Abstract

Zircons separated from an rhyolite sample in the Dong Trau formation, in the southern of Hà Tĩnh province were dated to determine the protolith age for the complex. Sixteen LA-ICP-MS U-Pb zircon analyses give concordant ages concentrated at 256 Ma (weighted mean). These results indicate the protolith age of the rhyolite (primary magma crystallization age). The value of this age are close to the analytical results pf the whole rock by Rb-Sr method and biotite Rb-Sr method. Therefore the crystallization age of the rhyolite from the Đồng Trầu formation corresponded period late Permian to early Triassic.