Presentation is about Dharwar craton in India. It covers most of the important aspects.

1. PRESENTED BY:
VISHAKHA NATHANI
M.Sc. GEOLOGY
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2.  Dharwar Craton – introduction and its extension
 Classification
 Difference between WDC and EDC
 Western Dharwar Craton
 Eastern Dharwar Craton
 Lithology
 Dharwar supracrustal rocks
 Sargur Group
 Bababudan Group
 Chitradurga Group
 Greenstone belts
 Younger granites
 Closepet granite
 Regional structure
 Metamorphism
 Life
 Economic importance of dharwarian rocks
 Summary
 Reference
CONTENT
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3. INTRODUCTION
The Archaean Dharwar Carton covering an area of about 4.5 lakh (0.45
million) km2 , the available geochronological ages spanning between 3.4 and
2.0 b.y.a. highlights the major early Precambrian events in the Craton and
The term Dharwar (Karnataka) Craton was introduced by the geological
survey of India in 1978..
The Dharwar Craton is one of the best-studied terrains of Peninsular India,
and is renowned for its greenstone/schist belts, grey gneisses, charnockites
and younger granites.
It is bounded to the south by the Pan- African Pandyan mobile belt (PMB); to
the north by the end- Cretaceous Deccan Trap underlain and fringed by the
Proterozoic (Purana) Kaldgi and Bhima basins.
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4. The contact between WDC and EDC is not sharp, and there is a
transition zone between the Chitradurga Shear Zone and Closepet
Granite.
Chitradurga Shear Zone marks the boundary between Western
Dharwar and Eastern Dharwar Craton apart from Closepet Granite
The Chitradurga Shear Zone is a narrow geosyclinal belt which
extends from Gadag in the north to Shrirangapatna in the south,
for a length of 460 km. The belt attains a maximum width near
Chitradurga .
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5. ESSENTIAL FEATURES OF
Dharwar Craton
DISTRIBUTION OF
CRATONS
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6. CLASSIFICATION
 The classification has been given by J. Swami Nath, M.
Ramakrishnan and M. N. Viswanathan in 1976 resulted in a
holistic stratigraphic model which was backed by a 1:500,000
scale geological map published in 1981.
 Essential features of this classification (Swami Nath and
Ramakrishan 1981) are the following (Table 3D-2)
 Dharwar Craton was divided for the first time into two tectonic
blocks WDC and EDC.
 {Ramakrishnan and R. Vaidyanadhan (2010) vol I geology of India PG
NO 103}
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7. WESTERN DHARWAR CRATON
WDC is located in southwest India.
Western Dharwar Craton (WDC) is occupied by vast areas of Peninsular Gneiss along with two
prominent super belts of
Bababudan – Western Ghats- Shimoga and
Chitradurga- Gadag belonging to the Dharwar Super Group.
WDC is bounded by EDC in east, Arabian Sea in west, to the south by a transition into
the southern-granulite terrain and the north is buried under younger sediments and the
Cretaceous Deccan Traps.
GORUR GNEISS is the oldest gneiss in WDC. It is a suite of trondhjemitic gneisses
with associated tonalities and granodiorites (TTG) .
Sargur Group of rocks have been deposited during 3130-2960 m.y.(3.1 – 2.9 by) .
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8. DHARWAR SUPERGROUP
Table 1: Regional stratigraphy of WDC (after Swami Nath and Ramkrishnan 1981)
Proterozoic mafic dyles
Charnockites (2500-2600 Ma)
Younger granites (2600 Ma)
Ranibennuer Greywackes with BIF, polemic conglomerate,
SubGroup mafic-felsic volcanic
Manganese and iron formations, Mafic-felsic
Stromatolitic carbonates, biogenic volcanic with
Vanivilas cherts, pelites quartzite’s and BIF, phyllites
SubGroup polymict conglomerates (basin center)
(Basin Margin)
Talya/Kaldurga Conglomerate= Metabasalt
And siliceous phyllites of Jagar valley
-----------------------------------------Disconformity----------------------------------------------------
Mulaingiri BIF with phyllites and rare ultramafic- mafic
Formation Sills
Santaveri Metabsalts, felsic volcanic (Galipuje felsites)
Formation local BIF, phyllites, cross-bedded quartzite
(Lakya)
Kalasapura Metabasalts, gabbros, ultramafic schists
Formation phyllites, quartzite’s, basal quartz pebble conglomerate (Kartikere conglomerate)
------------------------Deformed angular unconformity-------------
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9. EASTERN DHARWAR CRATON
The EDC is bounded to the north by the Deccan Traps and the BastarCraton, to the
east by the Eastern Ghats Mobile Belt, and to the south by the Southern Granulite
Terraine .
The Craton is composed of the Dharwar Batholith (dominantly granitic), greenstone
belts, intrusive volcanics, and middle Proterozoic to more recent sedimentary basins.
The supracrustal belts of the EDC are smaller in size than those of the western blocks
which are surrounded by gneisses and granites.
“older greenstone belts” that are either older or equivalent to the Bababudan Group of
the western block. Metabasalts from Kolar schist belt indicating that they are
contemporaneous with the Chitradurga Group of the western block (WDC).
OLDER GNIESS: Recognizable areas of older gneisses are not widespread in the EDC in
contrast to their extensive development in WDC.
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10. TABLE 2, SIMPLIFIED STRATIGRAPHY OF ARCHAEAN
DHARWAR CRATON
{RAMAKRISHNAN AND R. VAIDYANADHAN (2010) VOL I GEOLOGY OF INDIA } PG NO 104
Age Western Dharwar Craton
(WDC)
Eastern Dharwar Craton (EDC)
2500-2600 Ma
2600-2800 Ma
~ 3000 ma
31000-3300 Ma
3300-34000 Ma
Younger granite
(Chitradurga, Arsikere)
Charnockites
Chitradurga Group
Dharwar
SuperGroup
Bababudab Group
----- unconformity ----
Peninsular Gneiss
Sargur Group
Gorur Gneiss
Younger granite/ gneiss
(Close pet and equivalents)
Charnockites
Kolar Group
Yashwantanagar Formation
-----------------------------------
Enclaves of older gneiss
(?) Warangal Group
(?) Salem Group
Putative Basement
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11. Western Dharwar Craton (WDC) Eastern Dharwar Craton (EDC)
1. Dharwar schist belts-large, with volcanic ,
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 succession of :
(i) Basalt-arenite-BIF
(ii) Shelf facies at the margin and homo axial
pillowed basalt-BIF in deeper waters.
(iii) Greywackes-BIF-volcanic
1. Older sequence (Sargur Group) as narrow
belts and enclaves, abundant in the south
2. 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 volcanic, greywackes, BIF
(iii) Felsic volcanic, volcanogenic conglomerate
(‘Champion Gneiss’)
1. Older sequence (Warangal Group) mostly
as enclaves in the northeast; and Salem
Group(?) in the south
2. Low pressure (andalusite- sillimanite type)
metamorphisam.
Essential differences between Western Dharwar Craton (WDC) and Eastern
Dharwar Craton (EDC) (Ramakrishnan and R. Vaidyanadhan (2010) vol I geology of India PG NO 100 )
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12. LITHOLOGY OF WDC
 Based on the supracrustal lithological relationship between the Peninsular
gneiss and the supracrustal rocks, Swami Nath and Ramakrishnan (1981)
classified the supracrustal rocks of DharwarCraton into
 older Sargur Group and
 younger Dharwar SuperGroup:
SARGUR Group
 Age of Sargur is tentatively considered to be 3.4-3.0 b.y.
 Sargur Group found as belts enclaves ,narrow bands and stringers near Sargur
town, situated 40 km southwest of Mysore city .
 Sargur Group lithology include quartzite, quartz fuchsite-muscovite schists,
bedded barites sillimanite-garnet-staurolite-kyanitegraphite-corundum-quartz-
biotite schists, crystalline limestone, dolomites, calcsilicate rocks, amphibolite
(metabasaite), iron stones (oxide and silicate facies BIF) meta ultramafic and
anorthosites.
 The Sargur enclaves represent:
1. elongated and locally faulted synformal keels and
2. antiformal hinges
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13. YOUNGER DHARWAR SUPERGROUP
 The Dharwar supracrustal is deposited unconformably over a sialic
basement of tonalitic and granitic “Peninsular Gneiss” (Chadwick et al.,
1981).
 The supracrustal rocks of Dharwar Supercrustal are exposed as number
of schist belts; prominent among them are: Bababudan, Western Ghat,
Chitradurga, Shigegudda, Shimoga-North Kanara-Goa, Sandur, Kolar &
Hutti schist belts.
 Total thickness of these Dharwar schist belts is estimated to be 6 to 7
km .
 Age of the Dharwar SuperGroup -3.0-2.6 b.y.a.
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14. BABABUDAN GROUP
 Bababudan Group of rocks are exposed mainly in Bababudan, Western
Ghats, Shigegudda and Yadiyur-Karighatta arm of Chitradurga schist belt.
 Bababudan Group represents a typical mafic platformal association ending
up in prominent iron ore (BIF) cycle.
 The Bababudan sediments and Volcanics suggest nearshore to and
subaerial to shallow marine environment respectively (Chadwick et al.,
1985).
 The rocks of Bababudan Group are metamorphosed upto lower
amphibolites facies (garnet isograd) at the borders and green schist facies
at the core portions.
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15. CHITRADURGA GRANITE
 Elongated lenticular body of late to post-tectonic granite.
 60 km long and 15 km wide exposed near Chitradurga town.
 It is essentially biotite granite grading into granodiorite and quartz
monzonite.
 The potassic type granite is also evolved.
 The granite has yielded well fitted Pb-Pb and Rd-Sr isochrones
(~2600ma) and SIMS U-Pb zircon (~2610ma).
 Studies suggest the involvement of the gennesis basement in its
genesis.
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16. YOUNGER GRANITES IN WDC
 Late to post-tectonic Dharwar granites (~26000 Ma) that denote crustal
reworking in WDC.
 Other Granites are as follow
 Jampalnaikankote (J.N. Kote) Granite
 Arsikere and Banavara Granites
 Hosadurga Granite
 Chamundi Granite
 Alkali Granites and Syenite
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17. EASTERN DHARWAR CRATON
 The contact between WDC and EDC is not sharply defined, although the
Chitradurga Boundary Fault is taken as a convenient and conspicuous
marker.
 OLDER GNIESS: Recognizable areas of older gneisses are not
widespread in the EDC in contrast to their extensive development in WD
 Their mutual relation with the greenstone belts is a matter of debate.
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18. GREENSTONE BELTS OF DHARWAR SUPER GROUP
 The EDC is Characterized by volcanic-dominated, sediment-
impoverished and gold – rich greenstone belts, in contrast to those
of WDC.
 These greenstone belts are engulfed on all sides by younger
granitoids.
 They are popularly known as Easter greenstone belts because of
their geographic position in the craton.
 The linear arrays of superbelts in the EDC are the following:
 Ramagiri- (Penakacherla –Sirigeri ) – Hungund superbelt
 Lolar-Kadiri-Jonnagiri-Hutti Superbelt
 Veligallu-Raichur-Gadwal superbelt
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19. YOUNGER INTRUSION IN EDC
 The plutonic belts enclose a few scattered younger intrusions joga
granite occurring with in the Sandur belt contains fluorite and carbonate
yields SHRIMP U Page of 2570 Ma.
 Koppel syenite is an elongate, wedged-shaped intrusion trending NE
SW, which has steep bending in contact with host granite to the NW of
Sandur belt.
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20. CLOSE PET GRANITE
 The liner belt of Closepet Granite is having a length of nearly 500 kms
and an average width of 20-25 Kms. They are the most prominent of the
younger granite.
 close pet granite is a unique linear arcuate body consisting of diverse
granitic type.
 The most characteristic rock type of this class is coarse-grained
porphyritic granite with large-sized pophyroblasts of pink and grey
potash feldspar.
 Grey and pink porphyritic gneisses are also very common.
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21. REGIONAL STRUCTURE
 The structures of the Dharwar Super Group are
dominated by a set of mainly open to tight upright
synclines.
 Compressive deformation can be recognised.
 Their trends are variable and the plunge of their axes
range from sub-horizontal to sub-vertical.
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22. METAMORPHISM
 The Sargur Group of rocks is metamorphosed ranging from middle amphibolite
facies in central Karnataka to upper amphibolite and granuliefacies in southern
Karnataka
 There is progressive change of regional metamorphism from north to south in
the Dharwar Craton and it is related to increase in grade of metamorphism to
increasing depth of burial.
 Vishwanatha and Ramakrishnan reported two basic types of metamorphic
facies. On the western side of Closepet granite an intermediate pressure,
and on the eastern side, low pressure metamorphic assemblages were
recognized.
 On the western side of Closepet granite an intermediate pressure, and on the
eastern side, low pressure metamorphic assemblages were recognized.
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23. LIFE
 No fossils have yet been found from Dharwarian rocks.
 Mostly of them are sedimentary in origin.
OVERALL STRUCTURE
• EXTENSIVE FOLDING
• FAULTING AND INTENSE METAMORPHISM.
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24. ECONOMIC IMPORTANCE
OF
DHARWARIAN ROCKS
 The Archean Group of rocks, of which dharwars forms a very important
sun Group are regarded as the most important economic mineral bearing
Groups of India stratigraphy.
 Most of the economic minerals like those of iron, copper
manganese,lead,zinc, and gold etc. have come from rocks which broadly
belongs to Archean time but not coal and petroleum.
 As regards mineralization,
1. The western block is characterized by copper, iron and manganese
mineralization, whereas
2. The Eastern Block is known for gold, iron and manganese mineralization.
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25. SUMMARY
 The Dharwar Craton is one of the best-studied terrains of Peninsular India, and
is renowned for its greenstone/schist belts, grey gneisses, charnockites and
younger granites.
 Dharwar Craton was divided for the first time into two tectonic blocks WDC
and EDC.
 Dharwar ‘System’ in WDC was Grouped into two orogenic cycles separated in
time viz., the older Sargur Group (3100-3300 Ma) and the younger Dharwar
SuperGroup (2600-28000 Ma).
 Sargur and Dharwar successions are separated by deformed angular
unconformities at Bababudan, Sigegudda, Jayachamarajapura (J.C. Pura) and
Chatti Hosahalli. Elsewhere (Hole Narasipura Mayasandra), the two
successions are folded together into parallelism during the younger Dharwar
orogeny.
 In EDC, younger granitites dominate, with subordinate gneisses, together
constituting the Dharwar batholiths. The batholiths intrudes wholesale the
various units of Dharwar sequence (2600-2800 Ma)
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26.  The contact between WDC and EDC is not sharply defined, although the
Chitradurga Boundary Fault is taken as a convenient and conspicuous
marker
 The greenstone belts of EDC from linear arrays of what may be called
superbelts or composite belts that extent underneath the Cuddapah basin.
 Close pet Granite does not belong to the linear array.
 No fossils have yet been found from Dharwarian rocks.
 Structure: extensive folding and faulting and intense metamorphism.
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27. REFERENCES
 Ramakrishnan and R. Vaidyanadhan (2010) volume I Geology of India
published by the geological society of India PB 1922 Gavipuram, (PP. 99-180).
 D.N. Wadia, Geology of India 4th add., Publ. by The Macmillian company ltd.
Canada (PP. 60-70).
 Krishnan, M.S. (1982) Geology of India and Burma, C.B.S. Publ. and
Distributors, Delhi.
 R.kumar (1981) Fundamental of Historical Geology & Statigraphy of India (PP
139-161).
 WWW.Shodhganga.com
 WWW.vedamsbooks.com
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