Mineralogical and petrological constraints and tectonic implications of a new coesite-bearing unit from the Alpine Tethys oceanic slab (Susa Valley, Western Alps)

Researchers have identified a new Ultrahigh Pressure (UHP) oceanic unit in the Susa Valley, Western Alps, marked by the presence of coesite—a rare mineral indicating extreme pressure conditions. This discovery, analyzed through Raman spectroscopy and thermometry, suggests that the region once experienced subduction to mantle depths, similar to other UHP units like Lago di Cignana and Lago Superiore. The findings imply a previously underestimated extent of UHP oceanic slices in the Western Alps, challenging models of localized pressure and supporting the idea of a dismembered slab during exhumation.

Ghignone, S., Gilio, M., Borghini, A., Boero, F., Bruno, M., & Scaramuzzo, E. (2024). Mineralogical and petrological constraints and tectonic implications of a new coesite-bearing unit from the Alpine Tethys oceanic slab (Susa Valley, Western Alps). Lithos, 472-473, 107575. https://doi.org/10.1016/j.lithos.2024.107575