Carbonates of Chiknayakanhalli Schist Belt, Karnataka

Carbonates of the Chiknayakanhalli (CN halli) area include (i) dolomite, (ii) limestone, (iii) ankerite and (iv) calc-schist. Of these, dolomite is the most widely developed rock. chemically the CN halli carbonates cover a wide range from almost pure calcite and dolomite-ankerite to Mg-limestone, shaly limestone and cherty limestone/dolomite/ankerite. In their trace element content, the rocks are typically much depleted in comparison with carbonatites. Available evidence indicates overall primary chemical sedimentary deposition of the carbonates in a barred basin with a gradual rise in salinity, pH, temperature and Mg:Ca ratio of the environment. Evidence of dolomitization is limited to the border zones between limestone and dolomite and there is no recognizable indication of organic activity.