Search Results (105)

The Kalba–Narym metallogenic belt is located in East Kazakhstan, which displays rare metal mineralization. The Kvartsevoye rare metal Li–Ta–Nb deposit is located in the north-western ore district. This study presents the results of geological, mineralogical, geochemical, and geochronological analyses of rare metal granite pegmatites. Rare metal mineralization belongs to a field of variably differentiated pegmatites, including barren, quartz–albite–muscovite, muscovite, and muscovite–quartz–albite microcline mineral associations. This study established that the rare metal mineralization is localized in the quartz–albite–muscovite zone. The main concentrator minerals of rare metals are spodumene for Li and tantalite–columbite for Ta and Nb. Ar/Ar dating of the muscovite allowed us to establish the age of mineralization during the period of 288–285 Ma. The present study enabled the linkage of rare metal mineralization with the differentiation processes of the granites of the Kalba complex. Full article

The selection of grinding media significantly impacts the resulting mineral’s liberation degree and grinding quality; this is particularly impactful for granite pegmatite-type quartz. Accordingly, in this study, we investigate the effects of different grinding media on the breakage characteristics of muscovite granite pegmatite-type quartz, focusing also on quartz mineral flotation. An analysis of scanning electron microscope images reveals distinct fracture characteristics among different minerals. Notably, the fractal dimension of mineral fracture roughness in ball-milled products is larger compared to that of rod-milled products, which exhibit a smaller fractal dimension. This fractal dimension serves as a quantitative measure of the microscopic morphology of mineral fractures in the grinding products, establishing a relationship between the roughness of the fractures and the type of grinding medium used. Further analysis of particle size distribution and mineral dissociation indicates that the rod mill produces a higher yield of coarse fractions compared to both ceramic and steel balls, while the fine fraction yield is significantly lower than that of the rod mill and steel balls. Importantly, the rod mill enhances the dissociation degree of quartz, suggesting that it can improve the liberation of mineral monomers and increase the yield of qualified fractions during the grinding process while effectively reducing the phenomenon of overgrinding. Our flotation experiments demonstrate that the recovery rate of quartz using the rod mill is 2.59% and 5.07% higher than that achieved with the ball mill and ceramic mill, respectively. These findings provide theoretical support for the optimization of grinding media and enhancement of mineral flotation recovery. Full article

Spodumene-bearing pegmatites are geochemically anomalous among crystalline rocks and important critical mineral resources in the green energy transition. However, prospecting is challenging due to their small size and the fact that they are often covered by soil and vegetation. This study demonstrates that, rather than being a hindrance, soil cover can enhance geochemical exploration, at least at the prospect scale. This study examines the dispersion pathways of lithium (Li) and its pathfinder elements (Rb, B, Ga, and Sn) from pegmatites (<10 m thick) into metamorphic host rocks and further into overlying undisturbed soils in heavily forested, postglaciated terrain of northeastern Wisconsin, USA. Soil-sample traverses over the world-renowned, lepidolite-type Animikie Red Ace pegmatite and two nearby dikes reveal pronounced <20 m anomalies with up to 1400 ppm of Li, 450 ppm of Rb, 3100 ppm of B, 40 ppm of Ga, and 60 ppm of Sn, greatly exceeding the control soil concentrations from nonmineralized granite and pegmatites. Soils mirror both the magmatic fractionation and alteration of pegmatite bedrock and metasomatic halos in parent host rocks. Metasomatized amphibolite revealed the presence of a holmquistite-ferro-holmquistite mineral. This greenfield pilot exploration led to lithium-rich pegmatite discoveries within the district and demonstrates the applicability of proximal sensors for soil exploration in Wisconsin and beyond. Full article

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

The current work records for the first time the rare-metal pegmatites with mixed NYF-LCT located at Wadi Sikait, south Eastern Desert of the Egyptian Nubian Shield. Most of the Sikait pegmatites are associated with sheared granite and are surrounded by an alteration zone cross-cutting through greisen bodies. Sikait pegmatites show zoned and complex types, where the outer wall zones are highly mineralized (Nb, Ta, Y, Th, Hf, REE, U) than the barren cores. They consist essentially of K-feldspar, quartz, micas (muscovite, lepidolite, and zinnwaldite), and less albite. They contain a wide range of accessory minerals, including garnet, columbite, fergusonite-(Y), cassiterite, allanite, monazite, bastnaesite (Y, Ce, Nd), thorite, zircon, beryl, topaz, apatite, and Fe-Ti oxides. In the present work, the discovery of Li-bearing minerals for the first time in the Wadi Sikait pegmatite is highly significant. Sikait pegmatites are highly mineralized and yield higher maximum concentrations of several metals than the associated sheared granite. They are strongly enriched in Li (900–1791 ppm), Nb (1181–1771 ppm), Ta (138–191 ppm), Y (626–998 ppm), Hf (201–303 ppm), Th (413–685 ppm), Zr (2592–4429 ppm), U (224–699 ppm), and ∑REE (830–1711 ppm). The pegmatites and associated sheared granite represent highly differentiated peraluminous rocks that are typical of post-collisional rare-metal bearing granites. They show parallel chondrite-normalized REE patterns, enriched in HREE relative to LREE [(La/Lu)_n = 0.04–0.12] and strongly negative Eu anomalies [(Eu/Eu*) = 0.03–0.10]. The REE patterns show an M-type tetrad effect, usually observed in granites that are strongly differentiated and ascribed to hydrothermal fluid exchange. The pegmatite has mineralogical and geochemical characteristics of the mixed NYF-LCT family and shows non-CHARAC behavior due to a hydrothermal effect. Late-stage metasomatism processes caused redistribution, concentrated on the primary rare metals, and drove the development of greisen and quartz veins along the fracture systems. The genetic relationship between the Sikait pegmatite and the surrounding sheared granite was demonstrated by the similarities in their geochemical properties. The source magmas were mostly derived from the juvenile continental crust of the Nubian Shield through partial melting and subsequently subjected to a high fractional crystallization degree. During the late hydrothermal stage, the exsolution of F-rich fluids transported some elements and locally increased their concentrations to the economic grades. The investigated pegmatite and sheared granite should be considered as a potential resource to warrant exploration for REEs and other rare metals. Full article

The Bozhushan in southeastern Yunnan is a composite granite body that was formed by multi-phase magmatic intrusion. The genesis of the tourmaline-supergroup minerals occurring therein remains uncertain, as it has been the subject of only a limited number of studies. This investigation employs an integrated analytical approach combining EPMA, LA-ICP-MS, and boron isotope geochemistry, supplemented by detailed field geological investigations and petrographic observations of tourmaline textural characteristics. This study aims to elucidate the genetic relationships between distinct tourmaline varieties, establish temporal correlations between mineral crystallization stages and magmatic–hydrothermal evolution processes, and evaluate the petrogenetic significance of tourmaline geochemical signatures for regional mineralization events. This study analyzes tourmaline-supergroup minerals in granitic pegmatites and aplites, which occur as nodular, radial, and columnar aggregates. Most tourmaline crystals exhibit well-defined rhythmic zoning patterns, which are clearly observable under cross-polarized light microscopy. Chemical composition analysis has identified two tourmaline species: schorl and dravite. The formation of tourmaline is primarily of magmatic origin and is characterized by a magmatic–hydrothermal transition. It predominantly belongs to the alkali subgroup and is formed in Li-poor granitoids and associated pegmatites and aplites, Ca-poor metapelites, metapsammites, and quartz-tourmaline rocks. The inter-ionic substitution mechanism in this system is predominantly governed by Fe²⁺Mg₋₁ and (X_vacAl)(NaR²⁺)₋₁ exchange equilibria. Additionally, geochemical evidence indicates that the primary ore-forming fluids originate from granitic magmas, which are likely sourced from the partial melting of metasedimentary rocks. During the late Yanshan period, the upwelling of granitic magma in the Bozhushan area introduced a substantial heat source and mineralizing fluids, which interacted with the Cambrian units to form tungsten–tin mineralization. The geochemical data on tourmaline indicate that the Bozhushan granite body has considerable potential for ore mineralization. Full article

Rare metals such as lithium and beryllium are strategic mineral resources that play a highly significant role in the national aerospace, defense, and new energy industries. The western Kunlun–Songpan–Ganzi metallogenic belt is an important rare metal metallogenic belt in China that mainly consists of granite–pegmatite-type lithium–beryllium deposits with uncommon beryllium-only deposits. In the Jiulong area on the southeastern edge of this metallogenic belt, several deposits, including the Daqianggou lithium–beryllium, Luomo beryllium, Baitai beryllium, and Shangjigong beryllium deposits, have been identified. Unlike the northern areas of Jiajika, Ke’eryin, Zawulong, and the western regions of Dahongliutan and Bailongshan, this area contains beryllium-only deposits. In this paper, we examine representative beryllium deposits in the Jiulong area, including detailed petrographic observations and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) U-Pb isotope dating of cassiterite and columbite–tantalite, to define the metallogenic age and summarize the spatiotemporal characteristics of the beryllium mineralization in this area. The research results show that the Daqianggou lithium–beryllium deposit is dominated by spodumene and beryl mineralization, while the Luomo and Baitai beryllium deposits primarily feature beryl mineralization. The dating results indicate that the U-Pb ages of the cassiterite and columbite–tantalite in the Daqianggou lithium–beryllium deposit are 157.3 ± 1.7 Ma and 164.1 ± 0.8 Ma, respectively. For the Luomo beryllium deposit, the U-Pb ages of the cassiterite and columbite–tantalite are 156.1 ± 1.5 Ma and 163.3 ± 0.8 Ma, respectively. For the Baitai beryllium deposit, the U-Pb age of the columbite–tantalite is 188.8 ± 1.1 Ma. Therefore, the Jiulong area experienced two pegmatite-type rare metal metallogenic events: a beryllium–niobium–tantalum–molybdenum event at 197~189 Ma and a lithium–beryllium–niobium–tantalum–rubidium event at 164~156 Ma. Based on the reported metallogenic ages, we suggest that the western Kunlun–Songpan–Ganzi rare metal metallogenic belt experienced three rare metal metallogenic events at 210~200 Ma, 200~180 Ma, and 170~150 Ma. Regarding exploration directions, early Yanshanian beryllium mineralization predominates in the Jiulong area along the southeastern edge of the belt, and deep exploration of the early Yanshanian rare metal mineralization within this belt should be strengthened to facilitate new breakthroughs. Full article

Spodumene is a characteristic mineral in lithium-rich granitic pegmatites, serving both as a valuable mineral resource and an important gem material. This study incorporates three different color varieties of spodumene—pink to violet, yellow-green, and colorless—into a unified research framework. X-ray powder diffraction (XRD), electron probe microanalyzer (EPMA), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, ultraviolet–visible spectroscopy (UV-Vis), and photoluminescence spectroscopy (PL) were employed to systematically analyze the chemical composition, crystal structure, and spectroscopic properties of spodumene. Furthermore, the coloration mechanism and fluorescence emission of the different color samples were investigated and analyzed. The results indicate that the presence and mixed valence states of the transition metals Fe and Mn primarily influence the color and photoluminescence of the three types of spodumene. Mn³⁺ is the primary color-causing element in pink to violet spodumene, while Fe³⁺ is the primary color-causing element in yellow-green spodumene. Photoluminescence in all three color varieties is dominated by Mn²⁺. These findings contribute to a deeper understanding of the color and luminescence mechanisms of spodumene, expanding its potential applications as both a gem material and a luminescent material. Full article

Published Sn isotope data along with 150 new analyses of cassiterite and four granite analyses constrain two major tin isotope fractionation steps associated with (1) separation of tin from the magma/orthomagmatic transitional environment and (2) hydrothermal activity. A distinct Sn isotope difference across deposit type, geological host rocks, and time of ore deposit formation demonstrates that the difference in the mean δ¹²⁴Sn value represents the operation of a unified process. The lower Sn isotope values present in both residual igneous rocks and pegmatite suggest that heavier Sn isotopes were extracted from the system during orthomagmatic fluid separation, likely by F ligands with Sn. Rayleigh distillation models this first F ligand-induced fractionation. The subsequent development of the hydrothermal system is characterized by heavier Sn isotope composition proximal to the intrusion, which persists in spite of Sn isotope fractionating towards isotopically lighter Sn during hydrothermal evolution. Full article

Lithium is a strategic metal due to its use in green technologies, particularly battery manufacturing. It is on the US List of Critical Minerals and the European Union’s List of Critical Raw Materials. In Mongolia, there are three major types of potentially economic Li deposits: (1) Deposits related to granites, granitic pegmatites and associated rocks; (2) Li-rich clay deposits; (3) Salar (Li brine) deposits. The first type of mineralization is associated with the lithium–fluorine-rich peraluminous A-type granites and related rocks (greisens, pegmatites, ongonites, ongorhyolites). The mineralization includes Li and also Sn, W, Ta and Nb. Lithium is hosted in Li-rich micas, unlike the world-class Li-bearing pegmatite deposits where the bulk of Li is in spodumene. In Mongolia, particularly promising are Li brines of endorheic basins in the Gobi Desert with an arid environment, high evaporation rates and low precipitation. Full article

The Songpan–Ganzi Orogenic Belt (SGOB) is bounded by the South China, North China, and Qiangtang blocks and forms the eastern margin of the Tibetan Plateau. The Tiechanghe Granite is located at the junction of the southeast margin of the SGOB and the western margin of the Yangtze Block. To elucidate the genetic relationship between the Tiechanghe Granite and the surrounding molybdenum deposits in Western Sichuan, in this study, we conducted zircon U-Pb and molybdenite Re-Os isotopic dating. The results indicate that the Tiechanghe Granite predominantly consists of monzogranite, with minor occurrences of syenogranite, while the molybdenum deposits are mainly found in skarn and quartz veins. The laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) zircon U-Pb ages of the Tiechanghe Granite range from 162.9 ± 0.7 Ma (MSWD = 0.31, n = 25) to 163.4 ± 0.6 Ma (MSWD = 0.85, n = 26), and the LA-ICP-MS zircon U-Pb age of the pegmatite veins is 164.1 ± 0.9 Ma (MSWD = 1.3, n = 19). These ages are consistent with the weighted average Re-Os age of the Ziershi molybdenite (160.3 ± 1.6 Ma, n = 2) within the error margins. These findings and previously obtained magmatic and metallogenic ages for the region suggest that a magmatic and mineralization event involving granite, molybdenum, tungsten, and copper occurred at around 162–164 Ma in the study area. This discovery broadens the exploration perspective for mineral resources in the Jiulong area of Western Sichuan and the entirety of Western Sichuan. Full article

A significant amount of pegmatite has been discovered on the northwest margin of the Qaidam basin. Among this, the Jiaolesayi pegmatite, located in the northwestern margin of the Quanji Massif (Oulongbuluke micro-continent), shows rare element mineralization potential. Detailed field investigations, along with mineralogical, geochemical, and zircon U-Pb geochronological studies, were carried out on the pegmatite. The results show that the Jiaolesayi pegmatite is syenite, without obvious compositional zoning in the outcrop. It exhibits a peraluminous, high-K calc-alkaline nature with strong depletions in Eu, Sr, Ba, Ti, and P, and high contents of Nb, Ta, Y, Ti, U, Th, and heavy rare earth elements (HREEs), which are primarily concentrated in allanite-(Ce), euxenite-(Y), limonite, thorite, and zircon. The geochemical and mineralogical features of the syenite pegmatite indicate it belongs to the euxenite-type in the rare element class (REE) of the NYF family, with the characteristic accessory mineral being euxenite-(Y). Its 10,000 Ga/Al ratios (2.46 to 2.96), Zr + Nb + Ce + Y contents (998 to 6202 ppm), Y/Nb ratios (0.62 to 0.75), and Yb/Ta ratios (0.80 to 1.49) show an affinity with A₁-type granite. Zircons from the syenite sample yielded a weighted mean ²⁰⁶Pb/²³⁸U age of 413.6 ± 1.4 Ma, while the elevated U and Th concentrations in the zircons and Th/U ratios (0.04 to 0.16) suggest the possible influence of hydrothermal processes in the late-stage fractional crystallization. In the context of the regional tectonic evolution, the syenite pegmatite may have formed from a basic alkaline magma derived from an OIB-like melt with minor crustal contamination, under the post-collisional extension setting. Full article

The Marun–Keu complex plays a significant role in our understanding of the geological evolution of the Ural orogen; however, it remains poorly understood. This study aims to provide insights into the complex’s age, protolith composition, rock formation conditions, and its position in the geological history. The zircons from the host granitic gneiss are characterized by magmatic cores with an age of 473 Ma and metamorphic rims with an age of approximately 370 Ma. We suggest that the metamorphic rims were formed during eclogite metamorphism and that the metagranitoids hosting the eclogites experienced eclogite metamorphism simultaneously with the basic and ultrabasic rocks that are common in this area. Heterogeneous zircons were also isolated from the selvage of a pegmatite vein, in which four domains are distinguished, two to three of which can be identified within single grains, as follows: (1) igneous cores with an age of approximately 470 Ma and the geochemical characteristics of zircon crystallized in basic rocks; (2) zircons recrystallized during eclogite metamorphism with geochemical characteristics intermediate between those of the magmatic cores and true eclogitic zircon; (3) pegmatitic zircon, exhibiting the most sharply differentiated REE spectra of all four domains, characterized by a prominent positive Ce anomaly and a weakly expressed negative Eu anomaly; and (4) eclogitic zircon, observed in the form of veins and rims, superimposed in relation to the other three domains. The age of the latter three domains is within the error range and is estimated to be approximately 370 Ma. This indicates that the processes of eclogite metamorphism and the formation of pegmatites occurred at approximately the same time in the studied area. Full article

Himalayan leucogranite is an excellent target for understanding the orogenic process of the India–Asia collision, but its origin and tectonic significance are still under debate. An integrated study of geochronology, geochemistry, and in situ Sr-Nd-Hf isotopes was conducted for a tourmaline-bearing leucogranite in the eastern Tethyan Himalaya using LA-ICP-MS, X-ray fluorescence spectroscopy, and ICP-MS and LA-MC-ICP-MS, respectively. LA-ICP-MS U-Pb dating of zircon and monazite showed that it was emplaced at ~19 Ma. The leucogranite had high SiO₂ and Al₂O₃ contents ranging from 73.16 to 73.99 wt.% and 15.05 to 15.24 wt.%, respectively. It was characterized by a high aluminum saturation index (1.14–1.19) and Rb/Sr ratio (3.58–6.35), which is characteristic of S-type granite. The leucogranite was enriched in light rare-earth elements (LREEs; e.g., La and Ce) and large ion lithophile elements (LILEs; e.g., Rb, K, and Pb) and depleted in heavy rare-earth elements (e.g., Tm, Yb, and Lu) and high field strength elements (HFSEs; e.g., Nb, Zr, and Ti). It was characterized by high I Sr (t) (0.7268–0.7281) and low ε Nd (t) (−14.6 to −13.2) and ε Hf (t) (−12.6 to −9.47), which was consistent with the isotopic characteristics of the Higher Himalayan Sequence. Petrogenetically, the origin of the leucogranite is best explained by the decompression-induced muscovite dehydration melting of an ancient metapelitic source within the Higher Himalayan Sequence during regional extension due to the movement of the South Tibetan Detachment System (STDS). The significantly high lithium and beryllium contents of the leucogranite and associated pegmatite suggest that Himalayan leucogranites possess huge potential for lithium and beryllium exploration. Full article

The Barroso–Alvão region is an excellent setting for studying Li mineralization associated with granitic pegmatites and developing Li exploration techniques. Among the distinguished pegmatite types in this pegmatite field, the spodumene-bearing dyke from Alijó is a representative example of an Iberian Li–Cs–Ta (LCT) pegmatite currently under exploitation. In this work, we examine the internal evolution of the Alijó dyke and its external metasomatic effect on the surrounding metasediments, contributing to lithium exploration techniques. Electron microprobe analyses provided clues about the crystallization conditions and the degree of differentiation of the pegmatitic melt, whereas the external metasomatism induced by the spodumene-bearing pegmatite was studied through whole-rock geochemistry. The obtained results indicate that the primary crystallization of the studied dyke likely occurred at temperatures between 450–500 °C, with emplacement at shallow crustal levels of about 2–3 kbar. The high concentrations of trace elements such as Li, Cs, Rb, Be, Sn, Nb, Ta, Ge, U, and Tl in the pegmatitic melt suggests high availability of these elements, allowing their partitioning into an early exsolved fluid phase. The exsolution of this fluid phase, subtracting components such as F and B, from the pegmatitic melt would cause a significant undercooling of the melt. Moreover, the interaction of this expelled fluid with the country rock generated a metasomatic overprint in the surrounding metasedimentary host rocks. The metasomatic effect in Alijó is strongly influenced by the nature of the host metasediments, with a significantly higher grade of metasomatism observed in pelitic (mica-rich) samples compared to psammitic (mica-poor) samples collected at same distances from the dyke. The greisen developed close to the pegmatite contact reflects this metasomatic signature, characterized by the mobilization of at least B, F, Li, Rb, Cs, Sn, Be, Nb, Ta, and Tl. We cautiously suggest that whole rock Li concentrations greater than 300 ppm, combined with a minimum value of 1000 ppm for the sum of B, F, Li, Rb, Cs, and Sn in pelitic metasediments of Barroso–Alvão, may be indicative of a mineralized pegmatite in this region. Full article