A structural-metamorphic and geochemical study of the Hunt River supracrustal belt, Nain Province, Labrador
The southern Nain Province is characterized by several northeasterly trending supracrustal belts, Archean in age, which are infolded into a complex of polygenetic quartzofeldspathic gneisses. This thesis describes a petrological, geochemical and structural-metamorphic study of one of these belts, th...
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| Format: | Thesis |
| Language: | English |
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Memorial University of Newfoundland
1976
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| Online Access: | https://research.library.mun.ca/6851/ https://research.library.mun.ca/6851/1/ConradWayneJesseau.pdf https://research.library.mun.ca/6851/3/ConradWayneJesseau.pdf |
| Summary: | The southern Nain Province is characterized by several northeasterly trending supracrustal belts, Archean in age, which are infolded into a complex of polygenetic quartzofeldspathic gneisses. This thesis describes a petrological, geochemical and structural-metamorphic study of one of these belts, the Hunt River Belt, a predominantly mafic supracrustal sequence. -- The Hunt River Belt consists of a series of amphibolite schists (meta-volcanics), ultramafic lenses, and minor meta-sediments. The chemistry of the meta-volcanics displays close similarities to tholeiites found in the lowermost cycles of Archean greenstone belts. The ultramafics, containing preserved igneous textures, are considered to have intruded early into a developing volcanic pile. -- The thesis area has undergone a complex history of structural and igneous development. The earliest recognized widespread event (D₁) produced a strong tectonic fabric in the Hunt River Belt, and produced banded gneisses in the quartzofeldspathic rocks through thrusting and transposition, D₂ reflects a period of pure shear deformation and overprinted the area with a pronounced planar fabric. D₃ represents a period of tectonically active crustal uplift associated with magma upwelling and gave rise to heterogeneous deformation. D₄, a period of shallow level upright open folding, closed out the periods of folding and was followed by the development of megascopic faulting and diabase dyke intrusion. -- Each of the deformational episodes was accompanied by periods of plutonic activity which led to the development of distinct gneiss types. -- Mineralogical and microstructural evidence in the amphibolite schists and the quartzofeldspathic gneisses indicates that D₁, D₂ and D₃ all occurred within the amphibolite facies of metamorphism. D₄ and subsequent faulting occurred under greenschist facies conditions. |
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