Constraining the pressure-temperature evolution and geodynamic setting of UHT granulites and migmatitic paragneisses of the Gruf Complex, Central Alps

TitleConstraining the pressure-temperature evolution and geodynamic setting of UHT granulites and migmatitic paragneisses of the Gruf Complex, Central Alps
Publication TypeJournal Article
Year of Publication2019
AuthorsOalmann J, Duesterhoeft E, Moller A, Bousquet R
JournalInternational Journal of Earth Sciences
Volume108
Issue3
Date Published911-930
Abstract

Thermodynamic modeling of compositionally mapped microdomains and whole-rock compositions is used to constrain the pressure-temperature (P-T) evolution of sapphirine granulites and migmatitic paragneisses from the Gruf Complex of the Central Alps. The P-T paths and conditions estimated from granulite microdomains and whole-rock compositions are consistent with one another, indicating that the estimates from both types of compositions are accurate. The sapphirine granulites were heated to ultra-high temperature conditions of 900-1000 degrees C and 7.0-9.5 kbar as they were decompressed from ca. 800 degrees C and 9-12 kbar, resulting in garnet breakdown. In a subsequent step, nearly isothermal decompression led to the development of cordierite-bearing coronae and symplectites. By ca. 27 Ma, the sapphirine granulites had been exhumed to the midcrustal level of the migmatitic paragneisses, which were undergoing peak metamorphism at ca. 675-750 degrees C and 5-7 kbar. These results are consistent with a geodynamic model that invokes heat advection to the lower crust closely following the continental-subduction (ultra-high pressure) stage of the Alpine orogeny. The most plausible geodynamic model consistent with the results of this study is breakoff of a southward subducting lithospheric slab, resulting in asthenospheric mantle flow.

DOI10.1007/s00531-019-01686-x