Zircon U‐Pb Chronology and Hf Isotope From the Palawan‐Mindoro Block, Philippines: Implication to Provenance and Tectonic Evolution of the South China Sea

Abstract

AbstractThe continental margin of Southeast Asia evolved from a dominantly Andean‐type active margin during Mesozoic to a Western Pacific‐type since Late Cretaceous. With the spreading of the South China Sea, the Palawan‐Mindoro Block drifted from mainland Asia and the Cenozoic strata provide an excellent window to gain insights into the tectonic evolution of the margin of Southeast Asia. Here we present U‐Pb age and Hf isotopic data on detrital zircon grains from Cenozoic sedimentary rocks in the Palawan‐Mindoro Block, Philippines, to evaluate the provenance and tectonic evolution of the South China Sea. Zircon grains in Eocene‐Miocene sedimentary rocks from the Palawan‐Mindoro Block show a wide range in age from 60 to 2700 Ma, with four major age groups of 80–120 Ma, 160–180 Ma, 1600–2100 Ma, and 2200–2700 Ma. The εHf(t) of the zircon grains of the samples from Mindoro Island range from −39 to +13.7, and similar Hf isotopic composition is recorded in Paleogene and Neogene strata. Zircon U‐Pb ages and Hf isotopic data of the Eocene samples from the Palawan‐Mindoro Block show a similar pattern with those from Taiwan, which suggests that the Palawan‐Mindoro Block was attached to the margin of South China during Late Cretaceous‐Eocene times. The difference of zircon U‐Pb age composition in the Miocene samples between the Palawan‐Mindoro Block and Taiwan reflects southward drifting of the Palawan‐Mindoro Block and seafloor spreading of the South China Sea at that time.