Linking the Indochina block and Gondwana during the early Paleozoic: evidence from U-Pb ages and Hf isotopes of detrital zircons

To constrain the paleoposition of Indochina within Gondwana during the Early Paleozoic, we performed in-situ U-Pb and Hf isotope analyses on detrital zircons from three river sediment samples in the Truong Son Belt of the Indochina block. The age distributions yield dominant Neoarchean (~2.5Ga), Mesoproterozoic (1.7-1.4Ga), Grenvillian (~0.95Ga), and Pan-African (0.65-0.5Ga) age groups and minor Paleo- to Meso-archean zircons. Hf isotope compositions of zircons for each age group exhibit large ranges of εHf_(T), suggesting that the zircon host rocks have diverse sources. The oldest Hf model ages for zircons of Neoarchean, Grenvillian, and Pan-African age group yield ~3.7Ga or older, while those of Mesoproterozoic age group show ~3.3Ga. The remarkable similarity of age distribution and Hf isotope compositions among detrital zircons of Indochina and those of Tethyan Himalaya, western Cathaysia, and Qiangtang suggests that Indochina was located outboard of Qiangtang and south of South China in the Indian margin of Gondwana during the Early Paleozoic. Our results are consistent with the paleontological correlations of east Gondwana margin during the Early Paleozoic.