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Permian high-temperature metamorphism in the Western Alps (NW Italy)

Kunz, Barbara E.; Manzotti, Paola; von Niederhäusern, Brigitte; Engi, Martin; Darling, James R.; Giuntoli, Francesco and Lanari, Pierre (2018). Permian high-temperature metamorphism in the Western Alps (NW Italy). International Journal of Earth Sciences, 107(1) pp. 203–229.

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DOI (Digital Object Identifier) Link: https://doi.org/10.1007/s00531-017-1485-6
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Abstract

During the late Palaeozoic, lithospheric thinning in part of the Alpine realm caused high-temperature low-to-medium pressure metamorphism and partial melting in the lower crust. Permian metamorphism and magmatism has extensively been recorded and dated in the Central, Eastern, and Southern Alps. However, Permian metamorphic ages in the Western Alps so far are constrained by very few and sparsely distributed data. The present study fills this gap. We present U/Pb ages of metamorphic zircon from several Adria-derived continental units now situated in the Western Alps, defining a range between 286 and 266 Ma. Trace element thermometry yields temperatures of 580-890°C from Ti-in-zircon and 630-850°C from Zr-in-rutile for Permian metamorphic rims. These temperature estimates, together with preserved mineral assemblages (garnet-prismatic sillimanite-biotite-plagioclase-quartz-K-feldspar-rutile), define pervasive upper-amphibolite to granulite facies conditions for Permian metamorphism. U/Pb ages from this study are similar to Permian ages reported for the Ivrea Zone in the Southern Alps and Austroalpine units in the Central and Eastern Alps. Regional comparison across the former Adriatic and European margin reveals a complex pattern of ages reported from late Palaeozoic magmatic and metamorphic rocks (and relics thereof): two late Variscan age groups (~330 and ~300 Ma) are followed seamlessly by a broad range of Permian ages (300-250 Ma). The former are associated with late-orogenic collapse; in samples from this study these are weakly represented. Clearly, dominant is the Permian group, which is related to crustal thinning, hinting to a possible initiation of continental rifting along a passive margin.

Item Type: Journal Item
Copyright Holders: 2017 Springer-Verlag Berlin Heidelberg
ISSN: 1437-3254
Project Funding Details:
Funded Project NameProject IDFunding Body
Not Set200020-146175Swiss National Science Foundation
Keywords: Permian HT metamorphism; Western Alps; Adriatic margin; Zircon geochronology
Academic Unit/School: Faculty of Science, Technology, Engineering and Mathematics (STEM) > Environment, Earth and Ecosystem Sciences
Faculty of Science, Technology, Engineering and Mathematics (STEM)
Related URLs:
Item ID: 54803
Depositing User: Barbara Kunz
Date Deposited: 03 May 2018 08:34
Last Modified: 07 Aug 2019 14:29
URI: http://oro.open.ac.uk/id/eprint/54803
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