Field study of alkaline plutons in Tamil Nadu and Andhra Pradesh, South India, 1997-1998

Geological field study of alkaline plutons in Tamil Nadu and Andhra Pradesh was accomplished during December 1997 to January 1998, supported by the Monbusho Fund of the Japanese Government. The main purpose of the study was to elucidate the petrogenesis and sources of these alkaline plutons using geochronological, geochemical and mineralogical studies. For this purpose, several alkaline plutons were selected for field survey and collecting rock specimens. The Yelagiri, Sevattur, Samalpatti, Pikkili, Torappadi, Pakkanadu and Sivamalai plutons in Tamil Nadu and the Elchuru, Settupalle, Purimetla and Uppalapadu plutons, the Boggulakonda and Pasupugallu gabbro bodies and the Chintalacheruvu carbonatite outcrop in Andhra Pradesh were surveyed. In this survey, several geologically interesting features were observed. Almost all alkaline plutons surveyed in this study are considered to keep initial signatures of intrusive plutons. In the Tamil Nadu, the majority of the alkaline plutons are silica-saturated and oversaturated. On the other hand, the Andhra Pradesh plutons are silica-undersaturated. This difference probably reflects some petrogenetic and tectonic differences between these plutons.