A petrogenetic relationship between 2.37 Ga boninitic dyke swarms of the Indian Shield: Evidence from the Central Bastar Craton and the NE Dharwar Craton

Alice C.Y. Liao, J. Gregory Shellnutt, Kosiyathu R. Hari, Steven W. Denyszyn, Neeraj Vishwakarma, Chandra B. Verma

Research output: Contribution to journalArticle

4 Citations (Scopus)

Abstract

The Indian Shield is cross-cut by a number of distinct Paleoproterozoic mafic dyke swarms. The density of dykes in the Dharwar and Bastar Cratons is amongst the highest on Earth. Globally, boninitic dyke swarms are rare compared to tholeiitic dyke swarms and yet they are common within the Southern Indian Shield. Geochronology and geochemistry are used to constrain the petrogenesis and relationship of the boninitic dykes (SiO 2 = 51.5 to 55.7 wt%, MgO = 5.8 to 18.7 wt%, and TiO 2 = 0.30 wt% to 0.77 wt%) from the central Bastar Craton (Bhanupratappur) and the NE Dharwar Craton (Karimnagar). A single U-Pb baddeleyite age from a boninitic dyke near Bhanupratappur yielded a weighted-mean 207 Pb/ 206 Pb age of 2365.6 ± 0.9 Ma that is within error of boninitic dykes from the Dharwar Craton near Karimnagar (2368.5 ± 2.6 Ma) and farther south near Bangalore (2365.4 ± 1.0 Ma to 2368.6 ± 1.3 Ma). Rhyolite-MELTS modeling indicates that fractional crystallization is the likely cause of major element variability of the boninitic dykes from Bhanupratappur whereas trace element modeling indicates that the primary melt may be derived from a pyroxenite mantle source near the spinel-garnet transition zone. The Nd isotopes (ε Nd (t) = −6.4 to +4.5) of the Bhanupratappur dykes are more variable than the Karimnagar dykes (ε Nd (t) = −0.7 to +0.6) but they overlap. The variability of Sr-Nd isotopes may be related to crustal contamination during emplacement or is indicative of an isotopically heterogeneous mantle source. The chemical and temporal similarities of the Bhanupratappur dykes with the dykes of the Dharwar Craton (Karimnagar, Penukonda, Chennekottapalle) indicate they are members of the same giant radiating dyke swarm. Moreover, our results suggest that the Bastar and Dharwar Cratons were adjacent but likely had a different configuration at 2.37 Ga than the present day. It is possible that the 2.37Ga dyke swarm was related to a mantle plume that assisted in the break-up of an unknown or poorly constrained supercontinent.

Original languageEnglish
Pages (from-to)193-211
Number of pages19
JournalGondwana Research
Volume69
DOIs
Publication statusPublished - 2019 May 1

    Fingerprint

Keywords

  • Bastar Craton
  • Boninitic dyke swarm
  • Dharwar Craton
  • Geochemistry
  • Geochronology
  • Paleoproterozoic

ASJC Scopus subject areas

  • Geology

Cite this