Petrogenesis and tectonic implications of Early Cretaceous volcanic rocks from Lingshan Island in the Sulu Orogenic Belt

The Dabie-Sulu orogenic belt in eastern China marks the boundary between the Yangtze Block and the North China Block. Here we investigate a suite of volcanic rocks from Lingshan Island in the Sulu belt comprising rhyolite, trachyte, trachyandesite and basaltic trachyandesite. We present petrological, geochemical and zircon U-Pb ages and Hf-O isotope data with a view to gain insights on the petrogenesis and tectonic implications. SHRIMP II analyses of zircon grains from the rhyolite yield Pb-206/U-238 age of 127.6 +/- 1.3 Ma and LA-MC-ICPMS dating show 126.3 +/- 1.2 Ma and 1273 +/- 1.1 Ma, together constraining the eruption time as Early Cretaceous. LA-MC-ICP-MS analyses of zircon grains from the andesitic rocks yield Pb-206/U-238 ages of 129.0 +/- 1.6 Ma, 129.8 +/- 1.5 Ma and 130.9 +/- 1.0 Ma. Geochemically, the rhyolite shows shoshonitic features with low MgO and Cr, but high Na2O + K2O. The zircon grains from these rocks yield negative epsilon(Hf)(t) values and low 6180 values, and these together with the presence of Neoproterozoic inherited zircons suggest that the magma source involved melting of the Yangtze crust. The andesitic rocks, including basaltic trachyandesite, trachyandesite and trachyte, show a wide range of SiO2, Mg# values, and Cr, enriched in WE and LREE, depleted in HFSE (Nb, Ta and Ti), and have significantly negative zircon epsilon(Hf)(t) values, suggesting derivation from subcontinental lithosphere mantle that was metasomatized by felsic melts. Our results, integrated with those from previous studies suggest heterogeneous magma involving the mixing of mantle and crustal sources within an extensional setting in the Early Cretaceous. (C) 2018 Elsevier B.V. All rights reserved.