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Detrital zircon evidence for eclogite formation by basal subduction erosion; an example from the Yukon-Tanana composite arc, Canadian Cordillera

Jane A. Gilotti, William C. McClelland, C. R. van Staal and M. B. Petrie
Detrital zircon evidence for eclogite formation by basal subduction erosion; an example from the Yukon-Tanana composite arc, Canadian Cordillera
Special Paper - Geological Society of America (January 2017) 526: 173-189

Abstract

The Yukon-Tanana terrane lies within the North American Cordilleran accretionary orogen and contains strongly deformed, coherent eclogite-bearing units that are candidates for wholesale subduction erosion of large blocks of crust. The Yukon-Tanana terrane is a composite continental arc built on a peri-Laurentian substrate that experienced subduction on both sides before it was accreted back onto Laurentia in the Mesozoic. Along the present-day eastern margin of the terrane, eclogites are found as layers and lenses in quartzofeldspathic schist derived from both igneous and sedimentary protoliths, all metamorphosed together during the Permian. In the St. Cyr area, coherent slices of eclogite-bearing crust up to 30 km long and 1-2 km thick have been mapped. Phengite with Si = 3.3-3.4 per formula unit from the host schists indicates that they also record eclogite-facies metamorphism. Detrital zircon was recovered from six host-rock samples collected at three high-pressure (HP) localities (St. Cyr, Ross River, and Last Peak), and from two eclogite-free units. Samples from the eclogite-free units and Last Peak have detrital zircon signatures with prominent Mesoproterozoic and Paleoproterozoic peaks typical of the Snowcap assemblage, the peri-Laurentian substrate of the Yukon-Tanana terrane. Detrital spectra from the St. Cyr and Ross River HP localities contain Precambrian, mostly Mesoproterozoic, zircon with significant Paleozoic peaks that match ages of igneous events in the Yukon-Tanana terrane. The coherent slices of crust containing eclogite, meta-tonalite, and arc-derived metasedimentary rocks are interpreted as pieces of Yukon-Tanana terrane that were eroded from the arc during subduction of oceanic lithosphere and reaccreted to the arc prior to Mesozoic emplacement of the Yukon-Tanana terrane onto North America.


ISSN: 0072-1077
EISSN: 2331-219X
Coden: GSAPAZ
Serial Title: Special Paper - Geological Society of America
Serial Volume: 526
Title: Detrital zircon evidence for eclogite formation by basal subduction erosion; an example from the Yukon-Tanana composite arc, Canadian Cordillera
Affiliation: University of Iowa, Department of Earth and Environmental Sciences, Iowa City, IA, United States
Pages: 173-189
Published: 20170127
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 81
Accession Number: 2017-020559
Categories: Areal geology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: GSA Data Repository Item 2017109
Illustration Description: illus. incl. 2 tables, geol. sketch maps
N61°15'00" - N61°15'00", W133°00'00" - W133°00'00"
Secondary Affiliation: Geological Survey of Canada, CAN, Canada
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 201714
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