Characteristics of Mesoproterozoic felsic meta-volcanics from the Shillong Group of rocks, Meghalaya, North East India

摘要

Shillong Group comprises a thick meta-volcano-sedimentary sequence forming a part of Shillong Plateau and Mikir Hills. The litho variants of felsic meta-volcanics are characterized in detail based on their constituent material, textural variation, depositional feature and mode of eruption. Lava flows are characterized as porphyritic, spherulitic and aphyric type whereas pyroclastic deposits are classified as tuff breccia, lapilli tuff, tuff and ignimbrite. Fractured crystal and brecciated lithic fragments in tuff; fiamme and eutaxitic texture of ignimbrite suggest for subaerial eruption. The felsic meta-volcanics are rhyolitic to dacitic in composition and interbedded with tuffaceous phyllite, phyllite and quartzite.