Precambrian Geology of Peninsular India - PowerPoint Presentation

Slide1

Precambrian Geology of Peninsular India

Aravalli–Bundelkhand

Cratons

Singhbhum

craton

Bastar

Craton

Western

Dharwar

Craton

Eastern

Dharwar

Craton

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CRATON?

SHIELD?

Any Difference?

Slide3

Slide4

Aravalli-Bundelkhnad

Protocontinent

Dharwar Protocontinent

Singhbhum Protocontinent

Slide5

Description of CratonStabilization of blockTTG, greenstone, calc-alkaline to high-K

granitoids

Mafic

dykes

Proterozoic

sed

basins

Geochronological status

Age of Stabilization of Crtaon??

Slide6

Age of continent/ stabilization of craton

Traditionally oldest exposed rock gives age of the Continent

Rogers : Oldest rocks that stabilized to sustain a continent and could provide foundation for other rocks to deposit/settle on it :

Gives the Age of Continent

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Aravalli-Bundelkhnad

craton

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BGC I,

BGC II (

Mangalwar

Complex

),

Aravalli

SG

,

North Delhi SG (North Delhi Fold Belt)South Delhi SG (South Delhi Fold Belt)

Slide9

Aravalli craton

BGC : 3.3 to 2.5

Ga

BGC is composed of

migmatites

, gneisses (

3.3Ga

), meta-sedimentary rocks and minor amphibolite (

dismembered greenstone belts 2.8 Ga). BGC forms the basement for the

supracrustal rocks of Aravalli and Delhi fold Belts.2.5

Ga stabilization age for the southern segment of the Aravalli Craton

based on the uniformity of the Late

Archaean

and Early

Proterozoic

crystallization ages of

undeformed

granitoids

Aravalli

Supergroup

was

unconformably

deposited on this stabilized landmass.

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Neoarchaean

Undeformed

Granitoids

e.g.

Berach

,

Gingla,Ahar River,Untala

are intrusive TTG gneisses.TTG Gneisses ~3.3 Ga

Granitoids ~2.5 Ga

DismemberedVolcano-

sed

Greenstones

Occurring

Within BGC

2.8Ga

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Neoarchaean

Granitoids

2.6

Ga

to 2.4

Ga

Intrusive into

gneisses

Have

subduction related Geochemical features

Berach

Granitoids

have

sanukitoid

characteristics

(

subduction

related)

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Bundelkhnad Craton

GBF

separates

Aravalli

from

Bundelkhnad

Mainly

undeformed

late

Archaean

Granitoids

:

2.5

Ga

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Bundelkhnad Tectonic Zone (BTZ)

(Volcano-sed greenstones)

(Pati, 1999)

Mesoproterozoic

Vindhyan

basin

Phanerozoic

alluvium

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Bundelkhnad craton

Bundelkhand

Craton

into three distinct litho-tectonic units:

(1)

Archaean

highly deformed older gneisses–greenstone components (

very less)(2)

Undeformed multiphase granitoid plutons (most dominant

) and associated quartz reefs(3) Mafic dyke swarms

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Stratigraphy: Bundelkhnad

Granitoids

( 2.5Ga)

Volcano-sedimentary Greenstones

Gneiss

(3.3-2.7

Ga

)

Stabilization of the

craton

: 2.5

Ga

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3.3 Ga

2.7 Ga

High

P Met

18-20 Kb

Low P Melting

High P Melting

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Gneisses : 3.3 to 2.7

Ga

Undeformed

Granitoids

: 2.5

Ga

Mafic

dykes : 2.0

Ga

Gwalior : 1.9

Ga

Lower Vin 1.7

Ga

Upper Vin 1.1 to 0.7

Ga

)

Hindoli

Group :1.8

Ga

Malani

Ig

Suite MIS: 800-750Ma

Erinpura

Granite : 860-800Ma

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TTG (3.3 Ga)

TTG (2.7 Ga)

TTG (3.3 Ga)

TTG (2.7 Ga)

Formation of Continental Nucleus

at 3.3 Ga

Subduction

or tectonic

underplating

of

mafic

crust and melting of this

mafic

Crust gives rise to TTG

Slide20

Gneissic Crust

Granitoids (2.5 Ga)

Emplacement of Granitoids at 2.5 Ga

Partial melting of lower crust with or without mantle contribution gives rise to

granitoids

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Mafic Dykes (2.0 Ga)

Gwalior Basin (1.8 Ga)

Bijawar Basin

Emplacement of

mafic

dyke swarms may be linked to plumes

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CONCLUSIONS

Oldest Crustal Component

~3.3

Ga

Gneisses

Two generations

of Gneisses :

~3.3,

2.7

Granitoid emplacement

~ 2.5 GaAge of Stable crust

~2.5 GaBundelkhand-Aravalli

nucleus stabilized at

2.5

Ga

so that it could act as a stable crust to sustain continent and provided foundation for the other rocks including sedimentary rocks to deposit on it

Mafic

dyke swarms in

Bundelkhnad

: 2.0

Ga

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Aravalli –Delhi Mobile belt (ADMB)

ADMB consists of several

Paleoproterozoic

to

Neoproterozoic

supracrustal

terranes (terrain

vs terrane, any difference

??) that have been accreted to old basement gneisses.The terranes

are : (1) Aravalli Terrane(2)

Hindoli

JahajpurTerrane

(3)

Sandmata-Mangalwar

terrane

(4) North Delhi

Terrane

(5) South Delhi

terrane

(6)

Sirohi

Terarne

(7)

Malani

terrane

Slide24

Terrane

accretion

Slide25

Sedimentary Basins

Aravalli

and Delhi

Supergroups

represent the oldest sedimentary basins in the

Aravalli

Bundelkhand Cratons

Younger intracratonic basins of Mesoproterozoic–Paleozoic age outcrop to the west of Aravalli

Fold Belt and south and west of Bundelkhand Province: (1) The Marwar

Supergroup in the western part of the Aravalli mountain range in Rajasthan (2) the Vindhyan Basin

Slide26

Aravalli/Delhi sedimentary sequences

Both the Delhi and

Aravalli

meta-sedimentary sequences overlie the BGC

Both show evidence of

polyphase

deformation and metamorphism

AS subdivided into

Delwara

(lower), Debari (middle) and Jharol

(upper) GroupsDelwara (lower) and Debari (middle) :

Shelf sedJharol (upper) :

Deep sea

sed

Debari

Group composed of a basal conglomerate overlain by

metavolanics

,

quartzites

,

phyllites

, carbonates.

Younger

Jharol

Group is a

turbidite

sequence comprising

phyllites

,

schists

and a basal quartzite.

A N-S trending

ultramafic

body divides AS into eastern (shallow sea) and western (deep sea) segments

Slide27

Aravalli SG : Age

2075–2150 Ma

Pb–Pb

age for galena, presumably

syngenetic

with the basal

Aravalli

volcanics

. In the absence of any direct geochronologic evidence, this age is taken to represent the initiation of Aravalli sedimentation.

Intrusion of 1850 Ma Darwal Granite has generally been accepted as the closing age for deposition of the Aravalli

Supergroup.The ages of metamorphism in the Aravalli Craton are better constrained.

Sedimentation of

Aravalli

Supergroup

:

started : 2.1

Ga

,

Closed : 1850 Ma

Metamorphism : 1600-1700 Ma

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Aravalli

Supergroup

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Delhi SG

DSG subdivided into two main geographic terrains : North Delhi Fold Belt and South Delhi Fold Belt

Three fold

classification

:

Raialo

,

Alwar

and

Ajabgarh GroupsThe lowermost

Raialo Group : conglomerate, basic volcanics, marble and quartzite.

Overlying the Railo Group is the Gogunda Group (=

Alwar

Group): quartzite,

schists

and

metabasic

rocks.

The

Gogunda

Group is

disconformably

overlain by the

Kumbhalgarh

Group

(=

Ajabgarh

Group).

Kumbhalgarh

Group: carbonaceous

shales

, marbles,

phyllites

and relatively minor

quartzites

Kumbhalgarh

Group is overlain by the

Sirohi

and

Punagarh

(=

Sindreth

) Groups.

Sirohi

Group : marbles,

pelitic

schists

and

quartzites

Punagarh

Group:

arenaceous

sediments, bimodal

volcanics

,

shales

,

phyllites

and

schists

Slide30

Strata of the North Delhi Belt are well constrained to

1.8–1.7

Ga

with minimum and maximum depositional ages provided by cutting relationship of intrusive igneous rocks and

detrital

zircon age data, respectively

South Delhi Belt : 1200-750 Ma

Diachronous

character of ND and SD

(sedimentary formation in which apparently similar material varies in age from place to place)

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SDT : 1200-750 Ma

NDT: 1800-1700 Ma

Slide32

Paleopro

2.1 to 1.8

Ga

Paleoproteo

1.8

Ga

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The Vindhyan Basin is one of several ‘‘

Purana

” (ancient) sedimentary basins of the Indian subcontinent

Vindhyan

SG

Slide34

Stratigraphically, Vindhyan Basin can be divided into

two sequences

:

Lower

Vindhyan

(1.7

Ga

)

Sequence formed by

Semri Groups) : alternating formations of shale and carbonates with areas of sandstones and volcaniclastic units Upper

Vindhyan (1.1 to 0.7 Ga

) Sequence subdivided into: Kaimur, Rewa and

Bhander

Groups

Slide35

Semri sediments (1.7 Ga

)

unconformably

overlie the

BASEMENT ROCKS

of

1.8

Ga

Hindoli Group

2.5 Ga Bundelkhand

granites 2.5 Ga

Berach

Granite

The

Kaimur

rocks are intruded by the

1.1

Ga

Majhgawan

kimberlite

Slide36

Basement 2.5 -1.8

Ga

Lower Vin 1.7

Ga

Upper Vin 1.1

Ga

– 650Ma

Slide37

Lower Vin : 1.7

Ga

Upper Vin :

1.1 – 0.65

Ga

N

N

R

N

R

Slide38

VINDHYAN SUCCESSIONS

Lower Vin : 1.7

Ga

Upper Vin : 1.1 – 0.65

Ga

Slide39

Slide40

Vindhyan Supergroup, one of the largest and thickest Precambrian sedimentary successions of the world, outcropping over area.The largest of the so called "

Purana

" basins in India.

VS subdivided into the upper

Vindhyan

and the lower

Vindhyan

.

Lower Vindhyan is reliably constrained to the Paleo-Mesoproterozoic. Age Upper

Vindhyan sedimentary sequence is the subject of considerable controversy. Multiple hypotheses have been forwarded concerning basin closure: some argue for an early Neoproterozoic to late Mesoproterozoic

closure (~1050 Ma) of Upper Vindhyan sedimentation. The deposition of the Upper Vindhyan sequence closed near the end of the

Mesoproterozoic (~1000 Ma) whereas deposition in the Marwar basin was confined to the Ediacaran Cambrian interval (~570-521 Ma).

"

Purana

Basins" of India formed during distinct intervals of Precambrian time (

Paleo

-

Mesoproterozoic

,

Mesoproterozoic

and

Ediacaran

Cambrian). The formation of these sedimentary basins may be related to the supercontinents of Columbia (Lower

Vindhyan

),

Rodinia

(Upper

Vindhyan

) and

Gondwana

(

Marwar

).

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Slide42

Marwar basin This

Neoproterozoic

to Cambrian age asymmetric

intracratonic

sedimentary basin lies

unconformably

over the

Malani

Igneous Suite (MIS) and the rocks of Delhi Supergroup. The Marwar

Supergroup is found in western Rajasthan and the Marwar basin trends NNE–SSW with a slight westerly tilt.

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