The Contribution of the Petrological Iterative Approach in Reconciling the UHP Natural Data Set With Geodynamic Models in the Continental Western Alps

Pressure and temperature estimates of metamorphic terranes are increasingly retrieved from forward thermodynamic modeling coupled with isopleth thermobarometry. Although geodynamic reconstructions are mathematically derived, thermobarometric estimates are limited by a lack of quantitative constraints, especially on their uncertainties. This work explores the application of the statistically based approach of Bingo-Antidote on a chloritoid-garnet-bearing micaschist from a high-pressure unit in the continental Western Alps, Italy. Calculations highlighted a good match between the observation and the model at conditions that overlay the quartz-coesite polymorphic reaction. This result called for targeted investigations, which ultimately led to the recognition of coesite inclusions in the garnet domain modeled to be equilibrated at such conditions, pinpointing the pressure peak at ultra-high-pressure conditions. Our results show a so-far unexplored application of Bingo-Antidote as a straightforward and fast tool for guiding targeted investigations, such as the search for potential occurrences of otherwise elusive phases like coesite, which might be time-consuming if randomly applied. In addition, this contribution infers a possible architecture of the Dora-Maira Massif paleomargin, discussing it in the framework of existing geodynamic simulations.