Detrital zircon U Pb age distributions and Hf isotopic constraints of the Ailaoshan-Song Ma Suture Zone and their paleogeographic implications for the Eastern Paleo-Tethys evolution

Abstract

During the Late Paleozoic to Cenozoic, with the closure of the Tethys oceans, the East and/or Southeast Asia was amalgamated by individual blocks. In order to understand the Paleogeography of the Eastern Paleo-Tethys, a systematic U Pb dating on 11 samples have conducted to constrain the age and provenance of the elements forming the Ailaoshan-Song Ma mélange. These samples consist of the ophiolitic mélange zone (6 samples), the sedimentary cover of the Indochina block (4 samples), and the post-orogenic continental deposits (1 samples). The achieved detrital zircon age distribution, and the corresponding in-situ Hf isotopic recorder allow us to discuss the provenances of the materials involved in the tectonic processes during the subduction and collision. Three units (M1, M2, M3), which stand for the different segment of the suture zone , could be separated based on the differences in zircon age clusters and Hf isotopic values. These differences might be due to the variety of provenances. Combined with the previous works, especially our work on the Song Chay mélange zone, we concluded that both upper and lower plates are potential provenances for the mélanges between South China block and Indochina block. Along the suture zone, the component of the mélange presents a significant heterogeneity.