Two Neoarchean tectonothermal events on the western edge of the North Atlantic Craton, as revealed by SIMS dating of the Saglek Block, Nain Province, Labrador

The Saglek Block forms the northern part of the Nain Province and underwent widespread metamorphism at c. 2.7 Ga, producing the dominant gneissosity and intercalation of supracrustal sequences. Zircon dating of gneiss samples collected along 80 km of the Labrador coast from Ramah Bay in the north to...

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Bibliographic Details
Published in:Journal of the Geological Society
Main Authors: Dunkley, Daniel J., Kusiak, Monika A., Wilde, Simon A., Whitehouse, Martin J., Sałacińska, Anna, Kielman, Ross, Konečný, Patrik
Format: Article in Journal/Newspaper
Language:English
Published: 2020
Subjects:
The Saglek Block
tectonothermal events
Nain
Hebron
Saglek Bay
Ramah Bay
Hopedale
North Atlantic
Online Access:https://hdl.handle.net/20.500.12128/12459
https://doi.org/10.1144/jgs2018-153
Description
Summary:The Saglek Block forms the northern part of the Nain Province and underwent widespread metamorphism at c. 2.7 Ga, producing the dominant gneissosity and intercalation of supracrustal sequences. Zircon dating of gneiss samples collected along 80 km of the Labrador coast from Ramah Bay in the north to Hebron Fjord in the south confirms the widespread extent of high-grade metamorphism between 2750 and 2700 Ma. In addition, a distinct event between 2550 and 2510 Ma produced felsic melt with peritectic garnet in metavolcanic gneiss and granoblastic recrystallization in mafic granulite. Ductile deformation of granite emplaced at c. 2550 Ma indicates that this later event involved a degree of tectonism during high-T metamorphism. Such tectonism may be related to a hypothesized post-2.7 Ga juxtaposition of the predominantly Eoarchean Saglek Block against the Mesoarchean Hopedale Block, along a north–south boundary that extends from the coast near Nain to offshore of Saglek Bay. Evidence of reworking of c. 2.7 Ga gneisses by c. 2.5 Ga tectonothermal activity has been found elsewhere on the margins of the North Atlantic Craton, of which the Nain Province represents thewestern margin. In particular, a recent suggestion that c. 2.5 Ga metamorphic ages along the northern margin of the North Atlantic Craton inSWGreenland may record the final assembly of the craton could also apply to the western margin as represented by the rocks of the Nain Province.

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