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UBC Theses and Dissertations

Mineralogy concepts for research and teaching : the mineralogy of the Rau pegmatite group, its implications for pegmatite contamination, and a concept inventory to assess student understanding Scribner, Emily Don

Abstract

This dissertation presents a two-component study: (1) the effect of contamination on the mineralogy of the Rau pegmatite group and implications for pegmatite contamination and (2) a statistically validated concept inventory that can assess understanding of mineralogy concepts. The Rau pegmatite group, which is made up of 10 F-rich, barren to mixed NYF + LCT pegmatite dikes, is located in the Yukon Territory, Canada. The dikes are hosted in dolostone of the Bouvette Formation and were derived from the nearby Rackla pluton: a ~63 Ma, weakly peraluminous biotite-muscovite granite. The most evolved pegmatites of the group contain abundant rare element phases such as columbite group minerals, fluorcalciomicrolite, and REE-bearing fluoro-carbonate minerals. Elevated F activity during pegmatite crystallization is evident from F enrichment in multiple pegmatite zones. The Rau pegmatite dikes show clear evidence of being contaminated by their dolostone host rocks. Primary Ca-bearing minerals as well as carbonate pockets are present throughout the pegmatite dikes. Stable C and O isotopic signatures of carbonate minerals indicate that the pegmatite dikes were subjected to pre-emplacement contamination, whereas the presence of endo-contact skarns at the borders of some pegmatite dikes is evidence for post-emplacement contamination. An extensive meta-analysis of the pegmatite literature suggests that pegmatite contamination that can modify the mineralogy of a pegmatite is a much more common mechanism than is currently recognized. Future studies of pegmatites should include a more thorough investigation of the host rocks, and results should be interpreted while considering the potential influence of the host rock composition on pegmatite mineralogy. The Mineralogy Concept Inventory (MCI) is a statistically validated assessment that can be used to measure learning gains in introductory mineralogy courses. Development of the MCI was an iterative process involving expert consultation, student interviews, and statistical analysis. The MCI was implemented in undergraduate mineralogy courses at two different Canadian universities that employ different pedagogies: student-centred and instructor-centred. Although average pre-assessment scores were approximately the same, normalized learning gains were significantly higher in the course that uses a student-centred pedagogy. These results suggest that the use of a student-centred pedagogy can significantly increase learning of mineralogy concepts.

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