Universität zu Köln

Weber, Sebastian, Hauke, Matthias, Martinez, Raul E., Redler, Charlotte, Muenker, Carsten and Froitzheim, Nikolaus (2022). Fluid-driven transformation of blueschist to vein eclogite during the Early Eocene in a subducted sliver of continental crust (Monte Emilius, Italian Western Alps). J. Metamorph. Geol., 40 (3). S. 553 - 585. HOBOKEN: WILEY. ISSN 1525-1314

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Abstract

In the Penninic nappe stack of the Western Alps, high- to ultrahigh-pressure metamorphic ophiolites of the Zermatt-Saas Zone are associated with slivers of continental crust. In one of these slivers, Monte Emilius, the overprinting of pre-Alpine granulite-facies rocks by subduction-related, Alpine eclogite-facies meta-morphism can be studied. Mafic granulites were initially transformed into blueschists. In a second step, shear zones were developed in which the blueschists recrystallized to fine-grained, foliated glaucophane eclogites, and eclogite veins. The combination of petrographic and field observations as well as whole-rock compositions suggests that the eclogite assemblage formed only in shear zones where Ca-metasomatism induced a change in major element composition. These substantial differences in bulk rock composition demonstrate how spatially limited eclogitization may be controlled by chemical redistribution, the degree of fabric development, and associated metamorphic reactions along fluid pathways. Thermodynamic modelling of selected bulk rock compositions yielded only slightly different conditions of 1.8 +/- 0.1 GPa/550 +/- 50 degrees C for blueschist and 1.9-2.3 GPa/550 +/- 50 degrees C for eclogite, constraining Ca-rich fluid infiltration and transformation to a depth of similar to 60-70 km. Eclogitization occurred in the Early Eocene at 52.96 +/- 0.91 Ma, as indicated by a well-defined Lu-Hf garnet isochron.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Weber, Sebastian UNSPECIFIED UNSPECIFIED UNSPECIFIED Hauke, Matthias UNSPECIFIED UNSPECIFIED UNSPECIFIED Martinez, Raul E. UNSPECIFIED UNSPECIFIED UNSPECIFIED Redler, Charlotte UNSPECIFIED UNSPECIFIED UNSPECIFIED Muenker, Carsten UNSPECIFIED UNSPECIFIED UNSPECIFIED Froitzheim, Nikolaus UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-590851
DOI:	10.1111/jmg.12638
Journal or Publication Title:	J. Metamorph. Geol.
Volume:	40
Number:	3
Page Range:	S. 553 - 585
Date:	2022
Publisher:	WILEY
Place of Publication:	HOBOKEN
ISSN:	1525-1314
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language ZERMATT-SAAS OPHIOLITE; HIGH-PRESSURE METAMORPHISM; OCEANIC LITHOSPHERE; FACIES ROCKS; LU-HF; ZONE; ECLOGITIZATION; EVOLUTION; SLICE; NAPPE Multiple languages Geology Multiple languages
URI:	http://kups.ub.uni-koeln.de/id/eprint/59085