Geochemical characterization and petrogenesis of Proterozoic Khairagarh volcanics: implication for Precambrian crustal evolution

Abstract

The Khairagarh volcano-sedimentary sequence is exposed along the Kotri-Dongargarh Belt towards the north-eastern part of the Bastar Craton. This sequence is exposed south of the Central Indian Shear (CIS) and east of the Sakoli Group rocks. The Khairagarh volcanic sequence is represented by low-Ti, intermediate-Ti and high-Ti basalt-basaltic andesite series that probably represent varying degrees of partial melting of an enriched mantle source, thus they appear to be consanguineous. These rocks are associated with a sequence of high magnesium andesitic (HMA) rocks that follow a separate evolutionary trend, thus they appear not to be related to the basalt-basaltic andesite sequence. The presence of the two contrasting sequences probably indicates generation in a hot Andean-type subduction zone for the HMA, and Andean-type back-arc rifting for the basalt-basaltic andesite samples. The possibility of a relatively thick crust around 3.6 Ga in the Bastar Craton and the Amgaon Gneissic Complex, basement for the Khairagarh-Sakoli sequence, probably indicates that it was part of the Supercontinent Ur. The mantle extraction age of about 2.9 to 2.5 Ga, based on the Nd-model ages for the KhairagarhSakoli sequence, probably indicate that this part of the Central Indian Shield became part of the Supercontinent Columbia subsequently.

Geochemical evolution of basaltic flows from Dongargarh Supergroup, Bastar Craton, Central India

“…SiO2 ranges from 48-54 wt%, Fe2O3 from 8-16 wt%, MgO shows a little wide range from 3-15 wt% and Al2O3 from 11-15 wt%. Based on the Ti-content of the studied Basalts, these are subdivided into two groups; low-Ti basalts having Ti < 0.9 wt% and relatively high-Ti basalts having Ti > 0.9 wt% [1] [10] [13]. The plot of compiled data are showing the composition of basalt to basaltic-andesite in composition, lying in the sub-alkaline field in the total alkalis versus silica (TAS) diagram (Figure 1).…”

“…Asthana et al [3] categorised the Pitepani suits as high-Mg, low-Ti suits and low-Mg, high-Ti suits. Whereas Sitagota basalts show a wider range in concentration of these elements and can be grouped into high-Ti basalts and low-Ti basalts [1][10] [13].…”

Tectonic framework of southern Bastar Craton, Central India: a study based on different spatial information data sets

“…Neogi et al (1996) also ascribed that these lavas were erupted in a continental rift environment. Asthana et al (1996), and Longjam and Ahmad (2012) suggested that the Khairagarh mafic volcanics are similar to island-arc magmas and have been developed under Andean-type subduction zone environments for the high-Mg andesites and Andean-type back-arc rifting for the basalt-basaltic andesites. Adjacent to the Khairagarh Group, Sakoli bimodal volcanics are well exposed and constitute meta-basalts, rhyolite, tuffs, epiclastic rocks with metapelites, quartzites, arkose, conglomerates, and iron formations.…”

“…The Khairagarh Group is exposed in the south‐western margin of the Chhattisgarh Basin comprising low‐Ti and high‐Ti basalts (Asthana et al ., ). The depleted mantle model ages (Sm–Nd isotopic analysis) of these volcanics ranges from 2984 to 2489 Ma (Longjam and Ahmad, ). The rhyolites in the Nandagaon Group have been included under the Bhijili rhyolites, composed of thick stacks of felsic volcanics, un conformably overlying the gneissic rocks of the older Amgaon Group with a thickness of 4500 m (Sarkar, ).…”

The Indian Precambrian: correlations and connections

“…The subsequent three articles deal with the different geological aspects of the Bastar Craton. Longjam and Ahmad () investigate the Khairagarh volcanics, the magmas of which were extracted from an enriched mantle at 2.9–2.5 Ga, and accreted to the Columbia supercontinent along an Andean‐type subduction zone within a back‐arc setting. Mid‐Archaean to Palaeoproterozoic mafic dyke swarms in the Bastar Craton are investigated by Srivastava and Gautam (), who correlate their diversities and geochemical signatures to different degrees of partial melting in the mantle and suggest the involvement of plumes.…”