Chromites from meta-anorthosites, Sittampundi layered igneous complex, Tamil Nadu, southern India

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• 作者：Biswajit  ; Ghosh  ; ;   ; ^{bghosh_geol@hotmail.com} ; Ritam  ; Konar
• 关键词：Sittampundi Complex ; Chromitite ; Parental melt ; Tholeiitic basalt ; Eclogite-facies
• 刊名：Journal of Asian Earth Sciences
• 出版年：2011
• 出版时间：11 November 2011
• 年：2011
• 卷：42
• 期：6
• 页码：1394-1402
• 全文大小：1440 K

文摘

Chrome-spinels of anorthosite-hosted chromitite bodies from Sittampundi layered igneous complex, southern India, metamorphosed under eclogite-facies condition have been studied. Besides anorthosites as the dominant rock type discontinuous layers of peridotite, pyroxenite and lenses of gabbroic granulite/eclogite occur at the bottom of the complex. Chromite grains are deformed exhibiting features of intracrystalline deformation and exsolved needle shaped rutile inclusions. Chrome-spinels are of refractory grade with Cr₂O₃ and Al₂O₃ contents varying between 34?0 wt. % and 23?8 wt. % respectively. In the bivariate Cr# (=Cr/[Cr + Al]) vs. Mg# (=Mg/[Mg + Fe²⁺]) diagram, Sittampundi chromitites show close affinity with the Archean Fiskenaesset type deposit. The calculated Al₂O₃ values for the parental melt of Sittampundi chromitites are consistent with the Al₂O₃ content of mid-ocean ridge basalts whereas the values for FeO/MgO ratio are higher. It is suggested that an initial basic magma, similar to that of mafic granulite composition evolved in the magma chamber through fractionation of peridotite and pyroxenite to Fe,Al-rich basaltic melt, parental to the chromitite bands.