| Summary |
The Portis mine is a low grade gold deposit located in Franklin County, North Carolina. The mine area is underlain by a thick sequence of turbidite-deposited volcaniclastic sediments interlayered with felsic to mafic submarine pyroclastic units of the Spring Hope Formation. The entire sequence is believed to have been deposited on the flanks of a subduction-related volcanic arc terrane during the late Precambrian to early Cambrian. Epidote-amphibolite facies metamorphism has produced pervasive recrystallization and neomineralization of the Portis mine rocks. Late-stage hydrothermal activity has produced a localized zeolite facies overprint. Deformation is evident as a penetrative foliation parallel to the original bedding and as a less prominent crenulation cleavage inclined 30° to the bedding. A biotite mineral separate yielded a K-Ar age of 269 +/- 6 my. This age coincides with cooling at the end of the Alleghanian thermal event (325-275 ma) in the eastern Piedmont. Gold is associated with quartz veins located in the ore zone and adjacent rocks. The ore zone rocks are geochemically similar to Na- metasomatized vitric tuffs found in the Carolina Slate belt. Gold and silica precipitated within fractures in the ore zone that developed during compaction and metamorphic dewatering. |
| General note | "Presented to the faculty of the Department of Geology ... in partial fulfillment of the requirements for the degree Master of Science." |
| General note | Advisor: Richard K. Spruill |
| Dissertation note | M.S. East Carolina University 1987 |
| Bibliography note | Includes bibliographical references (leaves 75-82). |
| Genre/form | dissertations. |
| Genre/form | Academic theses. |
| Genre/form | Academic theses. |
| Genre/form | Thèses et écrits académiques. |
