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《Acta Geologica Sinica》 2000-01
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Geochemistry of the Anzishan Ophiolitic Complex in the Mian-Lue Belt of Qinling Orogen——Evidence and Implication of the Palaeo-ocean Crust

Xu Jifeng Yu Xueyuan Li Xianhua Zhang Benren Han YinwenGuangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, 510640 Geochemical Institute, China University of Geosciences, Wuhan, 430074  
The Anzishan ophiolitic complex is located in the eastern section of the Mian-Lue ophiolitic and tectonic melange belt, Qinling orogen, center China. It consists of serpentinized peridotites and metamorphased MORB-type mafic igneous rocks. The serpentinized peridotites (harzbur-gites and a few dunites) represent the upmost part of the palaeo-ocean mantle. Whereas the metamorphosed mafic igneous rocks, which are characterized by depleted LREE and very high Nd isotopic ratios similar to MORB, are remainders of the palaeo-ocean crust. These facts suggest that this complex is another typical ophiolite within the Mian-Lue ophiolitic and tectonic melange belt. The geochemical characters of the meta-mafic rocks reveal that this ophiolitic complex was most probably formed in a small ocean basin or back-arc basin. However, the Pb, Nd isotopic systems of the Anzishan ophiolitic complex from the eastern section are distinct from those of the ophiolites from the western section. The palaeo-ocean crust in Anzishan is probably older than the ophiolites in the western section of the Mian-Lue belt. Thus, the meta-mafic rocks of the Anzishan ophiolitic complex were derived from an isotopic mantle reservoir different from the those in the western section. This infers that the Mian-Liie ophiolitic and tectonic melange belt has a more complex evolution history than hitherto considered.
【Fund】: 国家自然科学基金(编号49603045)
【CateGory Index】: P597
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