ATIZA: The nature of lithospheric-mantle beneath Alpine orogenic belts. A comparison between Atlas, Zagros and Tibet from numerical approaches

The aim of this project is to study the present lithospheric structure of three anomalous regions along the Alpine-Himalayan belt: The Atlas, Tibet and the Zagros mountains. Although these three zones have a different geological history, with continental collision in the Himalaya and Zagros, and aulacogen structures in the Atlas, they show similar unusual characteristics: low seismic velocities, basic volcanism, an important dynamic topography component, and subcrustal mass deficit attributed to thinning of the lithospheric mantle.

Recent works in petrology have shown the dependence of the density of the mantle on its composition, temperature and tectonic evolution. With this project we aim to revise critically the mantle characteristics, the mineralogical composition, and its effect on density, and quantify the thickness variations of the three belts. This will permit us to characterize the mantle structure, evaluate the dynamic topography and its stage of evolution, and estimate the mechanical processes responsible for lithospheric mantle thinning (delamination, convective removal, slab break off, etc.).

To this end, we will use a combination of numerical techniques which integrate potential field equations (gravity and geoid) with isostatic (elevation), thermal (heat flow and temperature distribution), and petrophysical models. This novel use of petrophysical data will permit us to compare calculated seismic waves velocities (Vp, Vs), from the pressure, temperature and mineralogical composition, with existing seismic tomographic data.

Improving the understanding of the lithospheric structure beneath these orogens with a unified method will enable us to critically evaluate the various geodynamic models that have been proposed for these three regions.

PhD student: Lavinia Tunini

Proposal