Nepheline syenite represents the highly differentiated product of fractional crystallization in the Poudrette quarry at Mont Saint-Hilaire, Quebec. It also records a significant subsolidus overprint due to circulation of post-magmatic fluids. Annite, the ferrous-iron-dominant member of the biotite series, represents up to 20% of the typical nepheline syenites. / Hand samples cover the complete range of freshness, from unaltered to hydrothermally modified rocks. Identification of minerals and estimation of their abundances and compositions were obtained with optical microscopy and electron-microprobe analysis. I also used a combined approach of X-ray diffraction and high-resolution transmission electron microscopy. / With respect to annite composition, Fe/(Fe + Mg) varies from 0.74 (porphyntic nepheline syenite) to 0.98 (poikilitic nepheline syenite). Concerning the habit of annite, the melt composition controls the order of crystallization, which then in turn controls whether the annite is bladed and skeletal or oikocrystic. The rock from the Poudrette dyke is a hypersolvus nepheline syenite in which the bladed annite was a liquidus phase; therefore, the order of crystallization was "normal" (mafic mineral first), whereas in poikilitic nepheline syenite, this order was reverse. The proportion of Ti decreases with Fe/(Fe + Mg), whereas that of Mn increases; F and Cl contents are very low in spite of their availability. / The application of n-alkylammonium cation exchange reveals the presence of planar structural defects as a result of dehydrogenation-type reactions. The annite records the results of oxidation during cooling, i.e., open-system behavior in this degassing pluton.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.79209 |
| Date | January 2002 |
| Creators | Zangooi, Azin |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Master of Science (Department of Earth and Planetary Sciences.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001984151, proquestno: AAIMQ88334, Theses scanned by UMI/ProQuest. |
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