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The P-T path of eclogites in the St. Cyr Klippe, Yukon, Canada; Permian metamorphism of a coherent high-pressure unit in an accreted terrane of the North American Cordillera

Meredith B. Petrie, Hans-Joachim Massonne, Jane A. Gilotti, William C. McClelland and Cees Van Staal
The P-T path of eclogites in the St. Cyr Klippe, Yukon, Canada; Permian metamorphism of a coherent high-pressure unit in an accreted terrane of the North American Cordillera
European Journal of Mineralogy (November 2016) 28 (6): 1111-1130

Abstract

The St. Cyr klippe, part of the Yukon-Tanana terrane in Yukon, Canada, preserves fresh and retrogressed eclogite hosted by quartzofeldspathic schists. Petrology, mineral chemistry and compositional zoning combined with isochemical phase equilibrium (pseudosection) modeling shows that eclogites followed a clockwise pressure-temperature path. An amphibolite facies, pre-eclogite stage (pre-Stage I) preceded early eclogite-facies conditions of about 16 kbar and 510 degrees C (Stage I) and the peak pressure (Stage II), which reached up to 20 kbar and 670 degrees C. The peak observed and modeled eclogite-facies assemblage is garnet, omphacite, Na-rich amphibole, phengite, quartz and rutile. Pseudosections were modeled for varying Fe (super 3+) contents, and Fe (super 3+) = 20 % of total Fe is found to best match the pyrope and grossular content observed in garnet. Retrogression back to amphibolite-facies conditions (Stage III) followed a clockwise path as temperature decreased during decompression without passing through the chlorite stability field. U-Pb SIMS (secondary ion mass spectrometry) dating and trace-element analysis of zircon shows that the protolith of the eclogites formed within the Yukon-Tanana terrane during early arc activity, between 364 and 380 Ma. The rocks were then subducted to mantle depths and metamorphosed to eclogite-facies conditions during the Late Permian, between 267 and 271 Ma. These medium-temperature eclogites are part of a coherent high-pressure (HP) terrane that was tectonically eroded from the Yukon-Tanana composite arc in a subduction zone environment.


ISSN: 0935-1221
EISSN: 1617-4011
Serial Title: European Journal of Mineralogy
Serial Volume: 28
Serial Issue: 6
Title: The P-T path of eclogites in the St. Cyr Klippe, Yukon, Canada; Permian metamorphism of a coherent high-pressure unit in an accreted terrane of the North American Cordillera
Affiliation: University of Iowa, Department of Earth and Environmental Sciences, Iowa City, IA, United States
Pages: 1111-1130
Published: 20161128
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Germany
References: 81
Accession Number: 2017-005954
Categories: Igneous and metamorphic petrologyGeochemistry of rocks, soils, and sediments
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. sect., 5 tables, geol. sketch maps
N61°00'00" - N62°00'00", W133°30'00" - W132°49'60"
Secondary Affiliation: Universitaet Stuttgart, DEU, GermanyCanada Geological Survey, CAN, Canada
Country of Publication: Germany
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, copyright, Schweizerbart'sche Verlagsbuchhandlung. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201705
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