The chemical evolution of peridotites and felsic rocks included in or adjacent to them, and fluids during the hydrothermal alteration of these rocks is the subject of this study. Experiments using a flow-through hydrothermal apparatus, and studies of natural samples from the JM Asbestos chrysotile deposit in the Asbestos ophiolite, Quebec, were the means by which the various topics of this thesis were investigated. Open-system fluid-rock interaction was studied by flowing deionized water or a 0.1 m CaCl2 solution through olivine (Fo91) and lherzolite at a temperature of 300°C and a pressure of 300 bars. During these experiments, the original minerals (olivine, orthopyroxene and clinopyroxene) were altered to an assemblage, which consisted of serpentine-group minerals (conical, polygonal, and cylindrical fibers, and plates), brucite and magnetite. Reaction of lherzolite with deionized water and thermodynamic modelling indicate that the highest pH and calcium concentration are attained when pyroxenes are present in the unaltered rock, and that these parameters are at maximum in the presence of the buffering assemblage serpentine + brucite + diopside. Alteration of olivine by 0.1 m CaCl2 aqueous solution does not lead to the formation of secondary calcium phases. These results, supported by thermodynamic calculations, suggest that calcium-rich fluids can circulate through forsteritic olivine-rich lithologies without inducing calcium metasomatism. / In the JM Asbestos mine, these Si-Al lithologies are largely felsic dykes, which, based on geological relationships, are interpreted to have been emplaced after serpentinization of the host peridotites began, but before obduction of the Asbestos ophiolite onto the Laurentian continental margin. Slates underlying and in thrust contact with serpentinite are also locally rodingitized. Mass balance calculations suggest that the calcium responsible for the rodingitization of the slates may have been derived locally, whereas the calcium responsible for the rodingitization of the felsic dykes was most probably derived from a source remote from the dykes. The strong dilution in rodingites and nephrites of the low-solubility minor and traces elements P, Cr and Zr suggests that very large amounts of fluids were involved in calc-silicate metasomatism of the felsic dykes and adjacent serpentinites. / The absence of CO2 and presence of hydrocarbons (alkanes from methane to pentane) in the fluid inclusions of both episodes is an indication that the fluids responsible for calc-silicate alteration were derived from the serpentinites. (Abstract shortened by UMI.)
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.37799 |
| Date | January 2001 |
| Creators | Normand, Charles, 1963- |
| Contributors | Williams-Jones, Anthony E. (advisor) |
| 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 | Doctor of Philosophy (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: 001808723, proquestno: NQ70115, Theses scanned by UMI/ProQuest. |
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