Thermobarometry of the Rajmahal Continental Flood Basalts and Their Primary Magmas: Implications for the Magmatic Plumbing System

The Late Aptian Rajmahal Traps originated through Kerguelen-Plume-related volcanism at the eastern margin of Indian Shield. Clinopyroxene and whole-rock thermobarometry reveals that magmas crystallized P-T conditions ≤~5 kbar/~1100–1200 °C. These pressures correspond to upper crustal depths (≤~19 km). Modeling shows primary were last in equilibrium with mantle ~9 kbar/~1280 corresponding (~33 km) are consistent gravity data indicate a high-density layer lower below an upwarped Moho. Thus, probably represents anomalous mantle. It is likely mantle-derived accumulated Moho subsequently transported via trans-crustal faults/fractures crust where they evolved by fractional crystallization small staging chambers before eruption. In part plumbing system, buoyant melts from Kerguelen Plume may have moved laterally upward along base lithosphere accumulate erode lithospheric root. system was shaped tectonic forces related breakup Gondwana.