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1

Southern India

1.1 Geology and Crustal Evolution

IntroductionSouthern Indian craton today is divided into two regions: the Dharwar Province (DP) and the Southern Granulite Province (SGP) or Southern Granulite Terrain (SGT) (Fig. 1.1.1). The Dharwar Province, ever since the publication of results of excellent geological studies by the geologists of the

Gneiss’),

younger Dharwar Supergroup rocks,

Cambridge University Press978-1-107-00715-4 - Crustal Evolution and Metallogeny in IndiaSanjib Chandra Sarkar and Anupendu GuptaExcerptMore information

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2 Southern India

HyderabadWgl

Krm

PdKhm

GdRcHu

Pc

Hg

Jn

SdWestern Block

Dh-Sm

63274

51

Sargur

Mangalore

Moyar Shear

Bhavani

Cauvery Shear

Cochin

Tiruvanantapuram(Trivandrum)

Bangalore

Eastern BlockPn

Ko

VeKdRm

Jv

KI

Ts

Cuddapah

Chennai(Madras)

500 100 KmNe

BHUTANNEPAL

I N D I A

SouthernIndia

Kaladgi

Deccan TrapBhima

BANGLADESH

Location mapPAKISTAN

Ba

Cd

B R Hills

Nilgiri

Palghat-

Pha

nero

zoic

cove

r sed

imen

ts

Madurai

Achankovil ShearKKB

Shear

Late Proterozoiccover sequence

Eastern GhatsGranulites

Closepet Granite

Peninsular Gneissand granitesCharnockite-Enderbite/Khondalite

Greenstone beltsDharwar / Sargur

LEGEND

Fig. 1.1.1






1.1 Geology and Crustal Evolution 3

7 5° 7 6° 7 7° 7 8°

17°

16°

15°

14°

13°

12°

17°

16°

15°

14°

13°

12°

7 5° 7 6° 7 7° 7 8°

GR KP

Mysore

SG

Charnockite

Bababudan GroupPeninsular Gneiss(P and P )g1 g2

Sargur Group(High grade schists,ultramafics etc.)

Western schist belts(Dharwar-Shimoga,Chitradurga-Gadagschist belts)

Eastern schist belts(Sandur, Kustagi,Raichur, Hutti-Maski,Ramagiri, Kolarschist belts etc.)

Deccan TrapLEGEND

Bhima andKaladgi GroupsClosepet GraniteOther youngergranites

geochronology.There are a couple of Proterozoic intracratonic basins within the Dharwar Province. The Dharwar






4 Southern India

a b

dc

divided into two sub-provinces or blocks: the Western Dharwar and the Eastern Dharwar. The divide

Peninsular Gneiss and Granitoids of Western Dharwar There have been appreciable studies on the Peninsular Gneiss and the associated granitoids, the salient aspects of which are discussed here.

Gneisses of the Gorur – Hassan – Holenarsipur Area Banded grey gneisses, varying in

The Gorur Gneisses are high-SiO O3







Legend: pg1

gneiss with low Sri

Gundlupet Gneisses and Granitoid These rocks occur at the southern end of the high grade Sargur, or older schist belt. The gneisses have two facies: the earlier one is tonalitic and the later one

Honnali Gneiss and Granitoid

Anmod Ghat Gneisses

140 Ma






6 Southern India

Halekote – Kuncha – Tipur and Belur plutons

Chikmagalur Gneisses and ‘Granite’

110 Ma with a Sri Pb isochron

Chitradurga Gneisses and Granite The Chitradurga Gneisses are well-exposed, west of the

sensu stricto

‘Fertile Granite’ and Associated Pegmatites of Allapatna – Marlagalla – Chandra Area

Kanara Batholith

i

Arsikere – Banavara Granite

i

Londa Gneiss

Melukote – Katteri Gneisses

these gneisses contain kyanite, staurolite and garnet. HREE pattern and very low negative Eu







Summarygroups based on their characteristics outlined in the previous pages.

of the Peninsular Gneiss.

O

.

Western Dharwar Schist BeltsThe schist belts or the greenstone belts of western Dharwar block collectively occupy a fairly large

geology of the region.

Sargur Group The Sargur Group of rocks are now better exposed in Sargur, Holenarsipur,

to granulite facies in the south. Dunite, peridotite, pyroxenite and gabbro–anorthosite bodies are intrusive into the Sargur Group.






8 Southern India

Dharwar Supergroup







The Dharwar Supergroup is divided into two Groups: the lower Bababudan Group and the

3.03

Bababudan Group

Lithostratigraphy of the Bababudan Group at Bababudan (after Chadwick et al., 1985)

Formation

Unconformity

Banded Iron Formation (BIF)1

was deposited in a shallow shelf condition, but below the wave base, a condition that ensured its

1 In this treatment we have considered Banded Iron Formation (BIF) as a distinct litho-unit and hence its discussion has

been included in Part 1 of the Chapter. Related ores have been included in the, second part (Metallogeny). Moreover,

general aspects of a problem once discussed are not repeated.






10 Southern India

BIF, SiO O3 O3






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