Hf isotopes from Palawan Continental Terrane, Philippines-clues to the evolution of sediment sources

Abstract

The age spectra of detrital zircons in meta-sediments from Palawan Island, Mindoro Island, Tablas, and the Buruanga Peninsula of Panay Island in the Central Philippines provide evidence for the provenance of these zircons in the northern part of the Cathaysia Block, SE China. These islands form the western part of the Philippine archipelago and are part of the Palawan Continental Terrane (PCT), which is considered to be a rifted fragment of the continental margin of SE China which moved south from its original location as a consequence of the opening of the South China Sea (SCS). This rifted fragment contains records of the history of the continental margin of SE China. In this study, we present Hf isotopic compositions of previously dated zircon grains by U-Pb dating technique, in meta-sediments from PCT. The results indicate that for several age groups, in particular those of 80-93, 245-270, and 400-465 Ma, εHf(T) of the zircons from the PCT is higher than in corresponding zircons from mainland SE China implying greater contributions from the mantle to the magmas from which these zircons crystallized. This suggests that most of the zircons found in the PCT were not transported over long distances from the interior of the SE Chinese cratons but are derived from regional sources, which are represented by the Camarong Gneiss and the rhyolite in Mindoro.