Document Type
Thesis
Abstract
Kyanite quartzite is a distinctive and locally economically important rock type that occurs in numerous places in Virginia’s Piedmont Province, primarily in the Chopawamsic and Milton terranes. A similar occurrence is located at Hagers Mountain, North Carolina within the Hyco Formation in the Carolina terrane. Hagers Mountain also lies on the fringes of the Hyco Shear Zone, the tectonic boundary between the Carolina and Milton terranes. All Hagers Mountain rocks are dominated by fine-grained quartz and kyanite. Kyanite is typically white in hand sample, a distinctive feature shared with the VA occurrences. Other minerals include white mica, variable amounts of chloritoid, and sporadic rutile, ilmenite (?), and zircon. Country rock schists are dominated by quartz and white mica (sericite), with additional ilmenite (?) and zircon. In contrast to the VA occurrences, the dominant Fe-bearing mineral at Hagers Mountain is chloritoid, whereas pyrite is ubiquitous in the VA occurrences. This mineralogical difference prompted the current investigation, in addition to determining whether the models for the origin of kyanite quartzite in VA could be applied at Hagers Mountain. Major element compositions of eight samples are dominated by SiO» and Al,O3, with negligible amounts of CaO, NaxO, K20, MgO, and MnO. Amounts of Fe203(T) are typically <0.4 wt%, but crudely correlate with the amount of chloritoid. “Isocon” diagrams based on the approach by Gresens (191967) and Grant (1986) suggest slight to significant (up to 47%) mass loss for these rocks. Recent models for the origin of the Virginia rocks involve severe leaching in high-sulfidation hydrothermal fluids (Owens and Pasek, accepted for publication), resulting in quartz-kaolinite protoliths. A key feature consistent with this idea is an anomalous depletion in Ga relative to Al in most Virginia rocks. Significantly, Hagers Mountain rocks do not show this depletion. Thus, contrasts in hydrothermal fluid composition may account for the slight mineralogical and compositional differences between Hagers Mountain and the Virginia rocks, in particular a paucity of S in the petrogenesis of these rocks.
Date Awarded
2007
Department
Geology
Advisor 1
Brent E. Owens
Recommended Citation
Wilson, Shelbi E., "Geochemical Constraints on the Origin of Chloritid-bearing Kyanite Quartzite at Hagers Mountain, NC and Comparisons with VA Occurences" (2007). Geology Senior Theses. William & Mary. Paper 188.
https://scholarworks.wm.edu/geologyseniors/188
