Department or Program

Geology

Abstract

The Lewiston, Maine 15-minute Quadrangle is dominated by highly migmatized metasedimentary rocks, which are intruded by three apparently distinct pegmatite varieties, about which little is currently known. In order to classify these pegmatites according to several classification schemes, and to answer questions regarding their origins, the whole rock geochemistry of these pegmatites was analyzed through ICP-MS and ICP-OES, and their individual quartz grain geochemistry analyzed through LA-ICP-MS. The Muscovite + Tourmaline variety is found to be most similar to an LCT-leaning Mixed pegmatite, which likely crystallized at temperatures near 500 °C, and may have formed from either direct anatexis of the Sangerville Formation, or from residual granitic melts related to nearby granitoid units. The Garnet + Tourmaline variety is also found to be similar to an LCT-leaning Mixed pegmatite, which likely crystallized at a temperature similar to that of the Muscovite + Tourmaline variety, and may have potentially formed from the same source as that variety, after said source had become depleted in LREEs due to the first variety’s formation. The Biotite variety is found to be most similar to an NYF-leaning Mixed pegmatite, which likely crystallized at higher temperatures near 600 °C, and likely formed from direct anatexis of the Vassalboro Formation. Geochemical evidence suggests that it is therefore accurate to classify all Lewiston Quadrangle pegmatites as entirely distinct pegmatite varieties.

Level of Access

Open Access

First Advisor

Eshita Samajpati

Date of Graduation

5-2022

Degree Name

Bachelor of Science

Number of Pages

56

Components of Thesis

1 pdf file

Open Access

Available to all.

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