| Abstract Submission No. | ABS-1.2-0093 |
| Title of Abstract | Seismic Evidence of Deep Crustal Hydration in the Central Indian Ocean Basin |
| Authors | Lachit Singh Ningthoujam*, Sanjay Singh Negi, Amit Kumar, P Sion Kumari, John P Kurian |
| Organisation | National Centre for Polar and Ocean Research, Goa |
| Address | Geoscience LAB NATIONAL CENTRE FOR POLAR AND OCEAN RESEARCH HEADLAND SADA Vasco Da Gama, Goa, India Pincode: 403804 E-mail: lachit@ncpor.res.in |
| Country | India |
| Presentation | Oral |
| Abstract | The Central Indian Ocean Basin (CIOB) constitutes one of the most complex and dynamic geodynamic domains on Earth, sculpted by the interplay of long-term plate convergence, diffuse intraplate deformation, and hotspot activity. Its present configuration traces back to the early¿mid Cretaceous rifting between Antarctica and India, which initiated the formation of the Indian Ocean. The protracted rift-to-drift evolution of the Indian Plate was further modulated by repeated interactions between coeval mantle plumes and spreading centres, leaving a lasting imprint on the basin¿s tectonic and magmatic architecture. In 2015, a ~420-km long wide-angle reflection and refraction seismic profile was acquired in the CIOB using 12 nos. of 4-component ocean bottom seismometers (OBSs) south off Sri Lanka, which lies in close proximity to the Indian Ocean Geoid Low. This multicomponent OBS has provided us the opportunity to integrate the different components for investigating the processes driving intraplate deformation, lithospheric hydration, and tectonic evolution. In this study, we employ P- and S-wave arrivals recorded by these12 OBSs to construct high-resolution seismic tomography models for both P- and S-wave velocity structures. From these models, we derive spatial variations in the Vp/Vs ratio and corresponding estimates of Poisson¿s ratio. The results highlight pronounced anomalies within the deep crustal section, where Poisson¿s ratios (ν) exceed 0.29 in the lower crust. Such elevated values provide compelling evidence for extensive hydration of the crust, most plausibly facilitated by the infiltration of seawater along pervasive fracture and fault systems. This hydration process modifies the mineralogy and fabric of crustal rocks, reducing seismic velocities, enhancing ductility, and significantly altering the bulk physical properties of the lithosphere. Our findings underscore the critical role of fluid¿rock interactions in governing the mechanical behaviour of the oceanic crust and their broader implications for intraplate deformation and seismicity in the Central Indian Ocean Basin. |
| Keywords | Central Indian Ocean Basin, deformation, hydration, seismic |