【摘 要】
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There is a diversity of unusual minerals and mineral inclusions associated with podiform chromitites.The presence of these minerals suggests that grains of amphibolite(plagioclase,amphibole and zircon
【机 构】
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Department of Earth Sciences,The University of Hong Kong,Hong Kong,China
【出 处】
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International Workshop on: Ophiolites, Mantle Processes and
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There is a diversity of unusual minerals and mineral inclusions associated with podiform chromitites.The presence of these minerals suggests that grains of amphibolite(plagioclase,amphibole and zircon)and eclogite(coesite,kyanite and garnet)were present in the magmas from which chromite crystallized.Multiphase mineral inclusions demonstrate that podiform chromitites form from hydrous mafic magmas in suprasubduction zone environments.We propose a new model in which chromitite formation was involved in intra-oceanic subduction zones initiated in closing oceanic basins.Continued subduction carries oceanic and possibly continental crustal materials to deep levels where they are metamorphosed under greenschist,amphibolite and ecologite facies conditions.Tearing and breakoff of the subducted slab,possibly along the transitional contact between amphibolites and eclogites,create a slab window through which the underlying asthenosphere rises and melts to generate Cr-rich mafic magmas.
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