Date of Award

12-1981

Degree Name

Master of Science

Department

Geosciences

First Advisor

Dr. Richard V. McGehee

Second Advisor

Dr. W.D. Kuenzi

Third Advisor

Dr. L.J. Schmaltz

Access Setting

Masters Thesis-Open Access

Abstract

Precambrian X tectonites deformed between thermal domes in the northern Black Hills 1.7 B.Y.B.P. display variably trending isoclinal folds cross-cut by southeast trending slip-folds developed in discrete shear zones. Eugeosynclinal sedimentary rocks consisting of shale, quartzarenite , sublitharenite, and graywacke were metamorphosed to phyllite, quartzite, and metagraywacke during two syntectonic phases and one post-tectonic phase. The earliest syntectonic metamorphism was associated with development of isoclinal folds and may have produced amphibolite or greenschist facies. It was succeeded by retrograde metamorphism of greenschist facies syntectonic with and post-tectonic to development of southeast trending folds.

Mica, chlorite, iron oxides, and graphite are strongly developed parallel to isoclinal' fold axial planes and quartz c-axes display preferred orientation related to isoclinal fold axes. These minerals display weaker preferred orientation related to southeast trending folds. Chloritoid, Mn-garnet, chlorite, and mica display random orientation and may have developed concurrently with ubiquitous post-tectonic quartz veins.

Included in

Geology Commons

Share

COinS