Mantle heterogeneity and crust-mantle interaction in the Singhbhum craton, India: New evidence from 3340 Ma komatiites

Priyanka Bachhar, Dilip Saha, M. Santosh, Hai Dong Liu, Sanghoon Kwon, Amlan Banerjee, Sarbani Patranabis-Deb, Gautam K. Deb

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2 Citations (Scopus)

Abstract

The Singhbhum Craton in eastern India preserves the records of Paleoarchean - Mesoarchean oceanic crust dominated by ultramafic-mafic extrusive rocks (greenstones), and sialic rafts composed of tonalite-trondhjemite-granodiorite, together with younger granitoids constituting the composite Singhbhum granite batholith. The greenstone sequences, intruded by younger granitoids are entrained as synformal keels in the batholith. The lower greenstone sequence of eastern Iron Ore Group (IOG) is composed of peridotitic komatiite, and komatiitic basalt with minor chert and BIF, whereas the upper sequence has tholeiite to tholeiitic andesite. Here we report results from first direct dating of the Karanjharan spinifex-textured komatiite from the lower part of Badampahar greenstone sequence of IOG. LA-ICPMS U-Pb analysis of zircon grains in the komatiites yielded consistent weighted mean 207Pb/206Pb age of 3340 Ma, with closely similar Hf depleted mantle age (TDM) between 3357 Ma and 3432 Ma. The high MgO (25–35%), and low Al2O3/TiO2 (<10) and CaO/Al2O3 (2.3–3.7) ratios in the serpentinized Karanjharan komatiites suggest strong similarity with the Al-depleted komatiites from Barberton Mountainland, South Africa. The Badampahar komatiites have Gd/YbN in the range 2–3, and show depletion in incompatible elements including LREE, slight enrichment of MREE and near chondritic HREE, suggesting derivation from a depleted mantle source with garnet in the residue. Juvenile Paleoarchean mantle source is also suggested by positive εHf(t) (3.0–4.6) and broadly similar 207Pb/206Pb age and TDM age. Geochemical features of basalts from the upper greenstone sequence overlap with those of the lower greenstone sequence, but are more enriched in HFSE (Th, U) and LREE possibly due to contamination with continental crust or oceanic sediments. The variation in Al2O3/TiO2 ratios as well as Gd/YbN ratios from the Karanjharan komatiite and other coeval komatiites in the eastern IOG suggest Paleoarchean mantle heterogeneity and/or melt extraction from different depths.

Original languageEnglish
Article number105931
JournalLithos
Volume382-383
DOIs
Publication statusPublished - 2021 Feb

Bibliographical note

Funding Information:
DS acknowledges receipt of project grant from Indian Statistical Institute (ISI) to work on Archean greenstones in India ( A/C 5513C , 5755C , 9535C of FY2018-19 ). PB acknowledges receipt of ISI senior research fellowship. We thank colleagues at the KBSI, Korea for their valuable help with the zircon isotopic analysis. SK also acknowledges the partial support from the 2017R1A6A1A07015374 (Multi-disciplinary study for assessment of large earthquake potentials in the Korean Peninsula) and NRF-493 2019R1A2C1002211 through the National Research Foundation of Korea funded by the Ministry of Science and ICT, Republic of Korea . We are thankful to two anonymous journal reviewers for their helpful comments on an earlier version.

Funding Information:
DS acknowledges receipt of project grant from Indian Statistical Institute (ISI) to work on Archean greenstones in India (A/C 5513C, 5755C, 9535C of FY2018-19). PB acknowledges receipt of ISI senior research fellowship. We thank colleagues at the KBSI, Korea for their valuable help with the zircon isotopic analysis. SK also acknowledges the partial support from the 2017R1A6A1A07015374 (Multi-disciplinary study for assessment of large earthquake potentials in the Korean Peninsula) and NRF-493 2019R1A2C1002211 through the National Research Foundation of Korea funded by the Ministry of Science and ICT, Republic of Korea. We are thankful to two anonymous journal reviewers for their helpful comments on an earlier version.

Publisher Copyright:
© 2020 Elsevier B.V.

All Science Journal Classification (ASJC) codes

  • Geology
  • Geochemistry and Petrology

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