Styles of Alteration of Ti Oxides of the Kimberlite Groundmass: Implications on the Petrogenesis and Classification of Kimberlites and Similar Rocks

摘要: The sequence of replacement in groundmass perovskite and spinel from SK-1 SK-2 kimberlites (Eastern Dharwar craton, India) has been established. Two types occur the studied Indian kimberlites. Type 1 is found groundmass, crystallized directly kimberlite magma, it light rare-earth elements (LREE)-rich Fe-poor its ΔNNO calculated value −3.82 to −0.73. second generation (type 2 perovskite) replacing atoll spinel, was formed hydrothermal fluids, LREE-free Fe-rich very high (from 1.03 10.52). may be either replaced by anatase or kassite along with aeschynite-(Ce). These differences alteration are related different f(CO2) f(H2O) conditions. Furthermore, primary strongly altered secondary minerals, resulting redistribution (REE) and, potentially, U, Pb Th. Therefore, accurate petrographic chemical analyses necessary order demonstrate that magmatic before proceeding sort geochronological data using perovskite. Ti-rich hydrogarnets (12.9 wt %–26.3 % TiO2) were produced during late processes. attention must paid position Ca-Ti-garnets mineral their water content them classify rock based on occurrence.