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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]

The Tibetan Plateau is located in the eastern part of the Tethys-Himalayan megatectonic domain and consists of a series of microplates that successively accreted to the southern edge of the Eurasian Continent. These microplates have undergone complex evolutionary processes during rifting, drift and collision. The gravity and magnetic anomalies show that the anomaly characteristics on the Tibetan Plateau is significantly different in the north-south direction, from the Qaidam Microplate to the Lhasa Microplate. In this paper, we apply an improved Logistic Filter method, combined with the upward continuation of gravity anomalies, to identify multi-scale tectonic boundaries in the Tibetan Plateau region. The results show that the edge detection results correspond well in space with fracture zones and suture/ophiolite zones. Also, there are clear discontinuities along both sides of the middle and western sections of the Bangong-Nujiang Suture Zone and the eastern section of the Jinshajiang-Ailaoshan Suture Zone. We refined the boundaries of five microplates, including the South and North Qiangtang and the South, Central and North Lhasa, in the southern Tibetan Plateau. Then, we analyzed the evolutionary processes of these microplates and the transformation of the types to which the microplates belonged during different historical periods by combining relevant evidences from other geological records and plate reconstruction. These microplates are strongly related to the evolutionary history of the Tethys Ocean. The closure of the Neo-Tethys Ocean triggered a large-scale orogeny between the Indo-Asian continents, and these microplates were eventually accreted in the orogenic belt. We analyze the formation patterns and boundary types of microplates in the evolutionary process and then divide into three stages, i.e., rifting-derived, accretion-derived, and subduction-derived stages. The transformation patterns of microplate types at different stages provide a new perspective for the study of the evolution of mega-orogenic belts. • Tectonic interpretation and microplate division of the Tibetan Plateau with gravity and magnetic data. • Multi-scale edge detection at different depths on the Tibetan Plateau by the improved Logistic Filter method. • A transformation pattern of microplate types during the evolution of Qiangtang and Lhasa microplates. [ABSTRACT FROM AUTHOR]