Genesis of Highly Fractionated Ⅰ-Type Granites from Fengshun Complex: Implications to Tectonic Evolutions of South China
The South China Block is characterized by the large-scale emplacement of felsic magmas and giant ore deposits during the Yanshanian.We present zircon Hf isotopic compositions, whole-rock major and trace element compositions of the Fengshun complex, located in eastern Guangdong Province, South China.The Fengshun complex is a multi-stage magmatic intrusion.It is composed of two main units, i.e., the Mantoushan (MTS) syeno-monzogranites, alkali feldspar granites and the Hulutian (HLT) alkali feldspar granites.LA-ICPMS zircon dating shows that the complex emplaced in 166-161 and 139±2 Ma, respectively.Geochemically, the MTS granites show relatively various geochemical compositions with low REE contents (87.76×10-6-249.71×10-6), Rb/Sr ratios (1.19-58.93), pronounced Eu negative anomaly (0.01-0.37) and low Nb/Ta ratios (2.40-6.82).In contrast, the HLT granites exhibit relatively stable geochemical characteristics with high REE contents (147.35×10-6-282.17×10-6), Rb/Sr ratios (2.05-10.30) and relatively high Nb/Ta ratios (4.45-13.00).The isotopic data of the MTS granites display relatively enriched values, with Isr varying from 0.708 2 to 0.709 7, εNd(t) from-7.8 to-6.9 and εHf(t) from-7.4 to-3.2, in comparison with those of the HLT which areIsr=0.703 05-0.704 77, εNd(t)=-5--3.4 and εHf(t)=-0.7-1.8).The two-stage model ages of the MTS granites (T2DM(Nd)=1.51-1.59 Ga and T2DM(Hf)=1.26-1.48 Ga) are also higher than those of the HLT granites (T2DM(Nd)=1.21-1.34 Ga and T2DM(Hf)=0.96-1.10 Ga).Thus the MTS and HLT granites might originate from different sources.The former is more likely derived from partial melting of Meso-Proterozoic basement triggered by upwelling of asthenosphere and/or underplate of the basaltic magma and then extensive fractional crystallisation, similar to the genesis of Early Yanshanian granitoids of the EW-trending tectono-magmatism belt in the Nanling range.In comparison, the latter might have involved with asthenosphere component, similar to the Early Cretaceous granitoids of NE-NNE-trending granitoid-volcanic belt in coastal region, southeastern China.We propose that the MTS granites were mainly formed in Paleo-Tethyan post-orogenic extensional tectonic setting whereas the HLT granites were formed in the back-arc extensional tectonic setting.The period at 139 Ma represents the initial time of roll-back of the paleo-Pacific Plate in SE-trending.
Sr-Nd-Hf isotopes Late Mesozoic magmagtism highly fractionated Ⅰ-type granite post-orogeny roll-back South China
Zuomin Zhou Changqian Ma Caifu Xie Lianxun Wang Yuanyuan Liu Wei Liu
State Key Laboratory of Geological Processes and Mineral Resources, School of Earth Sciences,China U School of Earth Sciences, East China University of Technology, Nanchang 330013, China Faculty of Geosciences and Environmental Engineering, Southwest Jiaotong University, Chengdu 611756, Tianjin Research Institute for Water Transport Engineering, M.O.T., Tianjin 300456, China
国际会议
武汉
英文
444-460
2015-10-16（万方平台首次上网日期，不代表论文的发表时间）