The ~1.4 Ga A-type granitoids in the “Chottanagpur crustal block” (India), and its relocation from Columbia to Rodinia?

Sequeira, Nicole; Bhattacharya, Abhijit; Bell, Elizabeth A.

doi:10.1016/j.gsf.2020.12.017

Cited by 22 publications

(36 citation statements)

References 121 publications

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“…The GY-68 anatectic granitoid exhibiting shallow-dipping D 3 mylonite fabric (location in Figure 2a) is distinguished from the anatectic basement gneisses by the lack of S 1 -S 2 fabrics, and the presence of K-feldspar porphyroclasts. Also, GY-68 is somewhat unusual, for similar rocks in the interior parts of the CGC Sequeira et al, 2021) do not exhibit syn-D 3 anatexis. In GY-68, garnet occurs in small modal amounts (<5%).…”

Section: P-t Conditions Of Carapace Formationmentioning

confidence: 98%

“…Intergrowths of sillimanite and K-feldspar replacing muscovite are lacking, and no evidence exists for retrograde decomposition of garnet (Figure 8a). The garnets exhibit weak chemical zoning (Figure 8b) which is typical of most mica-schist hosted garnets in the CGC (Sequeira et al, , 2021, barring the southern margin of the CGC (Bhattacharya et al, 2019). In the analyzed garnet, the composition varies from Alm 82 Prp 07 Grs 02 Sps 09 in the grain interior to Alm 84 Prp 07 Grs 02 Sps 07 at the rim, that is, garnets show gentle rimward increase in almandine, a small decrease in spessartine towards the rim, pyrope shows a very slight increase rimward but grossular contents do not vary along the profile (Figures 8b and 8c).…”

Section: Table 1 Electron Probe Microanalytical Data and Structural Formulas Of Minerals In Gy-68mentioning

confidence: 99%

“…Prograde heating-loading in the supracrustal rocks has been documented by Bhattacharya et al (2019) in the southern margin of the CGC, and by Sequeira et al ( , 2021 in the east-central and western parts of CGC. In the absence of other heat sources, the authors attribute this heating of the supracrustal in the overlying carapace to the emplacement of expansive Early Neoproterozoic granitoids within the CGC (Bhattacharya et al, 2019;Sequeira et al, , 2021. In the absence of supra-solidus deformation textures in these Early Neoproterozoic granitoids, argue that the thrusting post-dated granitoid emplacements.…”

Section: The Tectonics Of the Accretion Zonementioning

confidence: 99%

“…The CGC is dominated by Early Mesoproterozoic (1.65-1.5 Ga: Acharyya, 2003;Chatterjee & Ghose, 2011;Chatterjee et al, 2010;Dey et al, 2019;Karmakar et al, 2011;Mukherjee et al, 2017Mukherjee et al, , 2018Mukherjee et al, , 2019Rekha et al, 2011) anatectic garnet-biotite gneisses, hornblende-clinopyroxene-garnet ± orthopyroxene bearing felsic orthogneisses; regional scale bands (tens to hundreds of meters wide) of garnet-sillimanite-K-feldspar metapelites, calc-silicate gneisses and mafic granulites, inter-banded with the regional scale anatectic felsic orthogneisses. The gneisses are intruded by massif anorthosites (1.5 Ga; Chatterjee et al, 2008), syenites, and Mid Mesoproterozoic (Mukherjee et al, 2017;Sequeira et al, 2021) to Early Neoproterozoic granitoids (Bhattacharya et al, 2016;Sequeira et al, , 2021. At higher structural levels, the steeply dipping N/NNW-striking penetrative fabrics in the gneisses and granitoids are re-oriented into a shallow-dipping carapace formed due to thrusting of an allochthonous supracrustal unit comprising muscovite-biotite schists (locally garnet, staurolite and sillimanite bearing) interleaved with meta-marls, meta-dolomites and amphibolites of Early Neoproterozoic metamorphic age (Bhattacharya et al, 2019;Rekha et al, 2011;Sequeira et al, , 2021.…”

Section: Cgc: Geological Backgroundmentioning

confidence: 99%

“…The gneisses are intruded by massif anorthosites (1.5 Ga; Chatterjee et al, 2008), syenites, and Mid Mesoproterozoic (Mukherjee et al, 2017;Sequeira et al, 2021) to Early Neoproterozoic granitoids (Bhattacharya et al, 2016;Sequeira et al, , 2021. At higher structural levels, the steeply dipping N/NNW-striking penetrative fabrics in the gneisses and granitoids are re-oriented into a shallow-dipping carapace formed due to thrusting of an allochthonous supracrustal unit comprising muscovite-biotite schists (locally garnet, staurolite and sillimanite bearing) interleaved with meta-marls, meta-dolomites and amphibolites of Early Neoproterozoic metamorphic age (Bhattacharya et al, 2019;Rekha et al, 2011;Sequeira et al, , 2021. The origin of these shallow platformal sedimentary sequences is unknown.…”

Section: Cgc: Geological Backgroundmentioning

confidence: 99%

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Early Neoproterozoic Accretion at the Northern Margin of the Chottanagpur Gneiss Complex, Eastern India

Sequeira

Bhattacharya

2021

Tectonics

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The study based on structural mapping, monazite chemical age determinations and analyses of P–T pseudosections explores the hitherto undocumented accretion dynamics of the northern margin of the Chottanagpur Gneiss Complex (CGC), Eastern India. In the Gaya‐Chatra‐Koderma sector straddling the northern margin of the CGC, the CGC block comprises a shallow‐dipping carapace of 1.5–1.4 Ga and 1.0–0.9 Ga mylonitized granitoids, intrusive into 1.6–1.5 Ga anatectic basement gneisses, and supracrustal rocks inter‐leaved with recumbently folded gneisses. The carapace, structurally overlying the steeply dipping high‐T fabrics in the basement anatectic gneisses exposed in the tectonic windows, formed due to top‐to‐the‐north thrusting of the allochthonous CGC supracrustal rocks over the ∼1.7 Ga undeformed granitoids and steeply dipping greenschist‐facies metamorphic rocks (∼1.8 Ga) in the northern block. Continued N‐S shortening caused steeply dipping ENE‐striking sinistral and ESE‐striking dextral shear zones that locally modify former structures in the CGC foreland. P–T pseudosection analyses indicate that locally developed Early Neoproterozoic garnet‐bearing leucosomes in a hornblende‐biotite granitoid formed by lower crustal decompression melting, whereas the structurally overlying mica schist in the shallow‐dipping carapace experienced mid‐crustal loading. We suggest the accretion strain accommodated by the foreland thrusts were contemporaneous with extensional detachment zones that exposed lower parts of the thickened orogen. The tectonic events in the CGC appear to correlate poorly with those in the Capricorn Orogen and the Albany Fraser Orogen in Western Australia.

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Section: P-t Conditions Of Carapace Formationmentioning

confidence: 98%

Section: Table 1 Electron Probe Microanalytical Data and Structural Formulas Of Minerals In Gy-68mentioning

confidence: 99%

Section: The Tectonics Of the Accretion Zonementioning

confidence: 99%

Section: Cgc: Geological Backgroundmentioning

confidence: 99%

Section: Cgc: Geological Backgroundmentioning

confidence: 99%

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Early Neoproterozoic Accretion at the Northern Margin of the Chottanagpur Gneiss Complex, Eastern India

Sequeira

Bhattacharya

2021

Tectonics

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Metamorphic evolution of the pelitic and mafic granulites from Daltonganj, Chhotanagpur Granite Gneiss Complex, India: Constraints from zircon U–Pb age and phase equilibria modelling

et al. 2021

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The Daltonganj region is located on the northwestern extension of the Chhotanagpur Granite Gneiss Complex in the eastern Indian Peninsula, which is characterized by pelitic and mafic assemblages of granulite facies rock. The pelitic granulites contain garnet, cordierite, biotite, plagioclase, K‐feldspar, sillimanite, and quartz. Petrographical interpretations divulge prograde and retrograde metamorphic events within mafic granulites, which consist of clinopyroxene, orthopyroxene, amphibole, plagioclase, biotite, and quartz. Field observation, petrography, phase equilibrium modelling, and U–Pb zircon geochronology of the pelitic granulites reveal two stages of metamorphic events along the clockwise P–T path. Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA‐ICP‐MS) zircon U–Pb age dating of pelitic granulites shows the detrital zircon ages from ~1,734 Ma to 1,677 Ma, and the possible metamorphic domains show the weighted mean age of 1,638 ± 22 Ma, which represents the timing of metamorphism. Subsequently, the magmatic emplacement of mafic granulites was recorded at 1,629 ± 6 Ma age by Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA‐ICP‐MS) zircon U–Pb dating which coincide with the timing of metamorphism of the pelitic granulite. Phase equilibrium modelling in the NCKFMASHTO system divulges the pre‐peak metamorphic stage at ~3.2 kbar and ~620°C and the first stage which is characterized by a peak metamorphic condition that ranges from 7.40 to 9.10 kbar and from 815 to 835°C during ~1,638 Ma with the mineral assemblage of garnet + sillimanite + biotite + plagioclase + K‐feldspar + melt + quartz + ilmenite. Sequentially, the retrograde metamorphism is observed by a nearly isothermal decompression stage at ~4.0 kbar/~790°C after 1,638 Ma, due to the appearance of garnet + cordierite + biotite + plagioclase + K‐feldspar + melt + quartz + ilmenite + magnetite. The formation of cordierite is due to the decompression and dehydration melting phases. The Nb, Sr, and Ti negative anomalies suggest their generation from crustal sources. The geochemical analyses constrain that the sedimentation of pelitic sediments was recorded along the convergent margin and encountered by a subduction‐related tectonic setting. The geochemical interpretation provides significant evidence that the protoliths of pelitic granulites were derived from the Singhbhum Mobile Belt, Mahakoshal Supracrustal Belt, and Bundelkhand Craton, while their metamorphism was processed by the continent–continent collision and followed by exhumation.

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Crustal architecture of North Singhbhum Mobile Belt, Eastern Indian Shield: Constraints from two‐dimensional and three‐dimensional modelling of Bouguer gravity and aeromagnetic data

2022

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The North Singhbhum Mobile Belt (NSMB) that lies in the Eastern Indian Shield between the Chotanagpur Granite‐Gneiss Complex (CGGC) and the Singhbhum Craton (SC) provides a unique opportunity to understand the Proterozoic crustal evolution of the Indian shield. In the present study, an integrated interpretation of petrophysical, Bouguer gravity, and aeromagnetic data was carried out to examine the crustal architecture and structural framework of the region. Three‐dimensional (3‐D) inversion of the aeromagnetic anomalies reveals that the magnetic basement depths range from 0.2 to 9.0 km in the region. The crustal models obtained from two‐dimensional (2‐D) and 3‐D forward modelling of potential field data reveal the Moho at 37–38 km depth beneath the NSMB and at a relatively deeper depth of 39–40 km and 40–44 km beneath SC and CGGC, respectively. Further, the distinct gravity high and the coinciding bipolar magnetic anomalies associated with the Dalma Formation can be attributed to the mafic/ultramafic intrusions. Gravity models across the Singhbhum Shear Zone (SSZ) and South Purulia Shear Zone (SPSZ) exhibit the crustal density inhomogeneity and Moho offset, typical of ancient suture zones of Precambrian terrains. In comparison, the absence of such crustal‐scale signatures across the North Purulia Shear Zone represents its intracratonic nature. Further, the Bouguer gravity and aeromagnetic signatures across the SPSZ, together with the crustal architecture and metamorphic ages, suggest that SPSZ marks the eastward continuity of the Gavilgarh‐Tan Shear Zone along which the amalgamation of northern and southern Indian cratonic blocks possibly took place at ca. 1.0–0.9 Ga.

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The ~1.4 Ga A-type granitoids in the “Chottanagpur crustal block” (India), and its relocation from Columbia to Rodinia?

Cited by 22 publications

References 121 publications

Early Neoproterozoic Accretion at the Northern Margin of the Chottanagpur Gneiss Complex, Eastern India

Early Neoproterozoic Accretion at the Northern Margin of the Chottanagpur Gneiss Complex, Eastern India

Metamorphic evolution of the pelitic and mafic granulites from Daltonganj, Chhotanagpur Granite Gneiss Complex, India: Constraints from zircon U–Pb age and phase equilibria modelling

Crustal architecture of North Singhbhum Mobile Belt, Eastern Indian Shield: Constraints from two‐dimensional and three‐dimensional modelling of Bouguer gravity and aeromagnetic data

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