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We investigated velocity and anisotropic structure of the crust beneath the eastern margin of the Tibetan Plateau to better understand its deformation and evolution mechanism. We performed H‐κ and Pms anisotropy analyses to obtain crustal thickness, Vp/Vs ratio, fast polarization direction, and splitting time from 711 stations, and further conducted quality control using slowness, harmonic and statistical analyses. The Songpan‐Ganzi Block has a large splitting time and a fast polarization direction roughly parallel to the GPS motion and SKS fast direction. It also shows an overall high but complex distribution of Vp/Vs ratio, and large variations in crustal thickness, indicating that crustal deformation is likely caused by crustal shortening and lower crustal flow. The northern Sichuan‐Yunnan Rhombic Block (SYRB) is featured by a thick crust and high Vp/Vs ratio, suggesting that the crust is likely inflated by partial melting lower crustal rocks. The subblock also exhibits a strong azimuthal anisotropy with a splitting time greater than 0.6 s. The fast polarization direction aligns with the nearly N‐S extended direction and rotates clockwise in front of the Emeishan Large Igneous Province (ELIP). The observed anisotropy agrees with aligned amphibole minerals under a simple shear condition, supporting a southward lower crust flow being diverted by the ELIP. Anisotropy measurements on the southern SYRB are less robust and widely scattered, suggesting a deformation mechanism different from the northern SYRB. In addition, the southeastern margin of the Sichuan Basin shows a systematic pattern of crustal anisotropy consistent with a pure shear deformation mechanism. Plain Language Summary: We studied the crustal structure and deformation beneath the eastern edge of the Tibetan Plateau. By analyzing teleseismic data from 727 stations, we measured crust thickness, Vp/Vs ratio, and azimuthal anisotropy using receiver functions. Our findings show a complex crustal behavior pattern in the eastern Tibet margin. In the Songpan‐Ganzi Block, crustal shortening and lower crust flow seem to be causing deformation. The northern Sichuan‐Yunnan Rhombic Block, with its thick crust and high Vp/Vs ratio, appears to be influenced by partial melting of lower crust rocks. And a southward lower crust flow being diverted by the Emeishan Large Igneous Province. The eastern and southern part of this block shows a different pattern, indicating a unique deformation mechanism. Additionally, the southeastern margin of the Sichuan Basin appears to undergo a distinct type of crustal deformation. Key Points: A new crustal model with much more reliable and denser Pms anisotropic measurements is built in the eastern Tibetan MarginSongpan‐Ganzi Block is likely deformed by crustal shortening and lower crustal flowChannel flow may exist in the west low velocity zone (LVZ) while absent at the east LVZ [ABSTRACT FROM AUTHOR]

Three halophilic archaeal strains, NEN8T, GDY88T and ZY14T, were isolated from a salt lake in Tibet and coarse sea salt samples from Guangdong and Hebei, China, respectively. These strains formed three separate clades (showing 94.4–95.8% and 87.1–89.4% similarities, respectively) and then clustered with the current Halorientalis members (showing 90.7–97.6% and 87.0–91.2% similarities, respectively), as revealed by phylogenetic analyses based on 16S rRNA and rpoB′ genes. The overall genome-related index, average nucleotide identity (ANI), in silico DNA–DNA hybridization (DDH), average amino acid identity (AAI) and the percentage of conserved proteins (POCP) values, among the three strains and members of the genus Halorientalis were 76.0–88.0%, 21.3–37.2%, 69.0–88.3% and 57.7–78.1%, clearly below the threshold values for species demarcation. Strains NEN8T, GDY88T and ZY14T could be distinguished from current Halorientalis species according to differential phenotypic characteristics. The major polar lipids of the three strains were phosphatidylglycerol (PG), phosphatidylglycerol phosphate methyl ester (PGP-Me), sulfated mannosyl glucosyl diether (S-DGD-1) and disulfated mannosyl glucosyl diether (S2-DGD). In addition, mannosyl glucosyl diether (DGD-1) was detected in strain NEN8T and phosphatidic acid (PA), posssulfated galactosyl mannosyl glucosyl diether (S-TGD-1) and sulfated mannosyl glucosyl diether–phosphatidic acid (S-DGD–PA) were observed in strain ZY14T. These results revealed that strains NEN8T (= CGMCC 1.17213T = JCM 34155T), GDY88T (= CGMCC 1.18548T = JCM 34481T) and ZY14T (= CGMCC 1.17178T = JCM 34154T) represent three novel species of the genus Halorientalis, for which the names Halorientalis salina sp. nov., Halorientalis marina sp. nov. and Halorientalis litorea sp. nov. are proposed. [ABSTRACT FROM AUTHOR]

Abstract: This study reports age, petrologic and geochemical data for andesites and dacites from the Late Triassic sedimentary strata of northern Hohxil, in the Hohxil–Songpan–Ganzi Block (northern Tibet), which constitutes the most voluminous Triassic strata on Earth. LA-ICP-MS zircon U-Pb analysis of dacite (210.4±1.9Ma) and whole rock 40Ar–39Ar analyses for both the andesites and dacites (211±2Ma and 210.9±1.6Ma) show that the rocks were almost contemporaneous. Both rock types are sodium-rich and calc-alkaline. The andesites, characterized by high MgO (up to 10wt.%) or Mg# (~70), TiO2, Al2O3, Cr, Ni, La/Yb and Th/La, but low Nb/Ta ratios, are geochemically similar to sanukitoids in southeastern Japan. The dacites are strongly peraluminous, and have high Al2O3 and La/Yb, low Y and Yb, coupled with negligible to positive Eu and Sr anomalies, comparable to slab-derived adakites in the circum Pacific arc system. Both rocks exhibit strongly fractionated platinum group element patterns, with Pt/Pt* (Pt anomaly), (Pt/Ir)N and Re/Os ratios higher than those of the primitive mantle. They have uniformly low εNd(t) values (−7.57–−9.59) and high (86Sr/87Sr)i ratios (0.7086–0.7106) that imply a continental rather than oceanic type magma source. We suggest that the northern Hohxil dacites were produced by partial melting of subducted sediments on the northward-subducting Songpan–Ganzi oceanic slab, and the high-Mg andesites were formed by subsequent interaction between the sediment-derived melts and mantle wedge peridotites. Taking into account the Triassic magmatic record from nearby regions, we suggest that the Late Triassic high-Mg andesite/dacite suites of northern Hohxil were generated in a forearc setting, and propose that double-sided subduction eventually closed the Songpan–Ganzi ocean during the Late Triassic. [Copyright &y& Elsevier]

The boninitic volcanic rocks from Rutog, western Bangong-Nujiang Suture Zone (BNSZ), are characterized by high MgO, SiO 2 but low TiO 2 contents and interpreted as the products of intra-oceanic subduction in earlier studies. Recently, we discovered new breccia-like boninitic volcanic rocks (mainly trachyandesite and trachyte) that overlie the Rutog ophiolitic peridotites in BNSZ. These volcanic rocks not only show typical boninitic petrographical features of porphyritic texture in which euhedral augite phenocrysts (ca. 5 vol%) are embedded in fine-grained groundmass composed of pyroxene, plagioclase, quartz and minor glass, but also display strong boninitic geochemical affinities with high Mg# (61.59–67.90), Al 2 O 3 /TiO 2 (40.31–55.97) ratios and low TiO 2 (0.26–0.35 wt%) contents. In addition, their rare earth elemental patterns show a slight right-dip pattern with (La/Gd) N values of ~1.28 and (Gd/Yb) N values of ~1.31. Given the evolutionary trend from magnesium-rich intermediate to acid series, the boninite-series are therefore used to describe the vlocanic rocks. Zircon U-Pb isotopic dating on these boninite-series volcanic rocks yielded an age of ca. 79.3 ± 2.0 Ma, after the closure of the Bangong-Nujiang Tethyan Ocean (BNTO) that occurred before 96 Ma. The newly recognized boninite-series volcanic rocks probably formed more than 20 Ma after the latest regional magmatism related to subduction process and thus the subduction setting is not suitable for these boninite-series volcanic rocks. The enrichment in compatible elements and depletion in high field elements indicate the Rutog boninite-series originated from a severely depleted mantle while several lines of evidence (e.g., the enrichment in light rare earth elements, large iron lithophile elements) imply that the mantle source has been modified by continental crust. Given the widespread Cretaceous high Sr/Y magmatic rocks within BNSZ, the Rutog boninite-series rocks may provide an example of the crust-mantle interaction as a result of the delamination in a partially thickened and cratonized convergent margin during the late Cretaceous within BNSZ, central Tibetan Plateau. • The intra-continental boninite-series volcanic rocks first found in Tibet. • The boninitic rocks formed in 79 Ma later than the closure of the Bangong-Nujiang Tethyan Ocean (BNTO). • They originated from mixed source of DM and continent crust/marine sediments. [ABSTRACT FROM AUTHOR]