Occurrence and possible tectonic significance of high-pressure granulite fragments in the Tulemalu fault zone, District of Keewatin, N.W.T., Canada
Fragments of garnet–clinopyroxene granulite with corona textures in ductilely deformed lower-amphibolite-grade quartzofeldspathic granitoid gneiss are exposed within the northeast-trending Tulemalu fault zone. The mineral association of the fragments is garnet–clinopyroxene–plagioclase(An 20 –An 22...
| Published in: | Canadian Journal of Earth Sciences |
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| Main Authors: | , |
| Format: | Article in Journal/Newspaper |
| Language: | English |
| Published: |
Canadian Science Publishing
1986
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| Subjects: | |
| Online Access: | http://dx.doi.org/10.1139/e86-181 http://www.nrcresearchpress.com/doi/pdf/10.1139/e86-181 |
| Summary: | Fragments of garnet–clinopyroxene granulite with corona textures in ductilely deformed lower-amphibolite-grade quartzofeldspathic granitoid gneiss are exposed within the northeast-trending Tulemalu fault zone. The mineral association of the fragments is garnet–clinopyroxene–plagioclase(An 20 –An 22 )–quartz–opaques–hornblende–biotite. Textural evidence suggests that hornblende and biotite are late overgrowth minerals. Garnet and clinopyroxene and (or) hornblende are separated by a narrow rim of plagioclase. Pressure–temperature estimates based on currently used geothermobarometers are of the order of 715–789 °C and 10.2–11.4 kbar (1 kbar = 100 MPa) for the garnet–clinopyroxene–plagioclase–quartz assemblage. The fragments are interpreted as relicts of deep-crustal materials, uplifted to higher levels probably as xenolithic rafts in a granitic melt along the fault zone during late Archean or Early Proterozoic ductile displacements. The growth of hornblende and the development of plagioclase reaction rims around garnet are believed to be due to isothermal decompression reactions during uplift.On the basis of limited geological data, paired gravity anomaly patterns, and aeromagnetic interpolation, the Tulemalu fault zone is postulated as representing the northeasterly extension of the Virgin River – Black Lake fault zones of Saskatchewan and represents an approximately 5 km wide ductile deformation zone that separates an Archean granulite terrane to the west from a relatively lower grade terrane composed of Archean supracrustal rocks to the east. |
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