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Provenance analyses of Lower to Middle Triassic strata from the Greater Youjiang Basin along with the Permian strata of Hainan Island, provide a record of the collisional assembly of the South China Craton and Indochina Block and their incorporation into Asia. Detrital zircons from Lower and Middle Triassic samples show similar overall age spectra ranging from Archean to Triassic with major age groups at 300–250 Ma, 480–420 Ma, and 1200–900 Ma, as well as at 400–300 Ma in one Triassic sample. Permian siltstones from Hainan Island, to the southeast of the Greater Youjiang Basin, record different age spectra with major age groups at 400–300 Ma and 530–420 Ma and subordinate components at 1200–900 Ma and 1900–1700 Ma. These age data in combination with available paleocurrent data and regional geological relations suggest that Precambrian detrital zircons were derived from the Precambrian basement or recycled from the overlying early Paleozoic sedimentary rocks that contain Precambrian detritus. Early Paleozoic detrital zircons were derived from igneous rocks in the South China Craton. Devonian-Triassic detrital zircons in the Triassic strata were likely sourced from coeval magmatic activity related to closure of Paleo-Tethys branch ocean that lay to the southwest, whereas 400–300 Ma detrital zircons in the Permian siltstones of Hainan Island were likely derived from a Paleozoic magmatic arc source that extended along the eastern-southeastern margin of China from Hainan Island to Japan in response to subduction of the Paleo-Pacific oceanic crust. Detrital zircon, trace element, and sandstone modal data for Permo-Triassic strata from the Greater Youjiang Basin indicate that the basin evolved from a trailing-edge passive margin setting to a peripheral foreland basin during closure of the Paleo-Tethys Ocean and collision between Indochina and South China. The initiation time of the foreland basin decreases from southeast to southwest across the basin, probably reflecting oblique collision. In contrast, the Permian strata on Hainan Island record a provenance history distinct from the Greater Youjiang Basin, which is related to late Paleozoic to Mesozoic subduction of the Paleo-Pacific Plate beneath South China. [ABSTRACT FROM AUTHOR]

Paleozoic paleogeographic and tectonic evolution of blocks within the eastern Tethyan Orogenic Belt remains ambiguous due to limited and fragmentary geological records. New detrital zircon U-Pb-Hf isotopic analyses integrated with published data from Paleozoic strata in Hainan Island reveal three significant changes in provenance, providing excellent insights into the assembly record with adjacent blocks. Detrital zircon age spectra of early Cambrian strata from Hainan Island yield a major peak at 1.17 Ga, resembling equivalent units from the Kontum Massif (South Indochina) and were likely sourced from Australia. Mid-late Cambrian successions contain a dominantly 1.78–1.40 Ga zircon population sourced from Precambrian rocks on the island. Detrital zircon age spectra of late Ordovician samples yield major age peaks of 0.97 Ga and 0.45 Ga that originated from India and Indochina, respectively. The two provenance shifts in the Cambrian-Ordovician strata are interpreted to result from the consumption of a branch of the Proto-Tethys associated with progressive amalgamation of the Kontum (South Indochina)-Hainan-Australia block and Truong Son (North Indochina)-India-South China block. The late Devonian-early Carboniferous succession encompass significant ca. 368 Ma zircons derived from arc-related rocks that formed during initial subduction of the main Paleo-Tethys Ocean. The lack of ca. 970 Ma Indian-derived zircons within the Devonian-Carboniferous units suggests that Hainan Island rifted away from Gondwana before the late Devonian. Late Paleozoic detrital zircon age pattern of Hainan Island coincides with that of Indochina and North Qiangtang, but is distinct from that of Gondwana and South China, indicating that the coherent Hainan-Indochina-North Qiangtang continental sliver was separated from Gondwana and South China by the main Paleo-Tethys Ocean and the Ailaoshan Ocean, respectively. • Hainan was linked with Australia and part of Indochina in the Cambrian, and was subsequently involved in the assembly of Indochina. • Hainan-Indochina-North Qiangtang block (HINQB) was a coherent continental sliver within the Paleo-Tethys Ocean during the late Paleozoic. • In the Carboniferous the HINQB was separated from South China by the Ailaoshan Ocean and from Gondwana by the main Paleo-Tethys Ocean. [ABSTRACT FROM AUTHOR]

[Display omitted] • Polyphase metamorphism is observed in the Baoban Complex, Hainan Island. • SIMS zircon U-Pb geochronological dating yielded a metamorphic age of 462 Ma. • The peak metamorphic conditions are 715–650 °C/0.91–0.86 GPa. • The Ordovician metamorphism is associated with accretionary event along the northern Gondwana margin. Understanding the metamorphic evolution of Hainan Island is crucial to constraining its geodynamic history. Here, we report evidence for a hitherto unknown early Paleozoic amphibolite-facies event that affected the Baoban Complex in southwestern Hainan Island and establish its role in the tectonic history of the northeast margin of Gondwana. SIMS and LA-ICP-MS zircon U-Pb dating reveals a polyphase metamorphic history, consisting of three age groups. Group 1 performed on the outermost zircon rim with the lowest concentration of HREE and U, gives a weighted average age of 462 ± 7 Ma that corresponds to the metamorphic stage of the crystallization of garnet. Group 2 displays moderate HREE and low Th/U ratios (less than 0.079). Concordant U-Pb ages range from 1371 to 1017 Ma which record metamorphism in the Mesoproterozoic. Group 3 consists of typical igneous-derived detrital zircons with ages ranging from 3095 to 1380 Ma. The age spectrum is consistent with the siliciclastic protolith lithologies of the Baoban Complex. P-T conditions for the garnet-forming stage (Di + Grt + An + Hb + Q) were estimated by geothermobarometry at 715–650 °C and 0.91–0.86 GPa, which is consistent with 708 ± 44 °C conducted on zircons of Group 1 through Ti-in-zircon thermometry. P-T estimates and zircon U-Pb ages reveal that the amphibolite-facies metamorphism occurred at 462 Ma. The end-Mesoproterozoic metamorphism overlapped in age with the assembly of Rodinia. Combing with regional tectonothermal history, we infer that the Ordovician amphibolite-facies metamorphism formed during accretionary orogenesis along the northern margin of East Gondwana. [ABSTRACT FROM AUTHOR]