A combination of petrological and joint chemical-mechanical inversion approaches to unravel deep geodynamic processes

• Applicant: Professor Dr. Evangelos Moulas, Ph.D.
• Subject Area: Mineralogy, Petrology and Geochemistry
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 512790090

Metamorphism involves all the processes related to the recrystallization of rocks at relatively high-temperature conditions. During their history, rocks experience a wide range of pressure and temperature conditions where many metamorphic processes take place. These processes include the chemical and mechanical re-equilibration of metamorphic microstructures. When metamorphic rocks are exhumed, they are commonly found in a state of “frozen” equilibrium. The main reason for the lack of complete re-equilibration upon exhumation is the occurrence of rocks in a continuously evolving environment that is characterized by progressively cooling temperatures. As temperature is a main factor in the chemical kinetics and the viscous deformation of rocks, rocks that experience significant cooling are prone to preserve evidence from their residence at high-temperature conditions. This evidence is commonly found in the form of chemically zoned crystals and residual stresses in mineral inclusions. Over the recent years, there has been significant progress in the fields of diffusion modelling and Raman-elastic barometry with numerous applications to natural rocks. Despite the fact that both chemical and mechanical equilibration are temperature sensitive, very few studies have attempted to combine the temporal information given by the two methods. Here, we propose to use a combination of well-established techniques (diffusion modelling and viscous relaxation modelling) to see the degree of re-equilibration in metamorphic rocks. By utilizing experimentally determined rates for diffusion or viscous relaxation in minerals, we can use inverse-modelling techniques in order to obtain cooling rates and temporal information of metamorphic processes. We will focus our application in well-characterized exhumed metamorphic rocks from subduction zones. In this way, we will be able to quantify slow metamorphic processes that are otherwise impossible to observe at natural conditions.

• DFG Programme: Research Grants