34 Conventional and Unconventional Critical Mineral Resources in the Eastern United States (Posters)

Saturday, 18 March 2023
1:30 PM - 5:30 PM
Grand Ballroom A–D

FORMING THE WORLDS LARGEST KYANITE MINE: EFFECTS OF PROTOLITH AND FLUIDS

Paper number: 34-5
Program: Theme Sessions
Time: 1:30 PM – 5:30 PM

Authors

Abstract

The world’s largest kyanite mine (Kyanite Mining Corporation) at Willis Mt. in central Virginia is within the Piedmont region of the Appalachian Mountains. The kyanite is found within quartzites and schists, which are part of the metasedimentary Arvonia Fm. Aluminosilicate deposits occur throughout the Blue Ridge and Piedmont terranes of the Southern Appalachians, where they are suggested to be associated with sedimentary protoliths that were altered in high-sulphidation epithermal systems (Owens & Hollingsworth, 2018). However, none are suggested to be as rich in kyanite as the Willis Mt. deposit. This work presents a combined field, petrographic and mineral chemical analysis of samples to determine conditions of metamorphism and effects of protolith composition on formation of the kyanite.

The analyzed samples from the mine consist of kyanite-bearing muscovite schist to kyanite quartzite composed of up to 55% kyanite with average crystal sizes from 2 to 15 mm. At the base of Willis Mt. a kyanite-bearing garnet mica schist and a kyanite quartzite were sampled for insights into the protolith composition. The kyanite-bearing garnet mica schist represents a metapelite, potentially with a volcanic-derived component, this sample is layered with a contact to a quartzofeldspathic rock. Micro-XRF analysis of this sample displays Ca and Mn zonation within the garnets, indicating growth during prograde metamorphism to amphibolite facies. As the samples lack indicators of multiple metamorphic events, modification of the protolith to form a composition dominated by Al2O3 and SiO2 likely occurred pre-metamorphism. The mineral assemblage of quartz + kyanite ± muscovite ± rutile ± pyrite ± plagioclase is in agreement with the high-sulphidation epithermal model. Micro-XRF analysis of a kyanite-bearing muscovite schist indicates enrichment in Fe, Cu, Mo and Ti, which further supports epithermal alteration of the protolith. This finding could be important for generating exploration models for other aluminosilicate deposits in the Appalachians.

Geological Society of America Abstracts with Programs. Vol. 55, No. 2

doi: 10.1130/abs/2023SE-385523

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