ABSTRACT

The area is underlain by sedimentary rocks which occupy the upper plate of the Ermont thrust sheet. These rocks range in age from upper Mississippian to lower Tertiary and are thrown into a series of steeply dipping to overturned asymmetric folds The thrust sheet is believed to be truncated by plutonic igneous rocks of the Pioneer Batholith. The plutonic rocks are generally described as biotite-hornblende quartz monzonite, however, they range in composition from quartz diorite to granite. It has been suggested that several separate plutons may actually be involved.

A fairly narrow belt of thermally metamorphosed sediments parallels the present visible igneous-sedimentary contact. However, in the northern part of the thesis area, this belt widens to become approximately one and a half miles in width, apparently indicating a rather shallow pluton emplacement The original sedimentary rocks along the surface igneous-sedimentary contact, within the thesis area, were generally impure limestones of the Mission Canyon and Amsden Formations which have since become tactities, skarns, and marbles. These tactites and skarns have been mineralized, primarily enriched with copper and tungsten.

A quantitative x-ray fluorescence analysis was performed to determine the copper, molybdenum, and tungsten content of the rocks within the thesis area. Samples from the Indian Queen and Greenstone mine areas contain an average content of 1.77 percent Cu, 0.016 percent Mo, and 0.036 percent W by weight Igneous, sedimentary, and metamorphic rock samples from areas away from the physical contact zone contain 0.0039 percent copper and 0.0093 percent Mo on the average. The presence of tungsten was not detected. At present the mineralized rocks within the area are not economically mineable. However, the metasomatized sediments of the Mission Canyon and Amsden Formations hold the most promise for future economic development.