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. Published U/Pb emplacement ages for Grampianage igneous units of Scotland and Ireland vary between c. 473.5 and c. 470 Ma. Magmatic advection provided significant heat for the Barrovian metamorphism, and 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, between c. 465 Ma for the biotite zone and c. 461 Ma for the sillimanite zone. Microstructural work on the timing of peak metamorphism has shown that 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 heating persisted in the high-grade regions. This thermal scenario is well explained by the presence of a large-scale extensional detachment that influenced the thermal regime by actively cooling units from above while metamorphic heating continued below the sequence. The spatio-temporal thermal pattern recorded by the Barrovian metamorphic series is consistent with regional metamorphism during crustal extension.
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nonGeographicDataset
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69941
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- External Publication
- Australian and New Zealand Standard Research Classification (ANZSRC)
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- Earth Sciences
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- Published_Internal
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2009-12-14T00:00:00
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