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T. C. Devaraju ¹, V. H. Uttangi ¹, J. J. M. M. M. Coolen ²

Affiliations
1 Department of Geology, Karnataka University, Dharwar 580003, IN
2 Institute of Earth Sciences, Free University, De Boelelaan, Amsterdam, NL

Abstract

Hogbomite analysing 59.94% Al₂O₃, 6.01% TiO₂, 0.21% V₂O₃, 21.02%, FeO, 0.14%, MnO, 9.66%, MgO and 1.06% ZnO occurs as a widely distributed mineral phase in the vanadiferrous Fe-Ti ore deposits of Madangere area. It occurs in well developed prismatic crystals, and small scales/rods/patches enclosed in magnetite ore grains, and locally as rims to spinel. While the coarse prisms of hogbomite bear characters of primary mineral phase, the small scales/rods/patches appear to represent exsolved phase and that forming rims to spinel is derived by the alteration of spinel. The mineral is reported for the first time from India.

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T. C. Devaraju ¹, V. H. Uttangji ¹, J. J. M. M. M. Coolen ²

Affiliations
1 Department of Studies in Geology, Karnatak University, Dharwad 580003, IN
2 Instituut Voor Aardwetenshappen, Vrije Universiteit, 1007 MC Amsterdam, NL

Abstract

Sheridanite with the formula (Mg_7.97 AI_2.64 Fe"_1.38 Ti_0.01 Mn_0.01) [(Si_5.3 Al_2.7) O₂₀)] (OH)₁₆ occurs as one of the main gangue minerals in the V-Ti-Fe deposits of Madangere. It is found chiefly as late stage pyrogenic mineral and to a very limited extent as secondary mineral after hogbomite.

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T. C. Devaraju ¹, J. J. M. M. M. Coolen ²

Affiliations
1 Department of Studies in Geology, Karnatak University, Dharwad 580003, IN
2 Instituut voor Aardwerenschappen, Vrije Universiteit, Postbus 7161,1007 MC Amsterdam, NL

Abstract

Electron microprobe analyses of coexisting phases in a basic scapolite-garnet-hornblende-two-pyroxene granulite from a Sargur supracrustal enclave near Doddakanya are presented. The results of various mineral geothermometers and geobarometers indicate temperature and pressure conditions of 810±20°C and 9.5 ± 0.5 kbar during metamorphic reequilibration. A comparison with other data from granulites of southern India shows that granulite-facies metamorphism of relatively high pressure is a common feature of the granulite region of the Archaean shield.

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