Is the southeast Coast Plutonic Complex the consequence of accretion of the Insular superterrane? Evidence from U-Pb zircon geochronometry in the northern Washington Cascades

Research Article| July 01, 1991 Is the southeast Coast Plutonic Complex the consequence of accretion of the Insular superterrane? Evidence from U-Pb zircon geochronometry in the northern Washington Cascades Nicholas W. Walker; Nicholas W. Walker 1Department of Geological Sciences, University of Texas, Austin, Texas 78713-7909 Search for other works by this author on: GSW Google Scholar Edwin H. Brown Edwin H. Brown 2Department of Geology, Western Washington University, Bellingham, Washington 98225 Search for other works by this author on: GSW Google Scholar Author and Article Information Nicholas W. Walker 1Department of Geological Sciences, University of Texas, Austin, Texas 78713-7909 Edwin H. Brown 2Department of Geology, Western Washington University, Bellingham, Washington 98225 Publisher: Geological Society of America First Online: 02 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (1991) 19 (7): 714–717. https://doi.org/10.1130/0091-7613(1991)019<0714:ITSCPC>2.3.CO;2 Article history First Online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation Nicholas W. Walker, Edwin H. Brown; Is the southeast Coast Plutonic Complex the consequence of accretion of the Insular superterrane? Evidence from U-Pb zircon geochronometry in the northern Washington Cascades. Geology 1991;; 19 (7): 714–717. doi: https://doi.org/10.1130/0091-7613(1991)019<0714:ITSCPC>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 SocietyGeology Search Advanced Search Abstract Zircon U-Pb geochronometry of orthogneisses and plutons in the southwestern crystalline core of the North Cascades, coupled with fabric and textural studies of the orthogneisses, plutons, and their metamorphic host rocks, indicates extensive synmetamorphic plutonism at 89-96 Ma. Metamorphic mineral assemblages define a culmination composed of an axial kyanitesillimanite zone rimmed by lower grade zones. High-grade index minerals are typically syntectonic to posttectonic. Metamorphic fabrics are characterized by an orogenparallel, northwest-striking, steep foliation that contains a subhorizontal stretching and mineral lineation interpreted to be the product of ductile strike-slip deformation. This fabric is crosscut by 96-92 Ma plutons yet is imprinted on 92-89 Ma orthogneisses, suggesting spatially diachronous fabric development during orogeny. Documentation of the spatial and temporal coincidence of magmatism with the peak of orogeny, together with the kinematic significance of the metamorphic fabric, precludes generation of the metamorphic fabric and plutons in response to thrust loading. We suggest that this part of the Coast Plutonic Complex evolved as a transpressional magmatic arc. 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.