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      https://www.ias.ac.in/article/fulltext/jess/109/01/0057-0065

    • Keywords

       

      Archean; anorthosite; Dharwar craton; Sm-Nd; Geochronology

    • Abstract

       

      Whole-rock Sm-Nd isochron ages are reported for two stratiform meta-anorthosite complexes emplaced into the Archean supracrustal-gneiss association in the amphibolite facies terrain around Holenarsipur, in the Dharwar craton, South India. While these metaperidotite-pyroxenite-gabbro-anorthosite complexes are petrologically and geochemically similar, they differ in the intensity of tectonic fabric developed during the late Archean (c. 2.5 Ga) deformation. They also differ in their whole-rock Sm-Nd isochron ages and initial Nd isotopic compositions: 3.285 ± 0.17 Ga,ɛNd0.82 ± 0.78 for the Honnavalli metaanorthosite complex from a supracrustal enclave in the low-strain zone, and 2.495 ± 0.033 Ga, ɛNd = -2.2 ± 0.3 for the Dodkadnur meta-anorthosites from the high-strain southern arm of the Holenarsipur Supracrustal Belt (HSB). We interpret these results as indicating that the magmatic protoliths of both meta-anorthosite complexes were derived from a marginally depleted mantle at c. 3.29 Ga but only the Dodkadnur rocks were isotopically reequilibrated on a cm-scale about 800 Ma later presumably due to the development of strong penetrative fabrics in them during Late Archean thermotectonic event around 2.5 Ga. Our results set a younger age limit at c. 3.29 Ga for the supracrustal rocks of the HSB in the Dharwar craton.

    • Author Affiliations

       

      Y J Bhaskar Rao1 Anil Kumar1 A B Vrevsky2 R Srinivasan1 G V Anantha Iyer3

      1. National Geophysical Research Institute, Hyderabad - 500 007, India
      2. Institute of Precambrian Geology and Geochronology, St. Petersburg, Russia
      3. Department of Inorganic and Physical Chemistry, Indian Institute of Sciences, Bangalore - 560 012, India
    • Dates

       
  • Journal of Earth System Science | News

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