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摘要
Southern Wengen complex is located in central Inner Mongolia, which belongs to the middle segment of the North China craton. There are dunite, troctolite and gabbro in southern Wengen complex. The distribution of the complex is NNE trending. The geochemical analysis results show that the complex is riched in MgO, low alkali and TiO2, whole massif oxide content is mainly controlled by a relative mix ratio among olivine, clino-pyroxene and plagioclase. The content of trace elements are generally low, Nb, Ta and Hf show slight loss, Pb, Sr show significant enrichment. The gabbro showed significant Nb, Ta negative anomaly and Pb, Sr positive anomaly. Gabbro is relative riched in trace element than dunite and troctolite, because of its origin in the late sage of crystallization separation processes. Sigma REE content of gabbro and dunite change largerly (1.41 x 10(-6) similar to 111.6 x 10(-6)), rare earth element distribution curve is slightly to the right slip type or flat type. Total rare earth content of ultrabasic rocks in the deep complex is extremely low, and with the degree increasing of crystallization separation, rare earth element content in rock rise rapidly, reflecting the proportion of intergranular residual melt rising. Using olivine and residual magma restricted nature of the parental magma balance method, the results show that the initial magma MgO = 11.73%, FeO = 11.38%, belong to the magnesia basaltic magma. The Sr-Nd of southern Wengen complex sample plots into mainly near EM I enrichment mantle end, speculated that it originated from mantle and contaminated crustal material in the chamber or in the rising processes. The analysis results of Zr, Y, Th and Ta incompatible elements such as the ratio of the ( discriminant magma evolution, based on Th/Nb ratio (>1) and low Nb/La ratio (<1) is further evidence show that southern Wengen complex initial magma contaminated crustal material in the process of emplacement. In these diagram, the projection point is more dispersed, also shows that the existence of assimilation hybrid effect. In the tectonic environment discrimination diagrams of Ta/Th-Zr and Nb, Th/Yb-Th/Nb and Ta/Th-Th/Yb, Nb/Th-Nb, samples from southern Wengen complex mainly fall into the plate (WPB), speculated that it formed in the plate extensional tectonic environment.
- 出版日期2014-12
- 单位中国地质大学（北京）
