The multiphase Ice River Alkaline Complex is located in the Main Ranges of the Rocky Mountains about 40 km east-southeast of Golden, BC, and comprises, in order of decreasing age: (1) a rhythmically-layered mafic complex; (2) carbonatite (concentrated as a plug in the centre of the complex); (3) a zoned nepheline syenite complex, and; (4) a dyke suite consisting of syenitic dykes, late alkaline lamprophyres, and carbonatites.
Petrographic, geochemical, and isotopic analysis of the dykes occurring along the eastern margin of the Ice River Alkaline Complex indicates that the syenitic dykes are the product of extensive fractional crystallization (Zr/Hf = 39 – 80; Nb/Ta = 19 – 305). These syenitic dykes can be subdivided based on mineralogy and composition into a nepheline syenite – nephelinolite group, a syenite – monzodiorite group, and an alkali feldspar granite dyke. The calculated Sm-Nd isochron age of the syenitic dykes (369 ± 15 Ma) is consistent with the accepted age of the complex (359 ± 3 Ma), and is supported by the Rb-Sr errorchron for the same samples, as well as preliminary U-Pb zircon dating. A solidification front (fractional crystallization) model has been described for the development of the Ice River Alkaline Complex, where the syenitic dykes represent structurally controlled periodic discharges from an evolving magma chamber.
Isotopic evidence coupled with a U-Th-Pb EPMA date of 165 ± 8 Ma for one of the examined discordant REE-rich carbonatite dykes, indicates that at least some of the carbonatites within the Moose Creek Valley are temporally and magmatically isolated from the Ice River Alkaline complex.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:UNB.1882/1085 |
| Date | January 2009 |
| Creators | Mumford, Thomas |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | en_US |
| Detected Language | English |
| Type | Thesis or Dissertation |
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