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The composition and geological evolution of pre-Cryogenian material in the Tibetan Plateau and its surrounding areas have played an important role in studying the formation and evolution of early supercontinents on Earth. This paper systematically summarizes the characteristics of pre-Cryogenian sedimentation, paleontology, magmatism, and metamorphism in the Tibetan Plateau and its surrounding areas. Based on existing data, the records of pre-Cryogenian sedimentation and paleontology are mainly concentrated in the Meso–Neoproterozoic, with relatively few records from the Paleoproterozoic or earlier. The oldest geological record is the Hadean detrital zircons in the metamorphosed sedimentary rocks of the Himalaya and Qamdo areas (ca. 4.0 Ga). The Tibetan Plateau and surrounding areas preserve records related to the formation and evolution of the Kenor supercraton, and the Columbia, Rodinia, and Gondwana supercontinents. Pre-Cryogenian basements can be divided into three types: Tarim-, Yangtze-, and Lhasa-type. The Tarim-type basement has a paleogeographic affinity with the northern margins of the Australian and Indian continents and lacks detrital zircon age peaks and magmatic-metamorphic records related to the Rodinia assembly (ca. 1.3–0.9 Ga). The Yangtze-type basement records volcanic activity related to global cooling in the latest pre-Cryogenian period and contains Meso–Neoproterozoic stromatolite and micropaleoflora fossils, as well as magmatic-metamorphic records related to Rodinia assembly (ca. 1.1–1.0 Ga). The Lhasa-type basement is characterized by Neoproterozoic rift-related sediment records (ca. 900 Ma) and high-pressure metamorphic events (ca. 650 Ma), with a prominent peak of detrital zircon ages of ca. 1.2–1.1 Ga. It is likely to have a paleogeographic affinity with the African continent. [ABSTRACT FROM AUTHOR]

The results of zircon U-Pb age dating and whole-rock geochemistry for the Late Cretaceous Nize granodiorite porphyries, combined with analysis of near-coeval structural deformation of the Lower Cretaceous Langshan Formation, provide new data to better understand the tectonic evolution of the northern Lhasa subterrane, central Tibet. Zircon U-Pb ages of 89.2 ± 0.3 Ma to 87.8 ± 0.3 Ma indicate emplacement during the Late Cretaceous. Granodiorite porphyry intrusions were contemporaneous with the development of a regional angular unconformity, overlain by the Upper Cretaceous Jingzhushan (or Abushan) Formation, within the collision zone between the South Qiangtang and Lhasa terranes. Geochemical data for Nize granodiorite porphyries indicate that they have a calc-alkaline composition enriched in large-ion lithophile elements and light rare earth elements and depleted in high-field-strength elements and heavy rare earth elements. High Al2O3 and Sr contents, low Yb and Y contents, and high Sr/Y ratios are similar to adakitic magmas. Structural analysis indicates two stages of deformation (D1 and D2), with D1 forming the focus of the present study. The D1 deformation is represented by large-scale faults and records two periods of faulting. These periods are recognized as early compressional thrust faulting and a dominant late stage characterized by normal faulting and extension, with the latter stages of D1 being near-coeval with the emplacement of the Nize granodiorite porphyries. The combination of zircon ages, geochemical data, and structural analysis indicates that the Nize granodiorite porphyries formed after collision of the South Qiangtang and Lhasa terranes. Adakitic magma derived from partial melting of the thickened lower or middle crust resulted from lithospheric delamination that may have been promoted by the convective removal of deeper lithospheric mantle. [ABSTRACT FROM AUTHOR]

[Display omitted] • The northward subduction initiation of the meso -Tethys Ocean was diachronous from the east (∼240–230 Ma) to the west (213–194 Ma). • The collision and slab breakoff during the closure of the Paleo-Tethys Ocean were vital to the northward subduction initiation. • The southward subduction of the meso -Tethys Ocean was initiated no later than the Middle Triassic. • The southward subduction was attributed to the closure of the Paleo-Tethys Ocean and the spreading of the NeoTethys Ocean. The initiation of subduction is widely recognized as a critical process associated with the evolution of the meso -Tethys Ocean. Here, we present zircon U–Pb, Lu–Hf isotope, and whole-rock geochemical data for a suite of Triassic–Jurassic magmatic rocks from the central Tibetan Plateau, with the aim of gaining insights into the subduction initiation of the Bangong–Nujiang Tethys Ocean (BNTO). Early Triassic trachyandesite (248 Ma) from the South Qiangtang terrane resemble intraplate magma and probably resulted from magmatic activity at the passive continental margin during the BNTO opening. Late Triassic S-type granodiorite (220 Ma) and Middle Jurassic SSZ-type gabbro (∼165 Ma) from the South Qiangtang terrane may result from the northward subduction of the BNTO oceanic lithosphere. Jurassic granitoids (I and S type; 193–177 Ma) and metamorphic rocks (179–174 Ma) from the Amdo and Jiayuqiao subterranes are related to the northward subduction of the BNTO oceanic lithosphere. Middle–Late Jurassic diorites (164–162 Ma) from the Central Lhasa subterrane have geochemical features of continental margin arc magma with a sediment component, and these are derived from the southward subduction of the BNTO oceanic lithosphere. Finally, this Triassic–Jurassic magmatic suite of various geochemical features was combined with the results of previous studies, and we suggest that the initiation of northward BNTO subduction was probably diachronous from the east (∼240–230 Ma) to the west (213–194 Ma). This initiation resulted both from collision and slab breakoff during the closure of the Longmuco–Shuanghu–Lancangjiang Paleo-Tethys Ocean and considerable density and rheology contrasts between the thick oceanic lithosphere and continental lithosphere. The southward subduction was initiated no later than the Middle Triassic and was attributed to the closure of the Sumdo Paleo-Tethys Ocean and the spreading of the Indus–Yarlung Zangbo NeoTethys Ocean. [ABSTRACT FROM AUTHOR]

The Tibetan Plateau is located in the eastern Himalayan–Alpine orogen, an area where previous research has focused on ophiolites and a high-pressure metamorphic belt, whereas comparatively little research has been undertaken on the Tibetan basement. Cambrian granitic gneiss crops out in the Duguer area of the South Qiangtang terrane in northern Tibet and yields zircon laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) U–Pb ages of 502–492 Ma, providing insight into the possible existence of basement rocks within the South Qiangtang terrane. The granitic gneisses are geochemically similar to high-K, calc-alkaline S-type granites, and Hf isotopic analysis of zircons within the gneisses yields negativeεHf(t) values (–7.4 to – 1.1) and old zircon Hf model ages (TDMC = 1757–1406 Ma). These granitic gneisses were generated by partial melting of ancient pelitic rocks, and the resulting melts were contaminated by a small amount of mantle-derived material. Combining our new data with previous research, we conclude that these Cambrian granitic gneisses developed in a post-collisional tectonic setting after Pan-African tectonism. This suggests that the South Qiangtang terrane might have the same early Palaeozoic crystalline basement as the Lhasa, Himalaya, Baoshan, Gongshan, and Tengchong terranes. [ABSTRACT FROM AUTHOR]

The tectono-magmatic evolution of the Bangong-Nujiang Tethyan Ocean (BNO) plays a crucial role in understanding the Tibetan Plateau accretion before the Cenozoic India-Asia collision. The microcontinents and oceanic plateau recognized recently within the BNO provide important clues for constructing the subduction process between BNO and the Qiangtang terrane. In this contribution, we provide a comprehensive overview of the multidisciplinary information from magmatism, metamorphism, stratigraphy, geochronology, geochemistry, Hf isotopic data, ophiolite suites, and paleomagnetism to gain insights into the spatially and temporally related geodynamic processes of the BNO. A compilation of geochronological data indicates that the emplacement of the diverse igneous suites occurred mainly during three stages: stage 1 (190–150 Ma), stage 2 (130–110 Ma), and stage 3 (110–70 Ma). The igneous suites, including granitoids, mafic intrusions and volcanic rocks, formed two arcuate E–W trending belts that parallel the Bangong-Nujiang suture zone and are correlated to the double sided subduction of the BNO. We infer that the BNO initially opened at ~270Ma between the Lhasa terrane and Qiangtang terrane, although the relationship between the BNO and Longmu Tso-Shuanghu paleo-Tethyan ocean is still unclear. Age data related to metamorphism, arc magmatism, supra-subduction zoneophiolites, and sedimentary strata indicate that the northward subduction of the BNO started at ~190 Ma, followed by the subduction of microcontinents beneath the Qiangtang terrane at 195 Ma. In contrast, the subsequent southward subduction of the BNO started at ~170 Ma, resulting in the opening of the Shiquanhe-Namuco ocean. As indicated by the high Mg volcanic suite, intra-ocean subduction within the BNO also occurred during 170-145Ma, possibly related to the resistance from subduction of ocean plateau and slab retreat. Based on evidence from petrology, isotope geochronology, and isotopic geochemistry, we also infer that the magmatic lull during 145-130Ma is related to the slab subduction of ocean plateau beneath the southern Qiangtang subterrane. The closure of the BNO was most likely diachronous, which started as early as Late Jurassic and continued to the late Early Cretaceous (120-110Ma). • Initial opening of BNO at ~270 Ma and northward subduction at ~190 Ma. • Southward subduction started at ~170 Ma, leading to the opening of SNO. • Ocean plateau mechanism for intra-ocean subduction of BNO and magmatic lull during 145–130 Ma. • Diachronous closure of the BNO initiated at 150 Ma and the final closure during 110–100 Ma. [ABSTRACT FROM AUTHOR]