Progressive structural reworking of the Uivak gneisses, Jerusalem Harbour, northern Labrador
The region around Jerusalem Harbour in northern Labrador is composed of a suite of metamorphic rocks of various ages and origins. The Uivak gneisses, containing Saglek dyke and pre-Uivak inclusions, are the deformed and metamorphosed equivalents of an igneous suite emplaced into the crust over 3.6 b...
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| Format: | Thesis |
| Language: | English |
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Memorial University of Newfoundland
1977
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| Online Access: | https://research.library.mun.ca/6887/ https://research.library.mun.ca/6887/1/AuthurBruceRyan.pdf https://research.library.mun.ca/6887/3/AuthurBruceRyan.pdf |
| Summary: | The region around Jerusalem Harbour in northern Labrador is composed of a suite of metamorphic rocks of various ages and origins. The Uivak gneisses, containing Saglek dyke and pre-Uivak inclusions, are the deformed and metamorphosed equivalents of an igneous suite emplaced into the crust over 3.6 b.y. ago. Tectonically intercalated with the Uivak gneisses are belts of metasedimentary and basic gneisses known as the Upernavik supracrustals. -- Both the Uivak gneisses and Upernavik supracrustals have been variably migmatized during a period of crustal instability manifested by metamorphism and deformation 3.1 b.y. ago. This 3.1 b.y. event was marked by the generation of a new series of gneisses, herein termed the Iterungnek gneisses. These younger tectonites are a composite, heterogeneous, suite derived both from the remobilization of the earlier Uivak gneisses through a mechanism of structural and metamorphic reconstitution and in situ anatexis, and synkinematic granitic intrusions. In areas where structural reworking has been dominant, the Uivak gneisses can be shown to have undergone progressive transposition until the earlier layering has been completely reoriented and gradually obliterated at the expense of the imposed (Iterungnek) foliation. Where anatexis has been the dominant mechanism, the gneisses show a gradation from lit-par-lit migmatites with Uivak characteristics into Iterungnek nebulites having a granular aspect. The rejuvenation of the Uivak gneisses was synchronous with the intrusion of weakly foliated granitic bodies which gave rise to megascopic agmatite zones where they were emplaced into or adjacent to the Upernavik supracrustals. -- Detailed petrological studies of all the major rock units in the area has shown that the reworking of the Uivak gneisses occurred under granulite facies conditions, which were superimposed on rocks with upper amphibolite facies assemblages. Mineral reactions observed in thin section indicate P-T conditions for the granulite metamorphism to be in the range of 10 ... |
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