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《Journal of Jilin University(Earth Science Edition)》 2007-05
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Formation Process of Sapphirine and Related Mineral Association in the High-grade Region of the Larsemann Hills,East Antarctica

REN Liu-dong1,WANG Yan-bin1,ZHAO Yue21.Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037, China2.Institute of Geomechanics,Chinese Academy of Geological Sciences,Beijing 100081,China  
Study of sapphirine and related mineral association in the high-grade region of the Larsemann Hills,East Antarctica,shows that sapphirine of the area is characterized by its magesio,iron-and aluminum-rich,but silico-poor feature,and the substantial intra-and intergrain changes in compositions.The change is mainly manifested by the Tschermark substitution(Mg,Fe) + Si = 2Al.In the high-grade metamorphism and anatexis process,in which sapphirine was formed,the multistage crystallization of minerals resulted in the complexity of the mineral association,such as the differentiation of leuco-and melano-components.Generally,the mafic-rich minerals formed earlier,and the differentiation of magnesio-and iron-components is responsible for the earlier presence of iron-rich minerals,i.e.,magnesio-rich minerals crystallized later,thus the successive associations of multistage occurred.The rock composition is an important but not the only critical factor for the occurrence of sapphirine.It is the mobilization of components that accounts for the formation of sapphirine.The multistage evolution of mineral association to some degree reflects the changing composition and opening of the setting.It can therefore,be deduced that the protolith from which sapphirine was derived is not necessarily magnesio-rich pelite.The heterogeneity of sapphirine in composition is related to the composition changes of the settings,not to the changes in pT condition.Sapphirine was formed at 840-880℃,not at the ultrahigh temperature condition(1000℃)previously thought.Its formation is thought to be related both to the filtration and diffusion processes during high-grade metamorphism and anatexis.
【Fund】: 国家自然科学基金项目(40172065 40572041);; 中国地质调查局地质调查项目(200413000023);; 国土资源部百名优秀青年科技人才项目
【CateGory Index】: P571
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