The Early Mesozoic Mantle Xenoliths and Their Melt/Fluid Metasomatism, Ningcheng Area, Inner Mongolia
详细信息
- 责任者：Shao Ji’an (The Key Laboratory of Orogenic Belts and Crustal Evolution ; Ministry of Education ; School of Earth and Space Sciences ; Peking University ; Beijing 100871 ; China) ; Zhang Cong
- 刊名：Earth Science Frontiers
- 出版年：2013
- 卷期：20(3)
- 关键词：地幔 ; mantle ; 捕虏体 ; xenoliths ; 内蒙古 ; Inner Mongolia
- 页码：p.170-179
- 图表：illus., 5 tables, 31 refs.
- 分类号：0400
- issnNo：ISSN1005-2321
- isbnNo：CN11-3370/P
摘要
The spinel-lherzolite xenoliths were discovered within a host rock of Early Mesozoic cumulate pyroxenite in Ningcheng Area of Inner Mongolia.The spinel-lherzolite is different from the host pyroxenite in mineral composition and Sr-Nd-Pb isotopic characteristics,showing features of pyrolite.Relative to the primary mantle,the spinel-lherzolite is characterized by high Fe,low Mg and Al,and rich K,Na,Ca,LREEs,and such incompatible elements as Rb,Sr,Ba,Th,etc.,and thus the xenoliths are considered as coming from a metasomatic enriched mantle.Further investigation of the textures formed by melt/fluid metasomatic reaction and the metasomatic minerals-phlogopite,pargasite,dolomite,and calcite-reveals that it is the melt/fluid metasomatism of the silicates and carbonates rich in K,Al,Ca,LREEs and incompatible elements that makes the pyrolite evolve towards more and more fertile and enriched due to decreasing Mg# and Fo and increasing Al and other incompatible elements.Measurements of REEs of the Cpx in-situ also demonstrate the existence of metasomatism.The developed shear textures are likely related to plastic rheomorphism caused by the upwelling diapirs of the asthenosphere.In connection to many geologic events happened to the ancient lithospheric mantle of North China,the authors believe that the characteristics of the concerned Early Mesozoic mantle are related to the evolution of the North China Craton itself at depth during a long period of time.
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