scholarly journals Eastern margin of the Coast Plutonic Complex, Mount Waddington map area, B.C.

1988 ◽  
Author(s):  
M E Rusmore ◽  
G J Woodsworth
Keyword(s):  
Eastern Margin ◽  
Plutonic Complex ◽  
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.

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

Magmatic evolution of the eastern Coast Plutonic Complex, Bella Coola region, west-central British Columbia

2009 ◽  
Vol 121 (9-10) ◽  
pp. 1362-1380 ◽  
Author(s):  
J. Brian Mahoney ◽  
Sarah M. Gordee ◽  
James W. Haggart ◽  
Richard M. Friedman ◽  
Larry J. Diakow ◽  
...  
Keyword(s):  
British Columbia ◽  
Eastern Coast ◽  
Magmatic Evolution ◽  
West Central ◽  
Plutonic Complex ◽  
Coast Plutonic Complex ◽  
Bella Coola

Obducted nappe sequence in the San Juan Islands – northwest Cascades thrust system, Washington and British Columbia

2012 ◽  
Vol 49 (7) ◽  
pp. 796-817 ◽  
Author(s):  
E.H. Brown
Keyword(s):  
British Columbia ◽  
Detrital Zircons ◽  
San Juan ◽  
San Juan Islands ◽  
Tectonic History ◽  
Plutonic Complex ◽  
Coast Plutonic Complex ◽  
History Of ◽  
Accreted Terranes ◽  
Thrust System

The San Juan Islands – northwest Cascades thrust system in Washington and British Columbia is composed of previously accreted terranes now assembled as four broadly defined composite nappes stacked on a continental footwall of Wrangellia and the Coast Plutonic Complex. Emplacement ages of the nappe sequence are interpreted from zircon ages, field relations, and lithlogies, to young upward. The basal nappe was emplaced prior to early Turonian time (∼93 Ma), indicated by the occurrence of age-distinctive zircons from this nappe in the Sidney Island Formation of the Nanaimo Group. The emplacement age of the highest nappe in the thrust system postdates 87 Ma detrital zircons within the nappe. The nappes bear high-pressure – low-temperature (HP–LT) mineral assemblages indicative of deep burial in a thrust wedge; however, several features indicate that metamorphism occurred prior to nappe assembly: metamorphic discontinuities at nappe boundaries, absence of HP–LT assemblages in the footwall to the nappe pile, and absence of significant unroofing detritus in the Nanaimo Group. A synorogenic relationship of the thrust system to the Nanaimo Group is evident from mutually overlapping ages and by conglomerates of Nanaimo affinity that lie within the nappe pile. From the foregoing relations, and broader Cordilleran geology, the tectonic history of the nappe terranes is interpreted to involve initial accretion and subduction-zone metamorphism south of the present locality, uplift and exhumation, orogen-parallel northward transport of the nappes as part of a forearc sliver, and finally obduction at the present site over the truncated south end of Wrangellia and the 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.

Seismic investigation of the Coast Plutonic Complex – Insular Belt boundary beneath the Strait of Georgia

1984 ◽  
Vol 21 (9) ◽  
pp. 1033-1049 ◽  
Author(s):  
Donald J. White ◽  
Ron M. Clowes
Keyword(s):  
Crustal Structure ◽  
Seismic Refraction ◽  
Unconsolidated Sediments ◽  
The West ◽  
Strait Of Georgia ◽  
Seismic Properties ◽  
Air Gun ◽  
Plutonic Complex ◽  
Major Fault ◽  
Coast Plutonic Complex

The Strait of Georgia, a topographic depression between Vancouver Island and the mainland of British Columbia, is considered to be the boundary between two tectonic provinces: the Coast Plutonic Complex on the east and the Insular Belt to the west. The allochthonous nature of the Insular Belt has been established, mainly on the basis of paleomagnetic measurements. Various tectonic models to explain the geological differences between the two provinces have been proposed. One of these suggests that the boundary is an old transform fault zone and is represented currently by a thrust fault along the eastern side of the Strait of Georgia. Other models propose that the Coast Plutonic Complex is a feature superimposed by tectonic and metamorphic events after the accretion of the Insular Belt. Such models do not require a major crustal discontinuity along the Strait of Georgia.In May 1982, a seismic refraction survey using a 32 L air gun and a radio telemetering sonobuoy system was carried out in the Strait of Georgia with the objective of investigating the nature of this boundary and determining the upper crustal structure. Three reversed profiles across the strait were shot; these are supplemented by several high-resolution reflection profiles from previous experiments. Two-dimensional models of the crustal structure across the strait have been constructed using a forward modelling ray trace and synthetic seismogram algorithm to match the travel times and amplitude characteristics of the data.Three basic layers or strata form the models, for which the maximum depth of reliability is 3 km. The first layer consists of unconsolidated sediments and Pleistocene glacial deposits, and the second represents Late Cretaceous – early Tertiary basin fill sediments that form the Nanaimo Group, the Burrard–Kitsilano formations, and the Chuckanut Formation. The third layer is likely the extension of the Coast Plutonic Complex beneath the strait, but the westerly limit of this unit is undetermined because of seismic properties similar to those of the Insular Belt volcanics. A local fault is located ~15 km northeast of Galiano Island on the west side of the strait. However, our study shows no evidence for a major fault along the strait. Thus those aspects of tectonic models that require the existence of a major transform or transcurrent fault boundary along the Strait of Georgia. may have to be revised.

Rb/Sr Ages and a profile of initial Sr87/Sr86 ratios for plutonic rocks across the Yukon Crystalline Terrane

1976 ◽  
Vol 13 (2) ◽  
pp. 319-330 ◽  
Author(s):  
P. C. Le Couteur ◽  
D. J. Tempelman-Kluit
Keyword(s):  
Quartz Diorite ◽  
Igneous Rocks ◽  
Slow Cooling ◽  
Precambrian Rocks ◽  
Quartz Monzonite ◽  
Plutonic Complex ◽  
Coast Plutonic Complex ◽  
Plutonic Rocks

Nine Rb/Sr apparent ages are reported for igneous rocks of the Yukon Crystalline Terrane. The oldest age (144 m.y.) is from the Triassic? Klotassin quartz diorite and is thought to be a hybrid age that probably reflects the effects of younger intrusives on rocks at least 190 m.y. old. Five ages of about 100 m.y. presumably reflect the cooling of the Coffee Creek quartz monzonite. K/Ar ages for this event are slightly younger than the Rb/Sr ages, suggesting slow cooling. Rb/Sr ages of 53 and 67 m.y. were obtained for the Ruby Range batholith and an age of 61–67 m.y. for the Nisling Range alaskite. The Rb/Sr ages obtained generally confirm recently determined K/Ar ages. There is a regional decrease in initial Sr87/Sr86 ratios, southwestward across the Yukon Crystalline Terrane. This may mean that Precambrian rocks extend under the Yukon Crystalline Terrane, but are absent under the adjoining Coast Plutonic Complex.

Magnetotelluric soundings, structure, and fluids in the southern Canadian Cordillera

1992 ◽  
Vol 29 (4) ◽  
pp. 609-620 ◽  
Author(s):  
D. Ian Gough ◽  
Jacek A. Majorowicz
Keyword(s):  
Upper Mantle ◽  
Apparent Resistivity ◽  
Fractured Rock ◽  
Effective Porosity ◽  
Fault System ◽  
Western Canada ◽  
Magnetotelluric Soundings ◽  
Plutonic Complex ◽  
Coast Plutonic Complex ◽  
Magnetometer Arrays

The Cordillera of western Canada lies in a region of oceanic and island-arc lithosphere accreted to North America during subductions of the last 200 Ma. Magnetometer arrays have shown the crust of the region to be highly conductive. Magnetotelluric (MT) soundings across the Intermontane and Omineca tectonic belts between 50°N and 54°N reveal structure in terms of electrical resistivity. Pseudosections of phase and apparent resistivity and preliminary resistivity–depth sections are shown for three transects. The resistivity range is from less than one ohm metre to several thousands of ohm metres. In old continental shields, crustal resistivities cover a similar four-decade range transposed up two decades, i.e., 102–106 Ω∙m. We show that the observed resistivities can be produced by water with NaCl and (or) CO2 in solution, at the high temperatures of the Cordilleran crust, in fractured rock of effective porosity 4–5%. The resistivity variations may represent varying fracture densities. By following structures from outcrops we infer that the more resistive rocks are probably granitoid plutons, with low fracture densities. The highly conductive basalts probably have higher fracture densities. Sections and phase maps indicate that granitoid plutons continue from the Coast Plutonic Complex, under a thin layer of basalt, across the southwestern half of the Intermontane Belt. Near the centre of the Intermontane Belt, in line with the Fraser fault system, highly conductive rock continues from the surface at least to midcrustal depths. Resistivities as low as 1 Ω∙m in the uppermost crust under the Cariboo Mountains, in the Omineca Belt, are ascribed to intense fracturing or mineralization. For the southernmost transect, between 50°N and 51°N, a phase pseudosection shows informative resemblances to the sections farther north. Resistivity–depth inversions at seven sites from six-decade MT data give penetration into the upper mantle, but some of these sites may be affected by static shift. All results fit the mantle upflow hypothesis advanced earlier by Gough.

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