T41B-2889
Tectonic Implications of Paleoproterozoic Deo Khe Granitoids in Northwestern Vietnam

Thursday, 17 December 2015
Poster Hall (Moscone South)
Thi Hong Anh Hoang1, Yongjae Yu1, Trung Hieu Pham2, Sung Hi Choi1, Vu Le Tu3 and La Mai Son4, (1)Chungnam National University, Daejeon, South Korea, (2)Faculty of Geology, University of Science VNU-HCM, Geology, Ho Chi Minh, Vietnam, (3)University of Mining and Geology, Ha Noi, Vietnam, (4)North Vietnam Geological Mapping Division, Ha Noi, Vietnam
Abstract:
An integrated study of petrographic description, zircon U/Pb geochronology, and Hf isotopic analysis was carried out on the medium-grained two-mica Deo Khe Granitoids (DKG) in northwestern Vietnam. U/Pb zircon ages were 1855-1873 Ma, interpreted as the time of magma crystallization. On the basis of Hf isotopic compositions, a single-stage Hf model ages were estimated as 3.3-2.8 Ga. Values of Hf isotopes εHf (t) range from -23.6 to -17.5, suggesting that the DKG are products of reworked Archean crustal rocks. A similar sequence of tectonic events including the presence of 2.8-2.9 Ga tonalite-trondhjemite-granodiorite (TTG) gneiss, metamorphic development of TTG gneiss at 1.9-2.0 Ga, and 1.85 Ga magmatic activity were recognized both in Yangtze block and northwestern Vietnam. Therefore we propose that basement rocks in northern Vietnam are similar to those found along southern China.

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