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Prismatine And Ferrohogbomite-2n2s In Granulite-Facies Fe-Oxide Lenses In The Eastern Ghats Belt At Venugopalapuram, Vizianagaram District, Andhra Pradesh, India: Do Such Lenses Have A Tourmaline-Enriched Lateritic Precursor?, Edward S. Grew, A. T. Rao, K.K. V.S. Raju, C. Hejny, J. M. Moore, D. J. Waters, Martin G. Yates, C. K. Shearer

Earth Science Faculty Scholarship

Fluorine-rich prismatine, (square,Fe,Mg)(Mg,Al,Fe)(5)Al-4(Si,B,Al)(5)O-21(OH,F), with F/(OH+F) = 0.36-0.40 and hercynite are major constituents of a Fe-Al-B-rich lens in ultrahigh-temperature granulite-facies quartz-sillimanite-hypersthene-cordierite gneisses of the Eastern Ghats belt, Andhra Pradesh, India. Hemo-ilmenite. sapphirine, magnetite, biotite and sillimanite are subordinate. Lithium, Be and B are concentrated in prismatine (140 ppm Li, 170 ppm Be, and 2.8-3.0 wt.% B2O3). Another Fe-rich lens is dominantly magnetite, which encloses fine-grained zincian ferrohogbomite-2N2S, (Fe2+ Mg,Zn,Al)(6) (Al,Fe3+,Ti)(16)O-30(OH)(2), containing minor Ga2O3 (0.30-0.92 wt.%). Fe-Al-B-rich lenses with prismatine (or kornerupine) constitute a distinctive type of B-enrichment in granulite-facies rocks and have been reported from four other localities worldwide. A scenario …