Integration of numerical modelling and gravity data to disclose the dynamics of the Gulf of Aden.

Bollino A., Regorda A., Sabadini R., Barzaghi R., Marotta A.M.
  Giovedì 15/09   10:00 - 13:00   Aula U - Giuliana Cini Castagnoli   IV - Geofisica e fisica dell'ambiente   Presentazione
Gulf of Aden is a young oceanic basin that offers an excellent opportunity to understand breakup processes during extension. Regional stress field or thermal upwelling of the asthenosphere, inherited zones of weakness and the rheological structure of the lithosphere are the factors contributing to the initiation of rifting and deformation of lithosphere. We use a 2D thermo-mechanical model to simulate the formation of oceanic crust and serpentinite due to the hydration of upwelling mantle peridotite. A strongly integration between modeling and gravitational data provided valuable constraints to our analysis. Our preliminary results show that: a) four main tectonic phases develop during rifting, each one characterized by particular distributions of velocity gradients and strain rates inside divergent crustal blocks, which allow us to determine when breakup occurs; b) the timing of mantle serpentinization is not affected by the initial thermal configuration of the system but is related to crustal thickness; c) the timing of mantle partial melting strongly depends on the thermal conditions in both lithospheric plates; d) evolution of the model with crustal and lithospheric thickness of 40 and 150 km, respectively, well fit with the geodynamic reconstruction of the Gulf of Aden, considering the timing of break-up that occurs 20 Myr after the onset of the extension for 0.05% percentage of mantle hydration (in agreement with magma-poor rift margins). Finally, the results obtained so far support the hypothesis that the Gulf of Aden developed as a slow passive rift in thin lithosphere with thick crust and that the variations in features along the passive margins could be related to lateral variations in the amount of H$_$2$$O in the mantle, which determines the different times of mantle melting.