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Abstract

Pegmatite mineralogy, petrology, and petrogenesis are important fields of study due to the complex geochemical relationships in pegmatites and their potential to host significant lithium, cesium, and tantalum. This thesis explores two petalite subtype pegmatites: the Tanco pegmatite, Manitoba, one of the world's most economically significant pegmatites, and the Prof pegmatite, British Columbia, the first significantly Li-mineralized pegmatite identified in BC. The Tanco pegmatite and the Prof pegmatite are of differing ages, geological settings, sizes and mineralogical associations. Comparing these pegmatites adds to our understanding of Li aluminosilicate formation and preservation. The dominant Li mineral in the Tanco pegmatite is spodumene found in spodumene-quartz intergrowths (SQUI), historically interpreted as pseudomorphs of petalite breakdown. This thesis uses X-ray microcomputed tomography to reveal the proportional variability of spodumene to quartz in SQUI. Three textural varieties of spodumene-quartz associations were identified and described in zones 45 and 50 of the Tanco pegmatite: (1) Classic SQUI with c-axis-oriented, oscillatory-zoned spodumene and quartz, interpreted to form from the breakdown of metastable virgilite; (2) spodumene-quartz symplectites (SQS) characterized by pervasive symplectite intergrowths interpreted to arise from coupled dissolution reprecipitation; and (3) macro spodumene-quartz intergrowths with randomly oriented, stubby crystals interpreted to have a magmatic origin. The Prof pegmatite is divided into four zones, with the central zone hosting the majority of Li mineralization. The tourmalines, Nb-Ta oxides and micas within the pegmatite record the geochemical evolution of the melt from more primitive Fe- and Mg-rich to a Li-, Mn- and Nb-rich assemblage. These changes reflect fractional crystallization and evolving melt chemistry that influenced pegmatite crystallization. Colorless elbaite rims in intermediate zones of nearby pegmatites could suggest Li mineralization at depth, making tourmaline geochemistry a useful regional exploration proxy. This research presents novel ideas about the origins and metallurgical implications of SQUI, the abilities of micro-CT to effectively analyze Li silicates, the first research on the mineralogy of the Prof pegmatite and how tourmalines can be used as an exploration tool in the Revelstoke region. This research emphasizes the importance of understanding pegmatite textures and geochemistry for effective exploration and mining.