Geochemistry and U-Pb zircon age of the Đèo Khế granite
La Mai Sơn, Hoàng Thị Hồng Anh, Bùi Thế Anh, Phạm Minh, Phạm Trung Hiếu
The Đèo Khế granite has been traditionally considered as a member of the Xóm 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 Đèo 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 Đèo 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 Đèo Khế granite obtained from this study is much younger than that reported previously (-2264 Ma). Thus, assignment of the Đèo Khế granite to Xóm Giấu complex should be further studied.
Người biên tập: TS. Nguyễn Thị Bích Thuỷ