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Water as a Petrologic Catalyst Driving ¹⁸O/¹⁶O Homogenization and Anatexis of the Middle Crust in the Metamorphic Core Complexes of British Columbia

Holk, Gregory J. and Taylor, Hugh P., Jr. (2000) Water as a Petrologic Catalyst Driving ¹⁸O/¹⁶O Homogenization and Anatexis of the Middle Crust in the Metamorphic Core Complexes of British Columbia. International Geology Review, 42 (2). pp. 97-130. ISSN 0020-6814. doi:10.1080/00206810009465072. https://resolver.caltech.edu/CaltechAUTHORS:20220826-716478700

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Abstract

In the Thor-Odin and Valhalla metamorphic core complexes, we have documented a remarkable uniformity of mineral δ18O values in the middle continental crust beneath the detachment faults. For example, in the Thor-Odin Complex, throughout an 8 km thick section of metasedimentary rocks and early Tertiary leucogranites in the hanging wall of the Monashee decollement (MD), quartz δ18O = 12.3 ± 0.5% (lσ S.D.) for metapelite (N = 11), 12.0 ± 0.1% for quartzite (N = 2), 12.6 ± 0.6% (N = 4) for < 1 m thick amphibolite layers, and 12.1 ± 0.4% (N = 24) for the concordant leucogranites. No exceptions have been found to this remarkable 18O/16O homogeneity except locally in a couple of thick amphibolites and within a ductile, relatively impermeable, marble-rich section. Similar zones of 18O/16O homogeneity associated with leucogranite genesis are observed throughout the mid-crustal section of the Valhalla Complex and just beneath the MD in the Monashee Complex, the only difference being that those rocks are overall 0.5 to 1.5% lower in δ18O than in the middle crust at Thor-Odin. These zones of pervasive homogenization in 18O/l6O must be a result of exchange with magmatic or metamorphic H2O, and these same volatiles appear to have been responsible for the leucogranite anatexis. A wide range in quartz δ18O from +8 to +16 within and below the MD suggests that this major thrust fault was impermeable to aqueous fluid flow during the partial melting stage; at that time, the basement appears to have been isolated from the mid-crustal metamorphichydrothermal system.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1080/00206810009465072DOIArticle
Alternate Title:Water as a Petrologic Catalyst Driving 18O/16O Homogenization and Anatexis of the Middle Crust in the Metamorphic Core Complexes of British Columbia
Issue or Number:2
DOI:10.1080/00206810009465072
Record Number:CaltechAUTHORS:20220826-716478700
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20220826-716478700
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:116594
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:30 Aug 2022 20:14
Last Modified:31 Aug 2022 17:03

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