Calcite-Graphite Isotope Thermometry Across the Western Part of the Central Metasedimentary Belt, Grenville Province, Southern Ontario

Dunn, Steven R.; Kotikian, Maneh; Achenbach, K. L.; Nesbit, Jacquie; Markley, Michelle

doi:10.1130/abs/2016am-287122

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“…And unlike the Robertson Lake Shear Zone and Carthage-Colton Shear Zone to the southeast (Figure 1b), the CMBbz also lacks sharp discontinuities in metamorphic grade. From the footwall (Muskoka terrane) to the hanging-wall (Hastings Low of the Elzevir terrane), the metamorphic grade decreases from 750°C and >8kbar to <500°C and <6 kbar (Anovitz and Essene 1990;Streepey et al 1997;Dunn et al 2016). Because there is no consensus in the literature on the CMBbz's name or exact boundaries, we follow Hanmer and McEachern's (1992) delineation, which includes some of the Central Gneiss Belt and Bancroft Terrane of Easton (1992).…”

Section: Tectonic Significance Of the Central Metasedimentary Belt Bomentioning

confidence: 99%

Monazite U–Th–Pb geochronology of the Central Metasedimentary Belt Boundary Zone (CMBbz), Grenville Province, Ontario Canada

et al. 2018

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The Central Metasedimentary Belt boundary zone (CMBbz) is a crustal-scale shear zone that juxtaposes the Central Gneiss Belt and the Central Metasedimentary Belt of the Grenville Province. Geochronological work on the timing of deformation and metamorphism in the CMBbz is ambiguous, and the questions that motivate our study are: how many episodes of shear zone activity did the CMBbz experience, and what is the tectonic significance of each episode? We present electron microprobe data from monazite (the U–Th–Pb chemical method) to directly date deformation and metamorphism recorded in five garnet–biotite gneiss samples collected from three localities of the CMBbz of Ontario (West Guilford, Fishtail Lake, and Killaloe). All three localities yield youngest monazite dates ca. 1045 Ma; most of the monazite domains that yield these dates are high-Y rims. In comparison with this common late Ottawan history, the earlier history of the three CMBbz localities is less clearly shared. The West Guilford samples have monazite grain cores that show older high-Y domains and younger low-Y domains; these cores yield a prograde early Ottawan (1100–1075 Ma) history. The Killaloe samples yield a well-defined prograde, pre- to early Shawinigan history (i.e., 1220–1160 Ma) in addition to some evidence for a second early Ottawan event. In other words, the answers to our research questions are: three events; a Shawinigan event possibly associated with crustal thickening, an Ottawan event possibly associated with another round of crustal thickening, and a late Ottawan event that resists simple interpretation in terms of metamorphic history but that coincides chronologically with crustal thinning at the base of an orogenic lid.

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Section: Tectonic Significance Of the Central Metasedimentary Belt Bomentioning

confidence: 99%

Monazite U–Th–Pb geochronology of the Central Metasedimentary Belt Boundary Zone (CMBbz), Grenville Province, Ontario Canada

et al. 2018

Self Cite

View full text Add to dashboard Cite

show abstract

Calcite-Graphite Isotope Thermometry Across the Western Part of the Central Metasedimentary Belt, Grenville Province, Southern Ontario

Cited by 1 publication

References 0 publications

Monazite U–Th–Pb geochronology of the Central Metasedimentary Belt Boundary Zone (CMBbz), Grenville Province, Ontario Canada

Monazite U–Th–Pb geochronology of the Central Metasedimentary Belt Boundary Zone (CMBbz), Grenville Province, Ontario Canada

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