Date of Award

1979

Degree Type

Open Access Thesis

Document Type

Master Thesis

Degree Name

Master of Science (MS)

Department

Physics, Geosciences, and Astronomy

First Advisor

Edmond G. Deal

Department Affiliation

Physics, Geosciences, and Astronomy

Second Advisor

Harry P. Hoge

Department Affiliation

Physics, Geosciences, and Astronomy

Third Advisor

Perry B. Wigley

Department Affiliation

Physics, Geosciences, and Astronomy

Abstract

The White Rock quadrangle is located in extreme west­ central North Carolina, at the northwest edge of the Blue Ridge thrust sheet. The geology of the north-central ninth of the quadrangle was mapped during this study. This map area primarily consists of Precambrian granitic gneisses of the Blue Ridge thrust sheet that are separated from metasedimentary rocks of the Wilhite Formation of the Ocoee Series by the Devils Fork fault.

Of the six metadiabase bodies mapped by Keith (1904) in the White Rock quadrangle, only three definitely contain outcrops of metadiabase. These bodies were metamorphosed to the chlorite and biotite zones of the greenschist facies during the early or middle Paleozoic. The degree of meta­morphic alteration varies both from one body to another and within an individual body. However, there does not appear to be any regular pattern of gradation within a body.

The primary factors controlling the degree of alteration seem to be the amount of water present during metamorphism and the metamorphic grade. Under lower grade, water-rich metamorphic conditions, the metadiabase tends to form a greenschist. With slightly higher grade, and/or more water-deficient conditions, metadiabase in the study area shows some tendency to follow a trend toward formation of an amphibolite.

Pegmatitic metadiabase, with plagioclase laths as long as 5 cm, is common in two of the bodies. Compared with reports in the literature, the pegmatitic variety is anomalously coarse and forms an unusually high percentage of the total amount of metadiabase in the study area.

The Cranberry Gneiss and Max Patch Granite make up most of the country rock in the study area. The Cranberry is predominantly a medium-grained, equigranular quartz monzonite. The Max Patch ranges in composition from a granite to a granodiorite. The texture of the Max Patch is coarse and commonly porphyritic, with orangish-pink alkali feldspar forming porphyroclasts as large as 6 cm in length. The Max Patch Granite and the Cranberry Gneiss appear to be of igneous origin in this area.

The Devils Fork fault may be early Paleozoic in age in this area, based on field observations at the supposed fault contact between a metadiabase body and the Wilhite Formation. Because the Ordovician(?) metadiabase seems to be relatively unsheared at the contact, the fault is apparently slightly older than the intrusion of the metadiabase.

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