Coesite in garnet-quartzite of Orco Valley (Western Alps): an additional UHP unit in the records of deeply subducted meta-ophiolites

Boero, Federica; Ghignone, Stefano; Gilio, Mattia; Borghini, Alessia; Scaramuzzo, Emanuele; Gasco, Ivano; Bruno, Marco

doi:10.5194/ejm-37-927-2025

Articles | Volume 37, issue 6

https://doi.org/10.5194/ejm-37-927-2025

© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/ejm-37-927-2025

© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 37, issue 6

Letter

|

11 Dec 2025

Letter |

| 11 Dec 2025

Coesite in garnet-quartzite of Orco Valley (Western Alps): an additional UHP unit in the records of deeply subducted meta-ophiolites

Federica Boero, Stefano Ghignone, Mattia Gilio, Alessia Borghini, Emanuele Scaramuzzo, Ivano Gasco, and Marco Bruno

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Latest update: 11 Dec 2025

Short summary

We report a new ultra-high-pressure (UHP) locality in the western Alps (Italy). Micro-Raman analyses of garnet-hosted inclusions reveal the metamorphic evolution from the prograde path to exhumation. The finding of coesite in the Internal Piedmont Zone (IPZ) meta-ophiolites of Orco Valley suggests that UHP localities represent remnants of a former level that underwent comparable conditions in the coesite stability field in the oceanic slab, from Lago di Cignana to Monviso Massif.