Prof. Lanari, Pierre

Computational Petrology and Geochemistry (ERC)


Prograde metamorphism, the progressive transformation of a rock under increasing pressure and temperature conditions, produces large amounts of fluids that have an important role for earthquake generation, arc magmatism, the growth of continental crust and for global geochemical cycles. Despite recent efforts, it remains challenging to recognize and quantify fluid fluxes in natural rocks and to model fluid pathways. The existing petrological modeling techniques are all based on the thermodynamic analysis of single rock types and neglect the chemical changes caused by fluid expulsion and the possible interactions with other rocks. The next frontier in metamorphic petrology is therefore to move our modeling capabilities from an isolated single rock system to an open and multi-rock system, in which fluids can flow in, react and flow out. This concept introduces several challenges from the quantification of fluid-rock interactions in natural samples to the integration of aqueous thermodynamics and fluid dynamics in the petrological models.

The primary objective of the project PROMOTING is to develop a brand-new framework for petrological modeling of fluid-rock interactions processes in different, coupled rock types during prograde metamorphism. The models will be calibrated on two key tectonic settings that shaped Earth: subduction of oceanic crust and differentiation of the continental crust. A cutting-edge petrochronological strategy is required to identify at which conditions and when fluid-rock interactions occurred in natural rocks.

State-of-the-art petrological model for a typical metasediment
State-of-the-art petrological model for a typical metasediment along a prograde PT trajectory from 550 °C, 1.5 GPa and 620 °C – 2.4 GPa and comparison with the natural record. (a) Mod-box diagram showing the evolution of the mineral assemblage at each step along this trajectory. Note that garnet and fluid are fractionated. (b) Fluid released during prograde metamorphism in g of water per kg of rock. (c) Predicted compositional zoning of a single crystal of garnet across an equatorial section. (d) Compositional map of a garnet porphyroblast in a metasediment involved in the Alpine subduction. The maps are assumed to show the compositional zoning across a near-equatorial section.