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Eastern dharwar craton

Eastern dharwar craton

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Eastern dharwar craton

  1. 1. SEMINAR ON EASTERN DHARWAR CRATON
  2. 2. C0NTENTS  INTRODUCTION  DHARWAR CRATON  EASTERN DHARWAR CRATON  STRATIGRAPHY OF EDC  GREENSTONE BELTS OF DHARWAR SUPERGROUP  CLOSEPET GRANITE  VERTICAL ZONATION OF THE CLOSEPET GRANITE  REGIONAL METAMORPHISM  CONCLUSION  REFERENCE
  3. 3. INTRODUCTION  A large portion of a continental plate that has been relatively undisturbed since the Precambrian era and includes both shield and platform layers.  The word craton was first proposed by the German geologist L. Kober in 1921 as "Kratogen", referring to stable continental platforms.  There are five Craton in Indian shield:- Dharwar Craton Bastar Ctaton Singhbhum Craton Aravalli craton Bundelkhand Craton
  4. 4. TECTONIC MAP OF INDIAN SHIELD
  5. 5. DHARWAR CRATON  Archean Dharwar Craton covers a total area of 4.5 lakh sq.kms.  Bounded by Pan-African Pandyan Mobile belt (PMB) towards the south, Cretaceous Deccan traps towards the north, Proterozoic (Purana) Kaladgi and Bhima basins, Neoproterozoic Eastern Ghats mobile belt towards (EGMB) toward east, Arabian sea towards the west and Archean Karimnagar granulite belt (KGM) toward north east  It consists of the greenstone schists belts, charnokites, grey gneiss,quarzite, marble, BIF, and the younger granites.  Divided into Eastern and Western Dharwar Craton seperated by the Chitradurga Shear Zone.
  6. 6. STRATIGRAPHY
  7. 7. CLASSIFICATION OF EDC  The component units are:  OLDER GNEISS: Older gneiss are not widespread in EDC, isolated U-Pb Zircon dates of over 3000 Ma are seen in some gneissic outcrops along the Western and Eastern margin of Greenstone belts like Kolar and the Ramagiri. (Putative basement).  WARANGAL GROUP: Lithologies mainly belong to quartzite–pelite-carbonate consisting of fuchsite quartzite, quartz pebble conglomerate, calc silicates, marble , cordierite -anthophyllite rocks, BIF. o These suites are similar to that of Sargur Group but for the lesser development of mafic and ultramafic suites ,it is named as Warangal Group. o Run parallel trends to those of Dharwar schist belts having similar metamorphic and migmatic history.
  8. 8. GREENSTONE BELTS OF DHARWAR SUPERGROUP  EDC is characterised by volcanics-dominated, sediment-impoverised and gold rich greenstone belts, in contrast of WDC.  The greenstone belts are engulfed all sides by younger granatoids.  The Yeswantanagar Formation of the Sandur belts has similarity to that of Bababuddan Group intruded by granite.  Most of the greenstone belts are corelatable with that of the Chitradurga belt of WDC.  The greenstone belts of EDC form linear arrays and are called superbelts or composite belts-extends underneath the cuddapah Basin .
  9. 9. IMPORTANT GREENSTONE SUPERBELTS OF EDC :  Ramagiri (Penakachela-Sirigeri)-Hungund superbelt:- Ramagiri-Penekacherla-Sirigeri Greenstone Belt, Hundgund Greenstone Belt  Kolar-Kadiri-Jonnagiri-Hutti superbelt:- Kolar Greenstone Belt,Kadiri Greenstone Belt, Jonnagiri Greenstone Belt, Hutti Greenstone Belt  Veligallu-Raichur-Gadwal superbelt:- Veligallu Greenstone Belt, Raichur Greenstone Belt, Gadwal Greenstone Belt,  Sandur superbelt
  10. 10. Hutti Greenstone belt  Rich in gold mineralisation called as Hutti Maski belt with southern extension to Siruguppaa  Cover an area of about 670 km2 consist of basic volcanic suite, minor BIF in basic acidic volcanics, greywackes and polymict, granite-clast conglomerate.  The Hutti-Maski belt has a NNW-SSE trend with a sharp hook shaped bend in the north towards SE.  The hook shape of the belt can be attributed to cross folds and also to the diapiric nature of the two phases of granatiod intrusions into the greenstone belt.
  11. 11. Kolar Greenstone Belt  Narrow linear schist belt intruded by diapric granites of Patna and Bisanattam, and by granodioritic gneisses on all sides.  It consists of amphibolites, BIF, cordierite-silliminite- fuchsite quarzites, calc-sillicate rocks, manganiferous chert and carbonate.  The overlying pillowed, agglomeratic and variolitic amphibolites are essentially tholeiites.
  12. 12. INDEX 1. mafic rock 2. volcanoclastic sediments (champion gneiss) 3. Banded ferruginous chert 4. granite and gneiss 5. granitic pluton Geological sketch map of Kolar Schist belt
  13. 13. CLOSEPET GRANITE  It is a unique linear body consisting of diverse granitic types.  The granites have easterly convexity that mirrors the configuration of the schist belts.  Named after the town of Closepet, named for Major Close, a British Army officer and now known as Ramanagaram.  It is 200 km long and 20-30 km wide plutonic belt bounded by shear zones  High precision Zircon ages of granite from different laboratories define a narrow age of 2510-2530 Ma.  It is divisible into two parts-southern and the northern separated near Kalyandurga by a Gap area.  The closepet granite is divided in to 3 depth zones 1.Root Zone, 2.Transfer Zone, 3.Intrusion Zone with a gap zone.
  14. 14. VERTICAL ZONATION OF THE CLOSEPET GRANITE
  15. 15. REGIONAL METAMORPHISM  It is of low-pressure facies series with typical pelitic assemblages of andalusite-cordierite-staurolite in amphibolite facies grading into cordierite-garnet- silliminite-hypersthene in granulite facies.  Metamorphic P-T conditions of EDC range from 670˚C/3kb in Sandur belt in the north, through 710̊C/4-5 kb in the middle to 750̊C/6-7kb in Krishnagiri-Dharmapuri area.  Low pressure metamorphism of EDC is caused by the abundance of younger granite providing the advective heat, which was lack in WDC.
  16. 16. CONCLUSION  Dharwar Craton is a classical greenstone-granite terrain, divided into Western and Eastern Dharwar Craton.  It is separated by the Chitradurga Shear Zone close to the Closepet Granite.  EDC consists of the older gneisses, greenstone belts of Dharwar super group, Closepet Granite and charnokites.  It is one of the best studied terrain of Peninsular India.  EDC is regarded as an Archean batholith that accreted on to the craton in the west along a diffuse zone of interaction
  17. 17. REFERENCE  Geology of India by M.Ramakrishnan and R. Vaidyanathan. Published by Geological Society of India: Vol.I, 2008 page: 48-50, 99-180  WEB: www.google.com:- www.mindat.org/loc-49196.html wikipedia.org/wiki/Dharwar_Craton

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