Institute: University of Calcutta
Title: Postdoctoral researcher
Country/Region: INDIA
Period: 2022/11/16-2023/01/20
Theme: Constraining lithospheric thickness of the spreading ridge-continental margin system: New insights from basalt geochemistry and its bearing on mantle heterogeneity
Host: Hikaru IWAMORI
Introduction: I am a Petrologist and geochemist from India and working as a postdoctoral researcher at the University of Calcutta, India. Prior to that, during my post-doc at Niigata University, Japan, I studied lower crustal gabbros from Oman ophiolite [collected during International Continental Scientific Drilling Program (ICDP) Oman Drilling project (OmanDP) in 2017-18] in order to understand the lower crustal formation at the fast-spreading oceanic crust. I received my Ph.D. in geology from Hokkaido University, Japan in 2017, where my work was mainly focused on the genesis of lower crustal primitive gabbroic rocks that formed at the fast-spreading East Pacific Rise (EPR) at Hess Deep Rift [sampled during Integrated Ocean Drilling Program (IODP) Expedition 345]. The goal of my ongoing research is to understand the full spectrum of processes that create and modify the fast-spreading oceanic crust and shallow mantle, involving fractional crystallization, assimilation-fractionation process, oxidation process, and ultimately the tectonic settings of spreading ridges.
Recently, I participated in the IODP expedition 396: Mid-Norwegian Continental Margin Magmatism as an onboard scientist (inorganic geochemist) at JOIDES Resolution (August-October, 2021). My main focus of this short-term project with Prof. Hikaru Iwamori is to combine the geochemical and multivariate statistical approach to the recovered basalt samples from the drilling program as well as the existing data from the region. Our key objective is to estimate crustal as well as lithospheric thicknesses and to examine the working hypotheses for the geochemical control for rift initiation, the formation of rifted margins, lithospheric plate formation (the lithosphere-asthenosphere boundary).

Research Report:

Mobility of the fragmented lithosphere (or plates) over a weaker asthenosphere and subduction (destruction of plates) in our planet earth is somewhat unique in the solar system. Consumption of plates in the subduction zone is counteracted by the generation of the new lithosphere at mid-oceanic ridge settings, where divergent plate motion leads to mantle melting and subsequent formation of new oceanic crust by crystallization of magma. However, the magma outcome is not equally distributed throughout the Earth instead it is believed to be intrinsically linked with the rate of plate spreading. The making of a self-sustaining divergent plate boundary usually traces back from the continental rifting (due to lithospheric thinning and/or uprising mantle plume) and is considered a fundamental step in the Wilson cycle. Usually, continental rifting under influence of mantle plumes causes enormous magmatic outpour in spite of significant investigation spanned through the last few decades it is still unknown how such excess volcanism took place in a surprisingly short duration and the major controlling geodynamic factors behind it. According to the Wilson cycle disassembly and assembly of the supercontinents starts with initial pre-drift extension followed by rift-to-drift phase, the initial opening of an oceanic basin, seafloor spreading, widening of the basin, subduction of oceanic lithosphere, closure of the basin, and finally continent-continent collision. A classic example of continental extension, breakup, and formation of new mid-oceanic spreading centres can be found in the Atlantic ocean. The North Atlantic Igneous Province eruptions started around 61-62 Ma and formed the northern Atlantic passive margins to the present state. It is still poorly unresolved that, what is the key mechanism behind the excess amount of magmatism in a surprisingly short duration causes the breakup of the northeast Atlantic.
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Fiscal Year: 2022