Geochemical and Sr‐Nd‐Hf‐Pb Isotopic Constraints the Petrogenesis and Origin of Basalts from the Southern Okinawa Trough

Okinawa Trough is a nascent spreading back-arc basin, developed between East China Sea continental shelf and the Ryukyu Arc–Trench System (Fig. 1), and its formation and evolution is intimately related to the subduction process of the Philippine Sea Plate beneath the Eurasian Plate since the late Miocene (Yan and Shi, 2014). Investigations on the Okinawa Trough have commenced since the 1970s or earlier (Lee et al., 1980; Letouzey and Kimura, 1985; Sibuet et al., 1998; Liang et al., 2001; Arai et al., 2017), and acquired a large amounts of geological and geophysical data. However, the insights on petrogenesis and mantle sources of the trough is inconsistent, although there is many studies focused on the petrology and geochemistry of the trough lavas (e.g., Shino and Kato, 2000; Hoang and Uto, 2006; Yan and Shi, 2014; Guo et al., 2018). Here we present Hf isotope ratios for six basaltic lavas from southwest and middle part of the Okinawa Trough for the first time. These data, combined with major, trace element and Sr-Nd-Pb isotopic compositions for these samples and data from literature, are used to constrain petrogenesis and the nature of mantle sources beneath the trough. *