Petrology of the Rocks of St. Mary Islands, Near Malpe, South Kanara District, Mysore State

The rocks of St. Mary Islands consist of dacite, rhyodacite and granophyre, showing close similarity in texture, mineralogy and petrochemistry, to similar rocks described from the islands of Salsette and Bassein, near Bombay. Based on the petrological study, it is surmised that the rocks of these islands are genetically connected with the Deccan Trap igneous activity. The study suggests a wider Deccan Trap igneous activity extending to several hundred kilometres south of the now known outcrops of trap. It also hints the association of a rhyolite magma with Deccan Trap igneous activity.