MAGNETIC PROSPECTING FOR HALLOYSITE CLAY AND COPPER SULFIDE DEPOSITS IN THE EAST TINTIC MINING DISTRICT, CENTRAL UTAH

The objective of this study is to explore the possibility of mapping anomalies in the Earth’s total magnetic field to determine the existence and location of deposits of halloysite clay and related copper sulfide ores between the town of Mammoth and the ghost town of Silver City in central Utah. Halloysite clay is believed to originate in a reaction between limestone and sulfide-rich hydrothermal fluids. The study area is adjacent to the historic Dragon Mine, from which one million tons of halloysite clay were extracted between 1952 and 1973. Halloysite clay can be sold for use in polymeric composites, microwave attenuating composites, and high-tech ceramics, and as a petroleum cracking catalyst, and currently sells for $1000 per ton of unprocessed ore. The feasibility of the study was tested by measuring in-situ the magnetic susceptibilities of outcrops of halloysite clay and associated rocks using the ZH Instruments SM-30 Magnetic Susceptibility Meter. Mean magnetic susceptibilities were 2.1 × 10^-6 SI units, 5.6 × 10^-5 SI units and 15.32 × 10^-3 SI units for halloysite clay, limestone and quartz monzonite, respectively, so that the magnetic contrast among the relevant rock bodies was strong. Thus far, three profiles of the total magnetic field have been measured using the Geometrics G-856 Proton Precession Magnetometer with average profile length of 914 m and spacing of 3 m. There is clear correspondence between magnetic anomalies and exposures of halloysite clay, limestone and quartz monzonite. The subsurface rock bodies are currently being modeled using the Interprex IX2D magnetic interpretation software package. There is some indication that it may be possible to trace the pathway of sulfide-rich hydrothermal fluids and associated copper sulfide ores using anomalies in the total magnetic field. Results will be reported at the meeting.