid filled the lower space of the extensional system, and crystallized as post-collisional MAG (i.e., the Koktokay MAG). Based on the genetic relationship among tectonics, petrogenesis, and metallogeny, the proposed model shows material and energetic conversion processes from syn-collisional granites to post-collisional granites with granitic–pegmatitic deposits

Ecological and geochemical assessment of soils in residential areas of Eastern Transbaikalia

Relevance. Environmental pollution by mining wastes is one of the most urgent environmental problems. Aim. To determine the degree of soil pollution in the residential areas of Eastern Transbaikalia. Objects. Total soil pollution according to the Saet formula (Zc) was studied in 30 settlements of Eastern Transbaikalia, including 14 settlements related to mining. Methods. In order to determine the degree of soil contamination, the settlements were grouped: settlements at gold ore, molybdenum lead-zinc and rare-metal deposits, as well as settlements not related to mining. The factual material was obtained during the research under the basic projects of the Institute of Natural Resources, Ecology and Cryology of the Siberian Branch of the Russian Academy of Sciences from 2000 to 2022. In addition, published data and materials of the territorial geological funds (Chita) were used. The X-ray fluorescence method was used to determine the concentrations of chemical elements in analytical laboratories of the Geological Institute of SB RAS (Ulan-Ude), ISP-MS of ZAO "SGS Vostok Limited" (Chita). Results. Among the considered groups of settlements the following indicators of total soil contamination degree (Zc) were established: mining settlements of lead-zinc deposits – 68.87; gold deposits – 30.67; molybdenum deposits – 32.25; rare-metal deposits – 0.03; settlements not related to mining activity – 0.32. According to the total degree of soil contamination Zс, the settlements of lead-zinc deposits correspond to extremely hazardous, molybdenum deposits – hazardous; gold deposits – moderately hazardous; the settlements of rare-metal deposits and the ones not related to mining activities – low levels of pollution.

Genesis studies of Li–Rb deposits in pegmatites from Bailongshan, western China: Evidence from chronology, fluid inclusions, and H–O isotope analysis

The Bailongshan Pegmatite deposit, located in the West Kunlun Orogenic Belt, Northwest China, is a newly discovered, super-large Li–Rb (Be–Ta–Nb) rare-metal deposit. Since complex magmatic-hydrothermal processes are responsible for the mineralization of such rare-element pegmatites, it is desirable to study the evolution and sources of ore-forming fluids to analyze the genesis of ore deposits. In this study, the 40Ar/39Ar plateau ages of muscovite and biotite were determined to be 171.36 ± 1.87 and 172.39 ± 1.66 Ma, respectively, indicating that the duration of hydrothermal mineralization was approximately 170 Ma. Based on the zonal nature of the mineral assemblage, the Bailongshan area was divided into four zones and stages (I–IV), namely the albite–quartz–lithium tourmaline (AQT, stage I), albite–quartz-bearing mica (AQM, stage II), albite–quartz–spodumene (AQS, stage Ⅲ), and spodumene–quartz (SQ, stage IV) zones. Among these, AQS and SQ were the main ore-bearing areas. In terms of the fluid inclusions found in quartz and spodumene, the different types include a gas-rich phase (V-type), a liquid-rich phase (L-type), a daughter mineral-bearing three-phase (S-type), and a carbon dioxide-bearing phase (C-type). In stage I, the homogeneous temperatures of the V- and S-type fluid inclusions varied from 365 to 415 °C, while their corresponding salinities were 8.5–12.9 and 44.8–47.2 wt% NaCl equiv., respectively. In stage II, the homogeneous temperature and salinity of the L-type inclusions were 315–365 °C and 9.9–13.3 wt% NaCl equiv., respectively, while in stages Ⅲ and IV, the homogeneous temperatures of the L- and S-type fluid inclusions were between 235 and 335 °C, while their salinities were 7.2–12.3 and 32.1–37.0 wt% NaCl equiv., respectively. Furthermore, for the C-type inclusions, the homogeneous temperature and salinity were 235–320 °C and 4.9–10.6 wt% NaCl equiv., respectively. The laser Raman results showed that the fluid in the metallogenic stage was an H2O–NaCl–CO2–CH4 system. Based on the homogeneous temperature and salinity results, the fluid capture pressure from stage III to stage IV was calculated to be 280–150 MPa, and the depth of the capture was >6 km. Moreover, the H–O isotope results suggested that the early ore-forming fluids are mainly magmatic hydrothermal fluids, whereas the later (stage IV) mineralizing fluids may be mixed with a small amount of meteoric water. The subsequent immiscibility of the fluid may be one of the factors responsible for the discharge and precipitation of minerals.

The Aspects of Radiation Safety When Working With Ore from the Tomtor Integrated Rare Metal Deposit in Yakutia, Used as a Modifying Additive in Welding Materials

The results of measurements of the content of radioactive elements in ore samples from the Tomtor integral rare metal deposit are considered with the aim of safe use of ore with rare earth elements as a modifier of the weld pool during the processes of manual arc welding and fusing. It was revealed using a semiconductor gamma spectrometer that a significantly larger proportion of ionizing radiation activity is represented by the thorium-232 family. It is noted that natural concentrate is added to the composition of welding materials in very small quantities, and during welding operations in the room next to the welder, the values of the exposure dose rate will correspond to the initial radiation background in the room, therefore, both the welder and those people who will be in contact with the welded materials will not receive additional radiation dose to the natural background. It was concluded that the process of manufacturing the welding materials, welding, fusing and the use of welded structures are completely safe in terms of radiation.

The characteristics of S-wave velocity and mineralization of the “Double Domes” structure in the eastern Tethys Himalaya

The Tethys Himalayan belt in the southern Qinghai–Tibet Plateau has been intruded by a large amount of leucogranite due to collisional orogeny. In addition, strong tectonic movements since the Cenozoic era have led to the formation of a series of dome structures accompanied by various types of mineralization. The Cuonadong Dome and Yalaxiangbo Dome, forming the “double dome” structure in the eastern part of the Tethys Himalayan Belt, are affected by different geological processes, resulting in differences in their deep structures and affecting the formation of polymetallic minerals. At present, geophysical research on the fine structure of the crust of the “double dome” structure is limited, making it difficult to fully understand the formation of different deep structures in the Tethys Himalayan dome belt. This hinders the progress of research on the genesis of dome structures and large-scale mineralization mechanisms in continental collisional environments. In this study, the ambient noise tomographic method was used to obtain the S-wave velocity structure of the upper crust of the Cuonadong Dome and the Yalaxiangbo Dome, and the following results were found: 1. there is a significant difference in the velocity structures of the two domes, with the core velocity structure of the Yalaxiangbo Dome showing an overall high velocity, extending downward for more than 9 km, while the core of the Cuonadong Dome exhibits low-velocity characteristics, with some high-velocity bodies occurring locally, which may be related to the later intrusion of leucogranite and extensional activity of the Cuona Rift. 2. There are significant differences in the S-wave velocities between the lead–zinc deposits and rare metal deposits in the study area; the lead–zinc deposits occur in basins and graben margins and have large variations in the S-wave velocity, which may be related to the involvement of basin brine in mineralization; below the tungsten–tin–beryllium deposits, the S-wave velocity exhibits high-velocity protrusions, with mineralization occurring at the front ends of the protrusions, which may be caused by crystallization differentiation of leucogranite. 3. The study area has abundant geothermal resources and obvious geothermal structural features. The low-velocity basin in the upper part of the upper crust is a heat storage layer, the low-velocity channel in the middle is a heat-conducting layer, and the lower part is a low-velocity heat source area that continuously supplies heat, forming a special geothermal structural model for the Cuonadong Dome and Yalaxiangbo Dome.

Trace element geochemistry of carbonatites and associated alkaline rocks of Mundwara Igneous complex, Sirohi district, Rajasthan, India

Carbonatites are widely recognized for their potential to host significant deposits of rare earth elements (REEs) and other rare metals. These igneous rocks, characterized by their high carbonate mineral content, are often rich in REEs, niobium, tantalum, and other valuable elements. This makes carbonatites key targets for mining and exploration. Carbonatites are believed to form from either primary carbonate magma derived directly from the mantle or from secondary melts. These secondary melts can originate from carbonated silicate magmas through liquid immiscibility or from the residual melts resulting from the fractional crystallization of silicate magmas. The coexistence of carbonatites and alkaline silicate rocks in most complexes, their coeval emplacement in many, and overlapping initial 87Sr/86Sr ratios supports the theory of their cogenesis. In this study, we aim to investigate the trace element geochemistry of carbonatites and coeval alkaline silicate rocks from the Mundwara Igneous Complex, Sirohi district, Rajasthan in India. Our trace element data indicate that the carbonatites and alkaline silicate rocks in this complex are products of fractional crystallization from two separate parental melts, formed through liquid immiscibility of a carbonated alkaline silicate magma.

Lithium capacity of Kazakhstan mineral resource base

Relevance. Weak knowledge of the territory of the Republic of Kazakhstan on lithium raw materials previously mined in the East Kazakhstan region. Aim. To study lithium raw material base in the Republic of Kazakhstan and prospects for the extraction of lithium raw materials. Methods. Content analysis of all information on the subject of the mineral resource base of lithium in the Republic of Kazakhstan. Results. Within the Republic of Kazakhstan, ore deposits of scapolite pegmatites and lithium-bearing greisens-hydrothermal growths are known along alkaline granites. Residual lithium reserves from previously developed rare metal deposits that are equivalent to 36.3 thousand tons of Li2O, predicted resources of known lithium occurrences are estimated at 140 thousand tons of Li2O. It is possible to develop known rare metal deposits with the extraction of tantalum, niobium, beryllium and associated extraction of spodumene concentrate. GRK «Ognevsky Mining and Processing Plant» is already planning to put back to mining of tantalum and beryl (with the associated extraction of spodumene concentrate – up to 2.5 thousand tons/year) at the Bakennoe deposit and processing the resulting ore concentrates at the operating Ulba metallurgical plant of Kazatomprom. With regard to lithium-bearing hydro-mineral resources of the Republic of Kazakhstan, the situation is more complicated, due to the data limitations on the completeness of formation water testing and the reliability of data on surface waters of stagnant lakes. Such oil and gas fields as Karachaganak (up to 196 mg/l Li2O), Kolkuduk (up to 130 mg/l Li2O), Teplovskoe (up to 82.5 mg/l), Urikhtau (up to 52 mg/l) and Western Opak (up to 45 mg/l) are known for high concentration of lithium in formation waters. First two deposits are ready for oil and gas development and production with an annual extraction of up to 1 thousand tons of lithium carbonate. With regard to the lithium content of stagnant lakes of the Republic of Kazakhstan, it should be noted almost total lack of reliable information on sampling their surface waters. Given the fact of finding industrially significant lithium-bearing hydro-mineral lake deposits in adjacent regions of China and Mongolia, it is necessary to intensify the thematic works to assess the lithium content of endorheic lakes throughout the Republic of Kazakhstan, with sampling not only of surface waters, but also of natural brine, lake mud, saline clayey rocks of solonchaks and takyrs.

Editorial for Special Issue: “Geochemistry and Mineralogy of Basic–Ultrabasic and Alkaline Intrusions and Related Magmatic Deposits”

Magmatic deposits are sources of strategic metals provided to the global market [...]

The giant Baerzhe rare-earth-element–Nb–Zr–Be deposit, Inner Mongolia, China, an Early Cretaceous analogue of the Strange Lake rare-metal deposit, Quebec

The Baerzhe deposit represents world-class mineralization of rare metals, in particular rare earth elements (REEs) and Nb, and shares mineralogical and geochemical similarities with the Strange Lake deposit in Canada. However, the mechanisms responsible for the rare-metal enrichment at Baerzhe are still under debate. Mineralization at Baerzhe is characterized by multiple stages of dissolution, re-precipitation and enrichment of rare-metal elements, as with the Strange Lake deposit. Zirconium was concentrated during magmatic fractionation of elpidite in a transsolvus agpaitic granite (Stage I), and was redistributed into zircon–quartz pseudomorphs during Na-metasomatism (Stage II). Rare earth elements, Nb and Be occur as a variety of mineral assemblages, mainly as pseudomorphs after complete replacement of unknown precursor minerals that are disseminated through the hematized transsolvus granites and were precipitated in three sequential stages (Stages III–V): Stage III is characterized by the mineralization of hingganite, aeschynite-(Y), columbite-(Fe) and euxenite-group minerals, accompanied by hematite alteration; the following Stage IV is defined mainly by monazite-(Ce) crystallization, and Stage V by the preceding REE minerals being replaced by light REE minerals (i.e. bastnäsite-(Ce) and fluocerite-(Ce)). The formation of various pseudomorphs as replacement for precursor minerals is also a common feature documented at Strange Lake. Our results call for a re-evaluation of the timing and role of meteoric waters at Baerzhe, which were suggested by previous researchers to have entered the ore-forming system prior to the mineralization of zircon. New in situ O isotopic analyses on pseudomorph-hosted mineral pairs and investigation of silicate melt–fluoride melt immiscibility through observations and analyses of melt inclusions could provide further insights into the nature of the Baerzhe system.

Analiza strukturalna i zróżnicowanie pegmatytów w starożytnym twierdzeniu, Giraúl IV, dystrykt pegmatytów Namibe, Angola

Since the early 60´s, in the past XX century, the Giraúl pegmatites have been known for their resources of beryl, mica and feldspars, which were exploited in a regular basis from Giraúl claims I to IV till 1974, during the Portuguese administration of Angolan territory. A broader exploration of this pegmatite field was performed by the ancient Lobito Mining Company (LMC) engaged in detailed geological mapping of the granitic pegmatites and the structural constraints of their location. A structural map of the region was than elaborated, combining the interpretation of aerial photographs with field work performed by the LMC geologists. Recently, a growing economic interest is attributed to these claims, in the region of Bulamucolocai, Pitau and Muvero desert-dry rivers (locally known as “Mulolas”), considering the Li, Cs, and Ta (LCT) metallic specialization of some pegmatite bodies and the occurrence of beryl and tourmaline gemstones, mainly, morganite (Cs-beryl), aquamarine and also elbaite-liddicoatite. Giant crystals of spodumene, up to 6 m in length, define individualized quartz + spodumene units inside some of the more typical LCT pegmatite bodies. Pollucite was identified in the main pegmatites of Giraúl IV claim and not in the adjacent igneous leucocratic breccias. These, in turn, correspond to a complex pegmatite assemblage, very peculiar in what concerns its selective metasomatic effect over some surrounding rocks, with the formation of rims of holmquistite amphibole in contact with gabbro and norite and schorl-dravite tourmaline in contact with gneissic to metapelitic hosts. The breccia-like granitic rock combines clasts of spodumene an K-feldspar with a matrix mainly composed of some quartz, albite and mica including tourmaline, garnet and F-apatite, as accessory minerals. In the same area, huge potassic pegmatites hold giant crystals of microcline and orthoclase and very little quartz, being unusual due to its high content of triplite – zwieselite and triphylite – lithiophilite primary phosphates. The overall composition of these pegmatites is more likely syenitic (low quartz content) than truly granitic. A high-resolution structural analysis of the LCT ensemble (pegmatite plus related lithotypes) is now proposed enhancing the unusual relations between granite breccia plugs, sill-like more typical pegmatites, irregular shaped isodiametric bodies and products of metasomatism. This approach will lead to the understanding of the true dimension, anatomy and inner fraccionation of the different LCT facies and rare-metal deposits with obvious consequences regarding mineral detection and resource – reserve estimation, through the proposal of a more suitable conceptual model to rule its exploration.

Age of the Zashikhinskoye Rare Metal Deposit (Eastern Sayan): Results of U–Pb (ID TIMS) Geochronological Studies of Metamictic Zircon

Age of the Zashikhinskoye Rare Metal Deposit (Eastern Sayan): Results of U–Pb (ID TIMS) Geochronological Studies of Metamictic Zircon

Response characteristics and detectability of pegmatitic rare-metal deposits using different grounded-wire configurations

The differential electrical dipole (DED) and differentially normalized electromagnetic method (DNME) have a stronger transverse magnetic field than the horizontal electric dipole (HED) and, thus, have been successfully used for resource exploration in conductive ocean environments. However, which of these two is more suitable for the exploration of resistive targets on land, such as pegmatite veins and ore-related mafic and ultramafic intrusions in mineral deposits, remains unknown. Thus, we conduct a comparative study of the DED, DNME, and HED based on forward modeling and application to a field survey. The signal amplitude of the horizontal electric field measured using the DED and DNME is substantially weaker than that obtained via the HED with the same source length and transmitting current. The lateral variation in the horizontal electric field response observed via the DNME reflects the change in the shallow electrical structure, indicating the spatial distribution of pegmatite veins, as verified by the 3D simulation results and data obtained in a field survey of pegmatitic rare-metal deposits in Lushi County, China. The DED and DNME exhibit similar abilities for detecting resistive targets. Both methods show higher detectability than HED based on 3D synthetic modeling. Our results indicate that the DNME, with its higher responses and better lateral resolution, is a better choice in field surveys on land than the DED.

Constraints of alkaline magmatic evolution on the enrichment and mineralisation of rare-earth elements in the eastern part of the northern margin of the North China Craton: a case study of the Baerzhe and Saima deposits

The eastern part of the northern margin of the North China Craton is a key metal metallogenic province in China, hosting many important rare metal and rare earth element (REE) deposits and having great resource potential. This study investigated the Saima deposit, a niobium (Nb) and tantalum (Ta) deposit and the Baerzhe deposit hosting zirconium (Zr), Nb and REEs. Based on previous LA-ICP-MS zircon U–Pb dating results obtained by the authors’ team, this study compared the whole-rock geochemistry and whole-rock Sr–Nd–Pb isotopes of an orebody with its surrounding rocks. The geochemical characteristics of both deposits are used to systematically review the evolution of the alkaline magma and the differences in the physical and chemical conditions for enrichment and mineralisation of late-stage rare elements and REEs such as Nb, Ta and Zr. Comparing the mineralisation of the Saima and Baerzhe deposits, the alkaline magmatic evolution plays a crucial role in the enrichment of rare-earth elements, which are generally formed in the late stage of alkaline magmatic evolution.

Geochronology, mineralization and prospecting implication of the Paleoproterozoic Shaliuquan Nb-Ta pegmatite deposit in the northern Tibetan Plateau

A large number of Archean and Paleoproterozoic pegmatite rare-metal deposits exist worldwide, but few Precambrian pegmatite deposits have been reported in China, especially in the Tibetan Plateau. The Precambrian pegmatite deposits are still poorly studied. The Shaliuquan pegmatite, located in Quanji Massif, is a rare pegmatite-type Nb-Ta deposit in the northern Tibetan Plateau. Columbite-tantalite group minerals (CGMs) from three pegmatite samples give the U-Pb ages of 1844.2 ± 8.1 Ma, 1831.2 ± 12.2 Ma and 1848.0 ± 18.7 Ma, respectively. The U-Pb ages of CGMs show that the Shaliuquan pegmatite is a rare Paleoproterozoic pegmatite rare-metal deposit in the Tibetan Plateau. This is supported by the Precambrian 40Ar/39Ar plateau age of muscovites from two pegmatite samples (1094–1518 Ma), representing the metamorphic events after formation. As for the formation of Shaliuquan pegmatites, we argue that the hydrothermal processes in the late stage of the pegmatite evolution play a vital role for the enrichment and mineralization of Ta, which is evidenced by texture and compositions of CGMs and zircons. The formation of the Shaliuquan pegmatites is a response to the assembly of the Columbia supercontinent. The discovery of the Precambrian Shaliuquan pegmatite deposit implies that the Quanji Massif in the northern margin of the Qaidam Basin, which has an ancient mature metasediments basement and thick continental crust, has great potential for prospecting the Paleoproterozoic pegmatite rare-metal deposits.

Quartz chemical composition and apatite thermochronology trace leucogranite evolution and thermal history in the Koktokay No. 3 rare metal deposit, Chinese Altai

Koktokay No. 3 pegmatite is a globally renowned rare metal deposit. Recently, rare metal-enriched leucogranite was identified within this deposit. The leucogranite is locally cut by No. 3 pegmatite and scattered as fragments among the pegmatite in some outcrops. In this study, we aimed to investigate the emplacement depth, thermal history, and evolution process of leucogranite based on quartz chemical composition and apatite thermochronology. Li, Al, P, Ge are the higher content elements in leucogranite quartz, and Ti is the lower content element (approximately 38.7, 178, 23.9, 2.7, and 2.0 ppm, respectively). The Al, Ti, and Li contents decreased from the core to the rim of the quartz. The leucogranite quartz compositions have a high Ge/Ti ratio, similar to that of the quartz in the Li-Cs-Ta pegmatites, particularly the Koktokay No. 3 pegmatite. This similarity indicates that the leucogranite was formed by a highly evolved melt. Using laser ablation-inductively coupled plasma-mass spectrometry, the U–Pb age of leucogranite apatite was determined as 189.4 ± 6.8 Ma, which is substantially younger than the previous columbite U–Pb age of No. 3 pegmatite, suggesting that the magmatic-thermal activity of No. 3 pegmatite had interfered with the apatite U–Pb closure system. The apatite low-temperature thermochronology results showed that the thermal history of leucogranite can be divided into two cooling stages: rapid cooling stage (180–155 Ma, 9.6–10.6 ℃/m.y.) and slow cooling stage (from 155 Ma to the present day, 0.8–1.0 ℃/m.y.). According to the thermal history, the exhumation and erosion of the Koktokay No. 3 rare-metal deposit is at least 5–6 km long. Leucogranite formation pressure is approximately 2.5 kbar (1.8–3.7 kbar), and the emplacement depth approximately 9.5 km (7–14 km).

Metallogenetic epoch and material source of Be-pegmatite differentiated from biotite granite in Mufushan complex

The Mufushan Complex (MFSC) is a significant rare metal mineralized in the central China district and is renowned for its marked economic value of rare metal deposits. While the main rare metal mineralization (RMM) stage in the MFSC relates to the magmatic event of two-mica monzogranite, the mineralization event related to biotite monzogranite remains unknown. To fill this gap, this study focuses on porphyritic biotite monzogranite and adjacent Be-rich pegmatite samples obtained from Changqing Pegmatite No. 1, which is situated in the southeastern part of the MFSC. We subjected these samples to zircon U–Pb dating and Hf isotope analysis using laser ablation inductively coupled plasma mass spectrometry (LA–ICP–MS) and utilized an electron probe X-ray microanalyzer (EPMA) and LA–ICP–MS to examine the major and trace elements present in the muscovite samples. Our findings revealed precise chronological data for the geological history of Changqing, pinpointing the intrusion age of biotite monzogranite to 145.8 ± 1.1 Ma and the crystallization age of Be-rich pegmatite to 144.9 ± 1.1 Ma, firmly situating these events within the Late Jurassic to Early Cretaceous epoch. Regarding isotopic composition, zircon εHf (t) for granite ranged from −9.29 to −5.09, and their corresponding TDM2 ranged from 1788 to 1520 Ma. Similarly, zircon εHf (t) for pegmatite ranged from −7.89 to −5.47, and their corresponding TDM2 ranged from 1699 to 1544 Ma. These isotopic signatures strongly indicate a shared origin for the initial magma of granite and pegmatite. The partial melting of the thick Lengjiaxi Group tasedimentary strata serves as a material source for RMM. The transition from granite to pegmatite exhibits remarkable constancy in the primary components of muscovite. By examining its geochemical attributes, we observed synchronous decreases in FeO, MgO, SiO2, MnO, Be, Rb, and Cs, coupled with synchronous increases in Nb and Ta contents, along with Ta/Nb values. These findings strongly imply that the Changqing biotite monzogranite and Be-rich pegmatite originate from the continuous differentiation and evolution of a common magmatic source, establishing a clear genetic relationship between them. The MFSC has its origins in three distinct stages of magmatic activity and RMM spanning from 160 Ma to 120 Ma. Considering the distribution patterns of similar pegmatite veins, the metallogenic potential observed during the biotite granite stage may serve as an external indicator of marked mineralization within large batholiths.

Tracing fluid exsolution and hydrothermal alteration signature of the Mufushan Nb–Ta–(Li–Be–Cs) deposit, South China: an apatite perspective

The appearance of hydrous magmas and the following separation of volatile-rich fluids through hydrothermal alteration are intricately linked to the formation of granitic rare-metal deposits, the principal source of worldwide Li, Be, Nb, Ta and Cs production. The lack of mineralogical information from the developing magmatic–hydrothermal system has, however, prevented a thorough comprehension of these processes. Apatite occurs as an accessory mineral in the metasedimentary (schist)–magmatic (muscovite monzogranite)–pegmatite (ore-free or ore-bearing pegmatite) rocks in the Mufushan Complex (MFSC) rare-metal ore field of northeastern Hunan, South China, potentially providing insights into Nb–Ta–(Li–Be–Cs) mineralization. To demonstrate that apatite can potentially record the magmatic–hydrothermal evolution of metasedimentary–magmatic–pegmatite systems, this study presents a combined textural and geochemical study of apatite from the MFSC granitic pegmatite-type rare-metal mineralization. The MFSC apatite textures and compositions have changed since it first crystallized (i.e. post-crystallization alteration). Apatite from the schist shows a homogeneous rim or homogeneous textures with cracks or inclusions (S-ap1) and a patchy core (S-ap2), indicative of a magmatic–hydrothermal origin. Apatite from the muscovite monzogranite (G-ap) displays altered and distinctive core–rim textures, with visible voids, mineral inclusions and cracks, suggestive of overprinting of early magmatism texture by hydrothermal fluid. However, compared with S-ap1, S-ap2 and G-ap, the pegmatite apatite shows more complicated textures; that is, P-ap1 (homogeneous bright and dark areas) and P-ap2 (replacement texture involving alteration rim, growth zonation, patchy and complex zoning patterns). P-ap1 underwent early magmatism and weaker post-hydrothermal overprinting, and P-ap2 reflects a magmatic–hydrothermal product. S-ap1 and S-ap2 yield lower intercept ages of 130.6 ± 1.8 and 128.4 ± 3.8 Ma, respectively, which are consistent with the transitional age of the magmatic–hydrothermal metallogenic environment in northeastern Hunan. G-ap and P-ap1 yield older ages of 136.3 ± 2.8 and 141.3 ± 6.7 Ma, respectively, which correspond to the age of magmatic early stage (Nb–Ta)-mineralization within uncertainty in northeastern Hunan. The Sr isotopic composition of apatite provides evidence for the provenance of the MFSC batholith in the rare-metal metallogenesis of the Lengjiaxi Group. Therefore, we hypothesize that apatite in granitic rare-metal deposits within metasedimentary–magmatic–pegmatite systems might be employed as a viable proxy to explore the textures and geochemical fingerprints of fluid exsolution and hydrothermal alteration. Supplementary material: Analytical techniques and the results for apatite grains in this investigation are available at https://doi.org/10.6084/m9.figshare.c.7038699