Higgins, Michael D., van Breemen, Otto (1992) The age of the Lac-Saint-Jean Anorthosite Complex and associated mafic rocks, Grenville Province, Canada. Canadian Journal of Earth Sciences, 29 (7) 1412-1423 doi:10.1139/e92-113
Reference Type | Journal (article/letter/editorial) | ||
---|---|---|---|
Title | The age of the Lac-Saint-Jean Anorthosite Complex and associated mafic rocks, Grenville Province, Canada | ||
Journal | Canadian Journal of Earth Sciences | ||
Authors | Higgins, Michael D. | Author | |
van Breemen, Otto | Author | ||
Year | 1992 (July 1) | Volume | 29 |
Issue | 7 | ||
Publisher | Canadian Science Publishing | ||
DOI | doi:10.1139/e92-113Search in ResearchGate | ||
Generate Citation Formats | |||
Mindat Ref. ID | 481792 | Long-form Identifier | mindat:1:5:481792:9 |
GUID | 0 | ||
Full Reference | Higgins, Michael D., van Breemen, Otto (1992) The age of the Lac-Saint-Jean Anorthosite Complex and associated mafic rocks, Grenville Province, Canada. Canadian Journal of Earth Sciences, 29 (7) 1412-1423 doi:10.1139/e92-113 | ||
Plain Text | Higgins, Michael D., van Breemen, Otto (1992) The age of the Lac-Saint-Jean Anorthosite Complex and associated mafic rocks, Grenville Province, Canada. Canadian Journal of Earth Sciences, 29 (7) 1412-1423 doi:10.1139/e92-113 | ||
In | (1992, July) Canadian Journal of Earth Sciences Vol. 29 (7) Canadian Science Publishing | ||
Abstract/Notes | U–Pb analyses of zircon and baddeleyite from the south-central and southeastern parts of the Lac-Saint-Jean Anorthosite Complex (LSJA) give an igneous crystallization age of 1157 ± 3 Ma. Parts of the anorthosite were deformed in the solid state and subsequently intruded by a diorite megadyke, which also gives a crystallization age of 1157 ± 3 Ma, indicating that crystallization and deformation of the anorthosite were essentially synchronous. The diorite megadyke was intruded into a north-northeast-trending shear zone and deformed by sinistral strike-slip movements. Emplacement was followed by intrusion of a subparallel leucotroctolite megadyke that again gives the same crystallization age and hence dates movement of the shear zone at 1157 ± 3 Ma. This short history of crystallization and synchronous deformation rules out slow diapiric rise as the emplacement mechanism for the anorthosite. Instead, anorthosite parental magmas probably rose up offsets in subvertical strike-slip shear zones to their present level.In the southwestern part of the LSJA an age of 1142 ± 3 Ma is interpreted to represent igneous crystallization. Contemporary thermal metamorphic effects recorded in the southeastern sector by growth of new zircon in granophyric segregations and zircon coronas on baddeleyite suggest this event was more widespread at slightly deeper levels. Evidence has not been found for a separate Grenville regional metamorphism.The emplacement into the LSJA at 1076 ± 3 Ma of two small leucogabbro intrusions was part of a widespread magmatic event similar to the main event at 1157–1142 Ma. |
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