Coronitic metagabbro and eclogite from the Grenville Province of western Quebec: interpretation of U–Pb geochronology and metamorphism
Abstract
We present new U–Pb and metamorphic data on high-pressure coronitic metagabbros from three distinct structural settings in the Parautochthonous Belt of the Grenville Province in western Quebec. Intrusive ages are (i) [Formula: see text], for metagabbro close to the Grenville Front, correlative with the Sudbury dykes, defined in Ontario; (ii) [Formula: see text] for an eclogitized lens at the base of the highest structural level (SL4), a new age for mafic magmatism in the western Grenville; and (iii) [Formula: see text] for metagabbro from SL4, interpreted as correlative with metagabbros from the Algonquin and Shawanaga domains in Ontario. Metamorphism in all cases is Grenvillian, with the best constrained age of 1069 ± 3 Ma for the metagabbro of SL4. Metamorphic grade increases from the Grenville Front to the south. The mafic rocks preserve relict igneous textures overprinted by garnet + clinopyroxene that developed as coronas and (or) pseudomorphs after igneous phases. The highest grade metagabbros contain omphacite and some lack primary plagioclase, therefore being eclogites. However, interpretation of textures and mineral chemistry indicates that they were equilibrated during decompression (at 1350 MPa and 720 °C, sample 51; and at 1200 MPa and 740 °C, sample 29), so maximum depths of burial remain unconstrained. Their evolution is interpreted as follows: (i) high-pressure metamorphism by burial of the Laurentian margin under accreted terranes thrust toward the northwest b…
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The northwestern part of the Parautochthonous belt, known as the Grenville Front tectonic zone (GFTZ), is characterized by front-parallel structures with dip-parallel lineations.
“The northwestern part of the belt, known as the Grenville Front tectonic zone (GFTZ), is characterized by front-parallel structures with dip-parallel lineations, and the various domains and terranes of the Parautochthonous belt are linked lithologically to the foreland and each other by the presence of deformed mafic dykes belonging to, or having chemical affinities with, the c45 1235 Ma Sudbury”
From The High Pressure belt in the Grenville Province: architecture, timing, and exhumation (2002) · cites this paper as Indares and Dunning 1997
U/Pb ages from relict eclogite bodies include a single determination of 1121 ± 10/12 Ma, six determinations of 1101-1069 Ma (all ± 4 Ma or less), and two less precise determinations of 1063 +48/-35 and 1048 ± 30 Ma.
“Estimated ages include a single determination of 1121 -+ 10 12 Ma, six determinations of 1101-1069 Ma (all ± 4 Ma or less), and two less precise determinations of 1063 -+ 48 35 and 1048 ± 30 Ma (see Fig. 2).”
From The High Pressure belt in the Grenville Province: architecture, timing, and exhumation (2002) · cites this paper as Indares and Dunning 1997
The various domains and terranes of the Parautochthonous belt are linked lithologically to the foreland and each other by the presence of deformed mafic dykes belonging to, or having chemical affinities with, the c45 1235 Ma Sudbury swarm.
“The northwestern part of the belt, known as the Grenville Front tectonic zone (GFTZ), is characterized by front-parallel structures with dip-parallel lineations, and the various domains and terranes of the Parautochthonous belt are linked lithologically to the foreland and each other by the presence of deformed mafic dykes belonging to, or having chemical affinities with, the c45 1235 Ma Sudbury”
From The High Pressure belt in the Grenville Province: architecture, timing, and exhumation (2002) · cites this paper as Indares and Dunning 1997
The HP terranes are characterized by pods and lenses of retrogressed eclogite with protolith ages of c45 1470-1403 Ma.
“The HP terranes lack Sudbury metadiabase, but are characterized by the presence of the 1170-1150 Ma, coronitic Algonquin metagabbro (Davidson and van Breemen 1988; Heaman and LeCheminant 1993) and by pods and lenses of retrogressed eclogite with protolith ages of c45 1470-1403 Ma (Indares and Dunning 1997; Ketchum and Krogh 1997, 1998).”
From The High Pressure belt in the Grenville Province: architecture, timing, and exhumation (2002) · cites this paper as Indares and Dunning 1997
The original granoblastic, eclogite-facies mineralogy is extensively overprinted by granulite- and amphibolite-facies assemblages, but compelling evidence of former eclogite parageneses is preserved locally.
“The original granoblastic, eclogite-facies mineralogy is extensively overprinted by granulite- and amphibolite-facies assemblages, but compelling evidence of former eclogite parageneses is preserved locally.”
From The High Pressure belt in the Grenville Province: architecture, timing, and exhumation (2002) · cites this paper as Indares and Dunning 1997
Indares and Dunning (1997) calculated a P-T of 1350 MPa and 720°C from the retrogressed assemblage, which they inferred to represent conditions at some stage of the unroofing.
“Indares and Dunning (1997) calculated a P-T of 1350 MPa and 720°C from the retrogressed assemblage, which they inferred to represent conditions at some stage of the unroofing.”
From The High Pressure belt in the Grenville Province: architecture, timing, and exhumation (2002) · cites this paper as Indares and Dunning (1997)
Some samples preserve evidence of a former eclogite-facies assemblage consisting of garnet-omphacite-kyanite, indicated by symplectite textures.
“For instance, clinopyroxene-plagioclase symplectite replaces presumed former omphacite; pyrope-rich garnet is surrounded by decompression collars of plagioclase-pargasite symplectite; and kyanite relics are surrounded by a symplectic intergrowth of corundum-hercynite ± sapphirine, pointing to a former assemblage consisting of garnet-omphacite-kyanite in some samples.”
From The High Pressure belt in the Grenville Province: architecture, timing, and exhumation (2002) · cites this paper as Indares and Dunning 1997
Maximum estimated P-T conditions in Lelukuau and Tshenukutish terranes, where garnet-kyanite clinopyroxenite and subordinate true eclogite are widespread, are similar to those for Molson Lake terrane, in the range 1400 to 1900 MPa and 770 to 920°C.
“Maximum estimated P-T conditions in Lelukuau and Tshenukutish terranes, where garnet-kyanite clinopyroxenite and subordinate true eclogite are widespread, are similar to those for Molson Lake terrane, in the range 1400 to 1900 MPa and 770 to 920°C (Indares 1997; Cox and Indares 1999 a , 1999 b ; Indares et al. 2000).”
From The High Pressure belt in the Grenville Province: architecture, timing, and exhumation (2002) · cites this paper as Indares 1997
The pervasive granulite-facies reequilibration of eclogite during the Ottawa orogeny in the western Grenville Province suggests a two-stage exhumation process involving a period of residence in the middle crust before emplacement on the Parautochthonous belt.
“In contrast, the pervasive granulite-facies reequilibration of eclogite during the Ottawa orogeny in the western Grenville Province suggests a two-stage exhumation process involving a period of residence in the middle crust before emplacement on the Parautochthonous belt (e.g., Indares and Dunning 1997).”
From The High Pressure belt in the Grenville Province: architecture, timing, and exhumation (2002) · cites this paper as Indares and Dunning 1997
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The High Pressure belt in the Grenville Province: architecture, timing, and exhumation
Rivers, T., Ketchum, J., Indares, A., & Hynes, A. (2002) · Canadian Journal of Earth Sciences · doi:10.1139/e02-025 · Cited by 124 · see citing works
Self-citation
- Authors
- Indares, A., & Dunning, G.
- ORCID
- Indares, Aphrodite
- Venue
- Canadian Journal of Earth Sciences
- Publisher
- Canadian Science Publishing
- Published
- 1997-07-01
- Volume
- 34
- Issue
- 7
- Pages
- 891-901
- ISSN
- 0008-4077 (ISSN-L)
- 1480-3313
- OpenAlex
- W2005635405
- Cited by
- 59
- References
- 0
- Citations by year
- 2025: 1 · 2024: 2 · 2023: 1 · 2022: 4 · 2021: 1 · 2020: 1 · 2019: 2 · 2017: 1 · 2016: 1 · 2015: 1 · 2014: 1 · 2012: 6
- FWCI
- 5.47
- Type
- journal article
- Language
- en
- Open access
- closed
- Locations
- Canadian Journal of Earth Sciences (publishedVersion)
- Funders
- McGill University
- Natural Sciences and Engineering Research Council of Canada
- Topics
- Physical Sciences › Earth and Planetary Sciences › Geophysics › Geological and Geochemical Analysis
- Physical Sciences › Earth and Planetary Sciences › Geology › Geological Studies and Exploration
- Physical Sciences › Physics and Astronomy › Astronomy and Astrophysics › Astro and Planetary Science
- Keywords
- eclogite, Grenville Province, U-Pb geochronology, high-pressure metamorphism, decompression, mafic magmatism, Grenville Front, exhumation, thrusting, accreted terranes, Laurentian margin, pseudomorphs, omphacite, western Quebec
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