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TitleConditions and timing of low-pressure - high-temperature metamorphism in the Montresor Belt, Rae Province, Nunavut
AuthorDziawa, C; Gaidies, F; Percival, J
SourceCanadian Journal of Earth Sciences vol. 56, no. 6, 2018 p. 654-671, Open Access logo Open Access
Alt SeriesNatural Resources Canada, Contribution Series 20190125
PublisherCanadian Science Publishing
Mediapaper; on-line; digital
File formatpdf (Adobe® Reader®); html
NTS66I/03; 66I/04
AreaMeadowbank River
Lat/Long WENS -97.5833 -97.2500 66.1667 66.0000
Subjectstectonics; igneous and metamorphic petrology; geochronology; geochemistry; tectonic history; metamorphism; foliation; gneissosity; faulting; intrusions; diabase dykes; fluid migration; crustal evolution; crustal thickness; pressure-temperature conditions; phase equilibria; modelling; radiometric dating; mineral assemblages; crystallization; whole rock geochemistry; bedrock geology; structural features; folds; synforms; shear zones; faults; faults, thrust; faults, extension; fault zones; electron probe analyses; petrographic analyses; garnet; alteration; andalusite; mica; Rae Province; Rae Domain; Montresor Belt; Montresor Group; Trans-Hudson Orogeny; Snowbird Tectonic Zone; Chesterfield Fault Zone; Chantrey Mylonite Zone; Paleoproterozoic; Precambrian; Proterozoic
Illustrationslocation maps; geological sketch maps; tables; photomicrographs; 3-D images; gravity profiles; bar graphs; plots; ternary diagrams; profiles; phase diagrams
ProgramGEM2: Geo-mapping for Energy and Minerals Rae Province, Chantrey-Thelon
Released2018 12 03
AbstractPressure-temperature-time (P-T-t) estimates for the Montresor Belt, obtained using phase equilibria and geospeedometry modelling integrated with in situ U-Th-Pb monazite geochronology, shed new light on the tectonometamorphic effects of the Snowbird phase of the Trans-Hudson orogeny. Typical metapelitic assemblages of the lower Montresor group consist of white mica, biotite, plagioclase, quartz, and andalusite, which in some rocks is partly or completely pseudomorphed by white mica. The observed assemblages reflect peak P-T conditions centring at approximately 575 °C and 3 kbar. Rocks with high bulk Fe/Mg contents contain compositionally zoned garnet, permitting the addition of further constraints on the conditions of metamorphism in the Montresor Belt: Core compositions of earliest-grown garnets indicate initial garnet crystallization at approximately 535 °C and 2.3 kbar, suggesting a nearly isobaric P-T path of prograde metamorphism with a gradient of approximately 50 °C/kbar. Chemical age-dating of monazite inclusions in garnet yields ages of ca. 1870 ± 9 to 1837 ± 9 Ma. Retrograde, pseudomorphic andalusite replacement by white mica at approximately 540 °C is inferred to have been controlled by variations in bulk rock chemistry. Morphologically corroded and chemically heterogeneous monazite adjacent to white mica pseudomorphs suggests that andalusite replacement took place at ca. 1792 ± 10 Ma, possibly associated with extension and movement along the detachment fault separating the upper and lower Montresor groups. Simulations of diffusion across chlorite- and biotite-filled cracks in garnet assumed to be coeval with andalusite replacement suggest that the rocks have experienced the retrograde event for at least 20 My.

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