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- Title
Metamorphic pressure variation in a coherent Alpine nappe challenges lithostatic pressure paradigm.
- Authors
Luisier, Cindy; Baumgartner, Lukas; Schmalholz, Stefan M.; Siron, Guillaume; Vennemann, Torsten
- Abstract
Pressure–temperature–time paths obtained from minerals in metamorphic rocks allow the reconstruction of the geodynamic evolution of mountain ranges under the assumption that rock pressure is lithostatic. This lithostatic pressure paradigm enables converting the metamorphic pressure directly into the rock's burial depth and, hence, quantifying the rock's burial and exhumation history. In the coherent Monte Rosa tectonic unit, Western Alps, considerably different metamorphic pressures are determined in adjacent rocks. Here we show with field and microstructural observations, phase petrology and geochemistry that these pressure differences cannot be explained by tectonic mixing, retrogression of high-pressure minerals, or lack of equilibration of mineral assemblages. We propose that the determined pressure difference of 0.8 ± 0.3 GPa is due to deviation from lithostatic pressure. We show with two analytical solutions for compression- and reaction-induced stress in mechanically heterogeneous rock that such pressure differences are mechanically feasible, supporting our interpretation of significant outcrop-scale pressure gradients. The geodynamic evolution of mountain ranges can be reconstructed using the pressure recorded by minerals in metamorphic rocks, under the key assumption that rock pressure is lithostatic. Here, the authors challenge the lithostatic pressure paradigm by showing that there can be significant outcrop-scale pressure gradients due to compression- and reaction-induced stress.
- Subjects
METAMORPHIC rocks; GEODYNAMICS; ROCK pressure; EXHUMATION; ARCHAEOLOGICAL assemblages
- Publication
Nature Communications, 2019, Vol 10, Issue 1, pN.PAG
- ISSN
2041-1723
- Publication type
Article
- DOI
10.1038/s41467-019-12727-z