The tectono-magmatic evolution of the Karakoram Terrane during the India-Asia collision remains debated, particularly concerning the timing, sources, and petrogenetic processes of post-collisional magmatism. Granitic pegmatites of the Shigar Valley, within the Karakoram Metamorphic Complex (KMC) of northern Pakistan, preserve a critical yet poorly constrained record of deep crustal reworking. We present integrated geochronological, isotopic, and geochemical data including U-Th-Pb monazite and cassiterite ages, Sm-Nd isotopes, and whole-rock chemistry to constrain their emplacement history and metallogenetic significance. Our results define a protracted, two-stage magmatic system. Stage I comprises late Oligocene (ca. 24 Ma) garnet-bearing pegmatites in the lower Shigar Valley. These are relatively volatile-poor, with epsilon Nd(t) values (-8.36 to -7.22) indicating derivation from a juvenile crustal source akin to the Baltoro granite. Stage II includes late Miocene-Pliocene (ca. 7.5-3.1 Ma) beryl-tourmaline pegmatites in the upper Shigar Valley. These highly evolved, volatile-rich (B, F, P) systems exhibit extreme fractionation (Rb/Sr > 100), pronounced negative Eu anomalies, and marked enrichment in rare metals (Be, Li, Nb, Ta). Their strongly negative epsilon Nd(t) values (-26.7 to -22.4) indicate an enriched, ancient crustal source, most plausibly generated by partial melting of Dassu felsic gneisses with pelitic input. The temporal overlap between this dual-stage anatexis in the KMC and leucogranite emplacement in southern Tibet implies a common geodynamic driver. We attribute this to a regional transition from crustal thickening to post-collisional extension, potentially linked to slab break-off, enabling episodic melting of heterogeneous crustal reservoirs. Thus, the Stage II pegmatites and associated leucogranites are co-genetic, representing a highly fractionated magmatic system. This petrogenetic model highlights the Dassu-Yuno sector as a prime target for critical rare-metal exploration, particularly within structurally controlled, fluid-mediated alteration zones.

Current classification schemes for granitic pegmatites are largely based on geochemical composition. Whole-rock geochemical analyses of granitic pegmatites are relatively limited due to internal heterogeneity in texture, mineral assemblage, and grain size, which introduces significant sampling bias. Current understanding of their composition is generally confined to their granitic nature. Albite-spodumene pegmatites, characterized by weak internal zoning and pervasive spodumene throughout the entire dike, differ from complex-zoned rare-element pegmatites. However, insufficient attention has been given to the compositional evolution, the occurrence and endowment of associated rare elements. The Qiongjiagang lithium deposit represents a typical example of this pegmatite type within the Himalayan region. Its fine-grained texture facilitates systematic sampling and comprehensive whole-rock geochemical analysis. Results from 174 whole-rock samples indicate that although the whole-vein lithium-mineralized pegmatite at Qiongjiagang is granitic in composition, the proportions of albite and quartz are significantly higher than that of K-feldspar, resulting in high Na/K ratios. A notable negative correlation is observed between Li2O content and (Na2O + K2O). Compared to typical complexly zoned pegmatites (e.g., the Tanco deposit in Canada), the Qiongjiagang pegmatite is slightly enriched in Li and Na but relatively depleted in Rb, Cs, and Ta. Whole-rock elemental correlation analysis and petrographic observations reveal that Rb and Cs are primarily hosted in K-feldspar, with generally low concentrations and only localized, sporadic enrichment in secondary mica. The whole-rock abundances of Nb and Ta are primarily controlled by the crystallization of discrete Nb-Ta oxide minerals. The precipitation of these minerals may be genetically linked to spodumene crystallization, whereby extensive spodumene growth promotes Nb-Ta oxide saturation along crystal margins, leading to higher Nb-Ta contents in Li-rich samples. Whole-rock Sn contents are governed by the abundance of cassiterite and are positively correlated with the proportion of Sn-rich spodumene. This study elucidates the compositional and mineralogical characteristics of albite-spodumene-type pegmatites and highlights the potential for integrated utilization of Nh-Ta mineralization associated with lithium-rich zones.

Near-surface high-sulfidation epithermal alteration-mineralization can be used to guide the exploration of deeper, concealed porphyry domains. The giant Rongna Cu-(Au) deposit is a recently discovered porphyry-high sulfidation epithermal system in the Duolong ore district, Tibet. We report μ-XRF in-situ data of alunite from different spatial positions of the Rongna deposit, complemented by quantitative chemical analysis by electron microprobe analysis (EMPA) and laser-ablation inductively-coupled plasma mass spectrometry (LA-ICP-MS), as well as in-situ sulfur isotope analysis of alunite and associated pyrite by laser-ablation multi-collector inductively-coupled plasma mass spectrometry (LA-MC-ICP-MS). Thin-section-scale μ-XRF mapping reveals significant compositional zoning in alunite, particularly in Pb and Sr, and helps to target subsequent in-situ quantitative analysis. In alunite, K2O content varies from 5.27 to 11.35 wt%, Na2O from below detection limit to 3.66 wt%, Rb from 3.11 to 32.0 ppm, Sr from 134 to 5,366 ppm, Pb from 95.3 to 18,944 ppm. Alunite has δ34S values ranging from 2.27‰ to 15.47‰ (average = 9.41‰, n = 82), whereas associated pyrite ranges from –15.12‰ to –0.59‰ (average = –6.85‰, n = 74). The chemical and isotopic composition of alunite shows significant heterogeneity at the hand-specimen/thin-section scale and the μm-scale, likely due to a variable degree of fluid overprint. Therefore, some chemical indicators of alunite that are relatively easily disturbed, such as Na2O/(Na2O + K2O) and Pb content, tend to scatter and are not suitable to be used as reliable vectors to the mineralization center. However, Rb and Sr show a distinctive spatial distribution pattern: Sr content in alunite increases toward the mineralization center, whereas Rb content and Rb/Sr ratio decrease.

To investigate the evolutionary processes and associated mineralization characteristics of spodumene pegmatites in the Himalayan region, we present cathodoluminescence, oxygen isotope, and trace element results for quartz from the newly discovered Qiongjiagang pegmatite-type lithium deposit in the Himalaya. Quartz samples from different lithologies were all homogeneous and unzoned according to cathodoluminescence images. Quartz trace element characteristics indicate that Qiongjiagang spodumene pegmatites were formed from highly evolved melts with early fluid exsolution. The fluid exsolution stage governed the trace element composition of hydrothermal quartz. The oxygen isotope values of quartz from tourmaline-muscovite granites (14.5‰), barren pegmatites (14.3‰), and spodumene pegmatites (14.9‰) demonstrate that the pegmatites and granites share a comagmatic evolutionary origin, closely related to the partial melting of Higher Himalayan metasedimentary rocks. Beryl in the spodumene pegmatite has significantly elevated δ18O values (18.9‰) and significant isotopic disequilibrium (Δ quartz−beryl=-2.8‰). We proposed that metamorphic fluids were likely involved in the formation of spodumene pegmatite. Our results suggest that there are quartz geochemical indicators that may be of specific use in exploration for Li resources in the Himalayan region including Al > 300 µgg− 1, Li > 70 µgg− 1, B > 4 µgg− 1, as well as ratios like Al/Ti (> 30) and Ge/Ti (> 0.2).

As one of the world's largest extensional structures, the South Tibetan Detachment System (STDS) is spatially and temporally associated with Himalayan leucogranites and spodumene pegmatites. This study investigates variably deformed leucogranites near the Qiongjiagang lithium deposit in southern Tibet (Everest/Himalaya region) using field observations, mineral crystallographic preferred orientations, rheological parameters, and zircon geochronology. Key findings include the following: (1) Leucogranites within the STDS record systematically variable strain, with weakly deformed bodies preserving primary magmatic fabrics and hosting abundant spodumene pegmatites at higher structural levels. (2) Zircons within strongly deformed leucogranites exhibit significant fluid alteration. Weakly modified zircons yield ages of ca. 24 Ma, while hydro-thermally altered zircons date to ca. 18 Ma. (3) Quantitative deformation analysis reveals that strongly deformed leucogranites record deformation temperatures of 450-590 degrees C, differential stresses of similar to 36.5-75.2 MPa, and strain rates of similar to 10-13 s-1 to 10-12 s-1, whereas weakly deformed leucogranites record higher temperatures (similar to 720 degrees C) and strain rates (similar to 10-10 s-1) under comparable stress conditions. (4) Comparative rheological analysis reveals that spodumene pegmatite emplacement requires specific mechanical conditions-a differential stress threshold of 26 MPa and strain rates of similar to 10-10 s-1. Through a case study of the Qiongjiagang lithium deposit, this work elucidates the role of the STDS in leucogranite emplacement and evolution and provides quantitative constraints on the rheological conditions that facilitate the formation of spodumene pegmatites within the STDS.

Granite-related Li-Nb-Ta deposits, characterized by extensive albitization within plutons, represent a novel lithium resource. The Ganfang area, one of the important granite-type lithium deposits in South China, features a vertical lithological sequence from top to bottom of stockscheider, albitized granite, and K-feldspar granite. The ore-bearing stratum is dominated by albitized granite. Our study focuses on elucidating the connection between magmatic differentiation, hydrothermal alteration, and lithium mineralization in albitized granites. By analyzing geochemical trends in apatite from stockscheiders, pegmatite veins, and altered granites, we aim to unravel the petrogenetic and metallogenic mechanisms of rare metal lithium. Apatite serves as a geochemical tracer, recording the intensity of fluid alteration processes and their impact on lithium enrichment. The U-Pb dating results (142.2-143.2 Ma and 128.8 Ma) of apatite from the stockscheiders and pegmatite vein show that mineralization in the Ganfang area occurred during the Late Yanshanian period and associated with the melting of the lower crust. Strontium (Sr), (La/Yb) N, and (La/Sm) N can indicate that mineralization in this area is closely associated with fluid activity. Our findings highlight distinct differences in trace element contents of apatite between upper ore-bearing albitized granite and lower barren K-feldspar granite, with specific trace element ratios (e.g., Ge-Ga, Ce/Pb-Th/U, TREE +Y-Mn/Fe, and Sr/Y-TLREE) serving as indicators of metallogenic potential. The ore-bearing albitized granite exhibits high concentrations of Ga and Ge, with a strong positive correlation between the two elements, this phenomenon may be related to the hydrothermal metasomatism of topaz. In addition, the ore-bearing granite exhibits relatively high Ce/Pb, light rare earth element (LREE), and total rare earth elements plus yttrium (TREE + Y) contents. This study indicates that lithium mineralization in the Ganfang area is closely linked to multistage fluid activity in a sealed-system, with a formation process involving the upward dissolution of Na and Li-rich fluids to form stockscheider, and followed by downward migration to replace fresh monzonite granites, forming ore-bearing albitized granite and barren Kfeldspar granite.

Extremely fractionated granitic rocks are commonly associated with rare metal deposits and show a SiO2 reversal point, where whole-rock SiO2 content switches from increasing to decreasing as the magma fractionates. This switch goes against expectations of continuous increase in SiO2 contents with magma differentiation. In this study, we investigated the Ganfang pluton that includes the Baishuidong deposit, China's largest granite-type lithium deposit. The SiO2 contents in the Ganfang pluton increase from 70.8 to 76.1 wt% before decreasing to 64.0 wt% as the rocks become increasingly fractionated and enriched in Li and other rare metals. Notably, Na2O, Al2O3, MnO, Zn, V, Ba, and Sc also exhibit reversal points as a function of SiO2, while rare metal elements, like Li, Rb, Cs, Nb, and Ta, show a continuously increasing trend. We find that the SiO2 reversal is caused by the crystallization of snowball quartz phenocrysts and their fractionation at late stages of magma evolution caused by increased F-content in the melt and stabilization of quartz as the liquidus phase. The reversal point coincides with the transition from a crystal-melt system, lacking an obvious fluid phase, to one dominated by fluid-magma (crystals plus melt) interaction. When this change occurs, Li contents rapidly increase from <1000 ppm to >6000 ppm, and micas become rich in Si and Li, gradually changing from muscovite to lepidolite. This is facilitated by the high concentrations of fluxing components in the melt, such as H2O, Li, F, and P, that decrease its viscosity and solidus temperature. This allowed for several steps of magma fractionation through efficient extraction of interstitial melt, further concentrating these elements eventually leading to crystallization of Li-rich micas and the mineralization.

Stockscheiders, a distinct category of pegmatite associated with the upper contact zones of rare-metal granites, represent a critical yet poorly constrained interface within magmatic-hydrothermal systems. Here, we investigate a topaz quartz stockscheider situated at the roof of the Jianfengling Li-F-rich granite (Nanling region, China) to constrain its petrogenetic conditions, emplacement timing, and role in rare-metal mineralization. UPb geochronology on cassiterite, wolframite, and monazite yielded Middle-Late Jurassic ages (153-160 Ma), demonstrating that mineralization was coeval with the emplacement of the underlying granite. Fluid inclusion assemblages are dominated by H2O-NaCl compositions; the ubiquitous heterogeneous entrapment of NbTa oxides indicates that oxide saturation preceded or coincided with fluid exsolution. Microthermometry and Ti-in-quartz thermobarometry constrain the P-T conditions to similar to 350-500 degrees C and similar to 240-390 MPa. LA-ICP-MS analyses of individual fluid inclusions reveal progressive depletion of K, Rb, Cs, Sn, Pb, and Zn during cooling, which is consistent with thermodynamic models of zinnwaldite crystallization. Although moderately enriched in Sn (generally <400 ppm), the fluid displays lower metal concentrations than those typical of W-Sn-mineralized granites (similar to 459 ppm), potentially indicating that the commercial prospectivity of the Jianfengling stockscheider is relatively limited. We conclude that this stockscheider formed during the initial stages of the magmatic-hydrothermal transition. Furthermore, the Jianfengling stockscheider likely served as an impermeable cap that promoted prolonged differentiation and large-scale fluid exsolution in the underlying magma. Stockscheiders may therefore provide a direct record of fluid evolution and represent a key exploration indicator for rare-metal deposits associated with highly evolved granites.

Understanding melt source evolution during arc-back-arc magmatism is essential for resolving crustal growth processes and the development of felsic-hosted volcanogenic massive sulfide (VMS) systems. Here we integrate new zircon HfO isotope data with published geochronological and whole-rock geochemical datasets to reassess the petrogenesis of Late Cretaceous arc and back-arc magmatic flare-ups in the eastern Sakarya Zone (ESZ), NE T & uuml;rkiye. Two high-flux magmatic episodes are recognized: a Turonian-Santonian pulse (similar to 92-86 Ma) forming the lower volcanic sequence (LVS), and a younger Campanian pulse (similar to 84-75 Ma) forming the upper volcanic sequence (UVS), accompanied by contemporaneous arc-related granitoids. Zircons from both LVS and UVS display predominantly positive epsilon Hf(t) values (+2 to +12) coupled with mantle-like delta O-18 (5.0-5.6 parts per thousand), but contain abundant inherited Mesoproterozoic-Paleozoic cores and show variable two-stage model ages (T-DM (c) = 0.4-1.4 Ga). Together with the peraluminous affinity of many felsic units, these features indicate that the dacite-rhyolite suites hosting VMS deposits were generated by melting of compositionally heterogeneous lower crust variably hybridized by juvenile basaltic inputs. Arc granitoids likewise record a transition from dominantly juvenile, I-type magmatism during the Coniacian-Santonian to more evolved, crust-influenced signatures during the Campanian. We propose that both flare-ups reflect repeated episodes of basaltic underplating and deep-crustal heating, producing voluminous felsic magmas capable of sustaining long-lived hydrothermal systems. The spatial and temporal coincidence between felsic-dominated flare-ups and VMS mineralization suggests that hybridized felsic magmas, rather than purely juvenile mantle melts, played a central role in generating the physiochemical conditions required for metal-bearing hydrothermal fluids in the ESZ.

Quartz chemistry is important for revealing fluid sources and evolution in hydrothermal deposits, but such information is lacking for many epithermal systems and deposit types. To investigate quartz chemistry in this system further, we collected representative samples of quartz from adularia-sericite epithermal Ag deposits in China and determined their chemical compositions. In adularia-sericite epithermal Ag-bearing systems, magmatic quartz from porphyry intrusions and host subvolcanic rocks displays SEM-CL spectral peaks at 360 and 415 nm and exhibits homogenous CL or weak zonal textures (alternating growth zones within individual quartz crystals). Trace elements in magmatic quartz have the lowest Sb concentrations (median = 0.1 ppm; n = 80). Hydrothermal quartz can be classified into type I and type II by CL false color and CL spectral peaks. Hydrothermal type I quartz has spectral peaks at 360 and 415 nm; it exhibits zonal or sector textures and is associated with base metal sulfides and minor Ag mineralization. Such hydrothermal type I quartz has low Sb concentrations (median = 4.5 ppm; n = 839), contains liquid-rich fluid inclusions, and is formed by cooling. The cooling trend is indicated by a positive correlation between the concentrations of Sb and Al, as well as between Li and Al. Hydrothermal type I quartz has an Fe center by electron spin resonance, whereas other centers are missing or weak at room temperature. In general, hydrothermal type II quartz mantles type I quartz. Hydrothermal type II quartz has an ultrahigh-intensity peak (by several orders of magnitude) at 580 nm, zonal textures, and is associated with abundant Ag mineralization. Hydrothermal type II quartz has the highest Sb concentrations (median = 71 ppm; n = 185), which remain constant as Al decreases on an Sb vs. Al plot. This quartz has colloform, bladed, or zonal textures and contains coexisting liquid- and vapor-rich fluid inclusions indicative of boiling. Additionally, this quartz has a significantly higher E'1 center intensity, suggesting a high concentration of oxygen vacancies associated with rapid crystallization. The mineral paragenesis, analytical results, and geochemical models show that, in these Ag-bearing epithermal systems, hydrothermal type I quartz associated with base metal sulfides precipitated during cooling, whereas subsequent growth-zoned hydrothermal type II quartz with high Sb concentrations and Ag-minerals precipitated during boiling. These results suggest that the CL texture and spectra, trace elements, and electron spin resonance data of quartz could identify veins with potential for Ag mineralization in epithermal systems.

The discovery of spodumene-bearing pegmatite in the Kangmar dome of the Himalayan orogen represents the first identification of lithium-rich pegmatites within the Tethyan Himalayan dome. These pegmatite dikes are predominantly located in the ductile shear zone in the southwestern part of the Kangmar dome, with the surrounding rocks of the thick-bedded marbleized limestone of the Permian Badingpu Formation. The main rare-metal minerals include spodumene, petalite, cassiterite, amazonite, beryl, columbite-tantalite, fergusonite, niobium rutile, and pyrochlorite. The geochemical analysis of whole-rock samples indicates that the lithium concentrations in the spodumene pegmatite samples ranges from 28.7 x 10 to 15251 x 10, with the highest Li, O content reaching 2.64%, which meets the industrial grade. Additionally, rare-metal elements such as Rb and Nb concentrations are also relatively high. Compared with spodumene pegmatites discovered in other regions of the Himalayan orogen, the Kangmar spodumene pegmatites are characterized by enrichment of heavy rare earth elements ((La/Yb)=0.11-0.75), higher Nb/Ta (3.65-8.84) and Zr/Hf (9.68-14.9) ratios, and a more pronounced negative europium anomaly (Eu/Eu 0.003-0.05). In-situ U-Th-Pb dating of monazite reveals that the spodumene pegmatites primarily formed during the Late Oligocene to Early Miocene (26-22Ma), which is consistent with the intrusion age of the beryl pegmatite dikes exposed in the core of the Kangmar dome (25Ma). This study suggests that there was Cenozoic magmatic activity in the Kangmar dome, and the spodumene pegmatites are product of intense fractionation of the leucogranite magmas. The discovery of the Kangmar spodumene pegmatites indicate promising lithium mineralization potential within the Tethyan Himalayan dome, and the ductile shear zones surrounding the dome should be the focus of further exploration for rare metal minerals.

This study focuses on the firstly discovered spodumene pegmatites in the Yadong area of the Himalayan orogen. Through detailed field investigations, petrographic observations, whole-rock major and trace element analyses, and U-Pb isotope dating, the pegmatites have been systematically studied. The spodumene pegmatite veins are nearly horizontally distributed near Quqingtang in the northern part of the Gaowu pluton, at elevations ranging from 3650m to 3931m. The outcrop widths vary, with most spodumene crystals being colorless, transparent, or grayish-white, exhibiting well-formed columnar shapes. The grain size varies significantly, and no obvious internal zoning structure is observed. The mineral assemblage includes albite, orthoclase, quartz, muscovite, as well as spodumene, petalite, beryl, cassiterite, columbite, which are rare metal minerals containing lithium, beryllium, niobium, tantalum, and tin. Spodumene is unevenly distributed, with contents ranging from 2% to 25%. Geochemical characteristics reveal that the spodumene pegmatites are characterized by high silica, strong peraluminous, alkali enrichment, and depletion in calcium, iron, magnesium, and phosphorus. It also shows the enrichment of Rb, Cs, Ta, and Hf, and depletion in Sr, Th, Eu, and Ti. Notably, the rare metal elements Li, Rb, and Cs reach high concentrations, with maximum values of 16017x10(-6), 2517x10(-6), and 819x10(-6), respectively. The rare earth elements exhibit light rare earth elements enrichment, significant fractionation between light and heavy rare earth elements, and a pronounced negative Eu anomaly with a tetrad effect, all indicating a high degree of magmatic differentiation and evolution in the Yadong region. Isotopic dating results show that the monazite Pb-208/Th-232 ages of the Yadong spodumene pegmatites can be divided into two stages: 21Ma and 18 similar to 17Ma. The lower intercept ages of cassiterite in the Pb-207/Pb-206-U-238/Pb-206 Tera-Wasserburg concordia diagram range between 18Ma and 16Ma. The monazite 208Pb/232Th ages of spodumene-free pegmatite samples range between 22Ma and 21Ma. In the Yadong region, spodumene exhibits diverse occurrences, including large prismatic crystals and acicular spodumene. The occurrence of mineralized pegmatites in the Yadong region is clearly controlled by the South Tibetan Detachment System (STDS), trending NW-SE, consistent with the strike of the Yadong Cross Structure (YCS), and they are discontinuously exposed along the YCS, and their formation process is consistent with the activity period of the STDS. The characteristics of these pegmatites are similar to those of the Qunggya Kang (Pusi La) and Gabo spodumene pegmatites, further reflecting the spatial consistency of lithium mineralization in the Himalayan orogen. The discovery of spodumene pegmatites in Yadong provides fundamental geological data for the study of rare metal mineralization and lithium resource exploration in the Himalayas, contributing to the understanding of the coupling relationship between tectonic-magmatic activities and rare metal mineralization. It also offers important references for future exploration of related rare metal deposits in the Himalayan orogen.

Tourmaline is a common associate mineral in granitic pegmatites. Most of granite-pegmatite systems in Himalaya are characterized by widespread occurrence of tourmaline. The Kuqu intrusion hosts several spodumene-bearing pegmatite dykes and develops complex rare-element mineralization types. In this study, a green tourmaline-bearing pegmatite located at the Sangyu village has been identified in the Kuqu intrusion. This tourmaline-bearing pegmatite is composed of dark green tourmaline-albite-K-feldspar-quartz-mica assemblage, yellowish green tourmaline-albite-K-feldspar-quartz-mica assemblage and colorless tourmaline-albite-quartz-mica assemblage, with occurrences of beryl, lepidolite, columbite-group mineral, microlite and fluorite. Tourmalines belong to alkali and calcic groups, including schorl, elbaite, fluor-elbaite and fluor-liddicoatite. Elbaite is divided into Fe-rich elbaite (FeO=3.36%similar to 7.17%) and Fe-poor elbaite (FeO=0.12%similar to 2.70%). Compared with Fe-poor elbaite, Fe-rich elbaite is rich in Fe and poor in Al, Li and Na, while F-elbaite is rich in Ca and F and poor in Na. Fluor-liddicoatite has the SiO2 and Al2O3 content ranges of 36.35%similar to 38.17% and 39.78%similar to 41.81% with high contents of Li2O*, CaO and F (2.27%similar to 2.59%, 2.37%similar to 3.48% and 0.99%similar to 1.26%) and low contents of Fe and Na (0.13%similar to 1.87% and 0.90%similar to 1.41%). The most calcic composition of fluor-liddicoatite corresponds to (Ca0.55Na0.30 square(0.16))(Li1.60Al1.34Mn0.02Fe0.02)Al-6(Si5.85Al0.15)O-18(BO3)(3)(OH3.39F0.61). The BSE images show that tourmalines are homogeneous, core-(mantle)-rim, irregular-zoned and patchy. The dark green tourmaline crystals (Type I) are composed of schorl core, schorl/Fe-rich elbaite mantle/patch, and Fe-rich elbaite rim or occasionally fluor-liddicoatite rim. The yellowish green tourmaline grains (Type II) are crystals composed of Fe-rich elbaite core and Fe-poor elbaite/fluor-elbaite/fluor-liddicoatite mantle/rim (Type IIa), or appear as irregular-zoned Fe-rich elbaite veinlets (Type IIb). The colorless tourmaline crystals (Type III) display various internal structures. Type IIIa are homogeneous Fe-poor elbaite/fluor-elbaite/fluor-liddicoatite grains; Type IIIb consist of Fe-poor elbaite core/mantle and Fe-poor elbaite/fluor-elbaite/fluor-liddicoatite rims with occasionally fluor-elbaite/fluor-liddicoatite core/mantle; Type IIIc are irregular-zoned and patchy grains, composed of Fe-poor elbaite and fluor-liddicoatite. All kinds of tourmalines show Li1.5Al1.5Fe-32+. Besides, the substitution mechanisms are square AlNa-1R-12+ in Type I schorl core, CaR2+Na-1Al-1 or CaONa-1(OH)(-1) in Type I and Type II Fe-rich elbaite, and CaLi2Na-1 square Al--1(-1) in Type III tourmalines. The micas coexisting with tourmalines are mainly muscovite, lepidolite, minor Li-muscovite and zinnwaldite with homogeneous, core-rim and irregular-zoned structures. The evolution sequences of tourmaline and mica are schorl -> Fe-rich elbaite -> Fe-poor elbaite -> fluor-elbaite -> fluor-liddicoatite and muscovite-Li-muscovite -> zinnwaldite/lepidolite, respectively. With increasing magma differentiation and evolution, tourmalines are gradually enriched in Li, Ca and F, and deficient in Fe with minor decreasing Ti, Zn and increasing Mn contents. Magma of the Kuqu green tourmaline-bearing pegmatite evolved towards the low-Fe and high-Li, Ca and F direction accompanied with crystallization and replacement of Fe-rich medium locally. The highly-fractionated magma, extremely fractional crystallization and Ca-F complexing contribute to formation of fluor-liddicoatite in the Kuqu intrusion. Discovery of schorl-elbaite-liddicoatite series and genesis of fluor-liddicoatite indicate that the pegmatites in Kuqu have very high degrees of magma evolution. The Kuqu intrusion is a favorable area to further look for lithium-rich pegmatite dykes with different types in Eastern Himalaya. The Himalaya orogenic belt becomes a significant highly-evolved pegmatite district and rare-element exploration potential area such as lithium.significant highly-evolved pegmatite district and rare-element exploration potential arca such as lithium.

The emplacement characteristics of the deposit offer crucial insights into its genesis, ore-controlling structures, and delineating exploration targets. The Qiongjiagang lithium orefield, as the first giant lithium orefield in the Himalayas, is characterized by its large scale and high grade, with well-preserved emplacement structural features for the spodumene pegmatite. Insights were gained through macroscopic, microscopic and mineral fabric analyses, including: (1) Along the northern boundary of the South Tibetan Detachment system (STDS) from north to south, the Bangsequ spodumene pegmatite occurs in len's shape (similar to 7.6km from the northern boundary of STDS, elevation of 5312m). The spodumene pegmatite in the main ore body of the Qiongjiagang orefield is thick plate or cyst shaped at the position of similar to 16.8km from the northern boundary of STDS with an elevation of 5364 similar to 5500m. The Qiongjiagangnan spodumene pegmatite is plate shaped at similar to 18.7km from the northern boundary of STDS with an elevation of 5548 similar to 5562m. (2) The main ore body in Qiongjiagang deposit has a foliation that is gentle in the center (dip angle 10 degrees similar to 23 degrees) and steep on the sides (dip angle 30 degrees similar to 50 degrees). The foliation dip directions range from W270 degrees to NW290 degrees in the western part, SE170 degrees to SW190 degrees in the central part, and SE130 degrees to SE160 degrees in the eastern part, overall forming a "hat-shaped" emplacement in the Rouqiecun Group. (3) The dip direction of spodumene growth lineation near the surrounding rock of the main ore body in Qiongjiagang ranges from SE155 degrees to SW190 degrees, with dip angles between 17 degrees and 40 degrees. Inside the spodumene pegmatite, the dip angles of spodumene growth lineation range from 21 degrees to 67 degrees, with some nearly horizontal. These spodumene lineations construct the spodumene pegmatite emplacement structure model for the main ore body in Qiongjiagang. (4) In aplite, feldspar, quartz and spodumene display consistent preferred grain shapes and crystallographic orientations. In spodumene pegmatite, these minerals maintain consistent grain shape preferred orientations, with feldspar and spodumene c- < 001> axes nearly parallel to the X-axis direction, and the quartz c- < 0001> axis parallel to the Z-axis direction. Based on the above understanding, this study proposes that along the northern boundary of the STDS to the south and with the increase in elevation, the spodumene pegmatite presents the in-situ structural characteristics of "lens shaped at the proximal low elevation, thick plate or cyst shaped in the middle, and plate shaped at the distal high elevation". These findings provide an important reference for the further study of the emplacement characteristics of the high Himalayan spodumene pegmatite and the search for new spodumene pegmatite outcrops. Moreover, this study offers valuable insights into the structural models and emplacement mechanisms of pegmatite lithium deposits worldwide.

Abstract The Qiongjiagang giant pegmatite lithium deposit, located in the central section of the Himalayan orogenic belt, mainly comprises the spodumene-bearing pegmatite type, marginally accompanied by a petalite-bearing leucogranite dike and a lepidolite-bearing pegmatite. Existing uncertainties around the niobium (Nb) and tantalum (Ta) mineralization characteristics and their genetic ties among three types of Li-rich dikes justify further research. To enhance comprehension, backscattered electron imaging, energy dispersive spectrometry mapping, and electron microprobe analyses were employed. Microscopic features suggest that the Nb-Ta mineralization from Qiongjiagang spodumene-bearing pegmatite appears as the result of saturation of early magmatic columbite after lithium (Li) quenching arising from poikilitic spodumene crystallization. Subsequently, autometasomatism of hydrosilicate liquid caused partial dissolution of magmatic columbite as well as replacement of early primary minerals, forming fluid-induced Ta-rich overgrown and interstitial microcrystals (metasomatic columbite and pyrochlore) in microfractures. Muscovite crystallization and high Ta solubility may cause Nb-Ta element fractionation of individual zoned columbite and declining Nb/Ta ratios between discrete columbite and microcrystals. Both the continuous whole-rock compositional evolution from granite to lepidolite-bearing pegmatite and the gradual manganese (Mn) enrichment and titanium (Ti) decline of columbite geochemistry imply that the three types of dikes originated from three batches of sequential pulses of Li-rich magmas, demonstrated by progressive tourmaline or biotite fractionation of parent magma. The distinct Mn/Fe variation of columbite and whole-rock geochemistry also suggests that the three types of Li-rich magmas were already highly evolved in the upper part of their parental granitic magma chamber, instead of only fractionating once they escaped to the host rocks. Consequently, the textures and composition of columbite not only provide valuable insights into the magmatic-hydrothermal evolution of spodumene-bearing pegmatite, they also emphasize columbite's potential as a tracer for the degree of differentiation of magma.

The formation of stockscheiders is closely related to the evolution of some granites and the rare metal mineralization in them,however,research on these rocks is still very weak.In this paper,we investigated the ore-forming biotite granite of Baiyinwula W-Sn deposit in southern Great Xing'an Range,and this biotite granite show obvious lithofacies zonation as follows:the deep part is the main medium to coarse-grained biotite granite,which upward transition to the fine-grained biotite granite,and the uppermost part is the stockscheider consisting of interlayered aplite and pegmatite.On the basis of detailed petrographic observation,electron probe point analysis and elemental mapping,and LA-ICP-MS trace element analysis of biotite in different lithofacies zonations and hydrothermal veins have been carried out in this paper.The results show that compared with the other two lithofacies,the magmatic biotite in the stockscheider has the highest FeO,MgO and Cl contents,and the lowest Al2O3,K2O,F,Li,Sn,W,Nb and Ta contents,indicating that the stockscheider has the lowest degree of evolution,while the fine-grained biotite granite has the highest degree of evolution.The development of alkali feldspar-dominated unidirectional solidification texture(UST),and growing rim of worm-like quartz and biotite in stockscheider,indicates that the formation of stockscheider is ascribe to the supercooling of water-rich magma and deep magma degassing.In short,the stockscheider was the earliest product compared with the deep granite,belonging to the early condensing edge of the magma chamber.After the formation of stockscheider,it can act as a cap to promote the evolution of the deep magma chamber and enrich incompatible elements such as Sn and W in the highest evolved phase of granite.Subsequently,fluid exsolution occurs and leads to mineralization.Overgrowth of hydrothermal biotite on magmatic biotite in the stockscheider and fine-grained biotite granite confirm the occurrence of this fluid exsolution process.The high Sn and W contents in biotite within different lithofacies of Baiyinwula indicate that the ore-forming granite providing the favorable conditions for mineralization.However,the Sn contents in hydrothermal biotite with different occurrences vary greatly,while the W contents are commonly high in all the biotite.This may imply that the Sn and W mineralization is formed by different batches of fluids,and both have good mineralization potential in this deposit.

Lithium and O isotopic compositions of zinnwaldite from magmatic (cassiterite), magmatic-hydrothermal transition (UST) and hydrothermal (tin-tungsten, molybdenum and copper-zinc) stages of the Weilasituo Sn polymetallic deposit and fluid inclusions in quartz are used to trace the magmatic-hydrothermal evolution. Fluid inclusion microthermometry and laser Raman analysis indicate that the H2O-NaCl-CO2-CH4 fluids associated with the Weilasituo deposit have high to medium-high temperatures and moderate salinities. The 67Li values of magmatic zinnwaldite decrease with magmatic differentiation, which cannot be explained by fractional crystallization alone and, therefore, reflect late-stage fluid exsolution. Lithium and O isotope fractionation during fluid evolution depends not only on the temperature, but also on fluid-rock reactions that affect the Li and O isotopic compositions of the fluids from the hydrothermal tin-tungsten stage and liquid-vapor phase separations that decrease 67Li and increase 618O of the fluids from the copper-zinc stage.

The incompatible elements lithium (Li) and boron (B) generally show different degrees of isotopic fractionation during magmatic differentiation and fluid exsolution in highly evolved granitic pegmatite systems. We use the magmatic-hydrothermal evolution of the Qiongjiagang pegmatite-type Li deposit to demonstrate how fractionation and phase separation control the Li and B isotopic compositions of whole rock samples. The investigated samples include tourmaline-muscovite granites, unmineralized pegmatites, aplites, spodumene pegmatites and their associated wall rocks. Our data show systematic Li and B isotopic compositional variations among the studied rocks. The spodumene pegmatites have much higher Li concentrations, lower S7Li values, and lower B concentrations and S11B values than the tourmaline-muscovite granites, unmineralized pegmatites and aplites, which suggests phase separation into a fluid-rich melt and a fluid-poor melt. The fluid-rich melt experienced multi-stage magmatic differentiation with fluid exsolution, which eventually led to the formation of spodumene pegmatites. In contrast, the fluid-poor melt evolved through single-stage magmatic differentiation, eventually forming unmineralized pegmatites and aplites. Interactions with wall rocks modified the Li and B isotopic compositions of some aplite and unmineralized pegmatite samples. The Li and B isotopic compositions of minerals extracted from tourmaline-muscovite granite, unmineralized pegmatite, and spodumene pegmatite samples were also analyzed. The Li and B isotopic compositions of these minerals span a wide range, which is controlled by two primary factors: (i) coordination of Li and B and (ii) crystallization history. The crystallization of most magmatic minerals increases the S7Li and S11B values of the residual melt (except for tourmaline, whose crystallization seems not to change the S11B values of the residual melt significantly). For minerals with the same coordination of Li and B, the S7Li and S11B values are higher for later crystallized minerals. As the S7Li and S11B values of magmatic minerals are affected by the amount of Li and B that has been removed from the melt before these minerals crystallized, bulk-rock S7Li and S11B values are generally more reliable tracers of the source and evolution of melts than the S7Li and S11B values of minerals that crystallized from such a melt. Only if the budgets of Li or B are dominated by one single phase, S7Li and S11B values of minerals and bulk rocks are the same.