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    • Keywords


      Sivamalai alkaline complex; Rb-Sr whole-rock isochron; initial strontium ratio; fractional crystallization; rare-earth element abundances

    • Abstract


      The Sivamalai alkaline complex comprises ferro-, pyroxene-hornblende- and nepheline-syenites. Field relations show that the nepheline syenites followed the emplacement of non-feldspathoidal syenites. Mineralogical data on the syenite suite have been reviewed. The Sivamalai alkaline rocks are not strongly enriched in rare-earth elements like most miaskites. Rb-Sr isotopic analyses of a suite of six samples from the various members of the complex define an isochron corresponding to an age of 623 ±21 Ma () and initial Sr ratio of 0.70376 ±14 (2σ). This is consistent with a model of fractional crystallization of a parent magma derived from an upper mantle source with apparently no isotopic evidence for more than one magma source for the complex. The Sivamalai alkaline complex represents a Pan-African alkaline magmatic event in the southern granulite terrane of Peninsular India.

    • Author Affiliations


      T V Subba Rao1 B L Narayana1 K Gopalan1

      1. National Geophysical Research Institute, Hyderabad - 500007, India
    • Dates

  • Journal of Earth System Science | News

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