Masters Theses

Date of Award

12-2001

Degree Type

Thesis

Degree Name

Master of Science

Major

Geology

Major Professor

Robert D. Hatcher

Committee Members

Hap McSween, Mike Clark

Abstract

This thesis examines the geology of the Scaly Mountain quadrangle in the eastern Blue Ridge of southwestern North Carolina. Particular emphasis was placed on determining the structure, timing, and emplacement mechanisms of the Rabun granodiorite pluton. The Scaly Mountain quadrangle was mapped in detail (1:12,000 scale). The mapping effort included collection of structural data from 1,333 data stations using a Brunton compass. Particular attention was paid to structural measurements that were taken within the Rabun pluton, including measurements of what are interpreted to be both magmatic flow foliations and tectonic foliations (two distinct foliations); folds, and the orientations of the folds and other linear structures; faults along the edge of the pluton in some areas; fractures; contacts with the surrounding country rock; and crosscutting dikes in the area. After the mapping was completed, the structural data were compiled at 1:24,000 scale and analyzed to determine deformation events, average orientations of folds and other linear structures, interrelationships of the tectonic units, an^ perhaps most importantly for this study, different fabric relationships that will provide clues about the emplacement history of the Rabun granodiorite. Conclusions drawn from this study are: (1) The Scaly Mountain quadrangle contains three tectonic units: the Chattahoochee thrust sheet, the Dahlonega gold belt, and the Shope Fork thrust sheet. (2) The rocks present in the Sealy Mountain quadrangle are: the Tallulah Falls Formation (graywacke-schist member), the Rabun granodiorite, the Otto Formation, the Coweeta Group (Coleman River Formation), calc-silicate rocks, amphibolites, and pegmatites. In addition there are surficial deposits of colluvium, alluvium, and ancient landslides. (3) There are six to seven deformation events represented in the rocks in the Scaly Mountain quadrangle. (4) Evidence for multiple deformation events can be seen along the trace of the Chattahoochee fault. The fault deforms the Rabun granodiorite, truncates structures in the surrounding country rock, and is itself folded. Evidence for multiple deformation events can also be seen in the surrounding country rock. There is an early foliation that is preserved in boudins. There are at least two generations of folding as well. (5) The Chattahoochee fault postdates the Rabun granodiorite. Evidence for this is the truncation of the Rabun pluton by the Chattahoochee fault. (6) The Rabun granodiorite consists of a medium-grained phase and a megacrystic phase. (7) The Rabun granodiorite contains a magmatic flow foliation and an overprinting tectonic foliation. (8) The Rabun granodiorite was emplaced by a combination of mechanisms either operating together or at different times during the pluton emplacement. These are: stoping, diapirism, outward displacement of the Earth's surface, the principle of effective stress, and dike-feeding of the pluton.

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