Earth, Atmosphere & Environment Sciences
Title : | Determining the primary magma composition of Rajmahal-sylhet Traps mafic rocks: Inferences on the dynamics of large-scale mantle melting and formation of continental Large Igneous Provinces |
Area of research : | Earth, Atmosphere & Environment Sciences |
Focus area : | Geology |
Principal Investigator : | Dr. Debajyoti Paul, Indian Institute of Technology (IIT) Kanpur, Uttar Pradesh |
Timeline Start Year : | 2024 |
Timeline End Year : | 2027 |
Contact info : | dpaul@iitk.ac.in |
Details
Executive Summary : | The proposed project will investigate the nature of mantle sources, dynamics of plume melting, and interaction of melt and continental crust in the origin of Rajmahal-sylhet Traps Large Igneous Province (LIP) with the help of newly generated elemental (major and trace elements) and isotopic (radiogenic sr-Nd-Pb and stable Ca) compositional data. In particular, the data generated for the mafic and alkaline rocks of known ages from Rajmahal and sylhet Traps (shillong Plateau) will provide "time-snapshots” of the chemical and isotopic composition of parcel of material transferred from a deep-seated mantle plume around 118 Ma ago. Compared to the Deccan Traps LIP that has been studied extensively for the past few decades generating extensive geochemical (including isotope) data for the mafic and alkaline rocks (and associated carbonatites), those for the Rajmahal-sylhet Traps are conspicuously scarce, which had led to a poor understanding of its origin. Therefore, the estimation of the primary magma composition, particularly the sr-Nd-Pb-Ca isotopic composition of these basalts proposed in this study will provide a direct comparison with those of the (65 Ma old) Deccan Traps rocks reported in the literature to constrain the temporal (chemical) evolution of mantle beneath the Indian shield and dynamics (the pressure, temperature, modal mineralogy, etc.) of melting within the plume. We propose to conduct a detailed field work to carefully select fresh tholeiitic basalts (and volcanic glass) and a suite of differentiated rocks and associated alkaline rocks (about 80 samples) from the Rajmhal Hills area and shillong Plateau and perform petrography and mineral chemistry, do U-Pb baddeleyite geochronology (-8-10 most primitive samples), obtain whole-rock major-trace element and radiogenic sr-Nd-Pb (- 50 samples) and stable Ca isotope (30 samples) compositions. Our major objectives are to (1) compare the similarity in age and chemical signatures between the Rajmahal-sylhet Traps rocks with those of Kerguelen plume-derived products of -118 Ma to establish a genetic link, (2) estimate the primary magma composition and compare with those for the Deccan Traps basalts to study temporal variation in the mantle source beneath the Indian shield, (3) understand the dynamics of large-scale mantle melting and develop a petrogenetic model that explains the origin of these mafic rocks in a continental LIP setting. Integration of all data will aid to develop a model that would explain source heterogeneity and plume-melting dynamics and the role of magma interaction with continental crust that led to the formation of Rajmahal-sylhet Traps rocks, which could be applicable to all major continental LIPs elsewhere. The proposed study has implications for evolution of the Indian shield and the underlying subcontinental lithosphere. |
Co-PI: | Dr. Anupam Banerjee, Indian Institute of Technology (IIT) Kanpur, Uttar Pradesh |
Total Budget (INR): | 70,11,720 |
Organizations involved