Position of South China and Indochina along northern Gondwana margin during the Ediacaran–Silurian period

Abstract

The South China Block (SCB) has often been taken as an integral member of Gondwana at its northern margin, but it remains contentious regarding when and how it joined Gondwana, its precise position in Gondwana, and what other continent(s) might have been adjacent to it at the time. This study reports new detrital zircon U-Pb and Hf isotopic data of twelve Ediacaran-Silurian siliciclastic samples from three field regions along the western margin of the SCB. They show two prevailing age populations of 810–790 Ma and 550–520 Ma, and minor ca. 2500 Ma, ca. 1850 Ma, ca. 1200 Ma and ca. 980 Ma peaks in various units. In combination with the regional lithofacies evolution, provenance analysis demonstrates that the uplifted western SCB provided a persistent supply of 810–790 Ma zircons from local Tonian granites to the Ediacaran-Silurian sediments, whereas the 550–520 Ma zircons were probably derived exotically from a magmatic arc. Provenance analysis also reveals that the SCB and Indochina have a close provenance linkage. We interpret that the exotic magmatic arc was along the northern Indian margin with the subducting lower plate carrying SCB-Indochina to eventually collide with Indian Gondwana during Cambro-Ordovician time. The uplift of the western SCB during the time likely reflects the far-field tectonic compression of the collision.