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Genesis of Highly Fractionated I-Type Granites from Fengshun Complex:Implications to Tectonic Evolutions of South China 被引量:17
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作者 Zuomin Zhou Changqian Ma +3 位作者 caifu xie Lianxun Wang Yuanyuan Liu Wei Liu 《Journal of Earth Science》 SCIE CAS CSCD 2016年第3期444-460,共17页
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 compo... 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 are ISr=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. 展开更多
关键词 Sr-Nd-Hf isotopes Late Mesozoic magmagtism highly fractionated I-type granite post-orogeny roll-back South China
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