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Rubidium (Rb) deposits mostly occur in the South China and Central Asia orogenic belts and are often closely associated with highly differentiated granites. This study investigates a newly‐discovered giant Rb deposit at Gariatong in the Central Lhasa terrane in Tibet. Detailed field studies and logging data revealed that the Rb mineralization mainly occurs in monzogranite and is related to greisenization. LA‐ICP‐MS U‐Pb dating of zircon yielded ages of 19.1 ± 0.2 Ma and 19.0 ± 0.2 Ma for greisenized monzogranite and fresh monzogranite, respectively. The monzogranites are characterized as strongly peraluminous, with high contents of SiO2, Al2O3, K2O and Na2O as well as a high differentiation index. They are enriched in light rare earth and large ion lithophile elements with significant negative Eu anomalies and depleted high field‐strength elements. Petrological and geochemical features of these ore‐related monzogranites suggest that they are highly fractionated S‐type granites, derived from remelting of crustal materials in a post‐collisional setting. The geochemistry of zircon and apatite points to a low oxygen fugacity of the ore‐related monzogranite during the magma's evolution. The discovery of the Gariatong Rb deposit suggests that the Central Lhasa terrane may be an important region for rare metal mineralization. [ABSTRACT FROM AUTHOR]

The Bangbule skarn lead‐zinc (Pb‐Zn) deposit (>1 Mt Zn + Pb) is located in the western Nyainqentanglha polymetallic metallogenetic belt, central Tibet. Lenticular orebodies are all hosted in skarn and developed in the contact zone between the quartz porphyry and carbonate strata of the mid Paleozoic Middle to Upper Chaguoluoma Formation as well as in carbonate and sandstone beds of the Upper Paleozoic Laga Formation. As a newly discovered skarn deposit, the geological background and metallogenesis of this deposit remain poorly understood. Detailed petrological, geochemical and geochronological data of the ore‐related quartz porphyry, helps constrain the mineralization age and contributes to discussion on the ore genesis of the Bangbule deposit. Both endoskarn and exoskarn are identified in the Bangbule deposit. From quartz porphyry to carbonate formation, the exoskarn is zoned from proximal garnet skarn to distal pyroxene skarn. Zircon U‐Pb dating results show that the quartz porphyry formed at 73.9 ± 0.8 Ma. Geochemical analysis results show that the quartz porphyry has high contents of SiO2 (71.40–74.94 wt%) and K2O + Na2O (3.76–8.46 wt%) with A/CNK values of 0.69 to 1.06. Besides, the quartz porphyry is enriched in large ion lithophile elements (LILEs) and light rare earth elements (LREEs) and have low εNd(t) (from –8.25 to –8.19) and high initial (87Sr/86Sr)i values (0.713611–0.714478). Major, trace elements and whole‐rock F concentration analysis results from the endoskarn samples show higher TFe2O3, MgO, CaO, Pb + Zn, W, Sn, Mo and F etc., and lower alkalis (K2O, Na2O, Sr and Ba) than those of fresh quartz porphyry, indicating that the early ore‐forming fluids were an Ca‐Fe‐F‐enriched fluid. Massive ore in the proximal skarn might be related to the high F content in the magma, which lowered the solidus temperature of the quartz porphyry magma and caused a lower temperature of the ore‐forming fluids, as well as facilitating the precipitation of sphalerite and galena. Based on the geochemical characteristics presented in this study, we propose that the ore‐related quartz porphyry was formed by partial melting of crust materials with some juvenile crustal component input. The partial melting of the middle‐upper crust after the initial enrichment of lead and zinc elements are important for the formation of Pb‐Zn deposits. The case study of the Bangbule deposit has proven that there is still a crust‐derived magmatic source region in the western segment of the central Lhasa terrane. Therefore, there is still great potential for Pb‐Zn mineralization and Pb‐Zn exploration. [ABSTRACT FROM AUTHOR]

The Baingoin batholith is one of the largest granitic plutons in the North Lhasa terrane. Its petrogenesis and tectonic setting have been studied for decades, but remain controversial. Here we report data on geochronology, geochemistry and isotopes of Early Cretaceous granitoids within the Baingoin batholith, which provide more evidence to uncover its petrogenesis and regional geodynamic processes. The Early Cretaceous magmatism yields ages of 134.4–132.0 Ma and can be divided into I‐type, S‐type and highly fractionated granites. The I‐ and S‐type granites exhibit medium SiO2, high K2O/Na2O with negative εNd(t) and εHf(t) values, whereas, the albite granites have very high SiO2 (79.04%–80.40%), very low K2O/N2O, negative εNd(t) and a large variation in εHf(t). Our new data indicate that these granitoids are derived from unbalanced melting in a heterogeneous source area. The granodiorites involved had a hybrid origin from partial melting of basalt‐derived and Al‐rich rocks in the crust, the porphyritic monzogranites being derived from partial melting of pelitic rocks. The albite granites crystallized from residual melt separated from K‐rich magma within the 'mush' process and underwent fractionation of K‐feldspar. We believe that the Early Cretaceous magmatism formed in an extensional setting produced by the initial and continuous rollback of a northward‐subducting slab of the NTO. [ABSTRACT FROM AUTHOR]

The Bangong–Nujiang collision zone (BNCZ) is an ideal area for studying postcollisional magmatism. A series of late Early Cretaceous Cu‐bearing magmas are found in this collision zone, which has implications for studying the sources of postcollisional magmas. We completed detailed fieldwork and reported zircon U–Pb and Hf‐isotopic and whole‐rock geochemical data on the Daguo volcanics, Shesuo monzogranite‐granodiorites, and Xiongmei granodiorite porphyries, which represented different types of the Cu‐bearing rocks in the BNCZ. The Shesuo samples are characterized by high contents of SiO2, K2O, and total alkali, with high contents of heavy rare earth elements (HREEs) and Y, and are enriched in large‐ion lithophile elements (LILEs), depleted in Nb and Ta, with a marked negative Eu anomaly (0.29–0.92). The Xiongmei granodiorite porphyries are characterized by moderate SiO2 and MgO, high Al2O3 contents, depletion in Nb, Ta, Ba, Sr, and Ti, enrichment in LILEs, high HREEs and Y contents, and relatively low Sr/Y ratios. Both Shesuo monzogranites and Xiongmei granodiorites belong to calc‐alkaline I‐type magmas, which are associated with a wide range of zircon εHf(t) values (−15.3 to +5.8; −15.4 to +3.2). These geochemical features suggest that the Xiongmei granodiorite porphyries and Shesuo monzogranite‐granodiorites are derived from the melting of a juvenile mafic crust with ancient crustal contamination, and the juvenile mafic crusts are derived from a lithospheric mantle enriched by slab melt (including recycled subducting sediments). The Daguo basalt is derived from the partial melting of a mantle wedge metasomatized by subduction‐related fluids and/or melts and the involvement of asthenospheric mantle. The Daguo intermediate‐felsic rocks are derived from the partial melting of a juvenile crust from a metasomorphic mantle wedge. Our study implies that the genesis of these Cu‐bearing magmas is associated with slab break‐off at the end of the southward subduction of the Bangong–Nujiang Ocean lithosphere. In addition, the postcollisional magmas are multisourced, with a juvenile component from either the metasomorphic lithosphere mantle or the juvenile crust, an ancient crustal component and a subducted‐related component from the recycled subducting sediments, the subducted slab, and/or the asthenosphere. [ABSTRACT FROM AUTHOR]