Thermobarometry of the Rajmahal Continental Flood Basalts and Their Primary Magmas: Implications for the Magmatic Plumbing System
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minerals-13-00426.pdf
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77f40b0086c29115f63769c120a3bf73
Author(s)
Chatterjee, Nilanjan
Ghose, Naresh C.
Date Issued
March 17, 2023
Publisher
Multidisciplinary Digital Publishing Institute
Citation
Minerals 13 (3): 426 (2023)
Version
Final published version
Abstract
The Late Aptian Rajmahal Traps originated through Kerguelen-Plume-related volcanism at the eastern margin of the Indian Shield. Clinopyroxene and whole-rock thermobarometry reveals that the Rajmahal magmas crystallized at P-T conditions of ≤~5 kbar/~1100–1200 °C. These pressures correspond to upper crustal depths (≤~19 km). Modeling shows that the Rajmahal primary magmas were last in equilibrium with mantle at P-T conditions of ~9 kbar/~1280 °C. The corresponding depths (~33 km) are consistent with gravity data that indicate a high-density layer at lower crustal depths below an upwarped Moho. Thus, the high-density layer probably represents anomalous mantle. It is likely that the mantle-derived magmas accumulated below the upwarped Moho and were subsequently transported via trans-crustal faults/fractures to the upper crust where they evolved by fractional crystallization in small staging chambers before eruption. In the lower part of the Rajmahal plumbing system, buoyant melts from the Kerguelen Plume may have moved laterally and upward along the base of the lithosphere to accumulate and erode the eastern Indian lithospheric root. The Rajmahal plumbing system was probably shaped by tectonic forces related to the breakup of Gondwana.
MIT Department
Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences
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DOI of Published Version
https://doi.org/10.3390/min13030426
