Geochemistry, geochronology, and tectonic implications of two quartz monzonite intrusions, Purcell Mountains, southeastern British Columbia

1988 ◽  
Vol 25 (1) ◽  
pp. 106-115 ◽  
Author(s):  
Trygve Höy ◽  
P. van der Heyden
Keyword(s):  
British Columbia ◽  
Rocky Mountains ◽  
Tectonic Evolution ◽  
Rocky Mountain ◽  
Normal Fault ◽  
Thrust Faults ◽  
Quartz Monzonite ◽  
Reverse Thrust ◽  
Early Late ◽  
Middle Proterozoic

The Reade Lake and Kiakho stocks are posttectonic mesozonal quartz monzonite porphyries that intrude dominantly Middle Proterozoic Purcell Supergroup rocks in southeastern British Columbia. K–Ar dates of hornblende from the Reade Lake stock range from 103 to 143 Ma. However, a U–Pb date of 94 Ma from zircon concentrates is interpreted to be the age of emplacement of the stock, suggesting the range and older K–Ar dates are due to excess 40Ar. A K–Ar date of 122 Ma for the hornblende from the Kiakho stock is believed to be a more reliable intrusive age.Both stocks cut across and apparently seal two faults that have played roles in the tectonic evolution of the Purcell anticlinorium and Rocky Mountain thrust belt. The Reade Lake stock cuts the St. Mary fault, an east-trending reverse thrust that crosses the Rocky Mountain trench and links with thrusts in the Rocky Mountains; the Kiakho stock cuts the Cranbrook fault, an older east-trending normal fault. Hence, the 94 Ma date on the Reade Lake stock constrains the latest movement on the St. Mary fault to early Late Cretaceous; and the 122 Ma date on the Kiakho stock appears to limit latest movement on the Cranbrook fault to Early Cretaceous. These faults and the intrusions are part of an allochthonous package, displaced eastward by underlying thrust faults during formation of the Purcell anticlinorium and more eastern thrusts in the Rocky Mountains.

A structural interpretation across part of the northern Rocky Mountains, British Columbia, Canada

1979 ◽  
Vol 16 (6) ◽  
pp. 1228-1241 ◽  
Author(s):  
Robert I. Thompson
Keyword(s):  
British Columbia ◽  
Rocky Mountains ◽  
Lateral Displacement ◽  
Rocky Mountain ◽  
Thrust Faults ◽  
Northern Rocky Mountains ◽  
Eastern Margin ◽  
The North ◽  
Structural Style ◽  
Mountain Front

The northern Canadian Rocky Mountains, as exemplified by the Halfway River map-area (94B) in British Columbia, consists of a rugged and mountainous structurally complex Foothills subprovince of large amplitude box and chevron-style folds in rocks of late Paleozoic and Mesozoic age, and a structurally diverse Rocky Mountain subprovince with open folds and apparently inconspicuous thrust faults in upper Precambrian to upper Paleozoic rocks; separating them is a narrow topographically subdued and heavily vegetated 'transition interval' comprising more penetratively folded and faulted shales and thin-bedded carbonate rocks of late Devonian and Mississippian age.Flat thrust faults, with displacements in the order of 10 km, which occur under the eastern margin of the Rocky Mountain subprovince (mountain front) extend across the 'transition interval' and beneath the western margin of the Foothills subprovince. These faults terminate within a décollement along the Devonian and Mississippian Besa River shale, as the displacement on them is transformed into disharmonic kink-type box and chevron folds in overlying units and into tectonic thickening within the Besa River shale. Because most of the major thrust faults along the Rocky Mountains are 'blind' and cannot be traced to surface exposures, one is left with the erroneous impression that very little lateral displacement (foreshortening) has occurred in the northern Canadian Rocky Mountains.The basic change from a well organized thrust-fault terrane in the southern Rockies to a more diverse fold terrane with few large mappable thrusts in the north is consistent with changes in the stratigraphic character of the rock prism that was deformed: the proportion of thick incompetent shale units increases northward, and major lateral carbonate to shale facies transitions traverse the eastern margin of the Rocky Mountain subprovince.Despite the differences in structural style from south to north, strain patterns within the northern Rocky Mountains are consistent with the lateral eastward movement of a detached prism of sedimentary rocks, and support the basic tenets of thin-skinned tectonics.

THE ATHABASCA VALLEY ERRATICS TRAIN, ALBERTA AND PLEISTOCENE ICE MOVEMENTS ACROSS THE CONTINENTAL DIVIDE

1967 ◽  
Vol 4 (4) ◽  
pp. 625-632 ◽  
Author(s):  
M. A. Roed ◽  
E. W. Mountjoy ◽  
N. W. Rutter
Keyword(s):  
British Columbia ◽  
Rocky Mountains ◽  
Late Stage ◽  
National Park ◽  
Rocky Mountain ◽  
Metamorphic Rocks ◽  
Jasper National Park ◽  
Continental Divide ◽  
Park Area

The Athabasca Valley Erratics Train contains a variety of low- to medium- grade metamorphic rocks, the most abundant of which is talcose schist, with lesser amounts of garnet schist and biotite–quartz schist. This erratics train occurs in and west of the Athabasca Valley west of Edson, Alberta. It is probably a late stage deposit of the same glacier that carried and deposited the Erratics Train, Foothills of Alberta. The metamorphic erratics were incorporated into a glacier that originated in the northern part of the Monashee Mountains and Premier Range of British Columbia. This ice movement is also recorded by numerous U-shaped valleys, which extend across the Continental Divide. Thus, during a brief period in late(?) Wisconsin time, the Cordilleran ice in the Rocky Mountains of the Jasper National Park area was partly derived from west of the Continental Divide and the Rocky Mountain Trench. These data agree with the inferred ice movements shown on the 1958 Glacial Map of Canada.

Geology, Paleoecology, and Palynology of some Oligocene Rocks in the Rocky Mountain Trench of British Columbia

1972 ◽  
Vol 9 (4) ◽  
pp. 460-470 ◽  
Author(s):  
W. S. Hopkins Jr. ◽  
N. W. Rutter ◽  
G. E. Rouse
Keyword(s):  
British Columbia ◽  
Rocky Mountains ◽  
Sedimentary Rocks ◽  
Rocky Mountain ◽  
Early Oligocene ◽  
Pollen Content

Mildly deformed sedimentary rocks of the Northern Rocky Mountain Trench were analyzed for their spore and pollen content. From these it was deduced that the rocks were of Early Oligocene (Chadronian) age. Two conclusions were reached: (1) at least mild deformation occurred in this portion of the Trench following the Early Oligocene and (2) Early Oligocene climate appears to have been essentially subtropical of a summer-wet, winter-dry type. These add further evidence to the theory that the Rocky Mountains were already of considerable elevation by Early Oligocene time.

Age and origin of Late Jurassic and Paleocene granitoids, Nelson Batholith, southern British Columbia

1993 ◽  
Vol 30 (12) ◽  
pp. 2305-2314 ◽  
Author(s):  
J. H. Sevigny ◽  
R. R. Parrish
Keyword(s):  
British Columbia ◽  
Rare Earth ◽  
Rare Earth Elements ◽  
Middle Jurassic ◽  
Late Jurassic ◽  
Alkaline Earth ◽  
Biotite Granite ◽  
Isotopic Data ◽  
Quartz Monzonite ◽  
Early Late

In the Middle Jurassic Nelson Batholith, southern British Columbia, young 40Ar/39Ar ages (i.e., 50–60 Ma) and distorted isobaric surfaces in the batholith suggest the possibility of Paleocene granitic plutonism. We present the results of a study undertaken to evaluate this possibility. Geochemical criteria successfully distinguish a suite of granitoids within the Nelson Batholith that differ from Nelson granites of similar SiO2 content. The granitoid suite is composed of 71.6–75.7 wt.% SiO2 leucocratic biotite granite and quartz monzonite with strong enrichments in alkaline, alkaline earth, and rare earth elements. Nd and Pb isotopic compositions suggest that biotite granite and quartz monzonite are not related. Biotite granite yields a U–Pb age of 158.9 ± 0.6 Ma (concordant zircons). Quartz monzonite crystallized at 61 ± 1 Ma, based on interpretation of titanite and zircon analyses. Zircons from this sample lie along a line from 61 to 160 Ma and demonstrate the presence of Middle Jurassic inheritance. Based on its petrographic and isotopic similarity to other Middle Jurassic plutons in the Nelson Batholith – Valhalla Complex area, we include the 159 Ma biotite granite with the Jurassic plutonic suite. This result demonstrates that magmatism in southern British Columbia was active at least until the early Late Jurassic (Oxfordian). The Paleocene (61 Ma) quartz monzonite that intrudes the southern Nelson Batholith is the structurally highest occurrence of "Ladybird" granite yet documented in southern British Columbia. Comparison of new and published geochemical and isotopic data for Paleocene granitoids throughout the southern Omineca Belt, British Columbia, suggests that these granitoids were not derived from a single, old crustal source.

Superimposed low-grade metamorphism in the Mount Fisher area, southeastern British Columbia—implications for the East Kootenay orogeny

1982 ◽  
Vol 19 (3) ◽  
pp. 476-489 ◽  
Author(s):  
M. E. McMechan ◽  
R. A. Price
Keyword(s):  
British Columbia ◽  
Late Cretaceous ◽  
Rocky Mountains ◽  
Regional Metamorphism ◽  
Low Grade ◽  
Canadian Cordillera ◽  
Windermere Supergroup ◽  
Granitic Intrusion ◽  
Block Faulting ◽  
Middle Proterozoic

Middle Proterozoic (~1500–1350 Ma) Belt–Purcell strata exposed in the Purcell and southwestern Rocky Mountains were affected by at least three distinct episodes of deformation and regional metamorphism. The oldest episode (1300–1350 Ma) apparently terminated Belt–Purcell sedimentation and involved folding, regional metamorphism, and granitic intrusion. The second episode (800–900 Ma) occurred during deposition of the Windermere Supergroup and involved uplift, block faulting, and low-grade regional metamorphism. Mesozoic–Cenozoic metamorphism, deformation, and plutonism overprinted the results of the earlier deformation and metamorphism.Illite crystallinity and muscovite polymorph ratios indicate that Purcell strata in the Mount Fisher area are in the lower green-schist to prehnite–pumpellyite facies of regional metamorphism. In the Steeples and Fisher blocks this metamorphism is related to structures that formed during the Late Cretaceous – Paleocene deformation. However, in the Sand Creek block the regional metamorphism is related to the development of a spaced cleavage that is folded by a Late Cretaceous – Paleocene nappe. Regional considerations suggest that this cleavage formed during the 1300–1350 Ma episode of deformation and metamorphism.The "East Kootenay orogeny" as currently defined embraces the two older episodes of tectonism. It is proposed that the term East Kootenay orogeny be restricted to designate the 1300–1350 Ma episode and that the term "Goat River orogeny" designate the 800–900 Ma episode of tectonism. The East Kootenay and Goat River orogenies appear to be correlative with the Racklan and Hayhook orogenies recognized in the northern Canadian Cordillera.

Imbricated terranes of the Cariboo gold belt with correlations and implications for tectonics in southeastern British Columbia

1986 ◽  
Vol 23 (8) ◽  
pp. 1047-1061 ◽  
Author(s):  
L. C. Struik
Keyword(s):  
British Columbia ◽  
Continental Shelf ◽  
Rocky Mountains ◽  
Rocky Mountain ◽  
East Central ◽  
Pillow Basalt ◽  
Shelf Sediments ◽  
Kootenay Lake ◽  
Southern Rocky Mountain ◽  
Bounded Sequences

The Cariboo gold belt of east-central British Columbia is divided into four fault-bounded sequences of distinct stratigraphy. They are, from east to west, the Cariboo (continental-shelf sediments), Barkerville (continental-shelf sediments and intercalated volcanics), Slide Mountain (rift-related submarine pillow basalt, chert, and diorite) and Quesnel (island-arc sediments and subaqueous volcanics) terranes. Each is separated from others by thrust faults. Grit, phyllite, limestone, and volcanics of the Barkerville terrane may be correlative with the Eagle Bay Formation near Adams Lake and the Lardeau Group near Kootenay Lake. Barkerville terrane may be part of a more regional rock package, Selkirk terrane, which is defined to include Kootenay terrane, Badshot Formation, and Horsethief Creek and Hamill groups. Selkirk terrane is (i) separated everywhere by a low-angle fault from the overlying age-equivalent but stratigraphically and structurally different Cariboo terrane and (ii) separated by a system of faults in the general location of the Southern Rocky Mountain Trench from the age-equivalent but stratigraphically and structurally different North American terrane of the Rocky Mountains.

Metamorphism in the Solitude Range, southwestern Rocky Mountains, British Columbia: comparison with adjacent Omineca Belt rocks and tectonometamorphic implications for the Purcell Thrust

1990 ◽  
Vol 27 (11) ◽  
pp. 1511-1520 ◽  
Author(s):  
L. P. Gal ◽  
E. D. Ghent
Keyword(s):  
British Columbia ◽  
Rocky Mountains ◽  
Rocky Mountain ◽  
Metamorphic Grade ◽  
Normal Faulting ◽  
Physical Conditions ◽  
Big Bend

Rocks of the Solitude Range, British Columbia, have been metamorphosed from chloritoid–chorite-zone to kyanite-zone conditions. The grade of metamorphism increases southwestward toward the Rocky Mountain Trench (RMT) and the Omineca Belt. Isograds crosscut lithologies and trend more northerly than deformation 2 (D2) structures and the RMT. They are thought to have been quenched syn- to post-D2. Pelitic (Mahto Formation) and calc-pelitic (Tsar Creek unit) rocks contain assemblages that reflect the increase in metamorphic grade. Physical conditions of metamorphism are estimated to be approximately 450–540 °C from the garnet to the kyanite zone; pressures averaged 6–7 kbar (1 kbar = 100 MPa). The pressures, temperatures, and metamorphic assemblages are very similar to those of the Adamant Range, which lies across the Purcell Thrust, to the southwest. This is in contrast with the Big Bend area, to the northwest, where differences in pressure across the Purcell Thrust (PT) have been documented. Two possible models to explain these contrasting relationships are presented. One model suggests that there was post-movement heating on the PT, which reduced the metamorphic contrast across the PT. The second model suggests that a combination of thrust and normal faulting, including warping of isobaric surfaces, has produced an apparently unbroken metamorphic sequence across the PT.

Reconnaissance of rockslide hazards in Kananaskis Country, Alberta

1987 ◽  
Vol 24 (3) ◽  
pp. 414-429 ◽  
Author(s):  
D. M. Cruden ◽  
T. M. Eaton
Keyword(s):  
Key Words ◽  
Rocky Mountains ◽  
Sedimentary Rock ◽  
Rocky Mountain ◽  
Friction Angle ◽  
Thrust Faults ◽  
Rock Masses ◽  
Canadian Rockies ◽  
Basic Friction Angle ◽  
New Facilities

Kananaskis Country is situated in the Front Ranges of the Canadian Rockies in southwestern Alberta. Sedimentary rock thrust northeastwards forms mountain ridges that trend northwest–southeast parallel to the major thrust faults. Older, Palaeozoic rocks—mainly limestone and dolomite—form the ridges and peaks. Younger, Mesozoic rocks—sandstones, quartzites, siltstones, shales, conglomerates, and coals—are more easily eroded and form mountain passes and valleys.A reconnaissance mapped 228 rockslides, 8 km2 of rockslide debris and 96 km2 of talus. The largest rockslide exceeds 50 × 106 m3. Rockslides are most probable in the Devonian Palliser Formation, then in the Permo-Pennsylvanian Rocky Mountain Group, Mississippian Rundle Group, Devonian Fairholme Group, Mississippian Banff Formation, and the younger detrital rocks. Rockslides are most probable on dip and overdip slopes, followed by reverse-dip slopes, oblique and strike-dip slopes, and underdip slopes. Large rock masses have not slid on slopes below their basic friction angle, [Formula: see text]The reconnaissance shows that certain facilities in valleys below steep mountain slopes are exposed to rockslide hazards, and provides a guide for the location of new facilities. Analyses of two mountain slopes show that there are large, hypothetical hazards in Kananaskis. Rockslides are likely and could be destructive. Key words: Front Ranges, Rocky Mountains, Alberta, rockslides, hazards.

LITHOPROBE seismic reflection imaging of Rocky Mountain structures east of Canal Flats, British Columbia

1988 ◽  
Vol 25 (9) ◽  
pp. 1339-1348 ◽  
Author(s):  
David W. S. Eaton ◽  
Frederick A. Cook
Keyword(s):  
British Columbia ◽  
Seismic Data ◽  
Seismic Reflection ◽  
Rocky Mountain ◽  
Normal Fault ◽  
Seismic Reflection Data ◽  
Middle Cambrian ◽  
Reflection Data ◽  
Processing Techniques ◽  
Surface Geology

LITHROPROBE seismic reflection data, coupled with information from industry seismic data and surface geology, image the thin-skinned structures of the western Rocky Mountains from the Main Ranges to the Rocky Mountain Trench near Canal Flats, British Columbia. Reprocessing of the LITHOPROBE seismic reflection line was conducted to improve resolution of upper-crustal features. Careful application of "conventional" processing techniques significantly improved the coherence of reflections from the first 6 s. A spatial semblance filter was applied to further enhance coherent signal, and residual-statics corrections were applied by cross correlation of unstacked data with semblance-filtered pilot traces.A near-basement reflection zone arising from Middle Cambrian strata is visible on an industry reflection profile at an approximate depth of 8 km beneath the Main Ranges. A similar reflection zone is imaged on the LITHOPROBE data at a depth of 11 km bsl but is interpreted as arising from Proterozoic strata. The autochthonous crystalline basement is interpreted as being below these layers and dipping about 2 °to the west. Geometric evidence is visible for several major thrust ramps involving the basal décollement and for an intermediate-level décollement that loses displacement into folds within the Porcupine Creek Anticlinorium. Reflections related to the Gypsum fault, the Redwall thrust, and the Lussier River normal fault are also imaged.

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