Fabrics and Deformation of Archean Metasedimentary Rocks, Ross Lake – Gordon Lake Area, Slave Province, Northwest Territories
Metagreywackes, which lie stratigraphically above metavolcanics fringing a granitic complex (part basement), exhibit late Archean multiphase fold structures. F 1 folds are large linear depressions and anticlinal culminations trending partly concordant with margins of the granitic complex. Open to is...
| Published in: | Canadian Journal of Earth Sciences |
|---|---|
| Main Author: | |
| Format: | Article in Journal/Newspaper |
| Language: | English |
| Published: |
Canadian Science Publishing
1975
|
| Subjects: | |
| Online Access: | http://dx.doi.org/10.1139/e75-067 http://www.nrcresearchpress.com/doi/pdf/10.1139/e75-067 |
| Summary: | Metagreywackes, which lie stratigraphically above metavolcanics fringing a granitic complex (part basement), exhibit late Archean multiphase fold structures. F 1 folds are large linear depressions and anticlinal culminations trending partly concordant with margins of the granitic complex. Open to isoclinal F 2 folds vary and curve in trend. Though usually near upright, some F 2 folds are overturned away from the complex and others towards F 1 depressions. F 3 folds are small-scale structures not present in most outcrops, but throughout a large region they are accompanied by a steep S 3 axial-plane schistosity striking NW to N.Original orientations of an S 2 schistosity, axial planar to F 2 folds, are preserved as inclusion trails in biotite porphyroblasts. Angular deflections from the trails show that regional horizontal flattening across the S 3 schistosity formed the F 3 folds and tightened curved trends of F 2 folds. Estimates of strain from the fabrics indicate no increase near the complex.As for folds in other Archean terrains, F 1 and F 2 folds could have developed mainly as gravity structures during diapiric uprise of a granitic basement. In contrast, the F 3 structures may reflect horizontal movements of early crustal plates. |
|---|