Geology

The geological formations of the district belong mainly to Archaean age along with rock of Proterozoic age. The former is represented by Khondalite Group of rocks, Charnockite Group of rocks, Migmatite Complex, Sathyamangalam Group of rocks, Bhavani Group of rocks and Kolar Alkaline rocks. The Khondalite Group includes garnet-sillimanite gneiss and quartzite which occur as small patches. The Charnockite Group occupies a major part of southern part of this district, and it is mainly charnockites along with some small bands of pyroxene granulites and magnetite quartzite. Two small patches of pyroxenite and gabbro are seen to occur in the pyroxene granulite near about 10 km. NE of Harur. The Migmatite Complex includes garnetiferous quartzofeldspathic gneiss and hornblende-biotite gneiss, the former exposed on the western part of the district. The Sathyamangalam Group of rocks include fuchsite quartzite, sillimanite mica schist and amphibolites. The Bhavani Group in this area includes fissile hornblende-biotite gneiss, granitoid gneiss and pink migmatite. Amphibolites with banded ferruginous quartzite and associated quartzo-feldspathic rocks (Chapion Gneiss) represent the Kolar Group and are found west and southwest of Veppanapalli. Following this there are basic intrusions occurring as dykes. The Alkaline Complex is represented by epidote-hornblende gneiss, ultramafics, syenite and carbonatite and these are distributed in the eastern part of the district. Innumerable basic dykes and felsites, quartz, barites and pegmatite veins form part of the Alkali Complex