Document Type

Thesis

Abstract

The focus of this study is coincidences of kyanite and K-feldspar in the Maidens gneiss of central Virginia’s Goochland terrane. Crawford (2001) and Shirvell (2003) discovered two regions of kyanite- and K-feldspar-bearing rocks in the Hewlett and Hanover Academy quadrangles. In the Maidens gneiss, as in most other alumino-silicatebearing rocks, it is very uncommon for K-feldspar to occur with kyanite, so this research focuses on the areal extent of this unit and the origin of the kyanite- and K-feldsparbearing rocks. Petrographic analysis of mineral assemblages in thin sections shows that there are four main rock types present in these samples: kyanite- and K-feldspar-bearing rocks, amphibolites, garnet-hornblende-plagioclase-biotite-quartz gneisses, and quartz-Kfeldspar- garnet gneisses. The kyanite and K-feldspar unit proved not to be one mappable unit, occurring in two separate lenses. Petrographically, low amounts of muscovite and a lack of sillimanite indicate no evidence for retrograde metamorphism; kyanite and Kfeldspar occur in textural equilibrium in thin section and there are apparent melt patches in hand sample, indicating a high-pressure metamorphism, instead. Future research should investigate the origin of these two areas of kyanite- and Kfeldspar- bearing rocks, as they may have formed independently of each other, or may have been created through an episode of folding and/or faulting. Further research beyond the scope of this project, such as quantitative testing using established geobarometers, electron microprobe analysis, etc., can more conclusively determine the origin of kyanite and K-feldspar in these samples.

Date Awarded

2008

Department

Geology

Advisor 1

Brent E. Owens

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