Hydrothermal hogbomite associated with vanadiferous-titaniferous (V-Ti) bearing magnetite bands in Bhakatarhalli chromite mine, Nuggihalli greenstone belt, western Dharwar Craton, Karnataka, India

摘要

Högbomite, a rare exotic mineral, is found to be associated with the vanadiferous–titaniferous (V-Ti) bearing magnetite bands at Bhakatarhalli, Nuggihalli greenstone belt, western Dharwar Craton, India. We report on a second occurrence of högbomite from the Dharwar craton in Karnataka, which is the sixth documented occurrence of this mineral from India. We evaluate the chemical characteristics of högbomite and associated Fe-Ti-minerals in an attempt to identify its formation as a primary hydrothermal mineral in a metamorphosed magnetite layer. We report here the presence of högbomite as a complex oxide of Fe, Mg, Al and Ti with accessory of Zn, V and Sn. Petrographic studies suggest the (V–Ti) bearing magnetite (Mt) contain spinel, högbomite, chlorite, martite, ilmenite (Il) and minor amounts of diaspore. The högbomite displays euhedral to subhedral textures, and is up to 250 μm along the grain boundaries of magnetite and ilmenite. In the samples studied, högbomite is prismatic, irregular and elongated in shape. The genesis of högbomite in veins between magnetite and ilmenite implies its precipitation from fluids without involving complicated reactions. Several models were proposed for the formation of högbomite; however, the subject is still debatable.