The Scotia–Quaal metamorphic belt: a distinct assemblage with pre- early Late Cretaceous deformational and metamorphic history, Coast Plutonic Complex, British Columbia

1991 ◽  
Vol 28 (6) ◽  
pp. 870-880 ◽  
Author(s):  
S. A. Gareau
Keyword(s):  
Late Cretaceous ◽  
Middle Devonian ◽  
Regional Metamorphism ◽  
Early Jurassic ◽  
Contact Metamorphism ◽  
Metamorphic Belt ◽  
Metamorphic History ◽  
Plutonic Complex ◽  
Coast Plutonic Complex ◽  
Early Late

The Scotia–Quaal metamorphic belt extends from Hawkesbury Island to Work Channel between the early Late Cretaceous Ecstall and the Paleogene Quottoon plutons. The belt consists of a Proterozoic?–Paleozoic metasedimentary and metavolcanic sequence, the Middle Devonian Big Falls orthogneiss, Early Jurassic orthogneiss, and Jurassic or Cretaceous mafic and ultramafic intrusive rocks. The assemblage may be correlative with Nisling terrane lithologies and may have shared a common history, at least from Early Jurassic time on, with rocks of Stikine terrane.Strong planar and linear fabrics, abundant folds, and scarcity of kinematic indicators characterize the belt's deformational style. Development of a strong foliation followed by three episodes of folding occurred between emplacement of the Middle Devonian Big Falls orthogneiss and early Late Cretaceous Ecstall intrusion. Paleogene fabrics occur in the Quottoon pluton and in the easternmost 1.5 km of the Scotia-Quaal belt. If a major Paleogene shear zone is postulated to explain the disparity in cooling dates, metamorphic histories, and structural styles between the western and central Coast Plutonic Complex, then it does not traverse the Scotia–Quaal metamorphic belt, but must be located within or at the western edge of the Quottoon pluton.Medium-pressure, epidote–amphibolite to upper amphibolite facies metamorphic conditions are preserved in the central region. Metamorphic grade increases gradually across the belt from west to east and from south to north. Regional metamorphism outlasted regional deformation. Contact metamorphism associated with Quottoon and Ecstall intrusion is apparent only in rocks of the southern region where regional metamorphic grades are lowest.

scholarly journals Crustal deformation and regional metamorphism across a terrane boundary, Coast Plutonic Complex, British Columbia

Tectonics ◽  
1987 ◽  
Vol 6 (3) ◽  
pp. 343-361 ◽  
Author(s):  
M. L. Crawford ◽  
L. S. Hollister ◽  
G. J. Woodsworth
Keyword(s):  
British Columbia ◽  
Crustal Deformation ◽  
Regional Metamorphism ◽  
Plutonic Complex ◽  
Coast Plutonic Complex

The western margin of the Coast Plutonic Complex on Hardwicke and West Thurlow Islands, British Columbia

1979 ◽  
Vol 16 (6) ◽  
pp. 1166-1175 ◽  
Author(s):  
Jo Anne Nelson
Keyword(s):  
Quartz Diorite ◽  
Contact Metamorphism ◽  
Contact Aureole ◽  
Western Margin ◽  
Late Mesozoic ◽  
The North ◽  
Early Mesozoic ◽  
Plutonic Complex ◽  
Coast Plutonic Complex ◽  
Maximum Contact

The western margin of the Coast Plutonic Complex, one of the major tectonic boundaries of the Canadian Cordillera, has been variously interpreted as an intrusive contact, a shear zone, and a suture zone joining the Early Mesozoic Insular Belt to the North American continent. A representative section of this boundary, exposed on islands in Johnstone Strait, is an intrusive contact along which a quartz diorite with peripheral mafic phases truncates Early Mesozoic sediments and volcanics of the Insular Belt. Concordant hornblende–biotite pairs and two whole rock biotite isochrons date the intrusion as Late Jurassic (151 Ma). Prior to intrusion the stratified units underwent prehnite–pumpellyite facies metamorphism and west-northwest block faulting.The contact aureole of the quartz diorite and its associated mafic phases involves greenschist and hornblende–hornfels facies assemblages. Total pressure in the upper Karmutsen Formation during contact metamorphism was less than 2.5 × 105 kPa. The maximum contact temperature was between 670 and 700 °C. Forcible emplacement of the intrusion caused penetrative deformation of wall rocks in the inner aureole. The maximum contact temperatures indicate that the plutonic bodies were at near-liquidus temperatures when emplaced.The contact on Hardwicke and West Thurlow Islands appears representative of most of the tectonic boundary between the southern Coast Plutonic Complex and the Insular Belt. The western margin of the Coast Plutonic Complex is thus a Late Mesozoic magmatic front, the western limit of the intense magmatism that generated the Coast Plutonic Complex. The formation of Georgia Depression over the province boundary was a later event, coeval with major uplift of the Coast Plutonic Complex.

Interpretation of isotopic ages and 87Sr/86Sr initial ratios for plutonic rocks in the Whitehorse map area, Yukon

1979 ◽  
Vol 16 (10) ◽  
pp. 1988-1997 ◽  
Author(s):  
Gregg W. Morrison ◽  
Colin I. Godwin ◽  
Richard L. Armstrong
Keyword(s):  
British Columbia ◽  
Oceanic Crust ◽  
Late Cretaceous ◽  
Canadian Cordillera ◽  
Initial Ratio ◽  
Eastern Margin ◽  
The North ◽  
Plutonic Complex ◽  
Coast Plutonic Complex ◽  
North American Craton

Sixteen new K–Ar dates and four new Rb–Sr isochrons help define four plutonic suites in the Whitehorse map area, Yukon. The Triassic(?) suite, defined on stratigraphic evidence, is the southern extension of the Yukon Crystalline Terrane and is correlative with plutonic suites in the Intermontane Belt in British Columbia. The mid-Cretaceous (~100 Ma) suite in the Intermontane Belt in the Whitehorse map area is time equivalent to plutonic suites in the Omineca Crystalline Belt to the east. Late Cretaceous (~70 Ma) and Eocene (~55 Ma) suites include volcanic and subvolcanic as well as plutonic phases and are correlative with continental volcano–plutonic suites near the eastern margin of the Coast Plutonic Complex. The predominance of the mid-Cretaceous suite in the Intermontane Belt in Whitehorse and adjacent map areas in Yukon and northern British Columbia suggests that this area has undergone posttectonic magmatism more characteristic of the Omineca Crystalline Belt than of the Intermontane Belt elsewhere in the Canadian Cordillera.87Sr/86Sr initial ratio determinations suggest that the southern extension of the Yukon Crystalline Terrane in the western part of the Whitehorse map area and in northern British Columbia includes Precambrian crust separated from the North American craton by Paleozoic oceanic crust of the Intermontane Belt.

U–Pb and K–Ar dates related to the timing of magmatism and deformation in the Cache Creek terrane and Quesnellia, southern British Columbia

1990 ◽  
Vol 27 (1) ◽  
pp. 117-123 ◽  
Author(s):  
N. Mortimer ◽  
P. van der Heyden ◽  
R. L. Armstrong ◽  
J. Harakal
Keyword(s):  
British Columbia ◽  
Early Cretaceous ◽  
North American ◽  
Late Jurassic ◽  
Early Jurassic ◽  
Early Permian ◽  
Magmatic Arc ◽  
Plutonic Complex ◽  
Minimum Age ◽  
Coast Plutonic Complex

U–Pb dating of zircon from the Guichon Creek batholith indicates an emplacement age of 210 ± 3 Ma. Comparison with previously published K–Ar (211–188 Ma) and Rb–Sr (205 and 196 Ma) dates reveals that intrusion, mineralization, cooling, and uplift of the batholith took some 20 Ma, spanning the Triassic–Jurassic boundary on the Decade of North American Geology (DNAG) time scale.The Mount Martley pluton and Tiffin Creek stock yield Late Jurassic dates of 155 ± 2 Ma (U–Pb, zircon) and 152 ± 5 Ma (K–Ar, hornblende), respectively, and provide a reliable minimum age (Kimmeridgian) for penetrative deformation in the Cache Creek terrane. K–Ar whole-rock dates from Cache Creek terrane and Ashcroft Formation argillites range from Early Permian (266 ± 8 Ma) and Early Jurassic (194 ± 6 Ma) to Late Jurassic, Kimmeridgian (154 ± 5 Ma). We interpret the younger dates as recording Middle–Late Jurassic tectonism and the older ones as possible relics from earlier deformation episodes.An Early Cretaceous K–Ar date (129 ± 5 Ma) for a lamprophyre dike that cuts the Nicola Group suggests that the Early Cretaceous magmatic arc of the Coast Plutonic Complex had an eastern alkalic fringe in the Intermontane Belt.

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