Paleozoic and Mesozoic high-pressure metamorphism at the margin of ancestral North America in central Yukon

Abstract

Research Article| May 01, 1998 Paleozoic and Mesozoic high-pressure metamorphism at the margin of ancestral North America in central Yukon Philippe Erdmer; Philippe Erdmer 1Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, Alberta T6G 2E3, Canada Search for other works by this author on: GSW Google Scholar Edward D. Ghent; Edward D. Ghent 2Department of Geology and Geophysics, University of Calgary, Calgary, Alberta T2N 1N4, Canada Search for other works by this author on: GSW Google Scholar Douglas A. Archibald; Douglas A. Archibald 3Department of Geological Sciences, Queen's University, Kingston, Ontario K7L 3N6, Canada Search for other works by this author on: GSW Google Scholar Mavis Z. Stout Mavis Z. Stout 4Department of Geology and Geophysics, University of Calgary, Calgary, Alberta T2N 1N4, Canada Search for other works by this author on: GSW Google Scholar Author and Article Information Philippe Erdmer 1Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, Alberta T6G 2E3, Canada Edward D. Ghent 2Department of Geology and Geophysics, University of Calgary, Calgary, Alberta T2N 1N4, Canada Douglas A. Archibald 3Department of Geological Sciences, Queen's University, Kingston, Ontario K7L 3N6, Canada Mavis Z. Stout 4Department of Geology and Geophysics, University of Calgary, Calgary, Alberta T2N 1N4, Canada Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1998) 110 (5): 615–629. https://doi.org/10.1130/0016-7606(1998)110<0615:PAMHPM>2.3.CO;2 Article history First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Philippe Erdmer, Edward D. Ghent, Douglas A. Archibald, Mavis Z. Stout; Paleozoic and Mesozoic high-pressure metamorphism at the margin of ancestral North America in central Yukon. GSA Bulletin 1998;; 110 (5): 615–629. doi: https://doi.org/10.1130/0016-7606(1998)110<0615:PAMHPM>2.3.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Eclogite and blueschist in the Yukon-Tanana and Slide Mountain terranes in the Yukon and Alaska preserve a partial record of middle Paleozoic, late Paleozoic, and early Mesozoic subduction and subsequent unroofing. Near Faro, eclogites are commonly mylonitized and partially retrogressed. The analysis of Fe-Mg exchange between garnet and clinopyroxene suggests temperatures (T) in the 400–500 °C range for eclogite, and jadeite (∼40 mol%) + quartz suggest minimum pressures (P) of 11–13 kilobar at that temperature range; clinopyroxene-garnet-epidote-quartz suggest pressure near 15 kilobar (PH2O=PS). Eclogite near Last Peak, which contains brown hornblende, late-stage oligoclase, and biotite, yielded P-T estimates up to 625 °C at a minimum pressure of 14 kilobar. Eclogite near Ross River yielded temperatures near 525 °C and a minimum pressure near 13 kilobar. The previously proposed Permian-Triassic age of high-pressure tectonism for the entire Yukon-Tanana terrane in the Yukon was inferred from isotopic dating of one eclogite and one blueschist in separate localities. In this study, isotopic 40Ar/39Ar analysis of white mica from eclogite in the Simpson range yielded a date of 344 ± 1 Ma. Eclogite and blueschist from Ross River yielded white mica 40Ar/39Ar dates of 267 ± 3 Ma and 273 ± 3 Ma, respectively. White mica in eclogite from Faro was dated at 260 ± 3 Ma. White mica in two eclogites from Stewart Lake, about 2 km apart, yielded 40Ar/39Ar dates of 228 ± 1 Ma and 346 ± 3 Ma. White mica in Last Peak eclogite, for which a concordant U-Pb zircon date is 269 Ma, yielded an integrated date of 236 ± 1 Ma. Overprinting in the blueschist facies and final cooling in some localities predated eclogite metamorphism in others. The cooling ages indicate significant plate convergence as early as Carboniferous time and either the existence of more than one subduction zone or continuous convergence and episodic exhumation above a single zone. When this is considered together with the range of ages of other high-pressure occurrences, the North American Cordillera is seen to be characterized by multiepisodic and diachronous high-pressure metamorphism. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.