Detrital zircon record from major rivers of Luzon Island: implications for Cenozoic continental growth in SE Asia.

The significance of continental crustal growth in the Phanerozoic has long been debated. As an active accretionary orogenic belt, SE Asia has been proposed to be one of the best archives for studying juvenile continental growth in the Cenozoic, despite the limited availability of data. Therefore, we conducted for the first time a comprehensive U-Pb and Hf isotopic analysis of detrital zircons separated from major rivers of Luzon Island, the largest landmass of the Philippine Archipelago. U-Pb ages of these zircons are predominantly <50 Ma, consistent with literature zircon U-Pb ages or whole-rock K-Ar ages. A sample from the central Sierra Madre, however, contains zircons with age clusters at 110-70 and 180-140 Ma, supporting the presence of Mesozoic basement rock units in that area. All dated zircons show positive and high εHf(T) values that plot close to the depleted mantle. Therefore, we argue that pre-Cenozoic continental materials played insignificant roles in the construction of Luzon Island, and that this part of the southeastern Eurasian margin consists predominantly of a juvenile terrane where substantial continental crustal growth occurred in the Cenozoic. [ABSTRACT FROM AUTHOR]