Geochemistry of sedimentary and igneous rocks in Sam Nua Depression Zone, Northern Vietnam

Abstract

The Sam Nua Depression Zone is a NW-SE trending tectonic unit exposed over 400 km from Northern Vietnam through Laos to Southwestern China. It represents the Northern periphery of Indochina block contiguous to South China block by Songma fault. It consists of Paleozoic, Mesozoic and Cenozoic sedimentary and igneous rocks with various chemical compositions. The Paleozoic passive continental margin sediments and the associated mafic-ultramafic rocks represent the remnants of Paleo-oceanic lithosphere that accreted into the northern edge of the Indochina block while the Triassic terrigenous, terrigeno-effusive and igneous rocks are related with continental arc setting. The Jurrasic and Cenozoic igneous rock occurrences preserve chemical characteristics of within plate tectonic setting.