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T-LAB: Global Maps of the Thermal Lithosphere-Asthenosphere Boundary Derived from Shear-Wave Tomography Models and Mineral Physics Constraints

The lithosphere-asthenosphere boundary (LAB) marks the base of the Earth’s outer layer where heat is transferred primarily by conduction as compared to prevailing convective heat transport below. Spatial variations in LAB depth reveal the differential evolution of tectonic systems (e.g., rifts and orogens), thus enabling a better understanding of geodynamic processes. Further, the topography of the LAB exerts control on the coupling of the lithosphere to asthenospheric flow, modulating the distribution of present-day stresses and active deformation of the tectonic plates. We have derived global depth variations of the LAB from temperature-converted shear-wave tomography models assuming that the threshold temperature between conduction and mantle convection is 1300 °C. Shear-wave velocity in the mantle is controlled by both in situ pressure-temperature conditions and mineralogical rock composition. Therefore, our velocity-to-temperature conversion builds on a framework of rock physical properties generated through a Gibbs free energy minimization to determine thermodynamically stable phase and mineral assemblages throughout upper mantle pressure and temperature conditions. In this data publication, we provide thermal LAB depths corresponding to one European-scale and three global-scale tomography models. The data release includes (i) a data description file with information on the input tomographic models, the conversion method and spatial variations in LAB depth (illustrated); and (ii) four data files with LAB depth values spatially sampled according to the input tomography models.

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