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The Pamir-Karakorum is one of the most important regions for our understanding the Tethys evolution. Although it is commonly known that the northward subduction of the Neo-Tethys Ocean induced the formation of the magmatic arc in Southern Pamir, the temporal-spatial configuration of the arc—back-arc during the Neo-Tethys evolution remains unclear. In this study, we report sedimentary feature, petrography, zircon U Pb ages and Hf O isotope compositions as well as bulk-rock and mineral geochemistry of the well-preserved Cretaceous volcanic sequence in Chinese Wahan Corridor at South Pamir. The volcanic sequence is mainly composed of phenocrysts- bearing basalt- andesites with minor rhyolite and volcaniclastic rock. Zircon U Pb ages reveal the basalt-andesite sequence erupted at 100–98 Ma. Bulk-rock geochemistry defines their potassic calc-alkaline signature and both their rock association and elemental geochemistry share most features of the continental arc volcanic sequences. On the other hand, they have variably enriched Nd isotope compositions with ε Nd (t) varying from −5.9 to −9.6, coupled with their enriched zircon Hf isotope signature with ε Hf (t) between −13 to −8. Whole-rock geochemistry and zircon oxygen isotope compositions (average δ18O = 7.74 ± 0.14) demonstrate that the primitive magma of the basalt-andesites were derived from partial melting of a metasomatized sub-continental lithospheric mantle and underwent variable assimilation fractional crystallization. Late Jurassic to Cretaceous volcanic-sedimentary sequences and coeval voluminous arc-like granodiorite and granites are widely distributed along the Southern Pamir. In the Central Pamir and further north, late Jurassic to Cretaceous sequences resemble features of back-arc basins. Taken together, we suggest that a northward low-angle or flat subduction of the Neo-Tethys Ocean along the Shyok zone was geodynamically related to the formation of the broad magmatic arc in South Pamir-Karakorum and the back-arc basins north of the South Pamir. [Display omitted] • Arc-like Cretaceous basalt-andesite sequence in Southern Pamir (SP) erupted at ~100 Ma. • Architecture of the late Jurassic-Cretaceous arc-back-arc at Pamir was constructed. • Flat subduction of the Neo-Tethys Ocean produced the Cretaceous igneous rocks in SP. [ABSTRACT FROM AUTHOR]

Highlights: [•] Basalts of the Sugetbrak Formation yield two ages of 615.2±4.8Ma and 614.4±9.1Ma. [•] Tarim may have involved in the breakup of Rodinia at its late stage. [•] The Sugetbrak basalts represent low-degree meltsproduced in a rifting environment. [•] The new ages put a constraint on the timing of the Yuermeinak glaciation in Tarim. [•] We correlate the Yuermeinak glaciation with other glaciations around the world. [ABSTRACT FROM AUTHOR]

The Yandangshan syenite is a representative Late Cretaceous igneous pluton cropping out in SE China. U-Pb zircon dating using LA-ICP-MS yielded a crystallization age of 98±1 Ma for the syenite. Petrographically and geochemically of shoshonitic affinity, it is enriched in LREE and LILE, and has a pronounced Nb-Ta trough in the primitive mantle-normalized trace element spider diagram. Zircon εHf(t) values vary from -3.04 to -7.71, displaying a unimodal distribution. The syenite also has high Sr [(87Sr/86Sr) i = 0.7086-0.7089], low Nd [εNd(t) = -6.57 to -7.64] isotopic ratios, plotting in the enriched mantle field on an εNd(t) versus (87Sr/86Sr) i diagram. We propose that the Yandangshan syenite was generated by pyroxene-dominated high-pressure fractional crystallization from basaltic magma that was derived from an enriched mantle source. Although coexisting Yandangshan rhyolites have Sr-Nd isotopic compositions similar to the Yandangshan syenite, they were not derived from the same source. Instead, the rhyolitic magma was produced by partial melting of crustal materials as a result of the underplating of basaltic magma. The crust-like Sr-Nd-Hf isotopic signature of the Yandangshan syenite is ascribed to mantle sources that were enriched by subducted sediments. Formation of Yandangshan syenite may represent roll-back of the subducting palaeo-Pacific plate and migration of the arc front to the Yandangshan area at ∼98 Ma. [ABSTRACT FROM AUTHOR]

• Diverse Cambrian metavolcanic rocks were reported in the NE Pamir. • The orogenesis in the NE Pamir occurred during the early Jurassic. • Building of the Cambrian accretionary complex at the NE Pamir. • Tectonic evolution from Proto-Tethys to Paleo-Tethys in the NE Pamir. The Pamir Plateau contains critical information on the tectonic evolution from the Proto- to Paleo-Tethys. In this contribution, we report geochronology, geochemistry and Sr-Nd isotopic compositions of diverse metavolcanic rocks in the Bulunkuole Group (BG) in the NE Pamir, to construct the architecture of the thick Cambrian volcanic-sedimentary sequence in the NE Pamir and to provide new insights into the tectonic evolution from Proto-Tethys to Paleo-Tethys. Our newly obtained zircon U-Pb ages combined with ages from literature reveal that these volcanic-sedimentary sequences were deposited during the Cambrian and metamorphosed during the Early Jurassic. The bimodal volcanic rocks (ca. 530 Ma) at the lowest BG show typical arc-like geochemical features, representing the initial arc produced by the southward subduction of the Proto-Tethys Ocean. Amphibolites (ca. 526 Ma) from the Maeryang area show an OIB-like affinity with high Nb/La ratios (0.75–1.01) and positive ε Nd (t) values (4.19–4.76), representing a seamount component in the Proto-Tethys Ocean. High-pressure mafic granulites to the north of Tashkorgan County exhibit E-MORB geochemical features. Combined with recent advances in the NE Pamir geology, we suggest that the southward subduction of the Proto-Tethys slab under the Mazar-Tianshuihai terrane initiated earlier than 530 Ma. Subsequent trench retreat led to the formation of the massive early Paleozoic accretionary wedge (BG) followed by the northward migration of arc magmatism to the BG. The Proto-Tethys Ocean at Pamir did not close in the early Paleozoic. Instead, it was finally closed during the early Mesozoic as revealed by the Early Jurassic amphibolite-facies metamorphism in the BG. [ABSTRACT FROM AUTHOR]

Abstract: The Nuomin volcanic field (NM for short) in northern Greater Xing'An Mountains is dominated by Quaternary monogenetic eruptions, forming lava flows covering an area of about 600km2. The lavas range from tephrite and basanite to trachybasalts, with high K2O contents between 2.6wt.% and 4.3wt.%, and K2O/Na2O between 0.78 and 1.08. These NM lavas are generally magnesian (Mg# between 0.59 and 0.78) and may contain useful information on the origin of potassic magmas in NE China. The NM lavas are characterized by relatively high (La/Yb)N (21.6–41.9) and enrichments in large ion lithophile elements (LILEs), but low in high field strength element (HSFE) concentrations. The NM lavas have negative εΝd(−0.8–−3.0), 87Sr/86Sr between 0.704661 and 0.704880, 206Pb/204Pb between 17.0 and 17.2, 207Pb/204Pb between 15.41 and 15.43, and 208Pb/204Pb between 37.0 and 37.3. Their trace element spider diagram and chondrite-normalized rare earth element (REE) diagram are similar to those of Wudalianchi lavas, but are different from the Halaha–Chaoer river lavas in central Greater Xing'An Mountains. Their REE characteristics indicate that the NM lavas originate from garnet stability field. Based on petrological and geochemical data, we propose that the delamination of K-rich lithosphere mantle trigger the Quaternary potassic volcanism in Northeastern China. [Copyright &y& Elsevier]

The early Paleozoic orogen in South China Block is an intracontinental orogen, and synchronous magmatism (440–390Ma) is mainly acidic with minor intermediate-mafic magmatism. Previous studies suggest that most of the early Paleozoic granites in South China belong to peraluminous S-type genesis while amphibole-bearing I-type granites are subordinate. However, our results indicate that considerable amounts of these early Paleozoic granites have characteristics of both S- and I-type granites. Thus, we propose to divide these granites into two groups: fewer of them are Group A with relatively high ε Hf(t) values (clustering within −3.0 to +9.0) and ε Nd(t) values (−5.2 to +1.3) as well as higher initial temperatures at 810–850°C, and most of them are Group B with relatively low ε Hf(t) values (clustering within −16.0 to −1.0) and ε Nd(t) values (−13.2 to −4.1) as well as relatively low initial temperatures at 700–830°C. The Xiawan monzogranite and Duntou granodiorite are typical Group A granitoids and yield zircon U–Pb ages of ca. 410Ma. These two granites are characterized by high SiO2 (between 67.59 and 74.87wt.%), metaluminous to peraluminous (A/CNK=0.96–1.48) compositions, and a negative correlation between P2O5 and SiO2. Their biotites belong to magnesium biotites, indicating that they have partial features of either I- or S-type granites. Duntou granodiorites exhibit higher ε Hf(t) values (clustering within +1 to +8) and ε Nd(t) values (−3.0 to +1.1) while Xiawan monzogranites show relatively low ε Hf(t) values (clustering within −1 to +5) and ε Nd(t) values (−5.0 to −3.7). Group B granitoids are represented by the Miao'ershan–Yuechengling batholith, which are characterized by high SiO2 (between 64.57 and 77.37wt.%), metaluminous compositions (A/CNK=0.90–1.24), and a negative correlation between P2O5 and SiO2. Yuechengling porphyritic amphibole-bearing biotite granites in this batholith contain abundant amphibole, indicating that they are I-type granites. Miao'ershan–Yuechengling batholith also exhibits relatively low ε Hf(t) values (−12.7 to −1.8) and ε Nd(t) values (−8.9 to −6.7). Geochemical and isotopic analyses on early Paleozoic granites, mafic enclaves and mafic to intermediate rocks demonstrate that the Group A granitoids including Xiawan and Duntou granites may be generated by AFC processes with interactions between asthenosphere-derived magma and metasedimentary rocks, and the Group B granitoids may be formed by AFC processes with interactions between synchronous basaltic magma and metamorphic basement. The post-collisional delamination and asthenospheric upwelling directly participate in the generation of Group A granitoids but indirectly induce the formation of Group B granitoids. [ABSTRACT FROM AUTHOR]

Neoproterozoic layered mafic intrusions occur along the northern margin of the Yangtze Block in South China. In this paper, we report the chemical compositions of clinopyroxene, plagioclase, and olivine from two major mafic intrusions at Bijigou (BJG) and Wangjiangshan (WJS), to constrain the parental magma characteristics and geodynamic setting. The olivine and plagioclase compositions indicate that the parental magma for BJG and WJS was an evolved tholeiitic magma with high FeO T /MgO ratios. An origin of arc magmatism is not supported by the following mineralogical and petrological observations: (1) the strong rift-affinity indicated by olivine, plagioclase and clinopyroxene geochemistry, (2) the absence of high anorthite in the cumulate rocks, (3) the paucity of abundant cumulus hornblende crystals, and (4) the lack of voluminous intermediate rocks in the rock associations. We propose that the BJG and WJS mafic-ultramafic intrusions formed under a rift extensional setting during 820–780 Ma. The subduction process ceased before 820 Ma and did not directly contribute to the generation of the BJG and WJS mafic-ultramafic intrusions. The arc-like Nb Ta depleted trace element pattern in the parental magma is inherited from the mantle metasomatized by earlier subduction processes. • The parental magma was evolved tholeiitic magma with an arc-like Nb-depleted nature. • Mineral chemistry and petrology suggest a rift extensional setting during 820–780 Ma. • The arc nature in the parental magma is inherited from earlier subduction processes. • The tectonic regime had changed from compression to extension prior to 820 Ma. [ABSTRACT FROM AUTHOR]

Although it is generally accepted that the Pamir was formed by long-term terrane drifting and accretion to the south margin of the Asia, the tectonic evolution during the Mesozoic remains unclear. The voluminous Cretaceous intrusions in the Southern Pamir-Karakorum provide key information for understanding the Mesozoic evolution in this region. In this contribution, we report detailed petrography, ages, mineral geochemistry, whole-rock elemental and Sr Nd geochemistry and in situ zircon Lu Hf isotopic compositions of the Early Cretaceous granitoids from the Chinese Wakhan Corridor, Southern Pamir. These granitoids are composed primarily of granodiorite and minor monzogranite and host dioritic enclaves. The granitoids were emplaced at 107–102 Ma, based on their zircon U Pb ages. They have 63–73 wt% SiO 2 , Mg# between 39 and 53 and ACNK mostly lower than 1.1, and are I-type granites. The granitoids display arc-like geochemical signatures characterized by LREE-enriched patterns, variable negative Eu anomalies (La N /Yb N = 11.38–23.27; Eu/Eu* = 0.36–0.74), and a significant Nb Ta trough (Nb/La = 0.24–0.41). Isotopically, the granitoids have negative whole-rock ε Nd (t) (−8.73–7.35) and zircon ε Hf (t) (−17.7–5.3) values. The coeval dioritic enclaves (ca. 104 Ma) contain 57–63 wt% SiO 2 , and have high Mg# (46–57), low Cr (6.86–79.50 ppm), and Ni (2.88–10.00 ppm). These enclaves exhibit arc-like trace element patterns (Nb/La = 0.34–0.43) with variable negative Eu anomaly (Eu/Eu* = 0.52–0.87), uniform whole-rock ε Nd (t) (−4.74–4.73), and a large range of zircon ε Hf (t) values (−13.3–3.7). In line with their rock association and geochemistry, we suggest that the dioritic enclaves were derived from melting of a phlogopite-bearing mantle source modified by subduction-related process, followed by fractional crystallization and later assimilation by granitic hosts. These Early Cretaceous granitoids were most likely generated by partial melting of the Precambrian lower crust with variable involvement of mafic magma parental to the dioritic enclaves. Our new data, combined with the previous studies, reveal that the widespread Early Cretaceous magmatism in the Southern Pamir-Karakorum were most likely generated by flat-slab subduction of the Meso-Tethys Ocean during the Cretaceous. • ca. 107–102 Ma granitoids and enclaves in the Wakhan Corridor were reported. • The dioritic enclaves were originated from metasomatized mantle source. • The granitoids were products of mixing of mantle- and crustal-melts in an arc setting. • The Early Cretaceous magmatism was generated by northward subduction of the Meso-Tethys. [ABSTRACT FROM AUTHOR]

The West Kunlun Orogenic Belt (WKOB) carries key information about the evolution of the Proto-Tethys Ocean. In order to have a better understanding of the early Paleozoic tectonic evolution of the WKOB and to unravel the process of the Tarim assemblage to Gondwana, we report field observations, petrography, ages, chemical and Sr-Nd-Hf isotopic compositions of the newly identified Cambrian mafic and granitic intrusions in the Mazar Terrane-Tianshuihai terrane (MZT-TSHT) at the interior of the WKOB. Our zircon U–Pb dating reveals that the mafic and granitic rocks in Tianshuihai Terrane (TSHT) emplaced at ca. 530 Ma, and that the mafic rocks in the Mazar Terrane (MZT) emplaced at ca. 500–490 Ma. Whole-rock major and trace element geochemistry defines a tholeiitic signature for these mafic rocks. Isotopically, the TSHT mafic rocks have depleted Nd isotope compositions with initial ε Nd (t) isotopes ranging from 2.74 to 3.60, whereas the MZT mafic rocks exhibit enriched whole-rock Nd isotope compositions with ε Nd (t) values ranging from −12.90 to −9.71. The distinct chemical and isotopic signatures argue that the Cambrian mafic rocks in the TSHT were derived from a depleted mantle source in an initial subduction setting, whereas the mafic rocks from MZT were derived from an enriched sub-continental lithospheric mantle source in an arc setting. The Cambrian granites in the TSHT show typical fractionated I-type granite elemental signatures, in line with their Nd-Sr-Hf isotope compositions. These Cambrian granites were most likely generated by partial melting of Mesoproterozoic (0.9–1.3 Ga) crustal sources due to underplating of the coeval mafic magma. Our results in combination with previous studies suggest that the Cambrian mafic and granitic rocks in the MZT-TSHT were generated by the southward subduction of the Proto-Tethys Ocean initiated at ca. 530 Ma. The long-term southward subduction led to the formation of the massive early Paleozoic accretionary wedge in WKOB. The Proto-Tethys Ocean finally closed at ca. 440 Ma as demonstrated by the amphibolite facies metamorphism of the accretionary complex and the middle to late Devonian molasses unconformably overlying the accretionary complex. This process caused the blocks in East Asia, including the Tarim, Qaidam and North Qilian, Yangtze and Indochina, to dock at the northern fringe of the Eastern Gondwana. Image 1 • ca. 530-490 Ma magmatic rocks were identified in the Western Kunlun Orogenic Belt. • The ca. 530 Ma mafic rocks formed in an initial subduction setting. • The ca. 490 Ma mafic rocks originated in an enriched SCLM in an arc setting. • Southward subduction of the Proto-Tethys Ocean initiated at ca. 530 Ma. [ABSTRACT FROM AUTHOR]