Age and isotopic character of Early Proterozoic basement gneisses in the southern Monashee Complex, southeastern British Columbia

Parkinson, Dave

doi:10.1139/e91-106

Cited by 52 publications

(35 citation statements)

References 23 publications

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“…These complexes display Paleoproterozoic cratonic ba ement, or core gneisses, composed of metapelites and migmatitic gnei es attributed to the Windermere Supergroup intruded by Proterozoic granodioritic gneisses (Wanless & Reesor, 1975;Armstrong et al, 1991;Parkinson, 1991). Partial melting and granite emplacement is mostly Early Tertiary in the Valhalla complex (Carr el al., 1987) but the extent to which Tertiary high-temperature metamorphi m has overprinted the Paleoproterozoic rocks is not well constrained in the other complexes (Parkinson, 1991(Parkinson, , 1992Carr, 1992). The core gneisse are unconformably overlain by a thick quartzite horizon and alternating pelitic and psammitic gneisses containing fairly continuous marble and quartzite trata ( fig.…”

Section: Parautochthonous Basement Gneissesmentioning

confidence: 99%

“…4, -Geologic map of the Shuswap metamorphic core complex at the latitude of the Thor-Odin dome, and summary of published geochronological data (CarI", 1990(CarI", , 1992Mathews, 1981;Parkinson, 1991Parkinson, , 1992Parrish et al, 1988, Parrish & Armstrong, 1987Wanless & Reesor, 1975). Circles represent sample locations and the numbers in the circle refer to the corresponding publication.…”

Section: 'Fmentioning

confidence: 99%

“…5) (Lane el al., 1989). This metamorphic event has been related to the Late Cretaceous early Tertiary evolution of the Cordillera based on geochronologic studies (Parkinson, 1991;Carr, 1992).…”

Section: 'Fmentioning

confidence: 99%

“…(Parkinson, 1991), and yielding ages from 1.87 Ga to 2.10 Ga for orthogneisse (Wanles & Reesor, 1975;Parkinson, 1991;Armstrong el al., 1991). However, the zircons how discordant ages with lower intercepts ranging from 175 Ma to 49 Ma indicating one or more events of lead loss during Mesozoic or Paleogene time.…”

Section: Metamorphismmentioning

confidence: 99%

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Formation of the Shuswap metamorphic core complex during late-orogenic collapse of the Canadian Cordillera: Role of ductile thinning and partial melting of the mid-to lower crust

Vanderhaeghe

Teyssier

1997

Geodinamica Acta

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The early Tertiary evolution of the Shuswap metamorphic core complex is characterised by low-angle crustal detachments and nearly isothermal decompression followed by rapid cooling of rocks in the footwall of the detachments. Previous work as well as our own observations suggest that Paleogene late-orogenic extension produced the main tectonic features of the region. Furthermore, structural analysis of the migmatites and published geochronological data indicate that partial melting of the mid-to lower crust was coeval with extension in the upper crustal levels, suggesting that these two processes are linked genetically. Consequently, we propose that the formation of the Shuswap metamorphic core complex corresponds to late-orogenic gravitational collapse of the Canadian Cordillera accommodated by normal faulting of the brittle upper crust and by ductile thinning of the mid-to lower crust. The initiation and amplification of extension during the Paleocene in the Shuswap metamorphic core complex are tentatively related to partial melting of the thickened crust which caused drastic mechanical weakening of the crust. RESUME. -L'evolution durant Ie Tertiaire du complexe metal1'lorphique du Shuswap est marquee par la formation de detachements crustaux subhorizontaux au-dessous dcsquels les roches ont subi une decompression quasi-isothennique, suivie d'un refroidissement tres rapide. L'etude des travaux publies sur Ie complexe metamorphique du Shuswap, ainsi que nos .observations de terrain, montrent que I'extension Department of Geology and Geophysics, University of Minnesota, Minneapolis, MN 55455 USA tardi-orogenique paleogene est 11 l'origine des structures majeures de cette region. L'analyse structurale des migmatites et les donnees geochronologiques indiquent que la fusion crustale fut synchrone de l'extension de la croute superieure, ce qui suggere que ces deux processus sont lies genetiquement. En consequence, nous proposons que la formation du complexe metamorphique du Shuswap corresponde 11 I'effondrement gravitaire de la Cordillere canadienne accommode par extension fragile de la croute superieure et par I'amincissement ductile de la croute mediane 11 inferieure. Nous proposons egalement que l'initiation et l'amplification de I'extension orogenique durant Ie Paleocene dans Ie complexe du Shuswap sont liees 11 la fusion de cette croute epaissie qui entralne un amollissement catastrophique de la croute.Mots des: Effondrement tardi-orogenique, metamorphic core complex, Shuswap, fusion partielie, migmatites, Cordillere canadienne, Colombie Britannique.

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Section: Parautochthonous Basement Gneissesmentioning

confidence: 99%

Section: 'Fmentioning

confidence: 99%

Section: 'Fmentioning

confidence: 99%

Section: Metamorphismmentioning

confidence: 99%

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Formation of the Shuswap metamorphic core complex during late-orogenic collapse of the Canadian Cordillera: Role of ductile thinning and partial melting of the mid-to lower crust

Vanderhaeghe

Teyssier

1997

Geodinamica Acta

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“…Crystallization ages of 1.87 and 1.99-2.1 Ga are also common to the basement rocks of the Monashee Complex to the south (Parkinson 1990;Parrish, in press). In northern British Columbia, the Sifton gneiss is 1.85 Ga old (Evenchick et al 1984).…”

Section: Correlation Of the Basement Rocks With The Shieldmentioning

confidence: 93%

Proterozoic gneisses of the Malton Complex, near Valemount, British Columbia: U–Pb ages and Nd isotopic signatures

McDonough¹,

Parrish²

1991

Can. J. Earth Sci.

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Proterozoic gneisses of the Malton Complex in the vicinity of Valemount, British Columbia, occur in a series of lithologically and structurally complex, fault-bounded slices of crystalline basement and interleaved cover. Gneisses of the Malton Complex span the Southern Rocky Mountain Trench and underlie the western part of the Rocky Mountain fold and thrust belt and the eastern part of the Omineca Belt of the Canadian Cordillera. Structural and stratigraphic relationships indicate that they formed the basement upon which an enigmatic quartzite unit and the Late Proterozoic Windermere Supergroup were deposited.The Yellowjacket and Bulldog gneisses, on the east side of the Rocky Mountain Trench, have yielded four U–Pb zircon crystallization ages of ca. 1870 Ma, with εNd(T) values of −2.6 to −3.4. The Hugh Allan gneiss, also on the east side of the trench but separated from the Yellowjacket gneiss by a major thrust fault, includes leucocratic granite gneiss having a zircon U–Pb age of [Formula: see text], which has intruded an older (undated) lithologically heterogeneous assemblage of gneiss. The basal Windermere succession of the Valemount region is inferred to be younger than ca. 740 Ma, since these intrusions are not found within the Late Proterozoic stratified rocks.Augen granitoid orthogneiss of the Malton Range on the west side of the Rocky Mountain Trench has been dated as [Formula: see text] using zircons. A second sample yields data suggesting an age between 2050 and 2100 Ma, but its interpretation is uncertain because of scatter in analyses and possible zircon inheritance. The latter sample has an εNd(T) at 1990 Ma of −2.6. Nd model ages for the Malton, Yellowjacket, and Bulldog samples range from 2.45 to 2.56 Ga, indicating that the igneous protoliths were derived from a source that probably had some component of Archean crustal material involved.The U–Pb ages and Nd model ages are quite similar to those of rocks underlying portions of Alberta and the western Canadian Shield, specifically the Fort Simpson terrane, the Great Bear magmatic zone, and parts of the Thelon–Taltson arc. This evidence, as well as structural and stratigraphic arguments, links the Malton Complex gneisses with those of the Canadian Shield, precluding their derivation by large-magnitude displacements from the southwestern United States. Structural analysis indicates that they restore to locations 100–200 km southwest of their present exposure.Structural, stratigraphic, and isotopic data indicate that the Southern Rocky Mountain Trench is not a suture.

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The Monashee décollement at Cariboo Alp, southern flank of the Monashee complex, southern British Columbia, Canada

McNicoll

Brown

1995

Journal of Structural Geology

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Age and isotopic character of Early Proterozoic basement gneisses in the southern Monashee Complex, southeastern British Columbia

Cited by 52 publications

References 23 publications

Formation of the Shuswap metamorphic core complex during late-orogenic collapse of the Canadian Cordillera: Role of ductile thinning and partial melting of the mid-to lower crust

Formation of the Shuswap metamorphic core complex during late-orogenic collapse of the Canadian Cordillera: Role of ductile thinning and partial melting of the mid-to lower crust

Proterozoic gneisses of the Malton Complex, near Valemount, British Columbia: U–Pb ages and Nd isotopic signatures

The Monashee décollement at Cariboo Alp, southern flank of the Monashee complex, southern British Columbia, Canada

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