Northern Monashee Mountains, Omineca Crystalline Belt, British Columbia: Timing of metamorphism, anatexis, and tectonic denudation

Abstract

Research Article| February 01, 1990 Northern Monashee Mountains, Omineca Crystalline Belt, British Columbia: Timing of metamorphism, anatexis, and tectonic denudation J. H. Sevigny; J. H. Sevigny 1Department of Geology and Geophysics, University of Calgary, Calgary, Alberta T2N 1N4, Canada Search for other works by this author on: GSW Google Scholar R. R. Parrish; R. R. Parrish 2Lithosphere and Canadian Shield Division, Geological Survey of Canada, 601 Booth Street, Ottawa, Ontario K1A 0E8, Canada Search for other works by this author on: GSW Google Scholar R. A. Donelick; R. A. Donelick 3Department of Geology, Rensselaer Polytechnic Institute, Troy, New York 12180-3590 Search for other works by this author on: GSW Google Scholar E. D. Ghent E. D. Ghent 1Department 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 J. H. Sevigny 1Department of Geology and Geophysics, University of Calgary, Calgary, Alberta T2N 1N4, Canada R. R. Parrish 2Lithosphere and Canadian Shield Division, Geological Survey of Canada, 601 Booth Street, Ottawa, Ontario K1A 0E8, Canada R. A. Donelick 3Department of Geology, Rensselaer Polytechnic Institute, Troy, New York 12180-3590 E. D. Ghent 1Department of Geology and Geophysics, University of Calgary, Calgary, Alberta T2N 1N4, Canada Publisher: Geological Society of America First Online: 02 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (1990) 18 (2): 103–106. https://doi.org/10.1130/0091-7613(1990)018<0103:NMMOCB>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 MailTo Tools Icon Tools Get Permissions Search Site Citation J. H. Sevigny, R. R. Parrish, R. A. Donelick, E. D. Ghent; Northern Monashee Mountains, Omineca Crystalline Belt, British Columbia: Timing of metamorphism, anatexis, and tectonic denudation. Geology 1990;; 18 (2): 103–106. doi: https://doi.org/10.1130/0091-7613(1990)018<0103:NMMOCB>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 The northern Monashee Mountains lie at the northern termination of a north-south zone of Eocene extension in the southern Omineca Crystalline Belt of British Columbia. Isotopic, structural, and petrogenetic studies in the northern Monashee Mountains document middle to Late Cretaceous regional metamorphism, two episodes of crustal anatexis, and a period of rapid cooling coincident with middle Eocene extension. Partial melting of geochemically and isotopically similar pelitic sources produced peraluminous granites during and postdating regional metamorphism at 100 Ma and 63 Ma, respectively. Rb-Sr muscovite-whole-rock isochrons from the younger granites give an age of 62.5 ±2.0 Ma. Rb-Sr isochron and U-Pb mineral ages are similar, indicating that the 63 Ma granites were emplaced into a terrane that had cooled to 500 °C or less by 63 Ma. Hornblende, muscovite, and biotite K-Ar and apatite fission-track mineral cooling ages from the northern Monashee Mountains are are 76.3 ±5.8 (n = 7), 51.4 ±3.5 (n = 6), 55.1 ± 2.7 (n = 10), and 45.0 ±2.9 (n = 3) Ma, respectively (mean age and standard deviation). Accelerated cooling, beginning with the emplacement of 63 Ma granites and ending at 45 Ma, occurred in response to ramping along a crustal-scale thrust fault followed by offset on the middle Eocene offset on the middle Eocene North Thompson normal fault. 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.