Geochemistry and U-Pb zircon age of the Đo Khế granite

La Mai Sơn, Hong Thị Hồng Anh, Bi Thế Anh, Phạm Minh, Phạm Trung Hiếu

The Đo Khế granite has been traditionally considered as a member of the Xm Giấu complex and was outcropped under the form of small intrusive bodies which have petrographical composition mainly of leucocratic granite, rich in K-feldspar. Zircons selected from two Đo Khế granite samples (V0857 and V0860) were analyzed for the U-Pb isotope by LA-ICP-MS which yielded crystallization age of ca. 1.85 Ga. This age value indicated the existence of a magmatic activity during Paleoproterozoic time in the Phan Si Pan zone, northwestem Việt Nam. This also shown that the Phan Si Pan zone may relate to the assemblage of Columbia supercontinent in Paleoproterozoic time. The new U-pb zircon results from our study, together with the emplacement age of the Đo Khế granite together with l.8-2.0 Ga metamorphic event recorded from granitogneiss of Ca Vinh complex and 1.9-2.0 Ga from orthogneiss of the River Red shear zone suggested that the Yangtze Block and the northwestem part of Việt Nam shared a similarity of magmatic-tectonic evolution during Neoarchean - Paleoproterozoic. Moreover the emplacement age of the Đo Khế granite obtained from this study is much younger than that reported previously (-2264 Ma). Thus, assignment of the Đo Khế granite to Xm Giấu complex should be further studied.

Người bin tập: TS. Nguyễn Thị Bch Thuỷ