Abstract

This report describes the general geology of the Bingham mine and presents a 1:9,600 scale detailed mine geology map. Important new contributions shown on this map include (1) a prealteration monzonitic classification of igneous rock, (2) the Ohio Copper dike in Copper Notch, (3) the Alice W. dike extending into the porphyry phases in Carr Fork, (4) reinterpretation of gradational granite porphyry as a zone of hybridization around quartz monzonite porphyry, surrounded by a zone of recrystallization, (5) more detailed mapping of small calcareous sandstone and limestone beds, and (6) the delineation of subsidiary folds related to the Bingham syncline.Six major igneous phases of the Bingham stock intrude folded sedimentary rocks of the Butterfield Peaks and Bingham Mine formations. The folding, along with left-lateral, northeast tear faults, accompanied thrusting. Early equigranular phases are quartz poor compared to the later porphyry phases; both are intermediate in composition. Stocks are emplaced mainly into the Apex fold which is interpreted as a second-order fold on the southwest limb of the Bingham syncline. Hydrothermal alteration and mineralization is genetically related to the quartz monzonite porphyry, the major porphyry phase, based on zone patterns around the top of the intrusion. Later, normal, northwest faulting cut the intrusions and is related to Basin and Range tectonics.

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