U-Pb zircon age of granitoid from the Điện Biên complex of Mường Tè area and its tectonic significances
Phạm Trung Hiếu
Granitoid rocks of the Điện Biên complex in the Mường Tè region are mainly distributed in the upper course of Đà river. Petrographical composition of the rocks varies from gabbro, gabrodiorite, diorite, granodiorite to granite with biotite and hornblende. Zircon separated from quartz diorite and granodiorite of the Điện Biên complex was use for age dating by LA-ICP-MS U-Pb isotope method, which yielded mean 206Pb/238U age of 280 and 277 Ma, corresponding to early Permian time. In combination with internal structure of zircon, these age values are considered as the emplacement age of granitoid. εHf(t) values from zircon vary from 4.92 to 9.27 with an average of 6.74 and the Hf model age (TDM1-TDM2) values concentrated around of 650 to 900 Ma. Hf isotope characteristics of rocks, in combination with the model ages, suggest that the granitoid was generated by partial melting of Neoproterozoic oceanic basalt.
Keywords: Điện Biên complex, granitoid, U-Pb, Hf zircon