Shuswap terrane of British Columbia: A Mesozoic “core complex”

Brown, Richard L.; Read, P B

doi:10.1130/0091-7613(1983)11<164:stobca>2.0.co;2

Cited by 72 publications

(24 citation statements)

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“…In the northern part of the Cordillera, most authors attributed the ductile fabric and the formation of the Cordilleran metamorphic core complexes to Mesozoic to Paleogene contraction associated with crustal thickening (Brown & Read, 1983;Mattauer el ai., 1983;Okulitch, 1984;Brown & Journeay, 1987) whereas the importance of Tertiary extension overprint was emphasised in the southern part (Armstrong, 1972;Davis & Coney, 1979;Wernicke, 1985). We Mathews, 1981;Parrish et al, 1988).…”

Section: Introductionmentioning

confidence: 99%

“…During Mesozoic and early Tertiary time, subduction and accretion of terrane on the we tern margin of ancient North America resulted in contraction and crustal thickening, trike-lip faulting, and extension (Monger & Price, 1979;Monger eta!., 1982;Gabrielse, 1985;Price & Carmichael, 1986;Parrish et at., 1988;Gabrielse et at., 1991;Struik, 1993). The amount of Paleogene extension, crustal anatexis, and granite intrusion that followed Mesozoic contraction is debated, and the age and significance of the ductile fabric in the hanging wall of the major detachment faults is controver ial (Price, 1986;Brown & Read, 1983;Brown & Journeay, 1987;Carr et al, 1987;Parrish et al, 1988;Carr, 1992). In contrast to most Cordilleran MCC, which show either a shallower structural level or a severe mylonitic overprint under lowgrade conditions, the Shu wap MCC has preserved high-grade fabrics.…”

Section: Introductionmentioning

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: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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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“…A number of different domeforming mechanisms have been invoked, including cross-folding (van Staal and Williams, 1983;Ramsay and Huber, 1987;Schwerdtner, 1990) and en echelon folding (Platt, 1980), uplift following the extensional unroofi ng in metamorphic core complex (e.g., Brown and Read, 1983;Brun and van ven Driessche, 1994;Kloppenburg et al 2001), kilometer-scale sheath folding (Lacassin and Mattauer, 1985;Goscombe, 1991), and magmatic or solid-state diapirism (e.g., Dixon, 1975;Bouhallier et al, 1995;Collins et al, 1998). Overall, despite a long history of investigation, the origin of gneiss domes remains controversial (e.g., Collins et al, 1998, vs. Kloppenburg et al, 2001.…”

Section: Introductionmentioning

confidence: 99%

“…Gneiss domes have been documented in several distinct tectonic settings, including the cores of collision-type orogens (e.g., Himalaya; Lee et al, 2000), extensional orogens (e.g., the Canadian Cordillera; Brown and Read, 1983;Vanderhaeghe et al, 1999) and in Archean cratons (e.g., the Pilbara and Dharwar cratons of Australia and India, respectively; Bouhallier et al, 1995;Collins et al, 1998). A number of different domeforming mechanisms have been invoked, including cross-folding (van Staal and Williams, 1983;Ramsay and Huber, 1987;Schwerdtner, 1990) and en echelon folding (Platt, 1980), uplift following the extensional unroofi ng in metamorphic core complex (e.g., Brown and Read, 1983;Brun and van ven Driessche, 1994;Kloppenburg et al 2001), kilometer-scale sheath folding (Lacassin and Mattauer, 1985;Goscombe, 1991), and magmatic or solid-state diapirism (e.g., Dixon, 1975;Bouhallier et al, 1995;Collins et al, 1998).…”

Section: Introductionmentioning

confidence: 99%

“…Gneiss domes are often encountered in metamorphic core complexes (e.g., Brown and Read, 1983;Brun and van den Driessche, 1994;Vanderhaeghe et al, 1999). The distinctive structural elements of all metamorphic core complexes are (1) a unidirectional distribution of stretching lineations (Brun, 1983;Lister and Davis, 1989), and (2) a brittle-ductile extensional detachment fault, with unequivocal sense of shear, separates the high-grade rocks of the footwall from low-grade, brittlely deformed, rocks of the hanging wall (Brun and van den Driessche, 1994).…”

Section: Introductionmentioning

confidence: 99%

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Migmatitic structures and solid-state diapirism in orthogneiss domes, eastern Grenville Province, Canada

Gervais¹,

Nadeau²,

Malo³

2004

Gneiss Domes in Orogeny

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In the Aguanish Complex of the eastern Grenville Province, foliation trajectories, along with the contacts between migmatized orthogneissic sheets, defi ne kilometerscale domes. We present a detailed structural analysis of three of these domes with an emphasis on the distribution of the principal stretching axes derived from conjugate fl anking shear bands (melt-fi lled extensional shear bands). Noteworthy structural elements formed synchronously with the development of the domes are (1) maximum and minimum stretching axes are distributed tangentially along the envelopes of domes and radially toward the cores of domes, respectively; (2) a radial distribution of elongation lineations in the core of the most exposed dome; (3) the local convergence of lineations and fold axes toward a vertical triple junction of foliation trajectories located between two of these domes and the adjacent supracrustal trough; and (4) the development of a horizontal foliation, overprinting a steeply dipping fabric, in the core of the most exposed dome. We argue that a melt-enhanced, solid-state diapiric model best explains the aforementioned features. At the regional scale, we suggest that this diapiric process resulted from the lateral escape of the thermally softened granitic middle-crust of the Aguanish Complex, which was pushed up to compensate for the sagduction (gravity-sinking) of the denser overlying Wakeham Group, previously overloaded by the emplacement of voluminous gabbroic sills. In turn, the thermal softening of the middle granitic crust can be related to the coupled effects of thermal blanketing by the gabbroic sills and underplating of hot anorthosite-mangerite-charnockite-granite magmas associated with the intrusion of a large Grenvillian anorthositic complex.

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Titanium concentration in quartz as a record of multiple deformation mechanisms in an extensional shear zone

Nachlas

Teyssier

Bagley

et al. 2014

Geochem. Geophys. Geosyst.

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Results of high precision analysis of Ti concentration ([Ti]) in quartz representing different recrystallization microstructures in a suite of progressively deformed quartzite mylonites show the effect of recrystallization on distribution of Ti in quartz. Petrographic observations and ion microprobe analysis reveals three texturally and geochemically distinct quartz microstructures in mylonites: (1) cores of recrystallized quartz ribbons preserve the highest [Ti] and are interpreted to have recrystallized via grain boundary migration recrystallization, (2) recrystallized rims and grain margins preserve a lower and more variable [Ti] and are interpreted to reflect the combined influence of subgrain rotation and bulging recrystallization, and (3) neocrystallized quartz precipitated in dilatancy sites has low ( 1 ppm) [Ti], reflecting the Ti content of the syndeformational fluid. Muscovite in nonmylonitic quartzite (at the base of the sampling traverse) is compositionally zoned, whereas muscovite in mylonitic quartzite shows a progressive decreasing in zoning in higher strain samples. Threedimensional phase distribution mapping using X-ray computed tomography analysis of rock hand samples reveals that Ti-bearing accessory phases are less abundant and more dispersed in higher strained mylonites compared to nonmylonitic quartzite. This study demonstrates the influence of dynamic recrystallization on Ti substitution in quartz and evaluates the Ti buffering capacity of aqueous fluids (meteoric versus metamorphic/ magmatic) as well as the distribution and reactivity of Ti-bearing accessory phases in a deforming quartzite. Results of this study suggest that Ti-in-quartz thermobarometry of deformed quartz is a sensitive technique for resolving the multistage history of quartz deformation and recrystallization in crustal shear zones.

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Shuswap terrane of British Columbia: A Mesozoic “core complex”

Cited by 72 publications

References 0 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

Migmatitic structures and solid-state diapirism in orthogneiss domes, eastern Grenville Province, Canada

Titanium concentration in quartz as a record of multiple deformation mechanisms in an extensional shear zone

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