Metamorphic potassium feldspar occurs locally in Sanbagawa psammitic and ferriphengite schists of the garnet and albite-biotite zones. The K-feldspar bearing samples are characteristi-cally free from chlorite and their typical mineral assemblage is quartz+K-feldspar+albite+phengite (Si=6.6-7.O per formula unit for O=22) ±epidote. Biotite, clinopyroxene (augite or aegirine) and/or grossular (58-60 mol%) -rich garnet occur in addition to the above assemblage in some samples. Phengite coexisting with K-feldspar and biotite shows a zonal structure with increasing Na/(Na+K) and decreasing Si from core to rim. The zonal structure implies that dP/dT of individual prograde P-T path of the higher-grade materials in the Sanbagawa belt was smaller than 12-25 bar/°C. The gentle slope of the P-T path may represent reheating at climax of the metamorphism and/or during exhumation of the higher-grade materials.

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Rb and Sr concentrations and Sr isotopic composition were analyzed for seven granitic rocks from the Otanabe granitic pluton in the northern Kitakami Mountains, northeastern Japan. Although their Rb concentrations are high, the Sr concentrations are rather low comparing with the other granitic rocks in the Kitakami Mountains. All of the samples from the Otanabe granitic pluton yielded single whole rock isochron of 118±8 Ma, and the initial. ⁸⁷Sr/⁸⁶Sr ratio is 0.7039±0.00016. The age indicates the time of emplacement of the Otanabe granitic pluton. The low initial ⁸⁷Sr/⁸⁵Sr ratio implies that incorporation of old continental crustal material into the original magma of the Otanabe granitic pluton is highly unlikely.

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Manganese ores at Kutinga occur as distinctly conformable bands in the khondalite suit of rocks of Eastern Ghats complex. The dominant manganese ore minerals include cryptomelane, psilomelane, pyrolusite, hausmannite, lithiophorite and wad. Quartz, chalcedony, orthoclase, garnet and kaolinite are the associated gangue minerals. Presence of high iron, high phosphorous, low to medium silica and dominance of CaO over MgO, K₂O over Na₂O, Ni over Co, Zn over Pb and Cu over Pb are the characteristics of this manganese deposit. Phosphorous occurs as discrete apatite inclusions within the quartz and orthoclase; and also adsorbed in the secondary manganese and iron minerals. Field characters, mineralogy and geochemistry of manganese ores suggest their formation as chemical precipitates, and the source of which appears to be continental erosion. Manganese formation along with the country rocks have been metamorphosed under granulite facies conditions, affected by granitisation and subsequently undergone supergene enrichment to give rise to the present deposit. These ores will be amenable to removal of silica, but will not respond well to removal of iron and phosphorous by physical beneficiation.

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