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摘要
Due to the inaccessible of the Laos, there are few papers about the Indochina plate in Laos. This paper reports new zircon U-Pb ages, Nd isotope and whole-rock major, trace element data for granites from the North Laos. Zircon LA-ICP-MS dating for the Nuna granite pluton yields weighted mean ages of 258.7 +/- 1.9Ma, 259.0 +/- 1.7Ma and 251.0 +/- 0.9Ma, suggesting that the crystallization age of the Nuna pluton is Late Permian. Petrological and geochemical data show that the pluton is characterized by high silicon (the average content of SiO2 is 72.94%), abundant ferrous (the average content of FeOT is 2.91%) and alkali ((Na2O+K2O) of granites with an average of 9.2%), depleted magnesium (the average content of MgO is 0.11%). Moreover, the granite is enriched in Zr, Hf, Rb, Th, U and LREE, depleted of Sr, Eu, Ti, Ba, and high magmatic crystallization temperature (with average temperature of 927 degrees C), indicating A-type granite geochemical characters. The granites have negative epsilon(Nd)(t) ratios (-2.4 similar to-2.1) and old second stage Nd model ages (1.20 similar to 1.22Ga), indicating they were mainly derived from Proterozoic crust. Compared with the two stages of the crustal growth in Indochina plates, we infer that the source of the Nuna A-type granites are mainly the Mesoproterozoic crust with a small volume of juvenile crust which derived from underplating of mantle material. Most plots of the Nuna granites in tectonic discrimination indicate a within-plate tectonic setting, in combination with their ages and the evolutionary history of tectno-magma in this region, we suggest that the Nuna granites are generated in a back-arc extensional environment within the Simao-Indochina plate during the subduction of the South China plate beneath the Indochina plate.
- 出版日期2017
- 单位中国地质科学院地质力学研究所
