New Uranium-lead (U-Pb) Zircon Geochronology of Sholayar Alkaline Syenite Complex, Kerala: Significance of Cryogenian Magmatism from the Southern Granulite Terrane of the Indian Shield

Abstract

ABSTRACT U-Pb age data from the leuco-syenite from the Sholayar Alkaline Syenite Complex (SASC) (10°17′59.9″N: 076°47′26.3″E) is presented in this study. The present sample contains alkali feldspar (orthoclase), oligoclasic plagioclase, diopsidic pyroxene, biotite and opaque minerals (magnetite and ilmenite). The modal data of constituent minerals is plotted over the IUGS classification diagram and the data plots fall within the syenite field. Obtained age (mean age 706.7 ± 8.4 Ma) largely corresponds to the Cryogenian period. In chondrite-normalized diagrams, the syenite shows some affinity towards well-studied silica over-saturated syenites of the Southern Granulite Terrane (SGT). The Ti-in zircon thermometry indicates the crystallization temperature in the range of 613° to 755°C. The reported zircon U-Pb age suggests evidence for Cryogenian alkaline magmatism in the SGT associated either with asthenospheric upwelling in an extensional setting or subduction related continental rifting.