Orbicular rhyolite of Dhiran area, Malani Igneous Suite, Barmer District, Western Rajasthan

摘要

Occurrences of large multi-shell orbicular structures in Malani Igneous Suite, Western Rajasthan has been reported for the first time. The orbicules occur in an Anorogenic, A-type rhyolite. The majority of the orbs comprise of a series of distinct shells (layers) viz. dark and light colour shells surrounding a core. The shells consist of orthoclase, sanidine, quartz (light colour shell) and orthoclase, iron oxide (magnetite & ilmenite), riebeckite and arfvedsonite (dark colour shell). The core and groundmass of the orbicules have identical composition.