The tectonic affinity of the quartzite unit is essential for reconstructing the Cenozoic evolution of the Eastern Himalaya Syntaxis. We presented new petrographic and zircon U-Pb geochronological data from the quartzite unit collected from the western boundary of the Namche Barwa syntaxis. The maximum depositional ages indicated multiple depositional stages at >1800, 1122-1136, 885, 451-493 and 54 Ma. Detrital zircon ages spanned from 50 to 3269 Ma with dominant populations at 500-900, 950-1400, 1550-1700 and 1750-2000 Ma. These age distributions suggested that the detritus were derived mainly from the Central Indian Tectonic Zone, Shillong Plateau and the Eastern Ghats Orogeny of the northeastern Indian subcontinent, and Western Australia. This provenance signature was distinct from the typical sequences of the Lesser Himalayan Sequence, Greater Himalayan Sequence and Tethyan Himalayan Sequence in the central-western Himalayas. Integrating our results with existing data from the Nyingchi Complex in the southern Lhasa terrane and Lesser Himalayan Sequence in the Eastern Himalayan Syntaxis, we proposed that the Namche Barwa syntaxis, Nyingchi Complex and Lesser Himalayan Sequence shared common source regions. Long-lived fluvial systems likely transported detrital material from northwestern Australia and the northeastern Indian subcontinent to these tectonic units.

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.

Abstract The East Kunlun Orogen (EKO) on the northern margin of the Tibetan Plateau experienced complex Late Paleozoic–Early Mesozoic tectono‐magmatic activities associated with the subduction and closure of the Paleo‐Tethys Ocean. Controversies remain regarding the timing and processes of the transition from subduction to collision and post‐collision, as well as the mechanisms of continental crustal growth. This study presents zircon U–Pb ages (257–202 Ma), whole‐rock geochemical data and Sr–Nd–Hf isotopic compositions for granitoids from the Nanshankou and Yeniugou areas in the EKO. The 257–246 Ma granitoids have variable Mg# values (34.9–49.7) and εHf(t) values (−4.9 to +1.1), and contain mafic enclaves, suggesting derivation from crust‐mantle magma mixing. The ∼235 Ma granitoids have low Mg# values (30.7–32.7), and enriched Nd–Hf isotopic compositions, indicative of partial melting of mafic lower crust. The 203–202 Ma adakitic granitoids show positive εHf(t) values (0.0 to +4.7) and relatively high Mg# values (45.3–48.7), pointing to partial melting of delaminated mafic lower crust with involvement of mantle‐derived magma. Integrating our results with regional geological data, we propose that the Paleo‐Tethys Ocean in the EKO experienced long‐term subduction during 278–240 Ma, accompanied by continental arc crustal growth. Following ocean closure at ∼240 Ma, the region entered a syn‐collisional stage (240–220 Ma) dominated by crustal remelting. The EKO then evolved into the post‐collisional stage at ∼220–200 Ma, with lithospheric delamination triggering vertical crustal accretion. This study constrains the subduction, collision, and post‐collision evolution and crustal growth of the EKO from Middle Permian to Triassic.

The closure of the Paleotethyan Ocean in the northern Tibetan Plateau formed a world-class rare-metal (Li, Be, Rb, Nb, and Ta) pegmatite metallogenic belt within the Dahongliutan-Hohxil-Songpan-Ganzi terrane of western China. Spodumene-rich pegmatites are hosted in the folded Triassic turbidites and often associated with Late Triassic−earliest Jurassic I-type and S-type granites. However, the parental affinity of these spodumene-rich pegmatites—whether from I-type or S-type granites—remains debated. To resolve this, we conducted geochronological and geochemical analyses of diorites, granodiorites, leucogranites, spodumene-free pegmatites, and spodumene-rich pegmatites from the Bailongshan ore field. Zircon U-Pb dating results show that the diorites intruded at 217.5−210.1 Ma, granodiorites at 212.3−205.0 Ma, and leucogranites at 215.1−196.2 Ma. Columbite U-Pb ages indicate emplacement of spodumene-free pegmatites at 220.9−196.2 Ma and spodumene-rich pegmatites at 213.9−194.7 Ma, suggesting synchronous magmatism during the Late Triassic−earliest Jurassic. Geochemically, hornblende-rich diorites and hornblende-bearing granodiorites show low SiO2, high MgO, metaluminous to weakly peraluminous signatures (Alumina Saturation Index [A/CNK] = 0.59−1.13), and calc-alkaline characteristics, and are typically I-type granites. Leucogranites containing muscovite, garnet, and tourmaline exhibit high SiO2, low MgO, strongly peraluminous signatures (A/CNK = 1.16−1.34), and high-K, calc-alkaline affinities. They are typically S-type granites, which show higher Rb/Sr and Rb/Ba ratios, indicating sedimentary rocks as their protoliths. Isotopically, S-type granites [87Sr/86Sri = 0.7111−0.7149; εNd(t) = −11.0 to −10.3; εHf(t) = −8.4 to −2.7] and pegmatites [87Sr/86Sri = 0.7182−0.7189; εNd(t) = −11.7 to −10.7; εHf(t) = −9.2 to −0.9] exhibit more enriched isotope compositions, similar to those of the wall-rock turbidites [87Sr/86Sri = 0.70803−0.7173; εNd(t) = −13.1 to −3.2], and are distinctly different from I-type granites [87Sr/86Sri = 0.7084−0.7098; εNd(t) = −6.8 to −6.3; εHf(t) = −6.2 to +0.9]. This implies that the pegmatites are derived from the S-type granites, not the I-type granites. The low temperatures (<750 °C) estimated by the Ti-in-zircon thermometer for both I- and S-type granites suggest that S-type granites were likely derived from fluid-fluxed melting of the Triassic turbidites, favoring extraction of rare metals from staurolite, biotite, and muscovite in metaturbidites during anatexis. The coeval I-type granites provided the external heat and exotic volatiles, promoting staurolite and mica breakdown in the metaturbidites and thus facilitating the release of rare metals into the S-type leucogranitic melts. This suggests that although rare-metal pegmatite mineralization in Bailongshan is primarily related to S-type granites, I-type granites also played a contributing role. The formation of the coeval Late Triassic−earliest Jurassic barren I-type and fertile S-type granites in Bailongshan is attributed to final bidirectional subduction, slab rollback, and delamination of the Paleotethyan oceanic slab.

The Sanchakou, Keteli, and Tielemu skarn tungsten (W) deposits have recently been discovered in the East Kunlun Orogenic Belt, northwestern China. However, the formation ages and petrogenesis of the W-fertile intermediate-felsic intrusions remain poorly constrained. In this study, zircon UPb dating results show that the intrusions formed in two epochs, Middle Triassic (similar to 250-238 Ma) and Late Triassic (similar to 230 Ma). The first epoch of intermediate-felsic intrusions (the similar to 242 Ma Sanchakou and Tielemu monzogranites and the similar to 238 Ma Keteli granodiorite) is closely associated with skarn W mineralization, except for the slightly older (similar to 247 Ma) and barren garnet-bearing monzogranite at Keteli. The similar to 250-238 Ma intrusions are mainly metaluminous and belong to the calc-alkaline to high-K calc-alkaline series. They show LREE-rich patterns with weak negative to positive Eu anomalies (La-N/Yb-N = 3.66-41.9 and Eu/Eu* = 0.52-1.10), enrichments in LILEs (e.g., Rb, K, Th, and U), and depletions in HFSEs (e.g., Nb, Ta, Ti, and P). In comparison, the similar to 230 Ma syenogranite exhibits similar geochemical characteristics, except for more pronounced negative Eu anomalies (Eu/Eu* = 0.20-0.28). All studied intrusions reveal a negative correlation between SiO2 and P2O5, indicating an evolutionary trend of I-type granitic melts. The two epochs of intrusions have relatively consistent zircon Hf isotopic compositions (epsilon(Hf)(t) = -7.7 to 3.2 and - 4.5 to -0.8, respectively), suggesting that they may have been derived from the partial melting of Meso-Proterozoic basement rocks with a minor addition of mantle-derived material. Moreover, the W-fertile intrusions show hydrous and weakly oxidized features, evidenced by relatively low zircon saturation temperatures (738-789 degrees C), Zr/Sr (0.11-0.70), and fO(2) values (triangle FMQ = 0.07-0.55). Based on new geochemical data and regional geological investigations, we propose that the Middle Triassic intrusions (similar to 250-238 Ma) formed during the late-stage of northward subduction of the Paleo-Tethys oceanic plate. In contrast, the Late Triassic (similar to 230 Ma) syenogranite was generated in a local extensional setting related to oceanic slab rollback following the collision between the East Kunlun and the Hoh-Xil-Songpan-Ganzi terranes.

Nephrite, as a rare jewelry with a long history, holds great economic value and cultural significance. The Eastern Kunlun Range possesses immense potential for nephrite resources controlled by tectonic evolution and magmatic activities during geological periods. However, the harsh environment and backward prospecting technology have led to stagnation of the nephrite exploration in this area. Remote sensing, as a rapidly advancing technology that is sensitive to mineral identification and structural interpretation, has played a critical role in the exploration of mineral deposits. This study summarized the geological characteristics of nephrite deposits in Nachitai area of the Eastern Kunlun Range, revealing that these deposits exhibit distinct mineral assemblages, lithological, and structural features. Various satellite data, including Landsat-9, GF-5B, and ASTER GDEM, were utilized to extract geological indicators associated with ore formation and discover new exploration targets. Landsat-9 multispectral image was used to preliminarily identify the known nephrite areas through false color composite (FCC) and selective principal component analysis (SPCA). GF-5B hyperspectral data were applied to detect tremolite, dolomite, and chlorite using spectral angle mapper (SAM). ASTER Global Digital Elevation Model (GDEM) data were used for the automatic interpretation of lineaments in the study area. The mapping results show a high degree of consistency with four known open pit mines. Ultimately, fourteen target areas with potential for nephrite formation were delineated through a comprehensive analysis of lithologies, mineral assemblages, and structures within the study area. The methodology proposed here provides a new perspective for jade prospecting in remote regions worldwide.

Understanding the Cenozoic growth history of the Himalaya-Tibetan Plateau (HTP) is essential for elucidating the underlying geodynamic mechanism and interactions among topography, biosphere and atmosphere. However, the spatial-temporal evolution of the HTP, especially that of the Paleogene Central Tibetan Valley (CTV), remains hotly debated. In this study, through radiometric geochronology, plant assemblages, oxygen and clumped isotope paleoaltimetries, we reconstruct the uplift history of the east-west-oriented Luolong Basin in eastern Tibet. Results show that the Luolong Basin was at 0.6 (+0.2/-0.4) km at ca. 54-46 Ma, then rose to 2.9 ± 0.9 km at ca. 44 Ma. The newly discovered Luolong Flora indicates the Eocene CTV extending into eastern Tibet, and that the valley was higher in the east, sloping to the west, inferring a westward progressive rise of the valley floor. Integrated evidence from paleomagnetism, magmatism and seismic tomography suggests that the birth of the near modern plateau is attributed to the stepwise delamination (drip) of the subducted Lhasa lithosphere from east to west.

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.

As one of the triple metallogenic belts in Tibet,Bangonghu-Nujiang(BN)metallogenic belt produces a series of porphyry-skarn deposits.In recent years,new discoveries were made in the prospecting and exploration in this belt,indicating significant potential for mineral exploration of the belt.In this cold alpine belt with a lack of geological research and information,conventional mineral exploration techniques fail.In this study,with reference to the metallogenic characteristics of typical porphyry copper deposits in the belt,including planar alteration,hydrous mineral groups in alteration zoning,and metallogenic models and exploration models,the alterations of wall rocks closely relevant to porphyry copper deposits were extracted from multi-resolution,multi-type remote sensing imagery.By integrating multi-source geoinformation of remote sensing and geology of metallogenic belt and ore concentration areas of different scales,respectively,prospecting areas of porphyry copper deposits were delineated.Using field verification and comprehensive geological evaluation,several prospecting areas with significant mineral potential were identified,geologically extending the BN metallogenic belt about 600km towards the central-eastern segment of the southern margin of the Qiangtang terrane.It is proposed that there exists a new metallogenic belt of porphyry copper deposits to the north of the known Duolong ore concentration area within the BN belt and the Qiangtang terrane,and a metallogenic event of porphyry copper deposits related to Late Jurassic magmatism occurred on the northern side of the BN belt and the southern margin of Qiangtang terrane.Conclusively,the remote sensing exploration techniques proposed in the study can greatly improve exploration of porphyry copper deposits in the BN belt,and the new metallogenic belt of porphyry copper deposits and the metallogenic event are significant for enriching the regional metallogenic theories and patterns of BN metallogenic belt,designing new scopes of mineral exploration,and deploying exploration work.

Greisen-type tin (Sn) mineralization has traditionally been attributed to the interaction between granite and reduced Sn2+-bearing fluid (with Sn oxidation). In this study, we present the magnetite-bearing and evolved mineral assemblages from topaz-fluorite (Zones 1-3) to primary greisen (Zone 4, quartz-muscovite-cassiterite) in the Paleocene Kalonta Sn-W deposit, southern Myanmar. Together with the typical unidirectional solidification textures (UST), melt/fluid inclusions in topazes and their low OH/(OH + F) ratios (< 0.04) indicate that the fluorine (F)-rich minerals from Zones 1-3 were likely crystallized from fluid-saturated and extremely F-rich melts. In addition, abundant magnetite grains (replaced by hematite) in Zones 1-4 strongly suggest that the oreforming melts and fluids are highly oxidized, which may have been achieved by fluid exsolution and/or "self-oxidation (H2O dissociation)" in the late-stage evolution of F-rich magmas. Therefore, the precipitation of hydrothermal cassiterite (Fe + Mn of 0-0.05 apfu and Nb + Ta of 0-0.003 apfu) in oxidized fluids (Sn dominated by Sn4+) could result from the reduction of HCl activity and hydrolysis of fluoride without Sn oxidation. This study thus points to a mechanism for cassiterite precipitation in greisen-type Sn mineralization that differs from the traditional model and may be more abundant than previously thought.

Widely distributed Oligocene-Miocene ultrapotassic volcanic rocks in the Lhasa terrane of southern Tibet have been associated with the melting of the lithospheric mantle, plateau uplift, and porphyry Cu-Au mineralization. This study presents the mineral chemistry of olivine and clinopyroxene phenocrysts, whole-rock major and trace element data, and zircon U-Pb geochronological and Hf isotopic data for the Sailipu primitive ultrapotassic volcanic rocks. The Sailipu volcanic rocks exhibit high MgO (5.6-11.4 wt%), Cr (386-981 ppm), Co (22-43 ppm), and Ni (95-423 ppm) concentrations and have highly fractionated rare earth elements [REEs; (La/Yb)N = 23-73] and high-Fo (89.1-90.8) olivine phenocrysts containing elevated NiO (up to 0.59 wt%), which suggests a pyroxenitic mantle source that partially melted in the garnet stability field. Their high K2O contents (4.8-8.0 wt%) and global subduction sediment-like trace element patterns suggest that the metasomatic agents, which reacted with mantle peridotites to form phlogopite-bearing pyroxenites, were dominantly derived from the melting of subducted continental sediments. Their high whole-rock Ba/La and Th/Nd ratios are consistent with this hypothesis. The Sailipu ultrapotassic volcanic rocks also exhibit low initial 176Hf/177Hf ratios that resemble those of Himalayan leucogranites, and high Ca contents in olivine phenocrysts, which is consistent with contributions from the sub- ducted carbonate-rich sedimentary strata on top of the thinned Greater Indian continental crust. The zircon U-Pb chronological data yielded concordant ages of 24.33 +/- 0.19 Ma, 21.20 +/- 0.62 Ma, and 17.05 +/- 0.31 Ma for different exposures of the Sailipu volcanic rocks, which establishes a maximum age of ca. 24 Ma for these rocks. The northwest-southeast spatial distribution and the southeastward decrease in age (80 degrees E-90 degrees E) suggest west-to-east tearing of the thinned Greater Indian slab, which caused asthenospheric upwelling and melting of the Tibetan lithospheric mantle. Geothermometric calculations show relatively high primary magma temperatures (similar to 1250 degrees C) that are consistent with asthenospheric upwelling. We propose a mechanism that could genetically link the coeval Cu-Au ore-forming granitoids with the ultrapotassic magmatism of the Gangdese belt. The ultrapotassic rocks supply a large-volume of external magmatic volatiles, particularly H2O, which could trigger melting of the Tibetan lower crust and lead to the generation of the ore-forming granitoids and the establishment of oxidizing conditions for porphyry deposits. The oxygen fugacity (log & fnof;O2 values of OFMQ) of the primitive Sailipu ultrapotassic volcanic rocks (OFMQ = 0.48 +/- 0.51 based on the Dol/melt V oxybarometer and OFMQ = 0.33 +/- 1.19 according to the magmatic zircon U-Ce-Ti oxybarometer) is slightly lower than that of porphyry Cu-Au ore-forming granitoids in the eastern Gangdese (OFMQ = +0.8 to +2.9), which suggests that the direct injection of ultrapotassic melts into ore-forming granitoids played a limited role in changing oxygen fugacity, but more oxidized fluids/ volatiles exsolved from these ultrapotassic melts may have facilitated the remelting of sulfide-bearing lower crust and/or directly scavenged sulfides from the mush-state reservoirs of the ore-forming granitoids in the middle-upper crust.

Stable calcium (Ca) and iron (Fe) isotopes could provide a new way to investigate granite petrogenesis, and their isotope fractionation mechanisms in felsic magmas have been increasingly understood through continuous efforts in recent years. However, comprehensive Ca and Fe isotope fractionation during highly fractionated magmas is still unclear. This study presents Ca and Fe isotope data for some fractionated granites from Southern Myanmar. The S56/54Fe values of the less fractionated Eocene granites range from 0.11 f 0.03 %o to 0.23 f 0.04 %o. The highly fractionated Late Cretaceous and Paleocene granites clearly exhibit 0.15 %o and 0.42 %o variations in S56/54Fe values, respectively. These S56/54Fe values are negatively correlated with those of Fe2O3T, TiO2 contents and (La/Yb)N ratios, suggesting that more evolved melts are enriched in heavy Fe isotopes, primarily as a result of fractional crystallization of Fe-rich minerals enriched in light Fe isotopes (e.g., biotite and ilmenite). Some Late Cretaceous granites with low Nb/Ta and Zr/Hf ratios display relatively low S56/54Fe values, which may be modified by exsolved fluids enriched in light Fe isotopes. Moreover, the S44/40Ca values of the Late Cretaceous, Paleocene, and Eocene granites range from 0.71 f 0.07 %o to 0.90 f 0.06 %o, 0.62 f 0.08 %o to 0.89 f 0.06 %o, and 0.66 f 0.06 %o to 0.75 f 0.05 %o, respectively. Most of the studied granites have relatively consistent Ca isotopic compositions with those of the continental crust. Combined with high S44/40Ca values (up to 0.90 %o), the studied granites have a weakly negative correlation between S44/40Ca values and Eu/Eu* ratios. This evidence suggests that fractional crystallization of plagioclase with light Ca isotopes may also be a reason for Ca isotope fractionation during felsic magma differentiation, in addition to crustal magma sources and crustal contamination. Additionally, a Late Cretaceous granite with a high (Dy/Yb)N ratio has the lowest S44/40Ca value (0.52 f 0.06 %o), possibly reflecting the presence of residual garnet in the source. The affirmation of significant Ca and Fe isotope fractionation in highly evolved melts strengthens the utility of Fe and Ca isotopes as tracers of magma differentiation.

The Longrong ore cluster is a recently discovered ore district in the western segment of the Bangong-Nujiang metallogenic belt (the Ban-Nu belt in short), Tibet. It is also the only one known ore cluster which develops both Fe mineralization (skarn type) and Cu mineralization (porphyry type dominated) in the Ban-Nu belt. It is located at the easternmost part of known Fe mineralization belt, and the westernmost part of known Cu mineralization belt in the western segment of the Ban-Nu belt. We present zircon U-Pb ages, bulk-rock geochemical and Sr-Nd isotope data, as well as zircon Hf isotope data to constrain the petrogenesis of the granitoids in this ore cluster. Zircon U-Pb data yielded ages of similar to 160Ma (154.7 similar to 163.4Ma, 2 sigma range) for granitoids associated with Fe mineralization, and similar to 120Ma (115.9 similar to 127.9Ma, 2 sigma range) for granitoids associated with Cu/Cu-Pb-Zn mineralization, which are consistent with the mineralization ages of known iron deposits and copper deposits in the western segment of the Ban-Nu belt, respectively. These granitoids are of high-K calc-alkaline affinity, with enrichment of light rare earth elements (LREEs) and large-ion lithophile elements (e.g., Rb, K, and Pb), and depletion of high-field strength elements (e.g., Ta, Nb), which are typical of the geochemical signatures of the arc magmas. The felsic magmatic rocks formed at similar to 160Ma may be related with assimilation and fractionation of amphibole, plagioclase and apatite from the coeval intermediate magma; while the felsic magmatic rocks formed at similar to 120Ma may be generated mainly by fractionation of amphibole, plagioclase, and monazite from the coeval intermediate magma. The two periods of Longrong granitoids have initial Sr isotopic ratios of 0.7066 similar to 0.7136, epsilon(Nd)(t) values of -8.6 to -5.4, and zircon epsilon(Hf)(t) values of -17.34 to -4.83, indicating old crustal materials added to them. Compared with contemporaneous granitoids from the Duolong ore cluster and the Qingcaoshan deposit, the similar to 120Ma Longrong granitoids sourced from a larger proportion of crustal materials, likely arising from the further distance from the subduction belt for the Longrong ore cluster. It is suggested that the similar to 160Ma granitoids in the Longrong ore cluster formed during normal northward subduction of the Bangong-Nujiang oceanic slab, and the similar to 120Ma Longrong granitoids formed during a period of magmatic flare-up following flat-slab subduction (145 similar to 125Ma). Both episodes of the granitoids sourced from a mixture of material from the metasomatized mantle wedge and the ancient Qiangtang continental crust.

Abstract The Lhasa‐Qiangtang collision closed the Meso‐Tethys Ocean, but the exact timing of this event remains hotly debated. Here, we present geochronological and paleomagnetic analyses conducted on Cretaceous volcanics from western Qiangtang to constrain the Lhasa‐Qiangtang collision in western Tibet. Our investigations yield a paleolatitude of ∼30.5 ± 5.0°N for western Qiangtang during ca. 110–100 Ma. A reanalysis of previously acquired Mesozoic‐Cenozoic paleomagnetic data from western Qiangtang suggests a stationary position during ca. 136–34 Ma. Examination of paleomagnetic data from western Lhasa reveals a significant reduction in northward paleolatitudinal motion during the Early Cretaceous, dropping from ∼12.3 cm/yr to nearly zero. Integration of our paleomagnetic findings with available geological records has led to conclude that the Lhasa‐Qiangtang collision in western Tibet occurred at ca. 132 Ma. Additionally, we infer that crustal shortening on the order of ∼1,000 km happened between Lhasa and Qiangtang during the Early Cenozoic.

The Bangong-Nujiang Ocean played an important role in the formation of the Tibetan Plateau prior to the Cenozoic India-Eurasia collision. However, there are still uncertainties about the subduction polarity and timing of the Lhasa-Qiangtang collision. We conducted sandstone petrologic and detrital zircon U-Pb-Hf isotopic analyses on the Cretaceous Wada melange, trench-fill strata and Duoni Formation in the Basu area in the eastern Bangong-Nujiang Suture Zone. The Wada melange (-114 Ma) exhibits block-within-matrix features and a detrital zircon U-Pb age spectrum characterized by multiple peaks at 114-180 Ma, 200-300 Ma, and 1800-2000 Ma. The trench-fill strata consist of coherent chert, sandstone, and mudstone, with a detrital zircon age spectrum dominated by a single peak at -120 Ma. The epsilon Hf(t) values of the 110-300 Ma detrital zircon grains in the Wada melange and trench-fill strata range from -20 to +10 and are consistent with those of the South Qiangtang Terrane. The epsilon Hf(t) values of the -120 Ma detrital zircons are all negative, and these grains were likely derived from a remnant Cretaceous arc in the South Qiangtang Terrane to the north. These data suggest that the accretionary wedge was derived from the South Qiangtang Terrane during the northward subduction of the Bangong-Nujiang Ocean. The Duoni Formation (-113 Ma) represents peripheral foreland basin deposits with the Lhasa Terrane as the basement. Provenance analysis indicates that these deposits received clastic material mainly from the South Qiangtang Terrane and to a lesser degree from the North Lhasa Terrane. Our results suggest that the Lhasa-Qiangtang collision occurred in the Early Cretaceous (-113 Ma) in the eastern segment of the Bangong-Nujiang Suture Zone.

In hydrothermal tin (Sn) systems, it remains unclear whether cassiterite precipitates from reduced or oxidized fluids. To resolve this issue, the geochemistry of magmatic garnet and cassiterite separated from fractionated muscovite-garnet granite in the Paleocene Bawapin Sn-W deposit was systematically investigated. CaO contents in Mn-rich garnet (spessartine) decrease from core to rim in single crystals and are negatively correlated with MnO/(MnO + FeO) ratios. These features suggest that garnet CaO content may be a good differentiation index for granitic magma evolution. Moreover, the Sn content in Mn-rich garnet increases with increasing Ca content and then decreases sharply at Ca contents of approximately 4300 ppm. Combined with evidence of Ta-rich magmatic cassiterite, the decreasing Sn content likely reflects the crystallization of magmatic cassiterite from the more evolved Sn-rich melts under oxidized conditions (fO(2) > Delta FMQ +1.5), in contrast to the reduced characteristics of the less-fractionated biotite monzogranite (fO(2) = Delta FMQ - 0.5). Late-stage oxidation might be attributable to fluid exsolution in the water-rich and Fe-poor granitic melts. This further indicates that hydrothermal cassiterite could precipitate in exsolved Sn4+-bearing fluids without Sn oxidation. This conclusion may provide a new perspective to our understanding of granite-related hydrothermal Sn systems worldwide.

Knowledge of the evolution of the Bangong-Nujiang Tethyan Ocean is crucial for reconstructing the paleography of the Tethyan Realm, given its significance as a key component of the eastern Tethys. Nonetheless, there has been uncertainty regarding both the timing and the processes involved in the closure of this ocean. This study focused on a 110-106 Ma igneous complex comprising basalts-basaltic andesites, trachyandesites, and granodiorites from the Sumxi area in the western part of the Qiangtang terrane of west-central Tibet. The basalts-basaltic andesites have SiO2 contents of 52.5-58.7 wt% and MgO contents of 2.89-4.63 wt%, and exhibit some arc-like geochemical signatures. However, these rocks also have elevated Nb contents (>10 ppm) and Nb/La ratios (>0.5), as well as enriched Sr-Nd isotopic composition [epsilon(Nd)(t) = -7.40 to -6.00], implying that they are products of a mantle source metasomatized by adakitic melts. The trachyandesites are characterized by intermediate compositions (SiO2 = 63.6-65.2 wt%), high Mg number (40-60), and more enriched epsilon(Nd)(t) values (-8.37 to -7.49). Comparing their geochemical composition to that of m & eacute;lange rocks, it is postulated that these trachyandesites were formed through the partial melting of a mantle source including m & eacute;lange matrix rocks within a subduction zone. The granodiorites exhibit adakitic geochemical features (Sr = 830.14-1032.70 ppm, Y = 14.86-15.37 ppm, Sr/Y = 54-68), indicating that they originated from the partial melting of a thickened lower crust in a continental arc setting. Our results, in combination with a synthesis of tectonomagmatism along the Bangong-Nujiang suture zone, provide convincing evidence for subduction of an oceanic plateau and subsequent slab roll-back. The Sumxi igneous complex, with its clear arc affinity, suggests that the Bangong-Nujiang Tethyan Ocean, or at least its western part, remained open until the late Early Cretaceous (ca. 106 Ma).

Lithium (Li) has grown to be a strategic key metal due to the enormous demand for the development of new energy industries over the world. As one of the most significant sources of Li resources, pegmatite-type Li deposits hold a large share of the mining market. In recent years, several large and super-large spodumene (Spd)-rich pegmatite deposits have been discovered successively in the Hoh-Xil–Songpan-Garzê (HXSG) orogenic belt of the northern Tibetan Plateau, indicative of the great Li prospecting potential of this belt. Hyperspectral remote sensing (HRS), as a rapidly developing exploration technology, is especially sensitive to the identification of alteration minerals, and has made important breakthroughs in porphyry copper deposit exploration. However, due to the small width of the pegmatite dykes and the lack of typical alteration zones, the ability of HRS in the exploration of Li-rich pegmatite deposits remains to be explored. In this study, Li-rich pegmatite anomalies were directly extracted from ZY1-02D hyperspectral imagery in the Zhawulong (ZWL) area of western Sichuan, China, using target detection techniques including Adaptive Cosine Estimator (ACE), Constrained Energy Minimization (CEM), Spectral Angle Mapper (SAM), and SAM with BandMax (SAMBM). Further, the Li-rich anomalies were superimposed with the distribution of pegmatite dykes delineated based on GF-2 high-resolution imagery. Our final results accurately identified the known range of Spd pegmatite dykes and further predicted two new exploration target areas. The approaches used in this study could be easily extended to other potential mineralization areas to discover new rare metal pegmatite deposits on the Tibetan Plateau.

Apatite is increasingly used as a tracer for petrogenetic and metallogenic processes. We present the cathodoluminescence (CL) texture, and composition of igneous apatite from the tungsten-bearing Zhuxi biotite granite and the nearby Zhenzhushan granite porphyry in the Late Mesozoic Jiangnan porphyry-skarn tungsten belt in South China. Most apatite grains show homogeneous CL-dark texture, but some apatite grains have CLdark cores and CL-bright rims, or CL dark-bright-dark-bright (from core to rim) growth zoning bands. The CLbright bands are Mn depleted. Apatite from the Zhuxi biotite granite has elevated W contents (mean: 0.16 ppm; n = 75) compared to the Zhenzhushan granite porphyry (mean: <= 0.02 ppm; n = 32). The CL-bright rims of apatite from Zhuxi have more W than the CL-dark cores, i.e. average 0.58 ppm W versus average 0.07 ppm W, respectively, implying that the late-stage magmatic system was enriched in W. The chondritic Y/Ho ratios (22-33) of Zhuxi apatite, and the similar or even slightly more elevated REE contents of the CL-bright rims, compared to the cores, rule out hydrothermal effects. The Zhuxi apatite samples have distinctly negative delta Eu, Frich and sulfur-depleted features, which are interpreted as signature of igneous apatite from magmatically evolved granitic intrusions associated with W deposits, while the inverse trend applies to apatite from Cu porphyry systems. In-situ microanalysis of apatite may be a useful exploration tool.

The post-collisional Qulong porphyry Cu-Mo deposit is the largest in the Gangdese Cu belt, southern Tibet. Despite many previous studies, the evolution of ore-forming fluids in the Qulong deposit remains controversial. Pyrite-bearing veins at Qulong can be divided into seven subclasses, including Mt-type, Bt-type, A-type, B-type, C-type, D-type, and E-type veins. To decipher the evolution of magmatic-hydrothermal fluids at Qulong, in situ LA-ICP-MS trace element and sulfur isotope compositions of pyrites from different veins were analyzed. The delta 34S values (+1.01%o to + 4.28%o) for pyrites indicate a magmatic sulfur source and the high Se/S ratios of pyrite at Qulong are consistent with hydrothermal fluids being mainly magma-derived. The low Co/Ni ratio (0.01-0.1) of pyrite in Mt-type vein suggests that the earliest magmatic-hydrothermal fluids may have contributed from mafic magma injection. From Mt- to Bt- to A-type veins, the delta 34S values in the hydrothermal fluids decrease as the temperature decreases, whereas the Cu and Co contents increase and the As and Ni contents decrease. In B- and C-type veins, the relatively high and stable Co and Ni contents and the range of delta 34S isotope values in pyrite indicate the existence of multiple-stages of magmatic-hydrothermal fluids during the main mineralization period. During the late stages of mineralization, the decrease of Co, Ni and As contents and increase of Cu in pyrite in D- and E-type veins, as well as the narrow range of delta 34S values, may be due to decreasing temperature as a result of fluid dilution caused by mixing with meteoric waters. The slightly negative delta 34S fluid values for chalcopyrite (-1.56%o to -0.75%o) in sample Q711-1968 also suggests the addition of external water at Qulong.