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    • Keywords


      Neoproterozoic; gabbro; Sirohi Group; geochemistry; SHRIMP zircon geochronology.

    • Abstract


      The study incorporates geochemistry and geochronology of a gabbro, located near Daba, from the Neoproterozoic Sirohi Group along the northwestern Canks of the Indian Shield. The Daba gabbro is massive, cumulate, undeformed and forms a linear body bounded by shear zones at margins. The Neoproterozoic Sirohi Group marks the end of the compressional tectonic regime and the emplacement of gabbro marks amalgamation processes of the Rodinia Supercontinent in the northwestern Indian Shield. The gabbro is characterized by enriched TiO2, P2O5, LILE, LREE, and HREE depletion; and high La/SmN, Gd/Yb$_N$, Zr/Nb ratios with no positive Eu anomalies and no Nb, Ta and Ti negative anomalies suggesting an Oceanic Floor Basalt (OFB) aDnity. The Ti–V plot of the Daba gabbro a firms OFB affinity, whereas this parameter for proximal mafics from the Delhi Supergroup shows Oceanic Island Basalts (OIB) aDnity. Primitive mantle normalized multi-element pattern and chondrite-normalized pattern for trace element and REE show OFB affinity. Depletion of Nb–Ta, P and Ti with a flat distribution of LILE and HFSE reflects limited degrees of crustal contamination (exception Zr positive anomaly). SHRIMP geochronology of magmatic zircons from the two gabbro samples has a well-defined ${}^{206}$Pb/${}^{238}$U Concordia at 825 ± 4 and 828 ± 4 Ma. This data corresponds to the gabbroic emplacement was almost synkinematic with felsic magmatism, coeval with the Sirohi orogeny (${\sim}$835 Ma), denoting the end of compression tectonic regime. This marks the closure of the Rodinia amalgamation process in the northwestern Indian shield.

    • Author Affiliations



      1. Department of Geology, Government College Sirohi, Sirohi, Rajasthan 307 001, India.
      2. National Water Mission, Government of India, CGO Complex, Block III, New Delhi, India.
      3. Geological Research Division, Korea Institute of Geoscience and Mineral Resources, Daejeon 305-350, South Korea.
      4. Department of Geology, Mohanlal Sukhadia University, Udaipur, Rajasthan 313 001, India.
    • Dates

  • Journal of Earth System Science | News

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      Posted on July 25, 2019

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