During the synorogenic phases of the Aravalli Geological Cycle, the Rakhabdev Ultramafic Suite intruded concordantly along the litho-contacts before beginning and during the first phase of Aravalli folding. The ultramafic rocks consist mainly of serpentinites and are extensively altered and metamorphosed to talc-carbonate rocks and talc and chlorite schists. The Talc and Talc Schist (Steatite) bodies present in the form of lenticular and irregular pockets, veins showing pinch and swell nature and impersistent bands in Serpentinites. The ultramafic bodies show lithological zoning, with a core massive and irregularly broken Serpentinite surrounded successively by the zone of less-foliated and shear talc-serpentine (Carbonate-Tremolite- Actinolite) rock; foliated and sheared Talc-Carbonate (Tremolite) rock; Talc-schist and Tremolite-Actinolite-Talc-bearing Dolomite and Tremolite-Actinolite (Chlorite-Talc) schist. Steatisation is much later to Serpentinisation. The process of steatisation can be attributed to carbon-dioxide metasomatism, shearing and metamorphic activities. At some places talc, tremolite, actinolite and chlorite associated with dolomitic patches, are the products of regional metamorphism of these rocks under green schist facies condition. Evidences are also available which indicates that the dolomitisation of serpentinites is due to replacement process. With increasing metamorphism, steatisation of dolomite take place particularly along shear planes, which seems to facilitate development of talc. In Rakhabdev Ultramafic Suite three stages of development of talc schist lenses observed: 1. Fine disseminations of talc within dolomite, 2. Progressive steatisation with increasing metamorphism, 3. Complete steatisation of dolomite.

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Keywords: Ultramafic Rocks, Serpentinites, Steatisation, Metamorphism, Aravalli Supergroup.