Western dharwar craton

1. SEMINAR ON
WESTERN DHARWAR
CRATON
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2. CONTENTS
 INTRODUCTION
 HISTORY
 WESTERN DHARWAR CRATON
 STRATIGRAPHY
 SARGUR GROUP
 BABABUDAN
 CHITRADURGA
 SCHIST BELTS
 SARGUR SCHIST BELT
 HOLE NARASIPURA SCHIST BELT
 CHARNOCKITES OF WDC
 YOUNGER GRANITES OF WDC
 ECONOMIC IMPORTANCE OF WDC
 CONCLUSION
 REFERENCE
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3. INTRODUCTION
 The Archaean Dharwar craton covers an area of 4.5 lakh sq km
is bounded in the south by the pan pacific Pandyan mobile
belt (pmb)and to the north the Deccan traps underline and
fringed by the Proterozoic (Purana) Kaladgi and Bhima basin.
Towards the east boundary is given by the Eastern Ghat mobile
belt and towards the west it is bounded by the Arabian sea which
separates India from Madagascar.
 The Dharwar craton is one of the best studied terrain of
peninsular India and its renowned for its greenstone schist belt
,grey gneisses charnockites and younger granites.
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4. HISTORY
 The craton is divided in to two tectonic blocks by
Swami Nath (1976 ) et al, they are western and
eastern block.
 Renamed respectively as the Western Dharwar
Craton (WDC) and Eastern Dharwar Craton (EDC)
by Rogers (1986)
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5. WESTERN DHARWAR CRATON
 Western Dharwar Craton is occupied by vast area of
peninsular gneisses
 Two prominent super belts are seen;
1. Bababudhan-Western ghats-shimoga and
2.Chitradurga- Gadag
belonging to the Dharwar Supergroup
 Southern part –narrow linear schist belts belonging to
the older Sargur group , like Holenarsipur , Nuggihalli,
Nagamangala
 The younger granites like Chitradurga , Hosadurga,
Arsikere occur as isolated pluton in the gneissic country
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7. STRATIGRAPHY
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8. The Gorur gneiss is the oldest gneiss and it consists
of trondhjemitic gneiss with associated tonalites and
granodiorites , U-Pb in zircon – 3500-3600 Ma
(SHRIMP- Sensitive High Resolution Ion MicroProbe)
 It consist of oligoclase,
subordinate microcline, quartz
and biotite or hornblende
 Geochemical studies indicate
that the gneisses are high –silica,
low –alumina trondhjemites
enriched in REE
 Gorur gneiss are found at
Ammod Ghat(goa),Tiptur,
Gundalpet and other places
Fig. Gorurgneiss
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9. Sargur group
 It occurs as linear Mafic- Ultra mafic belts
 Group of enclaves scattered throughout the
craton
 Rock types –ultra mafic ,mafic intrusive complex,
chert, BIF, garnet- biotite schist, sillimanite gneiss,
kyanite-staurolite gneiss.
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10. STRATIGRAPHY OF SARGUR GROUP
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11. BABABUDAN GROUP
 It overlies the Sargur group of rocks in the stratigraphic column.
 It consists of four formations: Kalasapura formation, Allampura
formation, Santaveri formation and Mullaingiri formation.
 The major rock types are metabasalts, BIF, gabbro, ultramafic
schists, phyllites, quartzites, conglomerate.
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13. SCHIST BELTS
 Sargur Schist Belt
 Holenarasipura schist belt
 Nuggihalli schist belt
 Bababudan schist belt
 Western schist belt
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14. Sargur Schist Belt
 It is a zone of schist enclaves and narrow bands near Sargur
town , situated 40km south west of Mysore city.
 The zone of enclaves extends from near Mysore to Kerala ,and
up to Nanjangud in the east
 Fresh outcrops of various lithologies were best exposed in the
canals of Kabini river near Sargur, and hence the name of Sargur
group.
 Rock types –Fuchsite quartzite, metapelites, carbonates and
calc-silicate rocks etc
 Mafic – ultra mafic rocks form one of the major components of
Sargur Schist Belt
 Mafic rocks are more abundant than ultra mafic rocks, and are
associated with iron formations.
 The ultra mafic rocks are essentially serpentinites and tremolite
– actinolite-anthophyllite-chlorite schists
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16. Structure
 The earliest recognizable structure in the narrow belts of
Sargur group is widespread schistosity parallel to the bedding,
intrafolial folds and migmatic banding
 Second phase of deformation has given rise to upright , tight to
isoclinal folds
 Third deformational phase has refolded the folds of second
generation
 The Sargur schist belt of WDC consist of several other minor
schist belts
.Manantavadi(Wayanad )schist belt
.Kasargod schist belt
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17. Holenarasipura schist belt
 It is a trident shaped schist belt
 The trident shape of the schist belt is due to the
deflection of schist's around bosses of
mavinkere granodiorite
 The Sargur and Dharwar succession are not well
exposed but deformed and metamorphosed
together during later Dharwar orogeny
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19. Other major schist belts of WDC are as follows
 Nuggihalli Schist belt- altered dunite ,tremolite-
actinolite-cummingtonite-anthophyllite-talc-chlorite-
magnetite schists
 Aladahalli belt
 Krishnarajpet belt
 Hadanur belt
 Melukote and Nagamangala belt
 Kalyadi belt
 Banavara belt
 Western Ghat belt
 Shimoga belt
 Chitradurga schist belt
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20. Charnockite of WDC
 They are associated with PGC, continue upto Moyar
Bhavani shear zone
 It shows spectacular transformation from the TTG
suite of peninsular gneiss are seen all along the
amphibolite granulite facies boundary from Manglore
and Coorg in the west to the Nanjangud in the east.
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21. Younger granite in WDC
 There are five types of granites found in
WDC
 Chitradurga
 Jn kotte
 Hosadurga
 Chamundi
 Arsikere
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22. Other intrusion in WDC
 Thagaduru layered basic intrusion
 Kunduru betta ring intrusion
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Western Dharwar Craton (WDC) Eastern Dharwar Craton (EDC)
1. Dharwar schist belts – large, with
volcanics, subordinate sediments.
2. Peninsular gneiss, (>3000 Ma)
basement having angular
unconformity with the Dharwar
marked by QPC. Basement gneiss
inliers within schist belts.
3. Three fold succesion of
I. Basalt-arenite-BIF
II. Shelf facies at the margin and
homotaxial pillowed basalt BIF in
deeper waters.
III. Greywackes- BIF-volcanics
4. Older sequence (Sargur group) as
narrow belts and enclaves
abundant in the south.
5. Intermediate pressure (Kyanite-
sillimanite type) metamorphism.
1. Dharwar greenstone belts- narrow
with dominant pillowed basalts.
2. Dharwar batholith (2500-2700 Ma)
intrusive on all sides. Diapiric
gneiss domes common.
3. Three fold succession of
I.Rare shelf sediments disrupted
into screens at the belt margins
II. Pillowed volcanics,
greywackes, BIF
III. Felsic volcanics,
volcanogenic conglomerate
(Champion Gneiss).
4. Older sequence ( Warangal group)
mostly as enclaves in the north
east and Salem group in the south
5. Low pressure ( Andalusite-
sillimanite type) metamorphism.

24. Economic Deposits:
 Magnesite
 BIF
 Chromite
 Vanadium-Titanium-Magnetite
 Copper-Nickel
 Asbestos and Soap stone
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25. CONCLUSION
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 Western Dharwar Craton is bounded to the east by the Eastern Dharwar
Craton, to the west by the Arabian Sea, and to the south by a transition
into the so-called ‘‘Southern Granulite Terrane.” The remaining
boundary to the north is buried under younger sediments and the
Cretaceous Deccan Traps.
 The division between the Western and Eastern Dharwar Cratons is
based on the nature and abundance of greenstones, as well as the age
of surrounding basement and degree of regional metamorphism.
 The WDC shows an increase in regional metamorphic grade from
greenschist to amphibolite facies in the north and granulite facies in the
south.
 The metamorphic grade increase corresponds to a paleopressure
increase from 3 to 4 kbar in the amphibolite facies to as much as 9–10
kbar (35 km paleodepth) in the highestgrade granulite-transition zone
along the southern margin of the craton.
 The Dharwar supracrustal rocks uncomformably overlie widespread
gneiss-migmatite of the Peninsular Gneissic Complex (3.0–3.3 Ga) that
encloses the Sargur schist belts08/12/17

26. REFERENCE
 Radhakrishna, B.P., Naqvi, S.M., (1986). Precambrian continental crust of India and
its evolution. 94, 145–166.
 Ramakrishnan .M and Vaidyanadhan R (2010).Geology of India, Geol.Soc.Ind., v.1,
pp. 189-208.
Websites:
www.springer.com
www.wikipedia.org
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