Evidence of crustal reworking in the Mesoarchean: Insights from geochemical, U-Pb zircon and Nd isotopic study of a 3.08-3.12 Ga ferro-potassic granite-gneiss from north-eastern margin of Singhbhum Craton, India

Chakraborti, Tushar Mouli and Ray, Arijit and Deb, Gautam Kumar and Upadhyay, Dewashish and Chakrabarti, Ramananda (2019) Evidence of crustal reworking in the Mesoarchean: Insights from geochemical, U-Pb zircon and Nd isotopic study of a 3.08-3.12 Ga ferro-potassic granite-gneiss from north-eastern margin of Singhbhum Craton, India. In: LITHOS, 330 . pp. 16-34.

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Abstract

Evidences of Mesoarchean crustal reworking are not very common in geological records, being only found from Precambrian terrains like Kaapvaal and Pilbara Cratons where it is preserved as anorogenic/post-collisional granitic activity of 3-3.2 Ga age. The present study focuses on a granitoid unit of similar age, found near the eastern margin of the Precambrian Singhbhum Craton of eastern India. This ellipsoidal, N-S trending, well-foliated granite-gneiss body is found within the polydeformed, metasedimenatry rocks of Singhbhum Group, belonging to the North Singhbhum Mobile Belt. LA-ICP MS U-Pb analysis of zircon grains from one sample give crystallization ages ranging from 3079.4 +/- 6.8 Ma to 3115 +/- 10 Ma. These rocks hereby dubbed as ``Bangriposi Granite Gneiss'', are composed of quartz, alkali feldspar, ferroan biotite (Fe/Fe + Mg: 0.7-0.9), titanite, illmenite, hastingsite, apatite, and numerous U-Th-REE- bearing accessory phases. They have high SiO2 (67-77 wt%) and Na2O + K2O (8.19-9.01 wt%), low CaO (0.35-1.5 wt%), MgO (0.05-036 wt%) and shows enrichment of Nb, Rb, Zr, Y, Th, and REEs, and depletion of Cr, Ni, U, with high FeOt/FeOt, + MgO(similar to 0.9), Ga/Al (2.04-3.51), (La/Yb)(N) (6.5-13), and low Eu/Eu* (0.11-0.47). Geochemically and mineralogically they are categorized as metaluminous to weakly peraluminous (A/CNK: 0.9-1.1) ferro-potassic alkali feldspar granites. These rocks show unequivocal affinities towards `A-type'' granites and from geochemical evidences it is suggested that the parent magma was produced in response to crustal anatexis under low foe with P-T estimates of -900 degrees C and 7-8 kbar. Geochemical modelling has revealed that the probable source was lower crustal amphibolites belonging to the Paleoarchean Older Metamorphic Group, which suffered low degrees (5-15%) of melting. Negative CNd values ( -0.5 to -1.5) are also in favour of reworking of older crust and their Nd isotopic signature bears similarities with other coeval anatectic granites. Bangriposi Granite-Gneiss, along with Mayurbhanj Granite and Bonai Granite, represent a major phase of Mesoarchean anorogenic/post-collisional granitic activity in Singhbhum Craton, indicating the onset of its stabilization. Similar Mesoarchean crustally reworked felsic units are encountered in Pilbara and Kaapvaal cratons suggesting a possibility of correlation with the hypothesized ``Vaalbara'' supercontinent. (C) 2019 Elsevier B.V. All rights reserved.

Item Type:	Journal Article
Publication:	LITHOS
Publisher:	ELSEVIER SCIENCE BV
Additional Information:	Copyright of this article belongs to ELSEVIER SCIENCE BV
Keywords:	Crustal reworking; Post-collisional granite; Ferro-potassic granite; Singhbhum Craton; Mesoarchean; Vaalbara
Department/Centre:	Division of Mechanical Sciences > Centre for Earth Sciences
Date Deposited:	17 May 2019 10:38
Last Modified:	17 May 2019 10:38
URI:	http://eprints.iisc.ac.in/id/eprint/62333

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