Evolution of the Labrador Geosyncline

Abstract

Research Article| September 01, 1970 Evolution of the Labrador Geosyncline ERICH DIMROTH ERICH DIMROTH Geological Exploration Service, Department of Natural Resources, Quebec 6, Canada Search for other works by this author on: GSW Google Scholar Author and Article Information ERICH DIMROTH Geological Exploration Service, Department of Natural Resources, Quebec 6, Canada Publisher: Geological Society of America Received: 29 Dec 1969 Revision Received: 23 Apr 1970 First Online: 02 Mar 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Copyright © 1970, The Geological Society of America, Inc. Copyright is not claimed on any material prepared by U.S. government employees within the scope of their employment. GSA Bulletin (1970) 81 (9): 2717–2742. https://doi.org/10.1130/0016-7606(1970)81[2717:EOTLG]2.0.CO;2 Article history Received: 29 Dec 1969 Revision Received: 23 Apr 1970 First Online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation ERICH DIMROTH; Evolution of the Labrador Geosyncline. GSA Bulletin 1970;; 81 (9): 2717–2742. doi: https://doi.org/10.1130/0016-7606(1970)81[2717:EOTLG]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 The Labrador “trough” is the preserved portion of an Early Proterozoic (Aphebian) geosyncline, extending from the Grenville Front at Wabush to Payne Bay, over 600 mi farther north-northwest. Archaean gneisses constitute the foreland to the west of the geosyncline, and remetamorphosed Archaean gneisses compose much of its eastern hinterland. It is the purpose of this paper to outline and correlate the essential geological features of the Labrador trough and to propose a working hypothesis on its origin.The basin filling represents two, or possibly three, tectonic cycles, each initiated by an orthoquartzite-limestone sequence (including iron formation in the second and third cycles), and culminating in deposition of shales and of flysch-type deposits in the external zone of the geosyncline, and in intense volcanic activity in the central and internal zones.The paleogeography of the first cycle is briefly examined. A rapidly uplifted area situated east of the geosyncline is the probable source of much clastic material. The basin center migrated westward during the preophiolitic stage, and a geanticline emerged during the early phase of the ophiolitic stage in the center of the geosyncline.Very large volumes of mafic volcanic and plutonic rocks erupted in the eastern and central parts of the geosyncline during the latter part of the tectonic cycles. The eugeosynclinal mafic rocks are mainly K-deficient tholeiites. Spilites and transitional types of basalts occur in subordinate volumes. Serpentinized ultra-basic sills are present.The Aphebian rocks of the Labrador trough were folded during the Hudsonian Orogeny. A tectonic section across the geosyncline is discussed. The basement below the western part of the geosyncline has not been involved in the Hudsonian deformation, whereas the Archaean underlying the central and eastern portions of the geosyncline was folded jointly with its cover. The relations between structural style, depth of burial and metamorphic grade are briefly examined.A late-kinematic and post-kinematic metamorphism of an intermediate pressure series overprinted the internal zones of the geosyncline. Hudsonian granites and migmatites are absent, and possible causes of their absence are discussed. 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.