The petrology of the Rossland volcanic rocks, southern British Columbia

A suite of hy-normative hawaiites, ne-normative mugearite, and calc-alkaline andesitic rocks from the Garibaldi Lake area exhibits fractionated, slightly concave-upward REE patterns (CeN/YbN = 4.5–15), heavy REE contents about 5–10 times the chondritic abundances, and no Eu anomalies. It is unlikely that the REE patterns provide information concerning partial melting conditions beneath southwestern British Columbia because they have probably been modified substantially by upper crustal processes including crustal contamination and (or) crystal fractionation. The REE contents of the Garibaldi Lake lavas are not incompatible with previous interpretations that (1) the hawaiites have undergone considerable fractionation of olivine, plagioclase, and clinopyroxene; and (2) the individual andesitic suites were derived from separate batches of chemically distinct magma that evolved along different high-level crystallization trends. In general, however, the andesites are characterized by lower light REE contents than the basaltic andesites. These differences in LREE abundances may reflect different amounts of LREE-rich accessory phases, such as apatite, sphene, or allanite, assimilated from the underlying quartz diorites.

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Nd isotopic characteristics of metamorphic and plutonic rocks of the Coast Mountains near Prince Rupert, British Columbia

Canadian Journal of Earth Sciences ◽

10.1139/e98-007 ◽

1998 ◽

Vol 35 (5) ◽

pp. 556-561 ◽

Cited By ~ 13

Author(s):

P J Patchett ◽

G E Gehrels ◽

C E Isachsen

Keyword(s):

British Columbia ◽

Volcanic Rocks ◽

Metamorphic Rocks ◽

Published Data ◽

Isotopic Data ◽

Crustal Component ◽

Coast Mountains ◽

Crustal Rocks ◽

Metasedimentary Rocks ◽

Plutonic Rocks

Nd isotopic data are presented for a suite of metamorphic and plutonic rocks from a traverse across the Coast Mountains between Terrace and Prince Rupert, British Columbia, and for three contrasting batholiths in the Omineca Belt of southern Yukon. A presumed metamorphic equivalent of Jurassic volcanic rocks of the Stikine terrane gives epsilon Nd = +6, and a number of other metaigneous and metasedimentary rocks in the core of the Coast Mountains give epsilon Nd values from +3 to +7. A single metasedimentary rock approximately 3 km east of the Work Channel shear zone gives a epsilon Nd value of -9. Coast Belt plutons in the traverse yield epsilon Nd from -1 to +2. The Omineca Belt plutons give epsilon Nd from -10 to -17. All results are consistent with published data in demonstrating that (i) juvenile origins for both igneous and metamorphic rocks are common in the Coast Belt; (ii) representatives of a continental-margin sedimentary sequence with Precambrian crustal Nd are tectonically interleaved in the Coast Mountains; (iii) Coast Mountains plutons can be interpreted as derived from a blend of metamorphic rocks like those seen at the surface, or as arc-type melts contaminated with the older crustal component; and (iv) Omineca Belt plutons are dominated by remelted Precambrian crustal rocks.

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Origin of the Tulameen ultramafic-gabbro complex, southern British Columbia

Canadian Journal of Earth Sciences ◽

10.1139/e69-040 ◽

1969 ◽

Vol 6 (3) ◽

pp. 399-425 ◽

Cited By ~ 28

Author(s):

D. C. Findlay

Keyword(s):

British Columbia ◽

Internal Structure ◽

Fractional Crystallization ◽

Volcanic Rocks ◽

Age Determination ◽

Upper Triassic ◽

Ultramafic Rocks ◽

Metasedimentary Rocks ◽

Gabbroic Intrusion

The Tulameen Complex is a composite ultramafic-gabbroic intrusion that outcrops over 22 sq. mi. (57 km2) in the Southern Cordillera of British Columbia. The complex intruded Upper Triassic metavolcanic and metasedimentary rocks of the Nicola Group, and on the basis of geologic relations and a K–Ar age determination (186 m.y.) is tentatively dated as Late Triassic.The principal ultramafic units — dunite, olivine clinopyroxenite, and hornblende clinopyroxenite — form an elongate, non-stratiform body whose irregular internal structure is best explained by deformation contemporaneous with crystallization of the rocks. The derivation of the ultramafic rocks is attributed to fractional crystallization of an ultrabasic magma. The gabbroic mass, which consists of syenogabbro and syenodiorite, partly borders and partly overlies the ultramafic body and was apparently intruded by it.The ultramafic and gabbroic parts of the complex probably formed from separate intrusions of different magmas, but the two suites have sufficient mineralogical and chemical features in common to indicate an ultimate petrogenic affinity of the magmas. Comparison of the Tulameen rocks with nearby intrusions of the same general age, in particular the Copper Mountain stock, suggests that they are members of a regional suite of alkalic intrusions. The possibility is also raised that these intrusions may be comagmatic with the Nicola volcanic rocks.

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VII.—Mesozoic Volcanic Rocks of British Columbia and Chile. Relation of Volcanic and Metamorphic Rocks

Geological Magazine ◽

10.1017/s0016756800149441 ◽

1877 ◽

Vol 4 (7) ◽

pp. 314-317

Author(s):

George M. Dawson

Keyword(s):

British Columbia ◽

South America ◽

Volcanic Rocks ◽

Geological Survey ◽

Metamorphic Rocks ◽

Coast Range ◽

Similar Relation

In Chile and adjacent regions of South America, Mr. Darwin, in his “Geological Observations,” has described a great series of Mesozoic rocks, which he calls the “porphyritic formation,” and which shows an interesting resemblance to certain rocks in British Columbia. These I had provisionally designated in my report in connexion with the Geological Survey of Canada for 1875, as the Porphyrite series, without at the time remembering Mr. Darwin's name for the Chilian rocks. Many of Mr. Darwin's descriptions of the rocks of Chile would apply word for word to those of British Columbia, where the formation would also appear to bear a somewhat similar relation to the Cascade or Coast Range, which that of Chile does to the Cordillera.

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Stratigraphy of Mesozoic Volcanic Rocks, northwestern British Columbia

10.4095/105514 ◽

1971 ◽

Author(s):

J G Souther

Keyword(s):

British Columbia ◽

Volcanic Rocks

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Crustal velocity structure of the southern Nechako basin, British Columbia, from wide-angle seismic traveltime inversion1This article is one of a series of papers published in this Special Issue on the theme of New insights in Cordilleran Intermontane geoscience: reducing exploration risk in the mountain pine beetle-affected area, British Columbia.

Canadian Journal of Earth Sciences ◽

10.1139/e11-006 ◽

2011 ◽

Vol 48 (6) ◽

pp. 1050-1063 ◽

Cited By ~ 6

Author(s):

A.L. Stephenson ◽

G.D. Spence ◽

K. Wang ◽

J.A. Hole ◽

K.C. Miller ◽

...

Keyword(s):

British Columbia ◽

Mountain Pine Beetle ◽

Velocity Structure ◽

Volcanic Rocks ◽

Sedimentary Rocks ◽

Velocity Model ◽

Seismic Profile ◽

Wide Angle ◽

Seismic Velocities ◽

Coast Mountains

In the BATHOLITHSonland seismic project, a refraction – wide-angle reflection survey was shot in 2009 across the Coast Mountains and Interior Plateau of central British Columbia. Part of the seismic profile crossed the Nechako Basin, a Jurassic–Cretaceous basin with potential for hydrocarbons within sedimentary strata that underlies widespread volcanic rocks. Along this 205 km-long line segment, eight large explosive shots were fired into 980 seismometers. Forward and inverse modelling of the traveltime data were conducted with two independent methods: ray-tracing based modelling of first and secondary arrivals, and a higher resolution wavefront-based first-arrival seismic tomography. Material with velocities less than 5.0 km/s is interpreted as sedimentary rocks of the Nechako Basin, while velocities from 5.0–6.0 km/s may correspond to interlayered sedimentary and volcanic rocks. The greatest thickness of sedimentary rocks in the basin is found in the central 110 km of the profile. Two sub-basins were identified in this region, with widths of 20–50 km and maximum sedimentary depths of 2.5 and 3.3 km. Such features are well-defined in the velocity model, since resolution tests indicate that features with widths greater than ∼13 km are reliable. Beneath the sedimentary rocks, seismic velocities increase more slowly with depth — from 6.0 km/s just below the basin to 6.3 km/s at ∼17 km in depth, and then to 6.8–7.0 km/s at the base of the crust. The Moho is found at a depth of 33.5–35 km beneath the profile, and mantle velocities are high at 8.05–8.10 km/s.

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Geochemistry, geochronology, and fluid inclusion study of the Late Cretaceous Newton epithermal gold deposit, British Columbia

Canadian Journal of Earth Sciences ◽

10.1139/cjes-2015-0068 ◽

2016 ◽

Vol 53 (1) ◽

pp. 10-33 ◽

Cited By ~ 7

Author(s):

Lijuan Liu ◽

Jeremy P. Richards ◽

S. Andrew DuFrane ◽

Mark Rebagliati

Keyword(s):

British Columbia ◽

Gold Deposit ◽

Late Cretaceous ◽

Gold Mineralization ◽

Volcanic Rocks ◽

Fluid Inclusion Study ◽

Epithermal Gold ◽

Epithermal Gold Deposit ◽

Felsic Volcanic ◽

Felsic Volcanic Rocks

Newton is an intermediate-sulfidation epithermal gold deposit related to Late Cretaceous continental-arc magmatism in south-central British Columbia. Disseminated gold mineralization occurs in quartz–sericite-altered Late Cretaceous felsic volcanic rocks, and feldspar–quartz–hornblende porphyry and quartz–feldspar porphyry intrusions. The mineralization can be divided into three stages: (1) disseminated pyrite with microscopic gold inclusions, and sparse quartz–pyrite ± molybdenite veins; (2) disseminated marcasite with microscopic gold inclusions and minor base-metal sulfides; and (3) polymetallic veins of pyrite–chalcopyrite–sphalerite–arsenopyrite. Re–Os dating of molybdenite from a stage 1 vein yielded an age of 72.1 ± 0.3 Ma (published by McClenaghan in 2013). The age of the host rocks has been constrained by U–Pb dating of zircon: Late Cretaceous felsic volcanic rocks, 72.1 ± 0.6 Ma (Amarc Resources Ltd., unpublished data, reported by McClenaghan in 2013); feldspar–quartz–hornblende porphyry, 72.1 ± 0.5 Ma; quartz–feldspar porphyry, 70.9 ± 0.5 Ma (Amarc Resources Ltd., unpublished data, reported by McClenaghan in 2013). The mineralized rocks are intruded by a barren diorite, with an age of 69.3 ± 0.4 Ma. Fluid inclusions in quartz–pyrite ± molybdenite ± gold veins yielded an average homogenization temperature of 313 ± 51 °C (number of samples, n = 82) and salinity of 4.8 ± 0.9 wt.% NaCl equiv. (n = 46), suggesting that a relatively hot and saline fluid likely of magmatic origin was responsible for the first stage of mineralization. Some evidence for boiling was also observed in the veins. However, the bulk of the gold mineralization occurs as disseminations in the wall rocks, suggesting that wall-rock reactions were the main control on ore deposition.

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A Paleozoic Zircon Age of the Westcoast Crystalline Complex of Vancouver Island, British Columbia

Canadian Journal of Earth Sciences ◽

10.1139/e74-169 ◽

1974 ◽

Vol 11 (12) ◽

pp. 1717-1722 ◽

Cited By ~ 4

Author(s):

J. E. Muller ◽

R. K. Wanless ◽

W. D. Loveridge

Keyword(s):

British Columbia ◽

Volcanic Rocks ◽

Vancouver Island ◽

Late Paleozoic ◽

Basement Complex ◽

Crystalline Complex ◽

Zircon Age ◽

Isotopic Evidence

Zircons from the Westcoast Crystalline Complex near Tofino, Vancouver Island, have yielded the following ages: 206Pb/238U = 265 ± 7 m.y.; 207Pb/235U = 263 ± 7 m.y.; and 206Pb/207Pb = 244 ± 20 m.y. A K–Ar date of an amphibolized dike from the same outcrop yielded 192 ± 9 m.y. This is the first supporting isotopic evidence that the 'basement' complex is derived from late Paleozoic Sicker volcanic rocks and was ultimately migmatized during the major Jurassic plutonic event of Vancouver Island.

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