Geochemical studies of the origins and effects of synorogenic crustal fluids in the southern Omineca Belt of British Columbia, Canada

Abstract

Research Article| September 01, 1995 Geochemical studies of the origins and effects of synorogenic crustal fluids in the southern Omineca Belt of British Columbia, Canada Bruce E. Nesbitt; Bruce E. Nesbitt 1Department of Geology, University of Alberta, Edmonton, Alberta T6G 2E3 Canada Search for other works by this author on: GSW Google Scholar Karlis Muehlenbachs Karlis Muehlenbachs 1Department of Geology, University of Alberta, Edmonton, Alberta T6G 2E3 Canada Search for other works by this author on: GSW Google Scholar Author and Article Information Bruce E. Nesbitt 1Department of Geology, University of Alberta, Edmonton, Alberta T6G 2E3 Canada Karlis Muehlenbachs 1Department of Geology, University of Alberta, Edmonton, Alberta T6G 2E3 Canada Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1995) 107 (9): 1033–1050. https://doi.org/10.1130/0016-7606(1995)107<1033:GSOTOA>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 MailTo Tools Icon Tools Get Permissions Search Site Citation Bruce E. Nesbitt, Karlis Muehlenbachs; Geochemical studies of the origins and effects of synorogenic crustal fluids in the southern Omineca Belt of British Columbia, Canada. GSA Bulletin 1995;; 107 (9): 1033–1050. doi: https://doi.org/10.1130/0016-7606(1995)107<1033:GSOTOA>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 Fluid inclusion and stable isotope investigations of 400+ samples of quartz ± carbonate veins and their zeolite to amphibolite grade host rocks from the southern Omineca Belt of the Canadian Cordillera have been used to determine origins, evolution, and effects of crustal fluids during and after orogenic activity. Correlations between fluid inclusion characteristics and tectonic and lithologic features indicate that salinities and gas compositions (CO2/CH4 ratios) are controlled by host rock lithology. High total gas contents are linked to high inclusion homogenization temperatures, which parallel increasing metamorphic grades.The δD values of the vast majority of vein-forming fluids range from −100% to −150% (Standard Mean Ocean Water [SMOW]), indicating meteoric water as the source of the fluids. The δ18OWater values of the fluids were homogeneous over large sections of the crust, with a typical range of δ18O values of 6% to 11% (SMOW). Homogenization of δ18O values of vein-forming fluids is believed to reflect interaction of the meteoric water with a variety of rock types at temperatures in excess of 350 °C. This process resulted in resetting of δ18O values of both fluids and rock units. The absence of vein formation from low δ18O water requires that mixing of ascending and descending fluids does not occur. Carbon and strontium isotope analyses indicate a strong degree of host rock control on these isotopic ratios.Synthesis of the results yields a model for the hydrogeology of the brittle crust consisting of moderately high permeabilities in fractured brittle rocks with deep convection of surface, meteoric water. The maximum depth of penetration of the fluids is limited by the rheological brittle/ductile transition at temperatures of 350 to 450 °C and depths of 10 km or greater. The vast majority of veins found in greenschist and lower grades of metamorphic rocks are formed on the upflow limbs of the meteoric water convection cells. 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.