Magmatic underplating beneath the Rajmahal Traps: Gravity signature and derived 3-D configuration |
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| Authors: | A P Singh Niraj Kumar Bijendra Singh |
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| Institution: | (1) National Geophysical Research Institute, Uppal Road, 500 007 Hyderabad, India |
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| Abstract: | The early Cretaceous thermal perturbation beneath the eastern continental margin of the Indian shield resulted in the eruption
of the Rajmahal Traps. To understand the impact of the magmatic process that originated in the deep mantle on the lower crustal
level of the eastern Indian shield and adjoining Bengal basin the conspicuous gravity anomalies observed over the region have
been modelled integrating with available geophysical information. The 3-D gravity modelling has delineated 10–15 km thick
high-density (ρ = 3.02 g/cm3) accreted igneous layer at the base of the crust beneath the Rajmahal Traps. Thickness of this layer varies from 16 km to
the west of the Rajmahal towards north to about 12 km near Kharagpur towards south and about 18 km to the east of the Raniganj
in the central part of the region. The greater thickness of the magmatic body beneath the central part of the region presents
itself as the locus of the potential feeder channel for the Rajmahal Traps. It is suggested that the crustal accretion is
the imprint of the mantle thermal perturbation, over which the eastern margin of the eastern Indian shield opened around 117
Ma ago. The nosing of the crustal accretion in the down south suggests the possible imprint of the subsequent magmatic intrusion
along the plume path. |
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| Keywords: | Rajmahal Traps mantle plume magmatism crustal underplating Bouguer anomaly |
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