Lithofacies analysis of volcanics and volcaniclastics of an ancient volcanic terrain with signatures of subaerial plinian volcanism: An example from Neoarchaean-Palaeoproterozoic Nandgaon Group, Bastar Craton, central India
The N–S trending Neoarchaean to Palaeoproterozoic Dongargarh–Kotri belt in the Bastar Craton in central India exposes bimodal volcanics and volcaniclastics of the Nandgaon Group. In this contribution, lithofacies analysis of the Nandgaon Group has been attempted mainly based on distribution of rhyolites, basalts and pyroclastics in this ancient volcanic terrain, their field characteristics and petrography. The study area in the central part of the belt around Dongargaon–Gotatola area can be two distinct domains based on distribution and composition of volcanics and volcaniclastics. Domain-I comprises coherent and autoclastic rhyolite, and Domain-II with basic lava and pyroclastics. The rhyolites of Domain-I can be further divided into feldspar quartz phyric, quartz phyric, aphyric, and autoclastic rhyolites. Basic lava of Domain-II includes basalt and andesitic basalt. The associated volcaniclastics are mainly coarse lapilli tuff, fine lapilli tuff and ash beds. Field characteristics of coherent lavas and volcaniclastics attest to phreato-magmatically controlled plinian to sub-plinian style of eruptions. Effusive and explosive eruptive processes through multiple vents gave rise to the observed volcanic sequences. This study indicates that subaerial volcanism initially led to formation of felsic ignimbrites and ash deposits followed by effusive rhyolite lava flows. Subsequently, mafic volcanism occurred giving rise to pyroclastic flows and surges, followed by effusive mafic lava flows.
Volume 130, 2021
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