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Cratons of india

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Cratons of india

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Cratons of india

  1. 1. Presented By Under guidance of Pramoda G H. T. Basavarajappa 2nd semester, Geology Professor Presentation on “CRATONS OF INDIA”
  2. 2. • Introduction • Dharwar Craton - WDC AND EDC • Baster Craton • Singbhum Craton • Bundelkhand Craton • Aravalli Craton • Conclusion • References CONTENTS:
  3. 3. INTRODUCTION 1. Cratons are the part of the earth’s continental crust which has attained stability and was least affected by deformation during the later periods. 2. Cratons are generally found in the interiors of tectonic plates. 3. They are characteristically composed ancient of crystalline basement rock, which may be covered by younger sedimentary rocks. 4. They have a thick crust and deep lithospheric roots that extend as much as a few hundred kilometers into the Earth's mantle. 5. A shield is part of the craton, where the basement rock crops out at the surface.
  4. 4. There are five major cratons in India. They are; 1. BASTAR CRATON 2. DHARWAR CRATON 3. SINGHBHUM CRATON 4. ARAVALLI CRATON 5. BHUNDELKHAND CRATON MAJOR CRATONS OF INDIA
  5. 5. Outline map of the shield showing the distribution of cartons
  6. 6. DHARWAR CRATON:-Dharwar craton is divided into two tectonic blocks in 1986 by Rogers. 1. Western Dharwar craton (WDC) 2. Eastern Dharwar craton (EDC)
  7. 7. WDC EDC SCHIST BELT LARGE WITH VOLCANICS, SUBORDINATE SEDIMENTS. NARROW, WITH GREENSTONE BELTS. PILLOW BASALTS. BASEMENT IS PENINSULAR GNEISS. UNCONFORMITY MARKED BY QPC.(<3000MY) DHARWAR BATHOLITH INTRUSIVE ON ALL SIDES .(2500-2700 MY) OLDER SEQUENCE (SARGUR GROUP)AS NARROW BELTS AND ENCLAVES, ABUNDANT IN THE SOUTH. OLDER SEQUENCE(WARANGAL GROUP) MOSTLY AS ENCLAVES IN THE NORTH. INTER MEDIATE PRESSURE METAMORPHISM. LOW PRESSURE METAMORPHISM. Comparison between WDC and EDC
  8. 8. WDC - It occupied by vast areas of peninsular India With 2 prominent super belts 1. Bababudan-western ghats-shimogga super belt • This super belt spread appro.300km long & 100-150km wide. • Schistose rocks occupying 3000km Sq. Remaining 1500km Sq. Occupied by basement peninsular gneiss. • Bababudan Schist belt occupies an area 2500km Sq. • A prominent but thin horizon of quartz pebble conglomerate. • This group dominantly made up of Metabasalt with interbedded cross-stratified quarzitites capped by a prominent BIF. Age is about 2700-2800MY.
  9. 9. • The Bastar craton (BC) is also called Bastar-Bhandara craton. It lies to ENE of the Dharwar craton (DC), separated from the latter by the Godavari rift. Located to the south of the Central Indian Tectonic Zone (CITZ) the Bastar craton is limited by three prominent rifts, namely the Godavari rift in the SW, the Narmada rift in the NW and the Mahanadi rift in the NE. • The Bastar craton is essentially formed of orthogneisses with enclaves of amphibolites, vestiges of banded TTG gneisses of 3.5–3.0 Ga, and low- to high-grade metasediments as supracrustals. • The gneiss/migmatites and amphibolites, constituting the early crustal component of the Bastar craton, are grouped under the Amgaon gneiss that resembles the Peninsular Gneiss Complex of the Dharwar craton. It craton. It ranges in composition from tonalite to adamellite. Amgaon gneisses occur in the north of Bastar craton and south of Central Indian Shear zone (CIS). Facts
  10. 10.  In Bastar craton the gneisses are classified into 5 types. These are: the Sukma granitic gneiss (Group 1), Barsur migmatitic gneiss (Group 2), leucocratic granite (Group 3) occurring as plutons with migmatitic gneiss, pegmatoidal or very coarse granite (Group 4), and fine-grained granite (Group 5) occurring amidst the Sukma gneisses.  The gneisses of Groups 1 and 2 are chemically and mineralogically similar to the Archaean TTG, while the gneisses of Groups 3, 4 and 5 are of granitic nature.  In the Bastar craton, three Archaean supracrustal units are recognized. First is Sukma metamorphic suite consisting of quartzites, metapelites, calc-silicate rocks, and BIF with associated metabasalt and ultramafic rocks
  11. 11. Grey gneisses and migmatites of TTG composition are exposed in southern Bastar and in Amgaon –Gadchiroli ares Banded gneisses occur as large raft within the dominant granitic gneisses of the ares These migmatites gneisses are dated at ~3000 Ma these gneisses are affected by the later thermal events of ~2500 Ma and ~2100 Ma Granulite Belts Bhopalpatnam granulite belt is about 300 km long and 30-40 km wide ,and trends NW-SE to the north of Godavari graben. The incipient charnockites are also reported to occur in the transitional domain .meta-peridolites contain olivine spinel and orthopyroxene.BIF and Mg-Al pelites are composed of orthopyroxene, sapphirine and spinel Quartzite are rich in sillimanite .calc-silicate rocks contain wollastonite scapolite and humite Recently reported younger age (1.6-1.9 Ga)) Gneissic Complex
  12. 12. • Singbhum craton is made of Archean rocks that are exposed in an area of 4000km.Sq in jharkhand and northern parts of the Orissa state. • Craton borded by Chhotanagpur Gneissic complex to the north, Eatern Ghats mobile belt to the southeast, Bastar craton to the south west and Alluvium to the east. • Singbhum Granite (I,II,II phases) with enclaves of (i) Older Metamorphic Group(OMG) and Older Metamorphic Tonalite Gneiss(OMTG). • Iron ore group(IOG), dominantly BIF at the margins of the Singbhum Granite. • Volcanics or greenstone belts (Simlipal,Dhanjori,Dalma etc) Key points
  13. 13. Major belts of CGGC 1. South Palamau –Gumla-Ranchi-Puruchi Belt. 2. Daltonganji-(Northern Palamau)- Hazarobagh Belt 3. North Garhwa-Chatra-Girdih-Deogarh-Dumukh Belt 4. The Bihar Mica Belt 5. Rajgir – Kharagpur Belt
  14. 14. Geodynamic Evolution • Older metamorphic group which yield same age as Metamorphic Tonalite Gneiss. • Zircon age in politic rock of OMG suggest that sialic crust had existed about 3.6Ga. Prior to the formation of OMG. • Singhbhum Granite – 1 in which xenoliths of OMTG Found. • Mesoarchean continental crust of SG-1 with enclaves OMG and OMTG rifted and formed greenstone belt of Badamphar group – Komatiites, pillowed tholeiitic, BIF and Fuchsite quartzite. • Closing of greenstone belt basins – granite intrusion (Phase 2 and 3). • Next cycle marked by volcanic and sediment association of 2.8Ga
  15. 15. Bundelkhand Craton is one of the Archean cratons in the Indian shield. It is exposed over 26,000 sq. km and is bound by the Son Narmada lineament in the south. Bundelkhand craton is separated from the Satpura mobile belt in the south and the Aravalli craton in the west by the proterozoic vindhyan besin and the northern part is overlain by the Indo-Gangetic alluvium The main components of the craton are 1) Enclave suite of supracrustal rocks within orthogneisses. 2) Bundelkhand granite associated with quartz reefs and rare felsic volcanic. 3) Mafic dyke swarms Facts
  16. 16. 1)Enclave suite of supracrustal rocks within orthogneisses Supracrustals Two prominent east-west trending belts of enclave are noticed i) Northern belt extending from karera to kabrai, kuraicha Jhansi Mauranipur and Mahoba ii) Southern belt from to Baraitha through Girar. Enclave are noticed at near panna and kalinjer. These belts have a regional trend of E-W with northerly dips. The enclaves consist essentially of BIF with amphibolites, ultramafics and minor quartzite, metapelite and marble. Ultramafic rocks are mainly peridotites, dunites, pyroxenites and gabbros closely associated with metabasic rocks and BIF.
  17. 17. 2) Bundelkhand granite associated with quartz reefs and rare felsic volcanic The vast country of Bundelkhand granite represents a large plutonic complex of batholithic dimension. Three types Granite; i)Coarse grained porphyritic granite. ii)Medium grained porphyritic granite. iii) Leucogranite, Felsic volcanic rocks: these rocks are associated with the granites at many places such as mahoba, bansi, and simra near prithipur they occur as grey to pink , fine to coarse grained and porphyritic felsic rocks.
  18. 18. Quartz Reefs The emplacement of NE-SW trending giant quartz reefs along brittle shear zones probably marks the end stage hydrothermal activity related to granitic plutonism. 3) MAFIC DYKE SWARMS A NW-SE trending swarm of Mafic dykes is a characteristic feature of Bundelkhand craton some of dykes have ENE trend, like the prominent mahoba dyke .The geometry of the main dyke swarms is attributed to E- W shearing stress, developed after cratonisation.
  19. 19. TECTONIC EVOLUTION • Bundelkhand and Aravalli cratons were traditionally regarded as interlinked, with the Bearch granite of Aravalli craton being considered as the equivalent of Bundelkhand granite. • Geochemical and Geochronological similarities have reinforced this comparison. The separation of two cratons with the evolution of Hindoli and Mahakoshal belts at the cratonic margin, was followed by the evolution of Vindhyan basin. • Bundelkhand craton witnessed N-S compression –induced deformation , metamorphism and emplacement of TTG gneisses produced by the partial melting of a garnet amphibolite parental source at 3000-3300Ma. Widespread collision-related arc magmatism represented by bundelkhand granite commenced probably at 2700Ma and culminated at 2500Ma.
  20. 20.  The region is characterized by the presence of dominantly three types of shear zones: E-W, NE-SW and NW-SE.  The E-W trending, vertical shear zones constitute the subject matter of the present study and the areas where these shear zones are exposed have been shown.  It may be noted that in addition to the E-W shear zones shown in this map, there are many such shears of relatively smaller extent that could not be shown because of the scale of the map, however, were studied because of their typical features, e.g. Jhankri, Kuraicha, Roni, etc.
  21. 21. Field photographs showing the typical occurrence of the vertical shear zones in the Bundelkhand terrain. The rocks are mylonites. (a) Near Shivgarh, (b) At Dhaura, (c) Near Koti, about 6 km SE of Babina, (d) North of Pura, about 5 km NW of Sukumwa Dam.
  22. 22. A & B- Ultramylonite showing high degree of grain-size reduction because of dynamic recrystallization Cataclasite showing angular grains set in a fine grained matrix.
  23. 23.  It occupies NW part of Indian shield covering an area of over 1 lakh sq.km.  It consists of Mewar craton in the east & Marwar craton in the west.  Aravalli craton is bounded to the east by Great Boundary Fault, to the west by sands of Thar desert, to the north by Indo-Gangetic alluvium and to the south by Son-Narmada-Tapti lineament.  Predominantly consists of quartzites, marbles, pelites, greywackes and volcanocs, exposed in Aravalli-Delhi orogen.  It is distinguished by the largest felsic volcanic province of India, 3rd in the world (Malani Igneous Suite). ARAVALLI CRATON
  24. 24. STRATIGRAPHIC CLASSIFICATION OF ARAVALLI SUPERGROUP: Aravalli Super Group Champaner Group Lunavada group Jharol Group Udaipur Group Delbari Group Delwara Group ------------Unconformity------------ Mangalwar/Sandmata Complex Mewar Gneiss with enclaves of Jagat Group
  25. 25. Delmar group :has an area over 300km with an average width of about 500m.The basement rock is orthoquartzite which is overlain by volcanic conglomerate(volcanic unit) Delbari group: it overlain the Delwara group consists of a thick horizon of petromict conglomerate,pebble arkose and feldspatic quartzite. The conglomerate has a maximum thickness of 2500m near Dabari Udaipur group: consist of thick accumulation of greywacke- phyllite intercalated with chemogenic and biogenic rocks. The greywacke-phyllite is overlain by dolomite associated with carbonaceous phyllite and quartzite.
  26. 26. Jharol group: consists of thick sequence of carbonate-free phyllite and arenite(as distal turbidites) Has an area of 200km with a width of 40km Lunavada group: It occupy the polygonal area in the south of the aravalli orogen.The bulk of the group consists of greywacke-phyllite with associated quartz arenite.The stratigraphy of the Luna group is not clearly established. Champaner group: occurs as rectangular outcrop and consists of subgreywacke,siliceous phyllite,pelitic schist,quartzite and petromict conglomerate.It is folded into an anticlinorium plunging to the west The stratigraphy status is unclear because it is seperated by the main fold belt
  27. 27. Neoproterozoic Marwar supergroup (500-550Ma Malani igneous Suite (720-750Ma) Sindreth/punagarh group (800-850Ma) Sirohi group (900Ma) Erinpura granite Mesoproterozoic Delhi supergroup (1100-900Ma) South Delhi fold belt (1600-1450Ma) North Delhi fold belt Palaeoproterozoic Hindoli group (1800-1700Ma) Sandmata complex (2200-1800Ma) Aravalli Supergroup & Mineralised Basin(Rajpura-Dariba etc) Neoarchean (2900-2600Ma) Mangalwar complex with Bhilwara Group Mesoarchean (3300-3000Ma) Mewar gneiss with Jagat group TECTONIC-STRATIGRAPHIC TABLE OF EVOLUTION OF ARAVALLI CRATON
  28. 28. ECONOMIC DEPOSITS: The major economic deposits are: Pb-Zn deposits (Zawar) Gypsum Marble (Macrana) BIF Mica (Jagat group) Copper (Khetri ) Tungsten (Degana, Balda and Sewariya-Govindgarh areas.)
  29. 29.  In general, the cratons are dominated by granite and metamorphic rocks, mainly gneisses, which imply a series of intense mountain making episodes (deformation and metamorphism) in the Precambrian time before the stable conditions set in. A common feature of these cratonic regions is the occurrence of greenstone-gneiss association, as found in other Archaean cratons of the world.  The Indian shield is made up of a mosaic of Precambrian metamorphic terrains that exhibit low to high-grade crystalline rocks in the age range of 3.6–2.6 Ga.  Cratonic blocks are described with respect to their geology, geochronology, and structural characteristics
  30. 30. Reference • Cratons and Fold Belts of India 2009 By Sharma Ram S Sharma. • Geological survey India website for images http://www.portal.gsi.gov.in/portal • http://www.sciencedirect.com/science/article

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