Tectonothermal evolution of contrasting metamorphic complexes in northwest Spitsbergen (Biskayerhalvøya): Evidence from 40Ar/39Ar and Rb-Sr mineral ages

Abstract

Research Article| May 01, 1990 Tectonothermal evolution of contrasting metamorphic complexes in northwest Spitsbergen (Biskayerhalvøya): Evidence from 40Ar/39Ar and Rb-Sr mineral ages R. D. DALLMEYER; R. D. DALLMEYER 1Department of Geology, University of Georgia, Athens, Georgia 30602 Search for other works by this author on: GSW Google Scholar J. J. PEUCAT; J. J. PEUCAT 2Centre Armoricain d Etudes Structurales des Socles, Centre National de la Recherche Scientifique, Laboratoire de Geochimie Isotopique et de Geochronologie, 35042 Rennes, Cedex, France Search for other works by this author on: GSW Google Scholar Y. OHTA Y. OHTA 3Norsk Polarinstitutt, Postboks 158, 1330 Oslo Lufthavn, Norway Search for other works by this author on: GSW Google Scholar Author and Article Information R. D. DALLMEYER 1Department of Geology, University of Georgia, Athens, Georgia 30602 J. J. PEUCAT 2Centre Armoricain d Etudes Structurales des Socles, Centre National de la Recherche Scientifique, Laboratoire de Geochimie Isotopique et de Geochronologie, 35042 Rennes, Cedex, France Y. OHTA 3Norsk Polarinstitutt, Postboks 158, 1330 Oslo Lufthavn, Norway Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1990) 102 (5): 653–663. https://doi.org/10.1130/0016-7606(1990)102<0653:TEOCMC>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 Email Permissions Search Site Citation R. D. DALLMEYER, J. J. PEUCAT, Y. OHTA; Tectonothermal evolution of contrasting metamorphic complexes in northwest Spitsbergen (Biskayerhalvøya): Evidence from 40Ar/39Ar and Rb-Sr mineral ages. GSA Bulletin 1990;; 102 (5): 653–663. doi: https://doi.org/10.1130/0016-7606(1990)102<0653:TEOCMC>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 Contrasting metamorphic sequences are exposed within a fault-bounded horst on Biskayerhalvøya, northwestern Spitsbergen. The Biskayerfonna Group is composed of variably pelitic metasedimentary rocks together with interlayered amphibolite. Amphibole within this sequence records 40Ar/39Ar isotope correlation ages of 429 and 437 m.y., which are interpreted to date cooling through appropriate argon closure temperatures following a late Caledonian amphibolite-facies metamorphism. Muscovite and biotite record slightly younger 4OAr/39Ar and Rb-Sr ages (400-430 m.y.), which are interpreted to date cooling through lower closure temperatures. The Biskayerfonna Group is tectonically imbricated with an older metamorphic complex (Richarddalen Group) composed of variably retrogressed eclogite, metagranite, foliated amphibolite, and various metasedimentary rocks. Amphibole within massive retrogressive assemblages derived from eclogite and wihin foliated amphibolite records 4OAr/39Ar isotope correlation ages between 500 and 542 m.y. These are interpreted to date cooling through appropriate closure temperatures following the initial high-pressure metamorphism. Rb-Sr ages recorded by muscovite and most biotite within the Richarddalen Group are markedly younger, ranging between 410 and 430 m.y. These ages likely record cooling following a late Caledonian metamorphic overprint that occurred at approximately the same time as initial prograde metamorphism of the Biskayerfonna Group; however, maximum overprint temperatures in the Richarddalen Group must have been less than prograde conditions in the Biskayerfonna Group because amphibole in the former shows no evidence of any isotopic rejuvenation. These relationships suggest that structural imbrication of the contrasting metamorphic sequences must have occurred during or immediately following late Caledonian metamorphism at ca. 429-437 Ma but prior to regional cooling between ca. 402 and 430 Ma. Phengitic muscovite within the Richard-dalen Group records 4OAr/39Ar plateau ages between 440 and 480 m.y. and displays no spectral evidence of subsequent rejuvenation. This suggests that the late Caledonian metamorphism must have been of variable intensity within the Richarddalen Group. 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.