• RANJIT NAYAK

      Articles written in Journal of Earth System Science

    • Petrological study of spinel peridotites of Nidar ophiolite, Ladakh Himalaya, India

      RANJIT NAYAK BIDYANANDA MAIBAM

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      Petrological study of the ultramafic rocks from the Nidar Ophiolite Complex (NOC) of the Indus Suture Zone is carried out. The study of Cr-spinels along with olivine and pyroxenes emphasizes the genesis and tectonic setting of the ultramafites. Olivine from the harzburgite is Mg-rich, with the molar ratio Mg# [$\rm{Mg/(Mg + Fe^{2+}}$)] varying between 0.91 and 0.94 and olivine in dunite between 0.92 and 0.94. Clinopyroxene from the harzburgite is $\rm{TiO_{2}}$ and $\rm{Na_{2}O}$-poor diopside ($\rm{Wo_{47–50}En_{47–50}Fs_{2–4}}$). Spinel in harzburgite shows wide Cr#, molar ratio varied between 0.26 and 0.72, and significantly higher in dunites with Cr# ranges from 0.69–0.85. Cr# of the peridotite spinel follow a depletion trend. Calculated equilibrium conditions of the samples are $800–900^{0}\rm{C}$ temperature, 32 and 40 kbar pressure, oxygen fugacity -0.09 to 0.55 log units above the FMQ buAer. Residual nature of the harzburgites and the presence of high and low Cr# spinels may be due to the genetic artifact of the different ultramafic units.

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