High Heat Generating Granites of Hyderabad, India

Abstract

Granites and rocks of granitic composition out cop over the entire Indian subcontinent. These rocks are found from the southern part of India (Kanyakumari) to the Himalayas on the north and represent a large age spectrum extending from one million (Nanga Parbat) to 2700 Ma (Darwad Craton) of south India. The outcrop area of these rocks is about 150000 sq km. The most striking feature of these granites is their ability to generate high heat due to high radioactive element content. For example, the uranium and thorium content of the Bundelkhand granites (age 2550 Ma) of Madhya Pradesh, India is 14 and 101 ppm respectively and the heat generated by these granites is 8 µW/m3. However, radioactive element data on all the granites occurring over the Indian sub-continent is not available. This is a pre-requisite to evaluate their suitability for EGS projects. With this objective, in 2017 we have initiated a state wide (Telangana State) programme to create a data base on uranium, thorium and potassium on granites and associated rocks. Initially we have selected northwestern part of Telangana State (Sangareddy district, where IITH is located) for this work. Granites are wide exposed in and around the IIT Campus (Indian Institute of Technology Hyderabad) in Sangareddy district. The uranium, thorium and potassium contents in these granites vary from 12-86, 20-107 ppm and 2-5% respectively. The radioactive heat generation and the surface heat flow over the area and the power generation capacity of these granites are discussed in the paper. This work is being continued in the current year.