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TitleHigh-pressure, ultrahigh-temperature 1.9 Ga metamorphism of the Kramanituar Complex, Snowbird Tectonic Zone, Rae Craton, Canada
AuthorSanborn-Barrie, MORCID logo; Camacho, A; Berman, R GORCID logo
SourceContributions To Mineralogy and Petrology vol. 174, issue 2, 14, 2019 p. 1-26,
Alt SeriesNatural Resources Canada, Contribution Series 20170251
PublisherSpringer Nature
Mediapaper; on-line; digital
File formatpdf (Adobe® Reader®)
NTS55I; 55J; 55K; 55L; 55M; 55N; 55O; 55P; 56A; 56B; 56C; 56D; 64M; 65D; 74O; 74P; 75A; 75B
AreaChesterfield Inlet; Baker Lake; Wholdaia Lake
Lat/Long WENS -96.0000 -88.0000 65.0000 62.5000
Lat/Long WENS-108.0000 -102.0000 61.0000 59.0000
Subjectstectonics; geochemistry; geochronology; mineralogy; tectonic evolution; metamorphism; thermal history; plate margins; magmatism; thermal analyses; pressure-temperature conditions; metamorphic facies; granulite facies; inclusions; thermobarometry; modelling; geochemical analyses; bulk composition; trace element analyses; crystallization; software; bedrock geology; lithology; metamorphic rocks; radiometric dating; uranium lead dating; zircon dates; petrographic analyses; Archean; Kramanituar Complex; Snowbird Tectonic Zone; Rae Craton; Churchill Province; Paleoproterozoic; Rae Margin; DOMINO; Precambrian; Proterozoic
Illustrationslocation maps; geoscientific sketch maps; photographs; photomicrographs; tables; profiles; phase diagrams
ProgramGEM2: Geo-mapping for Energy and Minerals Rae Province, Tehery-Wager Bay
Released2019 02 02
AbstractThe high-pressure (P) granulite-facies Kramanituar Complex, dominated by a metagabbroic-anorthositic suite with subordinate sillimanite- and kyanite-bearing diatexite and charnockite, is one of several complexes that demarcate the 1000 km-long Snowbird Tectonic Zone. Ti-in-quartz (TiQ) and Zr-in-rutile (ZiR) thermometry on inclusions in garnet in mafic and pelitic rocks establish that temperatures (T) exceeded 990-1000 °C, ~100 °C higher than recorded by Fe-Mg exchange thermometers. At 1000 °C, thermobarometry and forward modelling of both mafic and pelitic rocks from the complex define 14-15 kbar pressures, where TiQ and ZiR temperatures are in good agreement. The occurrence in diatexite of sparse prograde F-bearing biotite and high-T rutile inclusions in garnet rims, not cores, can be accounted for with a high-Ti solubility biotite model and the presence of fluorine. Forward modelling suggests that heterogeneities in both the composition and zoning of garnet reflect the effects of melt loss on bulk composition. Gabbroic rocks with coronitic and symplectitic reaction textures record high-T decompression to 8 kbar and 800 °C, also reflected by matrix quartz ribbons in diatexite which yield TiQ values between 655 and 824 °C at 8 kbar. Combined results define a clockwise P-T path for the complex at 1910-1896 Ma. South of the complex, a contemporaneous clockwise P-T path is recorded in semipelitic rocks that reached peak conditions of 690 °C and 8.1 kbar. Overall, results support tectonic reworking of the thickened (> 50 km) Rae margin from ca. 1910 Ma, culminating in ca. 1902 Ma mantle-derived mafic magmatism and rapid exhumation, potentially triggered by slab breakoff or lithospheric delamination.
Summary(Plain Language Summary, not published)
The Kramanituar Complex is one of several exposed complexes in the Archean western Churchill Province that are dominated by mafic plutonic rocks, with lesser supracrustal rocks. These complexes record moderate to intense degrees of ductile strain, typically manifested as kilometre-scale shear zones. Techniques to estimate the temperature (T) and pressure(P)these rocks experienced, yield peak T for both mafic plutonic and metasedimentary rocks in excess of 1000°C. Combined with corresponding P estimates of 14-15 kb (corresponding to a depth of ~50 km), these rocks record heating and burial, which is known from U-Pb zircon geochronology to have occurred between 1917-1910 Ma. Ensuing, rapid uplift (accompanied by removal of overlying crust) to mid-crustal depths of 27 km (~8 kb) took place by 1901 Ma. The results provide insight into both the consistency and some limitations of petrological methods to recover estimates of P and T, while documenting the first occurrence of ultrahigh-T metamorphism in the western Churchill Province.

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