18O/16O homogenization of the middle crust during anatexis: The Thor-Odin metamorphic core complex, British Columbia

Abstract

Research Article| January 01, 1997 18O/16O homogenization of the middle crust during anatexis: The Thor-Odin metamorphic core complex, British Columbia Gregory J. Holk; Gregory J. Holk 1Division of Geological and Planetary Sciences, Caltech 170-25, Pasadena, California 91125 Search for other works by this author on: GSW Google Scholar Hugh P. Taylor, Jr Hugh P. Taylor, Jr 1Division of Geological and Planetary Sciences, Caltech 170-25, Pasadena, California 91125 Search for other works by this author on: GSW Google Scholar Geology (1997) 25 (1): 31–34. https://doi.org/10.1130/0091-7613(1997)025<0031:OOHOTM>2.3.CO;2 Article history first online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share MailTo Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation Gregory J. Holk, Hugh P. Taylor; 18O/16O homogenization of the middle crust during anatexis: The Thor-Odin metamorphic core complex, British Columbia. Geology 1997;; 25 (1): 31–34. doi: https://doi.org/10.1130/0091-7613(1997)025<0031:OOHOTM>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 occurrence of isotopically uniform quartz (δ18O = 12.5‰ ± 0.5‰) and feldspar (10.9‰ ± 0.7‰) throughout different rock types indicates that much of a 6-km-thick section of the mid-crustal Selkirk allochthon underwent internally buffered 18O/16O homogenization during Paleocene melting and decompression as it moved up the Monashee thrust ramp. Areas of uniform δ18O are those with the most leucogranite or those subjected to severe anatexis. Only locally, in the most impermeable (or refractory) zones did 18O exchange among the rocks, leucogranite melts, and aqueous fluids fail to go to completion (i.e., in the deepest parts of the section, in a marble-rich zone, around some thick amphibolites, and in most garnets). Evidence for 18O/16O heterogeneity in the protoliths of these rocks is observed in stratigraphically correlative lower-grade units elsewhere in British Columbia, as well as in garnets that coexist with isotopically homogeneous quartz. In our model, 18O/16O homogenization accompanied muscovite dehydration and partial melting of pelites with only minor influx of external H2O, followed by release of magmatic H2O from these melts (triggering further melting of adjacent feldspathic assemblages) as they were uplifted 20 km during thrusting just prior to onset of detachment faulting. Locally, low δ18O in feldspar (down to −3.8) and profound quartz-feldspar 18O/16O disequilibrium were imprinted at shallow levels during meteoric-hydrothermal alteration associated with Eocene detachment faulting. 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.