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Ref ID: 28411
Ref Type: Journal Article
Authors: Lan, Ching-Yin
Chung, Sun-Lin
Shen, Jason Jiun-San
Lo Ching-Hua
Wang, Pei-Ling
Hoa, Tran Trong
Thanh, Hoang Huu
Mertzman, Stanley A.
Title: Geochemical and Sr-Nd isotopic characteristics of granite rocks from northern Vietnam
Date: 2000
Source: Journal of Asian Earth Sciences
DOI: 10.1016/S1367-9120(99)00063-2
Abstract: Five major felsic igneous suites from northern Vietnam, with ages from mid-Proterozoic to early Cenozoic, were studied. Representative granitic rocks from the Posen Complex (mid-Proterozoic) and the Dienbien Complex (late Permian to early Triassic) show geochemical characteristics similar to those of calc-alkaline to high-K calc-alkaline I-type granites. However, the former, located in the South China block, has significantly higher initial Nd isotopic ratios [εNd(T)=+0.7 to +1.5] and older Nd isotopic model ages (TDM∼1.7 Ga) than the latter [εNd(T)=−4.7 to −9.7
TDM∼1.3–1.5 Ga] which were emplaced south of the Song Ma Suture and thus in the Indochina block. The generation of both complexes may be attributed to subduction-related processes that occurred in two distinct crustal provenances with different degrees of mantle inputs. On the other hand, Jurassic to Cretaceous granitic rocks from the Phusaphin Complex, contemporaneous rhyolites from the Tule Basin, and late Paleogene granitic rocks from the Yeyensun Complex, all exposed in the South China block between the Ailao Shan–Red River shear zone and the Song Ma Suture, display geochemical features similar to those of A-type granites with intermediate εNd(T) values (+0.6 to −2.8) and younger TDM ages (0.6–1.1 Ga). These magmas are suggested to have been generated as a consequence of intraplate extension in the western part of the South China block (Yunnan), and to have been transported to their present position by mid-Tertiary continental extrusion along the Ailao Shan–Red River shear zone related to the India–Asia collision. Overall, the isotopic and model age data, reported in this study indicate that in northern Vietnam, the most important crust formation episode took place in the Proterozoic. Likewise, repeated mantle inputs have played a role in the petrogenesis of Phanerozoic granitic rocks.
Date Created: 2/8/2012
Volume: 18
Number: 3
Page Start: 267
Page End: 280