Geochemistry of Benstonite and Associated Carbonatites of Sevathur, Jogipatti and Samalpatti, Tamil Nadu, South India and Murun Massif, Siberia

Abstract Benstonite-Ba-Sr carbonatites are found only in two localities in the world the Murun massif in Siberia and Jogrpatti in Tamil Nadu, South India The specific feature of these carbonatites is high BaO (20-35%) and SrO (up to 10% as in the Murun carbonatites) concentrations These carbonatites jointly with calciocarbonatite varieties occur in carbonatite-alkahne complexes of Siberia and South India However, carbonatites of South India and Siberia differ m terms of the chemical composition, especially the trace and rare earth element contents In South India (Tamil Nadu area), carbonatites are found in three alkaline massifs Samalpatti, Sevathur, and Elagin Benstonite carbonatites are found only in the Samalpatti massif as a small dyke In the Murun massif carbonatites are separated from the silicate rocks and occur as a residual silicate-carbonate complex It comprises mcroclinites, pyroxene-microclmes, quartz-microcline-pyroxene-calcites, which contain calcite carbonatites and charorte rocks as schleiren and dykes Benstonite carbonatites form a horizontal body of 40 m thick in the southwestern part of the complex We examined and compared the geological and geochemical features of these two areas where Bensonite occurs in association with other carbonatites and discuss their origin The Indian carbonatites crystallized as the plutonic phase while Siberian ones formed m the near-surface area and effused on the Earth’s surface