Geology of Tamilnadu
The State of Tamil Nadu is the southern province of the Indian peninsula.
The rich and varied mineral resources of the State have contributed handsomely towards the development and industrialization of the State.
It is one of the leading States in the reserves of the minerals viz., Lignite, Garnet, Magnesite, Quartz, Feldspar, Clay, Limestone, Bauxite, Graphite and Granite.
Mining policies and practices in Tamil Nadu are Industry-friendly and pro-active.
The potential reserves of the various minerals, offer good business opportunities for investors.
Tamilnadu lies between N 8 00’ and N 13 30’ latitudes and E 76 16’ and E 80 18’ longitudes.
It is bounded by Andhra Pradesh and Karnataka States on the North and Kerala State on the West. A long coast line borders the Bay of Bengal on the east. The western coast in Tamil Nadu is short and it extends towards North into Kerala.
The Western Ghat hill ranges, the Sahayadri, topographically high terrain run continuously in NNW direction. Mahendragiri, Agastiyar Malai, Palani hills and Nilgiri hills are parts of the Western Ghats in Tamil Nadu.
Anaimudi and Doddabetta in South India, rising to altitudes of more than 2000m in the Western Ghats lie in Tamil Nadu and Kerala state.
The central part of the state constitute the Kalrayan, the Chitteri, the Pachai Malai, the Kollai Malai (Kolli Hills) and Shevaroy hills, which are southern and southeastern extensions of the Eastern Ghat hill ranges that border the Bay of Bengal in Orissa and Andraprdesh.
Tamil Nadu represents an important high grade metamorphic terrain of global importance.(Map)
Geologically divided into three zones viz., the Northern region and southern region divided by a central region.
The central region divides the North and South by a comparatively smaller East-West zone which is about 50 Km wide.
The central region is marked by two prominent tectonic zones viz., East-West trending Moyar-Bhavani-Attur (MBA) on the North and Palghat-Noyyil-Cauvery (PNC) in the South.
Largely made up of reworked gneisses carrying enclaves of older schists, amphibolites, Fuchsite quartzite, Banded magnetite quartzite, calc-granulites with limestone, and layered Anorthosite complex (Bhavani layered complex and Sittampundi complex).
Dolerites are comparatively less in this zone and are exposed with many younger granites of Proterozoic age.
Northern region is occupied by the amphibolite facies terrain, which is the Southern extension of Dharwar craton.
There is a transitional zone extending from Mangalore to Chennai that separates the amphibolite terrain from the predominantly Charnockite terrain of Chennai-Chengalpattu, Javadi, Shevaroy Hills, Chitteri and Kalrayan massifs.
The major metabasic occurrence in the North zone is the amphibolite in Vepanapalli-Maharajagadai area, which is the southern extension of the Kolar (Gold-bearing) schist belt, form the Kolar group of rocks.
There are many Banded Magnetite Quartzites (BMQ) which run to few hundred metres in length noticed throughout the Northern Tamil Nadu of which the major ones are the Kavuthimalai, Vediyappanmalai, Kanjamalai and Thirthamalai.
The intrusion of swarms of dolerite dykes are concentrated in Sholingar – Gudiyattam – Krishnagiri belt.
Important occurrences of alkaline complexes (comprising saturated syenites and carbonatites closely associated with ultra-basic rocks
Occurs to the south of the Palghat-Cauvery tectonic zone.
On the west of this zone charnokites form the massifs of the Western Ghats and the Eastern part is predominantly of gneisses.
This region differs from the Northern and Central regions by the predominance of meta-sedimentry rocks such as quartzites, sillimanite quartzites, calc-granulites, garnet and cordierite bearing meta-pelites.
This zone is totally devoid of dolerite dykes and banded magnetite quartzites.
In the Northern part of this region calc-silicates and crystalline limestone occur as thick sequences for a few tens of metres thickness.
Extensive limestone deposits are found from Palayam to Kiranur, Rajapalayam-Alangulam belt east of Varshanad hills and Talaiyuthu near Tirunelveli.
At the southern extremity of peninsular India and to south of the Achankoil shear zone consist of garnet-biotite-graphite gneisses and garnetiferous charnockite and khondalites (garnet-sillimanite-biotite-graphite), cordierite gneiss.