Deep Main Faults in South India

A system of deep, main faults containing carbonatite complexes and ultra basic to alkaline intrusions occurs in South India. The faults strike in a northeast-southwest direction across the Peninsula, and two main sets have been recognised at N 30°E and N 45° E. They occur in a block-faulted region in which some of the uplifted blocks form hills up to 2900 metres high and grabens have been downfaulted to as much as 1700 metres below sea level. Seismic records since the year 1800 show that the majority of earthquakes in the Precambrian Shield of South India are concentrated along one of the fault zones which is also the location of igneous intrusions, hydrothermal veins, pegmatiles and metasomatism. A positive gravity anomaly underlies this zone.

Minerals of economic importance occur in some of the intrusions. The most productive artesian wells drilled by the United Nations Groundwater Project in Tamil Nadu are located on one of the major faults of the system. It is thought that continued exploration with the aid of photogeology and geophysical surveys will reveal more of the deep, main faults, and possibly more ore bodies, in South India.