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Geochronological dating of detrital minerals from sedimentary rocks can provide invaluable records of the erosional and unroofing history of orogenic systems and link specific sources with their sinks in sedimentary basins. Aiming to establish a better understanding of the thermal and erosional evolution of the East Kunlun Orogenic Belt (E‐KOB), northern Tibet Plateau during the Mesozoic, integrated detrital U–Pb zircon, and 40Ar/39Ar muscovite dating was applied to Triassic and Jurassic strata in the southern E‐KOB in this study. Detrital U–Pb zircon ages of clastic rocks from Triassic and Jurassic formations show major age populations at 2,600–2,200 Ma, 2,000–1,700 Ma, 1,000–600 Ma, 530–340 Ma, and 320–220 Ma, while the 40Ar/39Ar dating of detrital muscovite yield dominantly Devonian ages with uniform early‐middle Devonian peak ages (380–405 Ma). Our new detrital U–Pb zircon and 40Ar/39Ar muscovite ages, combined with the previous palaeocurrent data and comparison with published U–Pb zircon, and 40Ar/39Ar muscovite ages of potential source areas, suggest that the E‐KOB was the major source for Triassic and Jurassic strata in the southern East Kunlun. Devonian detrital muscovite 40Ar/39Ar ages of the Triassic and Lower Jurassic strata are consistent with the age of syn‐ and post‐collisional magmatic activity in E‐KOB related with the post‐collisional thermal relaxation after closure of the Qimantagh back‐arc basin. The Lower Triassic sedimentary deposits were associated with the subduction of the Kunlun Ocean, which is part of the Palaeo‐Tethys Ocean. The E‐KOB‐derived material in Upper Triassic and Lower Jurassic formations implies that significant surface uplift, unroofing and erosion occurred during the Late Triassic and continued into the Early Jurassic in the East Kunlun region. [ABSTRACT FROM AUTHOR]

Abstract The Gangdese magmatic belt is oriented E–W and located between the Indus–Yarlung Tsangpo and Bangong–Nujiang suture zones in Tibet. It records the subduction of the Neo-Tethyan oceanic crust, Indian–Eurasian collision, and uplift of the Tibetan Plateau. Here we present new zircon U–Pb geochronology, Hf isotopic compositions, and whole-rock geochemistry of the granodiorites in the Sumdo area of the Gangdese Belt. Our aim was to identify the petrogenesis of granitoid rcoks and to clarify the early-stage evolution of the Neo-Tethyan Ocean during the Late Triassic to Early Jurassic. The granodiorites yield zircon U–Pb ages of 193–201 Ma, indicating an Early Jurassic magmatic event. They are metaluminous, with medium- to high-K calc-alkaline geochemistry, and show characteristics of I-type granitoids. They show enrichment in light rare earth elements (LREEs) and depletion in high-field-strength elements (HFSEs) in primitive-mantle-normalized spider diagrams, indicating that their initial magma was generated in a subduction-related active continental margin. They have negative ε Hf (t) values (−11.3 to −4.1) and crustal model ages (TC DM) of 1.50–1.95 Ga. Hf isotopes and whole-rock geochemistry indicate that the granodiorites were derived from partial melting of ancient lower-crust material mixed with mantle material. Our data, in combination with published geochronological and geochemical data, show that the Late Triassic–Early Jurassic arc magmatism in the Gangdese magmatic belt was formed by the northward subduction of the Neo-Tethyan oceanic crust beneath the Lhasa Terrane. Highlights • Ca. 201–193 Ma granitoids occur in the Sumdo area of the Gangdese belt, Tibet • The rocks were derived from crustal melting and subsequent crust-mantle magma mixing. • Coeval magmatism in the Gangdese Belt is related to the Neo-Tethyan Ocean. [ABSTRACT FROM AUTHOR]

Previous studies of the Southern Qiangtang (SQ) Terrane in Tibet have shown significant growth of continental crust during the late Mesozoic (ca. 170–120 Ma) through underplating of mantle-derived melts beneath ancient lower crust. However, the mechanism of crustal growth remains defective during the Late Jurassic. In this contribution, we report new zircon U–Pb ages, whole-rock major and trace element concentrations, and zircon Hf isotopic compositions of Late Jurassic rhyolites from the Duobuza area in the SQ Terrane. Zircon LA–ICP–MS U–Pb dating yields concordant ages and weighted mean 206Pb/238U ages of 151–149 Ma, indicating that the rhyolites were erupted during the Late Jurassic. The rhyolite samples yield high SiO2 (69.1–73.4 wt.%) and Na2O (3.82–6.49 wt.%) concentrations, high values of the differentiation index (95.4–98.5), moderate Al2O3 (13.1–15.5 wt.%) and K2O (2.55–3.26 wt.%) concentrations, and relatively low TiO2 (0.34–0.44 wt.%), MgO (0.14–0.67 wt.%), and MnO (0.01–0.10 wt.%) concentrations and Mg# values (8.9–33.5). They are enriched in Rb, Th, Ba, and Pb, depleted in Nb, Ta, Sr, Ti, and P, and yield negative Eu anomalies. These characteristics suggest that the Duobuza rhyolites represent medium- to high-K calc-alkaline, highly fractionated I-type granitoids. Variations in major and trace element concentrations indicate that the rhyolites underwent significant fractionation of Fe–Ti oxides, plagioclase, K-feldspar, hornblende, biotite, and apatite. The samples yield positive zircon εHf(t) values (+0.08 to +10.9) and young TCDM model ages (816–386 Ma), indicating that they were generated through partial melting of juvenile lower crust of the SQ Terrane. These data are distinct from those of Late Jurassic intermediate–felsic plutons in the SQ Terrane that generally yield negative εHf(t) values and ancient TCDM model ages. We suggest that the occurrence of the Duobuza rhyolites is the significant witness. The presence of juvenile lower crust beneath the SQ Terrane during the Late Jurassic (ca. 150 Ma) rather than during the Early Cretaceous (ca. 120Ma). The transition from ancient to juvenile lower crust has already began in the SQ Terrane during the Late Jurassic. [ABSTRACT FROM AUTHOR]