Reversals of movement sense in Lewisian brittle–ductile shear zones at Gairloch, NW Scotland, in the context of Laxfordian kinematic history
| Autor: | Lei Shihe, R. Graham Park |
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| Rok vydání: | 1993 |
| Předmět: | |
| Zdroj: | Scottish Journal of Geology. 29:9-19 |
| ISSN: | 2041-4951 0036-9276 |
| DOI: | 10.1144/sjg29010009 |
| Popis: | Synopsis Narrow (10–100 m wide) brittle–ductile shear zones in the Lewisian high-grade metamorphic complex of Gairloch, occur within broader ductile shear zones tens of kilometres across. The narrow belts contain ductile mylonites showing a sinistral sense of movement, which are cut and disrupted by brittle cataclasites indicating a dextral movement sense. These are in turn affected by sinistral brittle folds, and finally by N–S dextral pre-Torridonian faults. The ductile mylonites are thought to represent strain concentration during later stages of the high-grade Laxfordian D2 event at c. 1.7 Ga, associated with north-westwards overthrusting. The reversal to dextral shear shown by the cataclasites is linked with the regional D3 folds, steep shear zones and widespread, retrogression at c . 1.5 Ga, and ascribed to a re-orientation of the regional movement direction from NW–SE to N–S. The reversal of shear sense to sinistral during the D4 folding may be explained by clockwise rotation of the shear belts with respect to the regional shear direction as movement continued. The final change to N–S dextral faulting could be related either to late Lewisian strike-slip movements at c. 1.4 Ga or to Grenvillian movements at c. 1.1 Ga. |
| Databáze: | OpenAIRE |
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