Authors / CoAuthors
Viete, D.R. | Oliver, G. J. H. | Fraser, G.L. | Lister, G.S.
Abstract
New SHRIMP U/Pb zircon ages of 472.2 ± 5.8 Ma and 470.4 ± 6.1 Ma are presented for the age of peak metamorphism of Barrovian migmatite units. Magmatic advection is thought to have provided significant heat for the Barrovian metamorphism. Published U/Pb emplacement ages for Grampian-age igneous units of Scotland and Ireland define a minimum age range of c. 473.5 to c. 470 Ma for Barrovian metamorphic heating. The new U/Pb ages are consistent with attainment of peak Barrovian metamorphic temperatures during Grampian magmatism. U/Pb-calibrated 40Ar/39Ar ages for white mica from the Barrovian metamorphic series vary systematically with increasing metamorphic grade, between c. 465 Ma for the biotite zone and c. 461 Ma for the sillimanite zone. Microstructural work on the timing of metamorphism in the Barrovian metamorphic series has shown that peak metamorphism occurred progressively later with increasing peak-metamorphic grade. Younging metamorphic age with increasing metamorphic grade across the Barrovian metamorphic series requires that the sequence was cooled in the lower-grade regions while thermal activity continued in the high-grade regions. This thermal scenario is well explained by the presence of a large-scale extensional detachment that actively cooled units from above while the Barrovian metamorphic heating continued at greater depth in the footwall. The spatio-temporal thermal pattern recorded by the Barrovian metamorphic series is consistent with regional metamorphism during crustal extension.
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nonGeographicDataset
eCat Id
71983
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Keywords
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- External Publication
- ( Theme )
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- geochronology
- ( Theme )
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- metamorphism
- ( Theme )
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- tectonic history
- Australian and New Zealand Standard Research Classification (ANZSRC)
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- Earth Sciences
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- Published_Internal
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2011-06-03T00:00:00
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