PETROLOGICAL AND GEOCHEMICAL STUDIES TO IDENTIFY RARE METAL AND RARE EARTH RICH PHASES IN THE ALKALINE BELTS OF KUNAVARAM AND KUNDULURU, KHAMMAM DISTRICT, ANDHRA PRADESH, INDIA

Rare earth element mineral deposits are associated with highly evolved igneous rocks, either with alkaline (including carbonatities) or with per aluminous granites and pegmatite’s. Alkaline magmas are rare and unusually enriched in elements such as zirconium, niobium, strontium, barium, lithium, and the rare earth elements. When these magmas ascend into the Earth’s crust, their chemical composition undergoes further changes in response to variations in pressure, temperature and composition of surrounding rocks. The result is an astonishing diversity of rock types that are variably enriched in economic elements, including the rare earth elements.

Ever since the recent demarcation of 6 major alkaline provinces in India (Madhavan, 2002), the Bastar alkaline province has come to be recognized as the only province with a number of alkaline gneiss belts comparable to the Haliburton-Bancroft province of Canada. The Bastar province is confined to the eastern part of Bastar craton abutting the coastal granulite belt which is known for hosting several alkaline gneiss belts like the ones at Khariar, Rairakhol, Koraput, Kunavaram etc. The present work brings out certain salient geochemical characteristics of the alkaline belts exposed at Kunavaram and Kunduluru in Khammam district of Andhra.Pradesh, India. The Kunavaram belt extends for about 30 Km in NE-SW direction from Kunavaram in the North to Vinayakapuram in the South, with a width of about 2.5 Km. The major rock type being hornblende nepheline syenite and biotite nepheline syenite. The other rock types include syenites and melteigite, the latter are found in the form of autolithic masses at Rudramakota and Rangapur areas. The Kunduluru belt considered to be a satellite body of the Kunavaram belt, is located 20 Km NE of Kunavaram and is about 7 Km long and 0.5 Km wide. It is mainly composed of biotite nepheline syenite with a subordinate syenite component.

The major geochemical characteristics are presented here which suggest that these are miaskitic, with absolutely no peralkaline tendencies, whatsoever. The chondrite normalized REE patterns of Kunavaram-Kunduluru alkaline rocks clearly indicate enrichment in LREE. The mafic rich alkaline rock melteigite and pyroxene syenite are relatively more enriched in REE when compared to nepheline gneisses.