Universität zu Köln

Hauke, Matthias, Froitzheim, Nikolaus, Nagel, Thorsten J., Miladinova, Irena ORCID: 0000-0002-2808-0378, Fassmer, Kathrin ORCID: 0000-0002-4598-7457, Fonseca, Raul O. C. ORCID: 0000-0002-0897-4884, Sprung, Peter ORCID: 0000-0003-4862-1415 and Muenker, Carsten (2019). Two high-pressure metamorphic events, Variscan and Alpine, dated by Lu-Hf in an eclogite complex of the Austroalpine nappes (Schobergruppe, Austria). Int. J. Earth Sci., 108 (4). S. 1317 - 1332. NEW YORK: SPRINGER. ISSN 1437-3262

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Abstract

The Eo-Alpine high-pressure belt in the Austroalpine nappes consists of pre-Mesozoic basement rocks overprinted by eclogite-facies metamorphism during the Late Cretaceous. Parts of this basement were already eclogitized during the Variscan orogeny. Lu-Hf geochronology allowed to identify two high-pressure events in an eclogite body in the Schobergruppe, an Austroalpine basement complex south of the Tauern Window. Two samples from closely neighboring outcrops were studied. Both contain two garnet generations. In one sample, PRI3, garnet belongs almost exclusively to the younger (Alpine) generation with only rare preservation of relic cores. In the other sample, PRI4, Variscan garnet is merely coated by a thin rim of the second, Alpine generation, which is in equilibrium with the high-pressure matrix assemblage. In PRI3, two-point garnet-whole rock ages scatter between 97 and 104Ma, reflecting Alpine garnet growth with minor contamination by a Variscan component. In PRI4, two-point isochrons yield ages between 300 and 313Ma. The limited spread in these ages suggests minor contamination by Alpine garnet rims. We propose 97Ma as the maximum age for Alpine metamorphism, which is close to previously determined ages from other parts of the high-pressure belt, and 313Ma as a minimum age for Variscan metamorphism. Thermodynamic modelling infers that eclogite-facies conditions were reached in both events; during the Late Cretaceous, these were ca. 1.9GPa/650 degrees C. Variscan high-pressure conditions in PRI4 are inferred from the amount of garnet in the sample, which indicates at least 1.6GPa. We propose that the occurrence of Alpine versus Variscan garnet in eclogites depends on the intensity of Variscan and post-Variscan retrogression: the more prograde, Variscan garnet was removed during retrogression, the more garnet grew during the Alpine cycle.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Hauke, Matthias UNSPECIFIED UNSPECIFIED UNSPECIFIED Froitzheim, Nikolaus UNSPECIFIED UNSPECIFIED UNSPECIFIED Nagel, Thorsten J. UNSPECIFIED UNSPECIFIED UNSPECIFIED Miladinova, Irena UNSPECIFIED orcid.org/0000-0002-2808-0378 UNSPECIFIED Fassmer, Kathrin UNSPECIFIED orcid.org/0000-0002-4598-7457 UNSPECIFIED Fonseca, Raul O. C. UNSPECIFIED orcid.org/0000-0002-0897-4884 UNSPECIFIED Sprung, Peter UNSPECIFIED orcid.org/0000-0003-4862-1415 UNSPECIFIED Muenker, Carsten UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-146535
DOI:	10.1007/s00531-019-01708-8
Journal or Publication Title:	Int. J. Earth Sci.
Volume:	108
Number:	4
Page Range:	S. 1317 - 1332
Date:	2019
Publisher:	SPRINGER
Place of Publication:	NEW YORK
ISSN:	1437-3262
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language MOUNTAINS EASTERN ALPS; SM-ND; POHORJE MOUNTAINS; FACIES METAMORPHISM; TAUERN WINDOW; RB-SR; U-PB; ALUMINOSILICATE GARNETS; PROGRADE METAMORPHISM; TECTONIC EVOLUTION Multiple languages Geosciences, Multidisciplinary Multiple languages
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/14653