Date of Award

4-1983

Degree Name

Master of Science

Department

Geosciences

First Advisor

Dr. Ronald B. Chase

Second Advisor

Dr. Christopher J. Schmidt

Third Advisor

Dr. W. Thomas Straw

Access Setting

Masters Thesis-Open Access

Abstract

Peltitic schist, quartzofeldspathic gneiss, and calc-silicate rocks of the Precambrian Belt Supergroup hav ebeen intruded by granatic plutons of the northeastern Idaho batholith within the vicinity of the southern Bitterroot Range, Montana. These units were mylonitized along the eastern margin of the intrusive complex, with shear surfaces presently dipping approximately 20° to the east. Rhyolitic ash flows and associated mafic to felsic dikes developed on and within the granitic-metamorphic terrance during Tertiary time. Numerous northeast- trending and northwest-trending faults and joints are present throughout the mapped region.

The following events play a major role in the geologic history: 1) amphibolite- grade metamorphism, 2) emplacement of granitic plutons, 3) mylonitization resulting from crustal adjustments or forceful magmatic intrusion, and 4) volcanism associated with faulting, perhaps, as part of a caldera system.

Included in

Geology Commons

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