The Flin Flon – Athapapuskow Lake area, situated in the Flin Flon Greenstone Belt, Manitoba, consists of ocean-floor and island-arc assemblages, deformed and metamorphosed during the Trans-Hudson Orogeny (∼1.86–1.69 Ga). A new map of metamorphic mineral assemblages and isograds has been compiled that reveals a largely coherent regional metamorphic sequence increasing in metamorphic grade from prehnite–pumpellyite to amphibolite facies. Regional metamorphism postdates most of the deformation within the area, with the exception of the reactivation of major block-bounding faults. The regional prograde sequence has been subdivided into 10 metamorphic zones, separated by 9 isograds, that describe the transition from prehnite–pumpellyite to greenschist to amphibolite facies. The formation of contact metamorphic aureoles, pre-dating regional metamorphism, record conditions up to amphibolite facies. Equilibrium phase diagrams for the island-arc (low-Mg) and ocean-floor (high-Mg) assemblages were calculated and allow for the evaluation of the modelling techniques and determination of pressure–temperature conditions. Discrepancies between the modelling predictions and natural observations occur due to (1) limitations in the thermodynamic models for some of the complex minerals (e.g., amphibole); and (2) metastable persistence of some minerals to higher grade due to sluggish reaction kinetics. Notwithstanding these discrepancies, the modelling suggests that metamorphosed mafic rocks in the Flin Flon – Athapapuskow Lake area reached about 430–480 °C and 3.0–4.5 kbar. Peak metamorphic conditions within contact aureoles that preceded regional metamorphism did not exceed 500 °C (at a pressure between 2.7 and 4.4 kbar). The metamorphic field gradient records a transition from 250–300 °C/1.5–2.3 kbar to 430–480 °C/3–4.5 kbar (100–150 °C/kbar), defining a geothermal gradient of approximately 25–31 °C/km.
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Research Article|
April 03, 2020
Metamorphic and structural evolution of the Flin Flon – Athapapuskow Lake area, west-central Manitoba
Manuele Lazzarotto;
a
Department of Geoscience, University of Calgary, 2500 University Drive NW, Calgary, AB T2N 1N4, Canada.Corresponding author: Manuele Lazzarotto (email: manuele.lazzarotto@ucalgary.ca).
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David R.M. Pattison;
David R.M. Pattison
a
Department of Geoscience, University of Calgary, 2500 University Drive NW, Calgary, AB T2N 1N4, Canada.
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Paul G. Starr
Paul G. Starr
c
Department of Earth and Environmental Sciences, Boston College, 140 Commonwealth Avenue, Chestnut Hill, MA 02467, USA.
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Canadian Journal of Earth Sciences (2020) 57 (11): 1269–1288.
Article history
received:
18 Jul 2019
accepted:
24 Mar 2020
first online:
02 Nov 2020
Citation
Manuele Lazzarotto, David R.M. Pattison, Simon Gagné, Paul G. Starr; Metamorphic and structural evolution of the Flin Flon – Athapapuskow Lake area, west-central Manitoba. Canadian Journal of Earth Sciences 2020;; 57 (11): 1269–1288. doi: https://doi.org/10.1139/cjes-2019-0136
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Index Terms/Descriptors
- Canada
- Canadian Shield
- contact metamorphism
- deformation
- faults
- Flin Flon Belt
- Flin Flon Manitoba
- geothermal gradient
- greenstone belts
- heat flow
- Hudsonian Orogeny
- Manitoba
- metamorphic belts
- metamorphic rocks
- metamorphism
- mineral assemblages
- mineral composition
- North America
- numerical models
- P-T conditions
- petrography
- phase equilibria
- Precambrian
- tectonics
- Western Canada
- Athapapuskow Lake
Latitude & Longitude
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