Masters Theses

Date of Award

6-1973

Degree Type

Thesis

Degree Name

Master of Science

Major

Geology

Major Professor

Lawrence T. Larsen

Committee Members

Garrett Briggs, G. Michael Clark

Abstract

The East Fork mine consists of a series of open cuts in steeply dipping low-grade metasediments of the Late Precambrian (?) Ocoee Series. In general the metasedimentary units strike northeast and dip steeply to the southeast. However, interpretation of stratigraphy and structure is complicated by intensive local folding and faulting. Two large thrust faults occur in the southern part of the study area, and two or more thrust sheets comprise the bulk of Dixon Mountain in the eastern part of the study area. At the southern boundary of the study area, the Dunn Creek fault thrusts rocks of the Snowbird Group onto those of the Walden Creek Group. Nearby a smaller fault thrust a sheet of conglomerate of the Shields (?) Formation onto younger slates.

Pods of manganese oxide ore occur in the Walden Creek Group at the top of a laterally persistent dolostone bed. This bed elsewhere caps a sequence of limestone conglomerates that interfinger with lenses of sandy shale. Bedded phosphorite crops out approximately 400 feet northeast of the easternmost manganese mine and occurs in a slightly higher stratigraphic horizon. Earlier studies suggest that the manganese was leached from dolostone by underground water and redeposited as a manganese carbonate ore. Present field and analytical work indicated that the manganese ore formed as lenses and pods in dolostone. Structure and texture of the ore indicate subsequent fracturing, shearing, and local remobilization.

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