Petrology and geochemistry of the igneous complex of Mount Girnar, Gujarat, India

Abstract

The Girnar massif of Kathiwar plateau, Western India, occurs within the Deccan volcanic province and manifests a wide range of fractional crystallisation of the parent basic magma. Mineralogical variation in the suite comprising: gabbro-diorite-lamprophyric rock-nepheline syenite, has been studied in detail. The alkalinity of the suite is pronounced after crystallisation of gabbro and increases with fractionation of the magma. The history of fractional crystallisation has been influenced by growing water content of the magma followed by a depletion of water in the final residual liquid. Silicic porphyries developed in close spatial association with the Girnar massif, are established to have no genetic relation with the alkalic suite. Chemical variation for both major and minor elements in the suite is discussed.