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Martin Stewart

Martin Stewart first became interested in geology in grade one or two, during frequent visits to an avid mineral collector in his hometown of Ingersoll, Ontario. Little did he know that his modest collection of specimens would lead to a career in the geosciences. He became completely hooked during the summer of 1994 following his first year of undergraduate studies in geology at Carleton University in Ottawa. That summer he was working for the Ontario Geological Survey in the small northern Ontario community of Matachewan. He could hardly believe that someone was willing to pay him to spend his days exploring stunning wilderness territory by foot, canoe and other means necessary, Since that summer, his passion for rocks has grown through work with both the OGS and the GSC, Carleton University, University of Ottawa, several mining companies, and an 8-month stint working as a consultant on various projects. His work has provided him the opportunity to travel extensively in Canada and internationally and to meet people from all over the world.

His research has really taken off this year with two manuscripts now in press. The first is a detailed mineralogical study of plagioclase from the active volcano of Montserrat, and the second, a field-based comparison of pyroclastic avalanche versus cold rock deposits and its implications for hazard analysis at Mount Meager. While these are his most important scientific contributions to date, his fondest research project was a study of the mineralogical make-up of contemporary Inuit carving stones. The results formed an integral part of an exhibit of stone carvings at the McMichael Canadian Art Gallery, in Toronto, to celebrate the formation of Nunavut Territory. Martin says he derives great satisfaction from seeing that his work has a cultural impact.

Here is what he says about his PhD research project on geochemical dynamics of crystallization and vesiculation processes in natural magmatic systems:

My research project aims at developing physical-chemical models for the dynamics of crystallization and vesiculation (volatile production) processes within natural silicate magmas. To learn about these processes, I will develop computational models and compare them to natural systems. The ideal model will allow tracking of the physical conditions in a magma chamber (e.g. crystallinity, melt density, etc.).

My specific objectives are two-fold. First, I intend to develop a natural empirical model of crystal and volatile development from the deposits preserved at Mount Meager. Second I will develop theoretical algorithms based on the thermodynamic models of Ghiorso et al. (1983, Contr. to Min. and Petr.) and experimental data to predict the lines of descent of crystals, liquids, and volatiles present in a magma of a given composition. The Mount Meager model will provide the vehicle to test these theoretical algorithms which can then be applied elsewhere.

I am in the process of compiling a revised geological map and stratigraphy for the area based on field work from this past summer. Petrographic and electron microprobe analysis of textures, mineral relationships and compositions, and Nomarski differential phase interference contrast imaging will provide controls on the evolution of discrete portions of the magma over time and will elucidate the subliquidus evolution of the magma prior to eruption.

Bulk rock geochemistry, glass chemistry and determination of the volatile contents of both minerals and glass will allow analysis of the changes in the bulk magma being extruded over time. These stratigraphic changes represent the heterogeneities inherent within the magma chamber just prior to and during extrusion. Their character will depend on the nature of stratification within the magma chamber and the geochemistry of the drawup as the material is being extracted from the chamber.