A regional geological overview (a) and a detailed structural map (b) of western Indian passive margin depicting location of Laxmi basin in the northwest Indian Ocean. Solid, thin lines (in black) show regional seismic profiles from present and previous studies respectively.Thick, red part of the E–W oriented seismic profile IODP-04 is displayed in Fig. Grey circles with numbers mark locations of refraction seismic experiments.The LB basalts having Si O and incompatible trace element compositions.The geochemical imprints of LB lava are prima facie akin to island arc signatures, e.g., depletion in high-field strength elements (HFSE, e.g., Nb, Th, etc.) and enrichment in large ion lithophile elements (LILE, e.g., Cs, Rb, Ba, Sr) (Fig. Such peculiar characteristics of LB lava encouraged us to compare them with known arc environments. The FABs are believed to have formed through decompressional and minor fluid-flux melting of the mantle around the leading edge of the Pacific plate during initial stages of subduction.Our observations imply a relict subduction initiation event occurred in the Laxmi basin in the Late Cretaceous-Early Cenozoic that marks a significant Cenozoic plate reorganisation record in the northwest Indian Ocean.
Such successions typically begin with FAB and progress upwards to lavas with more depleted compositions before final highly depleted, boninites Detailed comparisons of N-MORB normalised HFSE and LILE profiles of LB basalts and FAB types from IBM display striking resemblances (Fig. Most of the LB lavas show light rare earth element (LREE) depleted patterns except for the two petrographically distinct samples as discussed above.Contemporaneous asymmetric seafloor spreading, transpressions and multiple ridge reorganisations produced a triangular geometry in the Mascarene basin and forced the India-SLR conglomerate to rotate counter-clockwise as it drifted away from Madagascar in the northwest Indian Ocean heralded seafloor spreading between the Seychelles and Laxmi ridge (LR) and effectively marked the onset of formation of the proto-Carlsberg ridge (Fig. The Seychelles-LR separation is considered as contemporaneous to Deccan volcanism (~68.5–60 Ma with peak magmatic activity around ~65 Ma) when the Reunion hotspot impinged beneath a waning Indian lithosphere (Fig. Decisive information about the LB is vital for deciphering the exact sequence that led to Gondwana breakup and subsequent rift-to-drift tectonics in the Indian Ocean.Furthermore, during this breakup the LB likely remained proximal to the Deccan volcanic province (DVP)Tectonic overview of northwest Indian Ocean.Passive continental margins with their vast global extent offer unique opportunities for exploring continental extension and crustal growth.The western passive margin of India inherits vital imprints of the Gondwana break-up and early evolution of the Indian Ocean, yet it is one of the least explored continental margins.