T154 GSA Mineralogy, Geochemistry, Petrology, and Volcanology Division Awards Session

Tuesday, 11 October 2022
8:00 AM - 12:00 PM
Mile High Ballroom 1D

A RETROSPECTIVE VIEW OF THE P-T PATH REVOLUTION IN METAMORPHIC PETROLOGY

Paper number: T154-6
Program: Technical Sessions
Time: 9:30 AM – 10:00 AM

Authors

Abstract

I will present an overview of early efforts to reconstruct pressure-temperature (P-T) paths, and the ways in which these paths changed the field of metamorphic petrology. I had the great good fortune to start my career just in time to help develop some of the methodologies of reconstructing P-T paths, and to see how these paths made metamorphic petrology newly relevant in the geosciences. Given the emphasis of the MGPV Distinguished Geological Career Award on field-based contributions, I will focus in particular on examples in which field data fundamentally changed the tectonic interpretation of metamorphic P-T data. I will return to my favorite field area, the Tauern Window of Austria/Italy, to show how a mismatch between petrologic data and early thermal models led to new fieldwork, and then to a new interpretation involving large-scale, orogen-parallel extension in one of the type localities of crustal thickening. Additional field and microscopic analysis showed that embrittlement of the crust began at elevated temperatures and depths, and that a succession of metamorphic reactions resulted in repeated rheological cycling at mid-crustal depths. All of these processes were a dynamic response to large-scale plate motions. Construction of P-T±t±d paths is now a standard methodology, facilitated in part by the ease of constructing pseudosections using thermodynamic modeling software packages. P-T paths have helped to broaden the scope of metamorphic petrology and make it a truly cross-disciplinary field. Metamorphic P-T data, coupled with field observations, are essential to understanding feedback effects between physical and chemical processes at depth in the earth’s crust, and then placing these processes in a geodynamic context. I hope that future students will continue to acquire the field and petrographic skills necessary to complement and go beyond the thermodynamic models.

Geological Society of America Abstracts with Programs. Vol. 54, No. 6

doi: 10.1130/abs/2022AM-377663

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