A new Integrated lithological model of the Iberian crust

The Earth’s crust hosts most of the geo-resources of societal interests (e.g. minerals, geothermal energy etc.). Integrative approaches combining geophysical and petrological observations to study the mantle assuming thermodynamic equilibrium are relatively common nowadays. However, in contrast to the mantle, where thermodynamic equilibrium is prevalent, vast portions of the crust are thermodynamically metastable. This is because equilibration processes are essentially temperature activated and the temperature in the crust is usually too low to trigger them. Consequently, the mineralogical assemblage of crustal rocks is mostly decoupled from the in situ pressure and temperature conditions, reflecting instead the conditions present at the moment of rock formation. Here we present a new methodology for integrated geophysical-petrological multi-data modelling of the crust. Our primary constraining data are fundamental mode Rayleigh wave surface wave dispersion curves determined by interstation cross-correlation measurements and teleseisms, as well as surface elevation (isostasy) and heat flow. Additional prior information is provided by P-wave velocities coming from controlled source and body wave tomography data. The inversion is framed within an integrated geophysical-petrological setting where mantle seismic velocities and densities are computed thermodynamically as a function of the in situ temperature and compositional conditions. In this work we develop a new parameterization of the crust where we first invert following global statistical correlations between Vp, Vs and crustal densities for different lithologies in a two-layered model. In a second step we compute the rock physical properties for different metamorphic facies and water contents using computational petrology to derive a plausible and consistent lithological model. In order to optimize the inversion procedure, we perform a sensitivity  analysis assessing the resolution of the different data sets. The new methodology is applied to the Iberian Peninsula and adjacent margins where we jointly invert for both the crustal and lithospheric mantle structure.