New constraints on the geodynamics of the Gulf of Aden from gravity field analysis

We perform a new gravity analysis in the Gulf of Aden with the aim to find new constraints on the geodynamic evolution of the area. Our analysis is developed within the frame of the new GO_CONS_EGM_TIM_RL06 global gravity model solution (Brockmann et al., 2021) that reflects the Earth’s static gravity field as observed by GOCE (Gravity field and steady-state Ocean Circulation Explorer). We analyzed the solution at different harmonic degree, to account for different depths of the sources. Terrain correction has been performed by means of a spherical tesseroidal methodology (Marotta and Barzaghi, 2017) and the obtained residual gravity pattern has been compared to the gravity disturbance predicted by means of a 2D visco-plastic finite element thermo-mechanic model that simulates the evolution of the Gulf of Aden, from rifting to oceanization, for different crust thickness and initial thermal configuration of the lithosphere (Bollino et al., 2022). The formation of oceanic crust and serpentinite due to the hydration of the uprising mantle peridotite has been also accounted. To be compliant with the geodetic residual gravity, we define a model normal Earth in terms of a horizontally uniform density distribution that, vertically, coincides with the density distribution predicted at the sides of the 2D model domain at the same time of the comparison. In order to perform the comparison between observed and predicted gravity features, data have been extracted along six profiles crossing the Gulf of Aden at different sectors, from the south-east to the north west. Our preliminary results indicate that the Gulf of Aden developed as a slow passive rift of a hot lithosphere with a thick crust, fixing the upper bound of crustal thickness in the surrounding of the Gulf of Aden to 40 km.

References

Bollino, A., Regorda, A., Sabadini, R., & Marotta, A. M. (2022). From rifting to oceanization in the Gulf of Aden: Insights from 2D numerical models. Tectonophysics, 838, 229483.

Brockmann, J. M., Schubert, T., & Schuh, W. D. (2021). An improved model of the Earth’s static gravity field solely derived from reprocessed GOCE data. Surveys in Geophysics, 42(2), 277-316.

Marotta, A. M., & Barzaghi, R. (2017). A new methodology to compute the gravitational contribution of a spherical tesseroid based on the analytical solution of a sector of a spherical zonal band. Journal of Geodesy, 91(10), 1207-1224.