Precambrian Zircon Age of Orthogneiss in the Shuswap Metamorphic Complex, British Columbia

1975 ◽  
Vol 12 (2) ◽  
pp. 326-332 ◽  
Author(s):  
R. K. Wanless ◽  
J. E. Reesor
Keyword(s):  
British Columbia ◽  
Metamorphic Complex ◽  
Gneiss Dome ◽  
Zircon Age ◽  
Core Zone ◽  
The Core ◽  
Basement Rocks ◽  
Proterozoic Basement ◽  
Shuswap Metamorphic Complex ◽  
Age Determinations

Pb-U age determinations carried out on zircon from granodiorite gneiss of the core zone of Thor-Odin gneiss dome have provided isotopic evidence for involvement of Proterozoic basement rocks in the Mesozoic structures of the Shuswap Metamorphic Complex. The study has revealed that the zircons originally crystallized [Formula: see text] ago and suffered an episodic loss of lead [Formula: see text] ago.

Geology of the Clachnacudainn Salient Near Albert Canyon, British Columbia

1972 ◽  
Vol 9 (11) ◽  
pp. 1447-1454 ◽  
Author(s):  
Richard A. Gilman
Keyword(s):  
British Columbia ◽  
Quartz Diorite ◽  
Metamorphic Complex ◽  
White Marble ◽  
Metasedimentary Rocks ◽  
The Core ◽  
Systematic Pattern ◽  
Selkirk Mountains ◽  
Shuswap Metamorphic Complex

The nature of the Clachnacudainn Salient of the Shuswap Metamorphic Complex has been investigated in the vicinity of Albert Canyon, British Columbia. A concordant, folded sheet of granodiorite to quartz–diorite gneiss lying between two contrasting panels of metasedimentary rocks is exposed along the Illecillewaet Valley between Albert Canyon and Revelstoke. The lower panel, consisting predominantly of quartzo–feldspathic schist, is exposed in the Woolsey Creek Window in the core of the Lauretta Dome, and in an adjacent antiform at Clachnacudainn Creek. The upper panel, comprised in part of quartzo–feldspathic schist and migmatite, contains, in addition, thick beds of white marble and white or light gray quartzite. Marble and quartzite of the upper panel are correlated with the Badshot limestone and the Hamill quartzite found east of Albert Canyon in the Selkirk Mountains. Within the granodiorite gneiss, axes of broad open folds trend northwest–southeast as do the mineral lineations. Folding within the metasediments is complex and has not been resolved into a systematic pattern. Crosscutting bodies of diorite, granite, and pegmatite are abundant in many parts of the area, cutting both the granodiorite gneiss and the metasedimentary rocks.

Gneissic Alkalic Rocks and Carbonatites in the Frenchman's Cap Gneiss Dome, Shuswap Complex, British Columbia

1974 ◽  
Vol 11 (2) ◽  
pp. 304-318 ◽  
Author(s):  
W. J. McMillan ◽  
J. M. Moore Jr.
Keyword(s):  
Regional Metamorphism ◽  
Lava Flows ◽  
High Grade ◽  
Metamorphic Complex ◽  
Sedimentary Deposits ◽  
Gneiss Domes ◽  
The Core ◽  
Igneous Origin ◽  
Eastern Border ◽  
Shuswap Metamorphic Complex

Frenchman's Cap dome is one of a series of gneiss domes along the eastern border of the high-grade Shuswap metamorphic complex. The granitic gneisses which compose the core of the dome are enclosed in an envelope of metasedimentary rocks.Before Shuswap metamorphism and deformation, the rocks of the sedimentary envelope were intruded by concordant bodies of alkalic rocks and carbonatite. Other carbonatite bodies appear to have formed at or extruded onto the surface. It is not certain whether these are exhalative sedimentary deposits, lava flows, or pyroclastic deposits.Criteria which can be used to distinguish igneous alkalic rocks from those of metasomatic origin were almost entirely destroyed by regional metamorphism. A few relict igneous textures show that at least some of the alkalic gneisses are of igneous origin.

Devonian Plutonism in South-Central British Columbia

1975 ◽  
Vol 12 (10) ◽  
pp. 1760-1769 ◽  
Author(s):  
Andrew V. Okulitch ◽  
R. K. Wanless ◽  
W. D. Loveridge
Keyword(s):  
British Columbia ◽  
Middle Devonian ◽  
Metamorphic Complex ◽  
Western Margin ◽  
South Central ◽  
Minimum Age ◽  
History Of ◽  
Shuswap Metamorphic Complex

An apparently tabular body of granitoid gneiss, 3 to 5 km wide and more than 70 km long, that lies along the western margin of the Shuswap Metamorphic Complex between Shuswap and Admas Lakes, shows intrusive relationships with Palaeozoic and older rocks and has yielded zircons whose minimum age is 372 Ma. This intrusion, together with other granitoid plutons in the area that appear to be related to it, provide evidence of widespread plutonism during Middle Devonian time near the western edge of the Paleozoic Cordillera geosyncline and necessitate significant revisions in the interpretation of the crustal history of this region.

Geology of the Matthew Creek metamorphic zone, southeast British Columbia: a window into Middle Proterozoic metamorphism in the Purcell Basin

2000 ◽  
Vol 37 (7) ◽  
pp. 1073-1092 ◽  
Author(s):  
C RM McFarlane ◽  
D RM Pattison
Keyword(s):  
British Columbia ◽  
Transition Zone ◽  
Ductile Deformation ◽  
Low Grade ◽  
Core Zone ◽  
The Core ◽  
Pelitic Schist ◽  
Metamorphic Zone ◽  
Structural Dome ◽  
Middle Proterozoic

Southwest of Kimberley, southeastern British Columbia, the Matthew Creek metamorphic zone occupies the core of a structural dome in Mesoproterozoic rocks of the Lower Aldridge formation (lower Purcell Supergroup). It comprises (1) a core zone of ductilely deformed sillimanite-grade metapelites, thin foliated mafic sills, and sheared quartz-plagioclase-tourmaline pegmatites; and (2) a thin transition zone of ductilely deformed metasediments which marks a textural and metamorphic transition between the core zone and overlying regionally extensive, brittlely deformed, biotite-grade semipelitic Lower Aldridge formation metasediments and thick Moyie sills. The core zone and transition zone in combination cover an area of 30 km2. The deepest exposed rocks in the core zone have a strong foliation and lineation (D1 deformation) formed during late M1 metamorphism at conditions of 580–650°C and 3.5 ± 0.5 kbar. The timing of this metamorphic-structural episode is constrained to the interval 1352–1341 Ma based on near-concordant U–Pb ages from monazite in pelitic schist near the mouth of Matthew Creek. Later, weaker metamorphic and deformation episodes variably overprinted the rocks of the Matthew Creek metamorphic zone. The juxtaposition of low-grade, weakly deformed rocks above high-grade, strongly deformed rocks across a zone of ductile deformation is interpreted to be due to a subhorizontal shear zone.

Insights into the metamorphic evolution of the Belt–Purcell basin; evidence from Lu–Hf garnet geochronology

2010 ◽  
Vol 47 (2) ◽  
pp. 161-179 ◽  
Author(s):  
N. A. Zirakparvar ◽  
J. D. Vervoort ◽  
W. McClelland ◽  
R. S. Lewis
Keyword(s):  
Metamorphic Complex ◽  
Mica Schist ◽  
Garnet Amphibolite ◽  
Metamorphic Evolution ◽  
Garnet Porphyroblasts ◽  
Core Zone ◽  
The Core ◽  
Northern Idaho

We have determined Lu–Hf garnet ages from spatially separated garnet bearing localities in northern Idaho. The Lu–Hf ages are diverse and reflect a progression of Mesoproterozoic metamorphic events. The oldest Lu–Hf garnet age determined in this study is 1463 ± 24 Ma for garnet within a kyanite schist exposed in the core-zone of the Boehls Butte metamorphic complex. A garnet schist from the Priest River complex yields a well-defined age of 1379 ± 8 Ma. A garnet–staurolite schist, a garnet–mica schist, and a gem-grade Idaho star garnet sample all from the general vicinity of Clarkia, Idaho, yield ages of 1064 ± 10, 1081 ± 20, and 1078 ± 17 Ma, respectively. A garnet amphibolite, also collected from the Boehls Butte metamorphic complex, yields an age of 1151 ± 41 Ma for garnet porphyroblasts and 137 ± 25 Ma for diffuse overgrowths. The Hf in all of the Proterozoic garnets is extraordinarily radiogenic with εHf values ranging from +1210 to +10546, which attest to both their high Lu/Hf ratios and their great antiquity. All of the samples analyzed in this study are from the rocks of the Mesoproterozoic Belt–Purcell Supergroup or its basement. These data provide evidence of polymetamorphism in northwestern Laurentia during the Mesoproterozoic.

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