Mineral chemistry, geochemistry and geophysical investigations of Simlipal volcanics from Eoarchean Singhbhum Craton (Eastern India): geodynamic implications of pervasive plume–lithosphere interaction
Publication Type:Journal Articles
Source:International Journal of Earth Sciences (2022)
Keywords:Simlipal volcanic complex Singhbhum craton · Mantle plume–lithosphere interaction · Mafic crustal exhumation and magmatic underplating · Geodynamical Implications · Asteroidal impact
Singhbhum craton in eastern India is one of the oldest and perhaps geologically and geophysically most complex geological terrains on the surface of the Earth, containing a number of intra-cratonic Archean volcanic suites. In the present study, we investigate Mesoarchean volcanic rocks of the Simlipal complex, a tiger reserve in the Mayurbhanj district of Odisha (India). Our results provide a new understanding of the regional geodynamic scenario of the Eoarchean Singhbhum craton, including the nature of plume–lithosphere interaction based on the detailed analysis of geological, geochemical and geophysical data. Whole-rock geochemical studies exhibit large variation in SiO2 (39.30–60.57 wt%), TiO2 (0.20–1.55 wt%), Al2O3 (4.45–15.63 wt%), MgO (5.25–37.00 wt%) and CaO (3.46–11.26 wt%) with low to moderately high Cr (50–1503 ppm) and Ni (36–550 ppm) contents. These rocks are cumulates to porphyritic and petrographically and geochemically, can be classified as ultramafic (lherzolite, pyroxenite), picrite, basalt, basaltic andesite, andesite and boninite. Their trace elements and HFSE/REE patterns indicate that they belong to the same parental magma. Rare earth elements and trace element patterns exhibit moderate fractionation with a coherent pattern of (La/Yb)n: 1.38–8.50, (Gd/Yb)n: 0.92–2.59 and (La/Sm)n: 1.11–4.40, consistent with polybaric melting. The present study suggests that these rocks were generated by decompressive melting of a mantle plume head at a depth of garnet to spinel lherzolite field together with fractional crystallization and crustal contamination in the subcontinental lithospheric mantle (SCLM), which is corroborated by the highly uplifted nature of this terrain, associated with positive gravity anomalies. This plume had a mantle potential temperature between 1400 and 1700 °C and pressure reaching 4.4 GPa. Massive upwarping of the lower crust to an extremely shallow depth of about 4 km from the surface, 21 km thick magmatic underplating above the Moho and the lithosphere asthenosphere boundary at 81 km, would support plume-induced active crust–mantle thermal interaction and extremely warm and deformed nature of the lithosphere beneath the Simlipal volcanic complex. Based on the findings of millerite (NiS), quench/spinifex texture and shock metamorphic features in these volcanic rocks, we infer that there could be a possibility that the suggested mantle plume in the study area may have been triggered by an asteroidal impact.