Haase K, Regelous M, Schöbel S, Günther T, de Wall H (2019)
Publication Type: Journal article
Publication year: 2019
Book Volume: 524
The Deccan flood basalts cover large parts of India and represent one of the largest volcanic provinces on Earth. We present geochemical and isotopic data on a magnetically defined stratigraphic section of lavas from the northern portion of the Deccan, the Malwa Plateau, which are dated at similar to 67.5 Ma. These are therefore some of the oldest Deccan lavas, erupted before the Main Deccan units further to the south. Although the younger Malwa Plateau lavas have undergone significant crustal contamination by at least two distinct crustal components, the older, more alkalic lavas are less contaminated and have similar isotope and trace element compositions to Reunion oceanic intraplate basalts. Our data therefore provide geochemical evidence for a contribution of the Reunion hotspot to the generation of the early Deccan flood basalts. Most lavas reflect fractional crystallization and assimilation of less than 10% of a crustal melt but samples with the highest SiO2 and Sr isotope compositions underwent more extreme crustal contamination. The composition of the least contaminated basalts from the Malwa Plateau suggests that the degree of partial melting increased significantly from the base to the top of the section. Most Malwa Plateau basaltic magmas formed by <5% partial melting of garnet peridotite in the Reunion mantle plume whereas the degree of melting in the Main Deccan Volcanic Province increased threefold and included MORB sources. Together, these geochemical variations indicate increasing degrees of melting between 68.5 and 65.4 Ma and a variation of the mantle sources from Reunion plume mantle to an increasing contribution from depleted upper mantle. These changes probably reflect lithospheric erosion by the mantle plume within 2 million years that allows melting of entrained upper mantle material. The geochemical data thus agree with geophysical models of significant thinning of cratonic lithosphere during the passage across mantle plumes. The magma evolution from alkaline to tholeiitic basalts observed in the Deccan flood basalts resembles that observed in early oceanic plume-related volcanism like Hawaii. (C) 2019 Elsevier B.V. All rights reserved.
Haase, K., Regelous, M., Schöbel, S., Günther, T., & de Wall, H. (2019). Variation of melting processes and magma sources of the early Deccan flood basalts, Malwa Plateau, India. Earth and Planetary Science Letters, 524. https://dx.doi.org/10.1016/j.epsl.2019.115711
Haase, Karsten, et al. "Variation of melting processes and magma sources of the early Deccan flood basalts, Malwa Plateau, India." Earth and Planetary Science Letters 524 (2019).