Mn-Pyroxenes from Gangpur Group of rocks, Goriajhar, Orissa, India [in Japanese]
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Mn-pyroxenes in Gangpur Group of rocks around Goriajhar area, Sundargarh district, Orissa, India, are recorded in two different assemblages, namely: Mn silicate-oxide and Mn silicate-oxide-carbonate rocks. The petrography and chemical composition of these pyroxenes indicate them to be Mn-aegirines. These pyroxenes, with the composition Na<sub>0.84-1.01</sub> Ca<sub>0.04-0.12</sub> Mn<sub>0.03-0.14</sub> Mg<sub>0.02-0.05</sub> Fe<sup>3+</sup><sub>0.83-0.95</sub> Al<sub>0.02-0.05</sub> [Si<sub>1.92-1.98</sub> O<sub>6</sub>], usually show ∼7 mol.% of johannsenite component in the carbonate assemblage with low diopside (∼4 mol.%) and jadeite (<2.5 mol.%) components in both the assemblages. Presence of fine hematite needles within the aegirines is the result of high grade metamorphism (almandine-amphibolite facies) in the area.
- Journal of Mineralogical and Petrological Sciences
Journal of Mineralogical and Petrological Sciences 92(10), 425-430, 1997-10-05
Japan Association of Mineralogical Sciences