Petrology and geochemistry of a boninite dyke from the western Bastar craton of central India

Abstract

The Dongargarh Supergroup along with the basal Amgaon Gneissic Complex constitutes the northwestern part of the central Indian Bastar craton. In the present study, we report a new finding of a boninite dyke intruded in the Amgaon gneisses of this area. The dyke composed of mainly pyroxenes, amphiboles and subordinate amount of plagioclase. The higher contents of SiO 2 (51-54 wt.%), MgO (12-14 wt.%), Ni (375-473 ppm), Cr (1416-1580 ppm) and very low TiO 2 (0.2-0.4 wt.%) are consistent with the boninite nature of the dyke as well as the unevolved primary nature of the source magma. The extraordinarily high CaO content (15.97-17.7 wt.%) with higher CaO/Al 2 O 3 (3.13-3.96) ratios classifies it as high-Ca boninite. The trace element ratios including Zr/Ti, Ti/V, Ti/Sc and Ti/Yb further show its geochemical similarity with the Archaean boninite. The dyke also shows negative high-field strength element (Nb, Ta and Ti) anomalies which are the characteristics of the boninite rocks reported elsewhere and along with the enriched light rare earth element pattern, it shows more affinity particularly with the northern Bastar boninite dyke. The mineralogical and geochemical similarities of the boninite dykes from the Bastar craton indicate a widespread boninitic event during the Palaeoproterozoic having a similar origin. These boninite dykes indicate the preservation of subduction-related signatures in the lithospheric mantle beneath the Bastar craton at the time of its evolution or may be during the convergence of the Bastar and Bundelkhand cratons.

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“…The dykes from Amgaon region represent a subduction related outgrowth of Columbia supercontinent due to the accretion of continental margins [55,56]. Hazarika, et al, (2019) identified mafic dykes of Boninitic compositions from Bastar Craton, earlier described by [63]. This boninite magmatism indicates the presence of remnant subduction-related signatures in the lithospheric mantle formed during the evolution of the Bastar Craton [56].…”

“…Like figure 6a the high silica samples plot separately with a compositional gap with higher Zr/Ti ratios (Figure 6b). For comparison we have considered published data on Proterozoic mafic magmatic rocks (dykes and flows) from the adjoining areas (Sakoli volcanics: [72], Amgaon Gneissic Complex basaltic and boninitic dykes [55,56], Amgaon Gneissic Complex amphibolitic and doleritic dykes [38] and Khairagarh volcanics [28]. Texturally and mineralogically they are similar to the mafic magmatic rocks of the adjoining areas, as described by the earlier workers [22,26,28,38,55,56,[72][73][74].…”

“…Granulites from Balaghat-Bhandara and Ramakona-Katangi Ganulite belts associated with Central Indian Suture (CIS) zone [41,28] and Bhopalpatnam and Karimnagar granulite belts are exposed in Western Bastar [36,[42][43][44][45][46]. Mafic dyke swarms of Bastar Craton include NWSE trending Keshkal swarm, Bhanupratappur swarm, Dantewara swarm, and Bastanar swarm, NNW-SSE trending Sonakhan swarm, N-S trending Lakhna dykes, ENE-WSW trending Bandimal dykes are well studied [11,22,42,[47][48][49][50][51][52][53][54][55][56][57]. Dongargarh, Malanjkhand, Abhujmar and Mul granites represent the diverse Proterozoic granites from Bastar Craton [37,56,[58][59][60][61][62].…”

“…Hazarika et al, (2020) have discussed the geochemistry of mafic dykes from Amgaon area, particularly from southern margin of central Indian suture (CIS), with those of northern Bastar Craton Lakhna (1.46 Ga) and Bandimal (1.42 Ga) dykes and inferred a widespread mafic magmatic event across the Bastar Craton circa.1.42-1.46 Ga. The dykes from Amgaon region represent a subduction related outgrowth of Columbia supercontinent due to the accretion of continental margins [55,56]. Hazarika, et al, (2019) identified mafic dykes of Boninitic compositions from Bastar Craton, earlier described by [63].…”

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

“…An intra-cratonic rift model given for the evolution of Dongargarh Supergroup by Neogi et al [19] and references therein, a subduction-related arc-magmatism model for KDMB has been proposed by Asthana et al [3], Khanna et al [10], and Santosh et al [25]. The geochemical signature of boninite dykes from the Dongargarh Supergroup also gives the subductionrelated characteristics [8]. Large igneous provinces model for the emplacement of Paleoproterozoic lamproites dykes [24] and mafic dyke swarms and mantle-derived mafic magmatism [31] in rift environment which was possibly induced by the plume.…”