Journal of Geological Society of India (Online archive from Vol 1 to Vol 78)

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Petrochemistry and Tectonic Significance of the Peralimala Alkali Granite, Cannanore District, Kerala


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1 Centre for Earth Science Studies, P. B. No. 2235, Trivandrum 695010, India
     

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The E-W elongated pluton of Peralimala, Cannanore district, Kerala, which is classified here as an alkali granite, occurs along the Bavali lineament, spatially associated with the late Proterozoic anorthosite-gabbro-granite-granophyre suite of the Ezhimala Igneous Complex. Perthitic K-feldspar, plagioclase of albite-oligoclase composition, quartz alkali amphibole, aegirine and sphene constitute the main mineralogy of the alkali granite. Chemically, the rock shows high content of alkalies with K2O values ranging up to 10.96 wt. percent. The extremely high levels of K, AI, Ba and Ba/Sr suggest the existence of a phlogopite-rich pocket in the mantle beneath the Bavali lineament from where the melt equilibrated. As peralkaline plutonism is a keynote of pre-rift tectonics, the occurrence of the alkali granite along the Bavali lineament is a manifestation of rift-related alkaline magmatism in this part of the western continental margin of India.
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  • Petrochemistry and Tectonic Significance of the Peralimala Alkali Granite, Cannanore District, Kerala

Abstract Views: 205  |  PDF Views: 8

Authors

N. G. K. Nair
Centre for Earth Science Studies, P. B. No. 2235, Trivandrum 695010, India
M. Santosh
Centre for Earth Science Studies, P. B. No. 2235, Trivandrum 695010, India

Abstract


The E-W elongated pluton of Peralimala, Cannanore district, Kerala, which is classified here as an alkali granite, occurs along the Bavali lineament, spatially associated with the late Proterozoic anorthosite-gabbro-granite-granophyre suite of the Ezhimala Igneous Complex. Perthitic K-feldspar, plagioclase of albite-oligoclase composition, quartz alkali amphibole, aegirine and sphene constitute the main mineralogy of the alkali granite. Chemically, the rock shows high content of alkalies with K2O values ranging up to 10.96 wt. percent. The extremely high levels of K, AI, Ba and Ba/Sr suggest the existence of a phlogopite-rich pocket in the mantle beneath the Bavali lineament from where the melt equilibrated. As peralkaline plutonism is a keynote of pre-rift tectonics, the occurrence of the alkali granite along the Bavali lineament is a manifestation of rift-related alkaline magmatism in this part of the western continental margin of India.