Paleogene metamorphism of an accretionary flysch terrane, eastern Gulf of Alaska

Research Article| December 01, 1982 Paleogene metamorphism of an accretionary flysch terrane, eastern Gulf of Alaska TRAVIS HUDSON; TRAVIS HUDSON 1U.S. Geological Survey, Gould Hall, APU Campus, University Drive, Anchorage, Alaska 99504 Search for other works by this author on: GSW Google Scholar GEORGE PLAFKER GEORGE PLAFKER 2U.S. Geological Survey, 345 Middlefield Road, Menlo Park, California 94025 Search for other works by this author on: GSW Google Scholar GSA Bulletin (1982) 93 (12): 1280–1290. https://doi.org/10.1130/0016-7606(1982)93<1280:PMOAAF>2.0.CO;2 Article history first online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share MailTo Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation TRAVIS HUDSON, GEORGE PLAFKER; Paleogene metamorphism of an accretionary flysch terrane, eastern Gulf of Alaska. GSA Bulletin 1982;; 93 (12): 1280–1290. doi: https://doi.org/10.1130/0016-7606(1982)93<1280:PMOAAF>2.0.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 Reconnaissance field studies have identified a regional metamorphic complex, at least 200 km long and 25 to 50 km wide, in the eastern Chugach Mountains, southern Alaska. The metamorphic complex was developed within the Cretaceous Valdez Group, a flysch sequence that was accreted to the continental margin during the Late Cretaceous or early Tertiary. The metamorphic complex shows the progressive development from subgreenschist and green-schist facies slate, phyllite, and semischist that is regionally characteristic of the Valdez Group, to biotite-plagioclase-quartz schist (± muscovite, cordierite, andalusite, staurolite, garnet, and sillimanite) in an intermediate zone, and amphibolite facies muscovite-biotite-plagioclase-quartz schist and gneiss (± sillimanite and garnet) in a higher-grade central zone. K-feldspar is characteristically absent in the amphibolite facies schists, but it is present in migmatitic rocks that are common to the central zone. The mineral assemblages and petrographic relations indicate that metamorphism took place under low-pressure intermediate-facies series conditions; partial melting took place at the highest grade of metamorphism. Melting produced granodioritic magmas in migma-titic rocks of the central zone that were emplaced as discrete plutons in both the intermediate zone and peripheral rocks of the complex. The timing of metamorphism as indicated by field relations and K-Ar data is about 50 to 65 m.y. ago and overlaps or is coeval with the emplacement, throughout the Gulf of Alaska region, of early Tertiary plutons that are thought to be anatectic in origin. The distribution of these plutons suggests that a high-temperature low-pressure metamorphic belt, about 1,800 km long, developed along the leading edge of the continental margin in late Paleocene to early Eocene time. 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.