The Petrology and Structural Fabric of Some Lower Paleozoic Calcareous Pelites in the Porcupine Creek Anticlinorium near Golden, British Columbia

The Lardeau Group is a heterogeneous assemblage of lower Paleozoic eugeoclinal strata present in the Kootenay Arc in southeastern British Columbia. It is in fault contact with lower Paleozoic miogeoclinal strata for all or some of its length along a structure termed the Lardeau shear zone. The Lardeau Group was deformed prior to mid-Mississippian time, as manifested by layer-parallel faults, folds, and evidence for early greenschist-facies metamorphism. Regional constraints indicate probable Devono-Mississippian timing of orogeny, and possible juxtaposition of the Lardeau Group over miogeoclinal strata along the Lardeau shear zone at this time. Further ductile deformation during the Middle Jurassic Columbian orogeny produced large folds with subhorizontal axes, northwest-striking foliation and faults, and orogen-parallel stretching lineations. This deformation was apparently not everywhere synchronous, and may have continued through Late Jurassic time northeast of Trout Lake. This was followed by Cretaceous(?) dextral strike-slip and normal movement on the Lardeau shear zone and other parallel faults. While apparently the locus of several episodes of faulting, the Lardeau shear zone does not record the accretion of far-travelled tectonic fragments, as sedimentological evidence ties the Lardeau Group and other outboard units to the craton.

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Tectonic implications of 40Ar/39Ar muscovite dates from the Mt. Haley stock and Lussier River stock, near Fort Steele, British Columbia

Canadian Journal of Earth Sciences ◽

10.1139/e06-048 ◽

2006 ◽

Vol 43 (11) ◽

pp. 1673-1684 ◽

Cited By ~ 8

Author(s):

Kyle P Larson ◽

Raymond A Price ◽

Douglas A Archibald

Keyword(s):

British Columbia ◽

Single Crystal ◽

Rocky Mountains ◽

Potassium Feldspar ◽

Canadian Rocky Mountains ◽

The West ◽

Lower Paleozoic ◽

Tectonic Implications ◽

West Limb ◽

Step Heating

The Mt. Haley and Lussier River stocks are located northeast of Cranbrook, B.C. near the south end of the Western Main Ranges of the Southern Canadian Rocky Mountains. Both are multiphase, potassium-feldspar porphyritic monzonite plutons that intrude lower Paleozoic miogeoclinal strata. They crosscut and thermally overprint the Lussier River fault and the thrust and fold structures in the east flank of the Purcell anticlinorium and the west limb of the Porcupine Creek anticlinorial fan structure. Muscovite from the Mt. Haley stock yielded a 40Ar/39Ar plateau age of 108.2 ± 0.7 Ma (2σ), and a single-crystal, step-heating analysis of muscovite from a skarn in the metamorphic aureole adjacent to the Lussier River stock gave a plateau date of 108.7 ± 0.6 Ma (2σ). These dates constrain the timing of thrusting and folding in this portion of the western Rocky Mountains and of the displacement along the Lussier River – St. Mary fault to pre-middle Albian.

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Basin to platform transition, Lower Paleozoic Strata of Ware and Trutch map areas, northeastern British Columbia

10.4095/104850 ◽

1979 ◽

Cited By ~ 1

Author(s):

M P Cecile ◽

B S Norford

Keyword(s):

British Columbia ◽

Lower Paleozoic

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Stratigraphic comparison of the Lardeau and Covada groups: implications for revision of stratigraphic relations in the Kootenay Arc

Canadian Journal of Earth Sciences ◽

10.1139/e92-105 ◽

1992 ◽

Vol 29 (6) ◽

pp. 1320-1329 ◽

Cited By ~ 3

Author(s):

Moira T. Smith ◽

George E. Gehrels

Keyword(s):

British Columbia ◽

Continental Margin ◽

Lower Paleozoic ◽

Pillow Basalt ◽

Structural Order ◽

Late Cambrian ◽

Quartz Arenite ◽

North Eastern ◽

Eastern Washington

The Lardeau Group is a heterogeneous assemblage of lower Paleozoic, outer continental margin strata present in the Kootenay Arc in southeastern British Columbia. From east to west, structurally lowest to highest, and what has been previously interpreted as stratigraphically lowest to highest, it consists of green and grey phyllite, argillite, limestone, and rare pillow flows (Index Formation); siliceous argillite and phyllite (Triune Formation); grey massive quartzite (Ajax Formation); siliceous argillite and phyllite (Sharon Creek Formation); alkalic(?) pillow basalt, breccia, and tuff (Jowett Formation); and quartzo-feldspathic wacke and phyllite (Broadview Formation).We propose a correlation between the Lardeau Group and the Covada Group and Bradeen Hill assemblage, both in north eastern Washington. The latter contain the same stratigraphic elements, in the same structural order, as those of the Lardeau Group. These include, from east to west, black and grey argillite and slate, chert, chert–quartz sandstone, limestone, and rare tuff, pillow flows, and quartz arenite (Bradeen Hill assemblage); alkalic(?) pillow basalt, breccia, tuff, and limestone (Butcher Mountain Formation); and quartzo-feldspathic wacke and slate (Daisy Formation). However, the sense of facing, and hence the stratigraphie sequence in the Covada Group and Bradeen Hill assemblage, is reversed in relation to the Lardeau Group, with the quartzo-feldspathic wacke unit the oldest and slate and argillite the youngest. Because the degree of preservation (and consequently the evidence for facing and age) of the units in northeastern Washington is superior to that of the Lardeau Group, we suggest that (1) the Lardeau Group may be inverted relative to the sequence as originally defined; (2)the Lardeau Group may range from Late Cambrian (Broadview Formation) to Devonian (Index Formation) in age; and (3)further work is warranted to test this hypothesis. This correlation unites lower Paleozoic stratigraphic units along several hundred kilometres of the ancient continental margin.

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Mississippian volcanic assemblage conformably overlying Cordilleran miogeoclinal strata, Turnagain River area, northern British Columbia, is not part of an accreted terrane

Canadian Journal of Earth Sciences ◽

10.1139/e05-045 ◽

2005 ◽

Vol 42 (8) ◽

pp. 1449-1465 ◽

Cited By ~ 1

Author(s):

Philippe Erdmer ◽

Mitchell G Mihalynuk ◽

Hubert Gabrielse ◽

Larry M Heaman ◽

Robert A Creaser

Keyword(s):

British Columbia ◽

Volcanic Rocks ◽

Sedimentary Rocks ◽

Lower Paleozoic ◽

Magmatic Arc ◽

Structural Relationships ◽

Geochemical Study ◽

Tectonic Contact ◽

Back Arc ◽

T Values

A Paleozoic volcanic assemblage exposed in northern British Columbia, near the Turnagain River, previously considered to be part of an accreted terrane, was reported to be in depositional contact with a part of the Cordilleran miogeocline. This paper presents an integrated field, UPb geochronology, SmNd isotopic, and geochemical study across the basal contact of the volcanic assemblage. Strongly evolved εNd(T) values, between 13 and 21, from samples of lower Paleozoic sedimentary rocks exposed below the volcanic rocks, and correlated with Atan Kechika Road River Earn strata of the miogeocline farther east, support a North American miogeoclinal affinity, consistent with previously established regional stratigraphic and structural relationships. Nd isotopic data from the volcanic assemblage contrast significantly with data from the sedimentary rocks and record a mantle source (εNd(T) values between +4.0 and +7.0), consistent with a magmatic arc or back arc; negative Nb anomalies are similarly compatible with either arc- or back-arc-related magmatism. A concordant 339.7 ± 0.6 Ma UPb zircon date was obtained from the volcanic assemblage. The mixed gradational contact between the miogeoclinal and volcanic rocks is marked by interlayering of finely laminated grey and green phyllites on the scale of centimetres, with no evidence of a tectonic contact. Bedding at the contact is folded into tight outcrop-scale folds that are intruded by an Early Jurassic (187.5 ± 2.9 Ma) granodiorite. On the basis of all available evidence, the contact is interpreted as a facies transition. The Mississippian volcanic assemblage may link the miogeocline with the early development of an Angayucham Slide Mountain basin.

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173 Ma U–Pb age of felsite sills (Kaslo River intrusives) west of Kootenay Lake, southeastern British Columbia

Canadian Journal of Earth Sciences ◽

10.1139/e92-046 ◽

1992 ◽

Vol 29 (3) ◽

pp. 531-534 ◽

Cited By ~ 3

Author(s):

Moira T. Smith ◽

George E. Gehrels ◽

David W. Klepacki

Keyword(s):

British Columbia ◽

Second Phase ◽

The West ◽

West Side ◽

Lower Paleozoic ◽

Upper Proterozoic ◽

Third Phase ◽

Phase Deformation ◽

Kootenay Lake ◽

Middle Proterozoic

U–Pb geochronological analyses of five zircon fractions from a lineated and foliated monzonite sill on the west side of Kootenay Lake are discordant and yield a lower intercept age of 173 ± 5 Ma, interpreted as the minimum crystallization age. An upper intercept of 1710 ± 180 Ma is interpreted as the average age of inherited components, and is consistent with contamination by Middle Proterozoic detritus in Upper Proterozoic to lower Paleozoic strata. The sills are interpreted as pre- to syn-kinematic with respect to regional second-phase or possibly third-phase deformation, thus further constraining the timing of Mesozoic orogeny in the Kootenay Arc, and may represent an early, foliated phase of the Nelson Batholith.

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Significance of a Cambrian date from galena lead-isotope data for the stratiform Cottonbelt deposit in the Monashee Complex, southeastern British Columbia

Canadian Journal of Earth Sciences ◽

10.1139/e88-145 ◽

1988 ◽

Vol 25 (9) ◽

pp. 1534-1541 ◽

Cited By ~ 12

Author(s):

T. Höy ◽

C. I. Godwin

Keyword(s):

British Columbia ◽

Isotope Ratio ◽

Lead Isotope ◽

Yukon Territory ◽

Lower Paleozoic ◽

Magnetite Layer ◽

Monashee Complex ◽

Selkirk Mountains ◽

Lead Zinc ◽

Isotope Analyses

The Cottonbelt deposit is a large stratiform lead–zinc–magnetite layer within cover rocks of Frenchman Cap dome in the Monashee Complex in southeastern British Columbia. Lead-isotope analyses of galena samples from the deposit plot close to the Cambrian–Hadrynian boundary on lead-isotope ratio diagrams and are similar to analyses of Early Cambrian stratiform deposits in the Anvil Camp in the Yukon Territory. These data suggest that the Cottonbelt deposit and host succession are Cambrian in age, in contrast to other interpretations that suggest considerably older ages for the cover succession of Frenchman Cap dome. These cover rocks, therefore, are considered calcareous and pelitic facies of lower Paleozoic shelf rocks now exposed in the Kootenay Arc to the southeast and the Selkirk Mountains to the east.

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