Vitric Tuff from Archipelago Group (Mio-Pliocene), South Andaman

Vitric tuff is being reported from Archipelago Group of South Andaman. The tuff is composed of delicately shaped glass shards with variable amount of microlites and broken phenocrysts of quartz, plagioclase and mica. Major oxide analyses show dacitic composition of the tuff. Petrographic and XRD studies show that the glass is altered to clinoptilolite and analcime. The sedimentary structures in tuff beds suggest these as products of ash turbidite.