Electronic Thesis and Dissertation Repository

Thesis Format

Integrated Article

Degree

Master of Science

Program

Geology

Supervisor

Linnen, Robert L.

Abstract

The Wekusko Lake pegmatite field is part of the Green Bay Group of pegmatites located near Snow Lake, Manitoba, Canada. Within this field, there are at least 13 spodumene-bearing pegmatites of varying degrees of mineralization. The abundance of white micas and the chemical affinity to incorporate Li and other trace elements into its crystalline structure makes white micas an ideal indicator mineral. The evolution of a melt can be tracked using trace elements in white mica. The K/Rb ratio vs Cs is used to determine a link between increasing evolution and increased Li contents of both the white mica and the pegmatite. White mica compositions were examined using portable Raman and LIBS to evaluate whether Li contents can be determined in the field. The LIBS was able to identify the pegmatites dikes with the highest Li contents, which can be applied to real-time decision-making during exploration.

Summary for Lay Audience

The Wekusko Lake pegmatite field is part of the Green Bay Group of pegmatites located near Snow Lake, Manitoba, Canada. Pegmatites are a key source for Li and rare metals (e.g., Sn, Cs, Ta, Nb), which are become increasingly more important in society. Spodumene is the primary mineral from which Li in obtained. The majority of pegmatites are barren and contain little Li. Distinguishing between Li-rich and Li-poor pegmatites can be challenging in the field without laboratory testing if spodumene is not visible.

As a pegmatite melt crystallizes the remaining melt becomes more enriched in rare metals, this process is called evolution. White micas are the third most abundant mineral in pegmatites and are able to incorporate trace elements (e.g., Li, Cs, Rb, Nb, Ta) into their crystal structure, relative to the concentration of those elements in the melt. Using the trace element concentration of the white mica, the evolution and therefore mineralization potential of the pegmatite can be estimated.

Laboratory testing to determine the chemical composition of rock is a time consuming and can bottle neck exploration projects trying to plan the next target. Portable LIBS is able to identify the Li contents of white micas and provide near instantaneous result. The white mica Li contents can be used to plan new targets for exploration.

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