Madison Dean, BSc
M. Dean1, T. Cawood1, B. Dyck1
1Department of Earth and Environmental Sciences, University of British Columbia - Okanagan, Kelowna, British Columbia, Canada
The topic of how lithium-rich pegmatites are formed is widely debated. The three main genetic models include pegmatite formation from 1) low-degree anatexis of metasediments, 2) S-type granite melts that have undergone extreme fractionation, and 3) remelting of pre-enriched granites during crustal reheating. A unique outcrop on Mount Begbie near Revelstoke, British Columbia, is being analyzed to settle this debate. Here, we present data from Li2, an enriched pegmatite that contains the lithium minerals lepidolite, elbaite, and petalite. At an outcrop scale, the direct transition from migmatite to mineralized pegmatite is observed. This makes Li2 the ideal candidate for testing the anatexis model of pegmatite formation by documenting how mineral chemistry varies from migmatite, through barren pegmatite, to the mineralized pegmatite zone. Analysis is being done through 1) identification of partial melt reactions based on microstructure and mineral assemblages of representative thin sections, 2) use of micro X-ray fluorescence to document different phases within the rocks, and how their proportions vary between each outcrop sample site, 3) confirming mineral identification and creating element maps of minerals through scanning electron microscopy, and 4) analysis of the trace element composition of major minerals in the migmatite to mineralized pegmatite through laser ablation inductively coupled plasma-mass spectrometry. Narrowing down how lithium rich pegmatites form will allow for better prediction of the distributions of mineralized pegmatites, enabling more efficient exploration for lithium and other critical metals.