Quantifying the Pressure, Temperature, and Timing of Metamorphism in the Montresor Belt, Nunavut, Canada

Dziawa, Carolyn

doi:10.22215/etd/2016-11560

Cited by 1 publication

(2 citation statements)

References 83 publications

(227 reference statements)

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“…At the boundary between the footwall complex and overlying upper Montresor units near the southwestern end of the belt, the footwall complex consists of muscovite-andalusitesillimanite-garnet schist indicating middle-amphibolite facies conditions (3.3 kbar, 575 o C) at 1861-1844 Ma (Berman et al 2015a;Dziawa 2016). The schistosity dips moderately northwest and is concordant with well-preserved bedding in the structurally overlying, weakly deformed sandstone, siltstone and minor carbonate units of the upper Montresor group.…”

Section: R a F Tmentioning

confidence: 99%

“…A small outlier of kaolinitic sandstone adjacent to the Amer belt was assigned an assemblage 4 designation and correlated with upper Montresor strata 110-180 km to the northeast (op cit.). However, in the Montresor belt proper, structural reconstruction indicates that the upper Montresor rocks were deformed by D 1 thrusts and a D 2 extensional detachment prior to development of the upright Montresor syncline (Tschirhart and Percival, 2016; Percival and Tschirhart, submitted).The D 2 low-angle, extensional fault is responsible for juxtaposing the greenschist-facies upper Montresor rocks with the amphibolite-facies lower Montresor units in the structural footwall complex(Percival et al 2015b;Dziawa 2016). Combined, the geochronological, structural and metamorphic observations support assignment of upper Taken together, the age constraints for the Montresor group suggest a minimum gap of ca.…”

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confidence: 99%

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U–Pb zircon geochronology and depositional history of the Montresor group, Rae Province, Nunavut, Canada

2017

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Paleoproterozoic metasedimentary successions of the northwestern Canadian Shield provide records of tectonic events, but the definition of depositional ages has proved elusive. Although previously poorly understood, the Montresor belt of western Nunavut yields new insight into the 2.2–1.8 Ga time window. On the basis of U–Pb analyses of detrital zircon in sedimentary rocks and igneous zircon in sills, we conclude that arenite of the lower Montresor group was deposited between 2.194 and 2.045 Ga, and arkose of the upper Montresor group after 1.924 Ga, adding constraints on the Rae cover sequence. The lower Montresor arenite yielded an older group (3.05–2.58 Ga) and a younger, more tightly constrained group (2.194 ± 0.014 Ga). Four of six zircon grains analyzed from a gabbro sill within the lower Montresor have discordant 207Pb/206Pb ages (2.71, 2.66, 2.53, and 2.39 Ga) and are considered to be inherited, whereas two grains provide an age of 2045 ± 13 Ma, interpreted to date crystallization and providing a minimum age for the lower Montresor package. Upper Montresor arkose contains detrital zircon with probability density peaks at 2.55–2.25 and 2.1–1.92 Ga, together with scattered older grains (3.8–2.65 Ga). The youngest grain yields an age of 1924 ± 6 Ma, establishing a maximum age for sandstone deposition. Provenance is inferred to have been from the west, where igneous sources of 2.5–2.3 Ga (Queen Maud block) and 2.03–1.89 Ga (Thelon orogen) are known. Collectively, the new ages suggest a minimum 120 million year gap between deposition of the pre-2045 ± 13 Ma lower and post-1924 ± 6 Ma upper parts of the Montresor group. Similar age constraints may apply to other parts of the Rae cover sequence.

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Section: R a F Tmentioning

confidence: 99%

mentioning

confidence: 99%