this content is prepared from various sources and has used
TRANSCRIPT
This content is prepared from various sources and has used the study material from various books, internet articles etc. The teacher doesn’t claim any right over the content, it’s originality and any copyright. It is given only to the students of PG course in Geology to study as a part of their curriculum.
Stratigraphy of Singhbhum Craton
Singhbhum Craton lies in vicinity of two Proterozoic mobile belts: Satpura Mobile Belt in the east, north and north-west; Eastern Ghat Mobile Belt in the south. Singhbhum Craton is separated from Bastar Craton by Mahanadi Graben.
Age: Archean to Paleoproterozoic
-comprises of Paleoarchean and Mesoarchean tonalitic and granodioritic granites and gneisses and abundant occurrences of BIFs, closely associated with basic volcanics and ultrabasic intrusives.
-all these rocks have undergone regional metamorphism of the amphibolite facies.
-Singhbhum Craton is believed to have evolved as a consequence of multiple phases of compressive deformation related to Singhbhum Orogeny.
Northern Boundary marked by Singhbhum Shear Zone (Copper Belt Thrust)
Southern Boundary marked by Sukinda Thrust (amalgamates the low grade metamorphics of Singhbhum Craton with the high grade metamorphics of EGMB)
Singhbhum Shear Zone separates the Singhbhum Craton from the Chhotanagpur Gneiss
Sukinda Thrust separates the Iron Ore group from the Gondwanas
CHAMPUA GROUP (OMG)
SARAIKELA GNEISS (OMTG)
IRON ORE
GROUP
SINGHBHUM GRANITE TYPE B,
PHASE III)
SINGHBHUM GROUP
DHANJORI GROUP
SINGHBHUM GROUP
BESOI GRANITE (SINGHBHUM
GRANITE TYPE A, PHASE I &II)
SIMLIPAL VOLCANICS
DALMA VOLCANICS
CHAIBASA FORMATION
DALBHUM FORMATION
DARJIN GROUP
PALEOARCHEAN
MESOARCHEAN
NEOARCHEAN
PALEOPROTEROZOIC
TG
LITHOUNITS OF THE SINGHBHUM CRATON
CHAMPUA GROUP (OMG)
SARAIKELA GNEISS (OMTG)
IRON ORE
GROUP
SINGHBHUM GRANITE (TYPE
B, PHASE III)
BESOI GRANITE (SINGHBHUM GRANITE
TYPE A, PHASE I &II)
DARJIN GROUP
PALEOARCHEAN
MESOARCHEAN
NEOARCHEAN TG
ARCHEAN LITHOUNITS
• 6 major lithotectonic units are recognizable
• five exhibit amphibolite-facies metamorphism;
sixth is free from deformation and metamorphism
• these five lithounits have undergone multiple
phases of deformation during the Singhbhum
Orogeny.
CHAMPUA GROUP:
-oldest lithostratigraphic unit of the Singhbhum Craton
- south of the SSZ
- known as Older Metamorphic Group and consists of predominantly hornblende-schists with
quartzites and quartz mica-schists, metamorphosed pelites and sandstones associated with
ferromagnesian lithologies to the SW of Champua.
- transformed by amphibolite-facies metamorphism.
- age: 3600 to 3300 My
SARAIKELA GNEISS:
- intrusion of tonalite in the Champua
Group led to the evolution of
metamorphics and tonalites.
- known as Older Metamorphic Tonalite
Gneiss.
- derived from partial melting of
amphibolites of the OMG.
BESOI GRANITE (SINGHBHUM
GRANITE TYPE A):
- a large batholithic complex, which
embodies a number of plutons, was
emplaced in three pulses, first two of which
occurred at a very short temporal span.
- divided into Singhbhum Granite Type
A (phase I & II) and Singhbhum Granite
type B (phase III).
- different bodies of granite are separated
by partition of metamorphic rocks.
- xenoliths of rocks of Champua Group and
Saraikela Gneiss occur all over the granite.
- biotite granodiorite, grading to
trondhjemite.
- age: 3300-3200 My
Iron Ore Group:
- lies unconformably over Besoi Granite
- mildly metamorphosed, predominantly
ferrugenous sediments associated with basic
volcanics
- occurs in three belts- Noamundi-Jamda-Koira,
Gorumahisani-Badampahar and Tomka-Daitari
- in all the three belts the BIF is closely
associated with lavas and tuffs.
- IOG forms a synclinorium in the Jamda-Koira
valley.
- age: 3145 My
- sedimentation started before the intrusion of
3120 My old Singhbhum Granite Type B.
Stratigraphic Succession of
IOG in the iron ore belts
Singhbhum Granite (Type B, phase III):
- makes the larger part of the batholithic complex
- represents the third phase of magma emplacement
- intrudes IOG at some places
- biotite-granodiorite to adamallite, biotite trondjhemite
and leuco-granite
- age: 3163 to 3042 My
Darjin Group:
- lies to the west of Singhbhum batholith complex
- little metamorphosed and undeformed sedimentary rocks
- cross-bedded and ripple marked conglomeratic sandstones, arlosic sandstones, shales,
carbonaceous phyllites and dolomitic limestones
Tamperkola Granite:
- intrudes Darjin Group
- pink coloured alkali feldspar dominated granite
- marks the last thermal event of the Neoarchean in the eastern part of the Indian Shield.
Evolution of Singhbhum Craton lithology in the Archean
PROTOCONTINENT DURING ARCHEAN
CRUST
MANTLE PLUMES
PROTOCONTINENT
TENSIONAL STRETCHING
DEPRESSION
CHAMPUA GROUP (OMG) Sediments which got deposited in the basin were metamorphosed to amphibolite facies
PLUME
Partial melting of protocontinent and underlying crust generated tonalitic magma
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Emplacement of tonalitic magma contributed to
the synkinematic growth of OMTG
SARAIKELA GNEISS (OLDER METAMORPHIC
TONALITE GNEISS)
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Continuation of granitic magmatism
OMG
OMTG
BESOI GRANITE (SINGHBHUM GRANITE TYPE A, PHASE I & II)
OMTG
OMG
SBG-A
NNE-SSW ORIENTED SHALLOW WATER BASIN
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Ferrugenous and siliceous sediments; emplacement of BIF and basic lavas; intrusion of gabbro and related ultrabasic magmas
THERMAL PERTURBATIONS IN THE SUBCRUSTAL LEVEL OF THE
ELONGATED MICROCONTINENT
IOG
DEFORMATION AND METAMORPHISM CONTINUED AND FOLDED IOG AS A
SYNCLINORIUM
OMG
OMTG
SBG-A
IOG
SINKING OF SIALIC CRUST
DIFFERENTIAL MELTING
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SINGHBHUM GRANITE TYPE B; PHASE III
OMG
OMTG
SBG-A
IOG
SBG-B
Subsidence in the western part
OMG
OMTG
SBG-A
IOG
SBG-B
Shallow basin of the Darjin Group
little metamorphosed and undeformed
sediments
OMG
OMTG
SBG-A
IOG
SBG-B
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TAMPERKOLA GRANITE
Last thermal event of the Neoarchean in the eastern part
of the Indian Shield