Abstract

The U-Pb zircon (LA-ICP-MS) age of trachyrhyolite and rhyolite collected in the Tú Lệ Depression ranges mainly from 93 to 118 Ma, corresponding to the Early-Late Cretaceous. These results conform to almost all published ages. The rhyolite sample which yields the age of 256 Ma may have genetic relation with Permian felsic rocks in the Sông Đà intracontinental rift. This sample, perhaps, belongs to the basement of the Tú Lệ Depression.

The Tú Lệ Depression is an independent structure; it was filled mainly with alkaline-subalkaline felsic extrusive rocks, while in the Sông Đà intracontinental rift mafic-ultramafic extrusive rocks are widespread.