Geology and Source Characterise of the dyke straddling in the west coast deccan

Abstract

The West Coast of the mainland Deccan Volcanic Province is characterized by extensive exposures of Late-Cretaceous-Paleogene basaltic lava flows intruded by numerous dykes. Field work was carried out at Korlai Fort and Murud area to document dyke morphology, orientation, and internal structures. Petrography and XRF geochemistry classify the dykes into two groups: olivine-tholeiite dykes (Korlai, N–S swarm) and alkaline/lamprophyre dykes (Rajapuri-Murud). Tholeiitic dykes are hypersthene-normative while alkaline dykes are nepheline-normative. The dichotomy suggests derivation from different mantle depths — spinel-harzburgite field for tholeiites and garnet stability field for lamprophyres. Dyke orientations indicate emplacement controlled by regional NNW-SSE tectonics related to the Panvel Flexure and Indo-Seychelles rifting, while dyke offsets are controlled by pre-existing cooling joints in host basalt.