Stratigraphy and structure of the northwestern Flank of Frenchman Cap Dome, Monashee complex, British Columbia: preliminary results

1985 ◽  
Author(s):  
R J Scammell
Keyword(s):  
British Columbia ◽  
Preliminary Results ◽  
Monashee Complex

P–T history and kinematics of the Monashee Décollement near Revelstoke, British Columbia

1989 ◽  
Vol 26 (2) ◽  
pp. 231-243 ◽  
Author(s):  
Larry S. Lane ◽  
Edward D. Ghent ◽  
Mavis Z. Stout ◽  
Richard L. Brown
Keyword(s):  
British Columbia ◽  
Shear Band ◽  
Late Cretaceous ◽  
Hanging Wall ◽  
Multiple Criteria ◽  
Early Eocene ◽  
Kinematic Indicators ◽  
Metamorphic Assemblage ◽  
Monashee Complex

Microstructural and petrofabric analyses of mylonites from the Monashee Décollement demonstrate that the hanging wall was displaced eastward over the footwall. Microstructural kinematic indicators include shear-band foliation, asymmetric strain shadows, and S–C fabrics. Quartz c axes locally exhibit asymmetric fabrics that are consistent with the microstructural evidence for sense of shear. The kinematic evidence is reliable because multiple criteria coexist within individual specimens.Metamorphic assemblages from footwall Monashee Complex pelites at the Revelstoke damsite indicate that the peak metamorphic assemblage was sillimanite–K-feldspar–biotite–almandine–quartz ± plagioclase. Biotite–garnet geothermometry and garnet–plagioclase–sillimanite–quartz geobarometry set broad constraints on metamorphic temperatures but closer constraints on pressures, near 650 °C and 630 MPa.Comparison of these data with Late Cretaceous hornblende cooling ages from the same locality indicates that the metamorphism is at least as old as Late Cretaceous. Complex microstructures relating to repeated mylonitization and annealing render difficult the correlation of metamorphic conditions with mylonitic fabrics. Early mylonitic textures predate the metamorphic equilibration and thus are pre-Late Cretaceous in age. Postmetamorphic mylonites are well preserved, but their ages are poorly constrained. The present interpretation favours a Late Cretaceous to Paleocene age relating to compressional tectonics. However, an Early Eocene age relating to extensional shearing cannot be excluded.

Paleozoic plutonism in southeastern British Columbia

1985 ◽  
Vol 22 (10) ◽  
pp. 1409-1424 ◽  
Author(s):  
Andrew V. Okulitch
Keyword(s):  
British Columbia ◽  
Clear Relationship ◽  
Granitic Gneiss ◽  
Granitoid Pluton ◽  
Quartz Monzonite ◽  
Monashee Complex ◽  
Devonian Age ◽  
Tectonic Slice ◽  
Affected Country ◽  
Made In

U–Pb dates from zircons indicate that plutonic events occurred during the Paleozoic in the Omineca Crystalline Belt in southeastern British Columbia. In the Kootenay Arc, granitoid cobbles in conglomerate of the Carboniferous Milford Group were derived from quartz monzonite and diorite plutons of probable Ordovician age. Near Little Shuswap Lake, gneissic granitoid units have yielded Cambro-Ordovician ages. At least one episode of deformation affected country rocks of unknown age before intrusion. In the Monashee Complex south of Thor–Odin Nappe in South Fosthall Creek, lineated quartz monzonite is of probable Ordovician age. Comparison of fabrics suggests that at least one episode of metamorphism and deformation occurred prior to intrusion. No clear relationship between the cobbles and these plutons can be demonstrated because major faults lie between them, but substantial revision to accepted models of Paleozoic paleogeography of this region will have to be made. In the Clachnaeudainn tectonic slice east of the Monashee Complex, granitic gneiss is of Paleozoic, possibly Siluro-Devonian, age. This pluton appears to be involved in all phases of deformation that affected its country rocks. Near Quesnel Lake, parts of a composite gneissic granitoid pluton appear to be of Devonian or earliest Carboniferous age.

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