A Preliminary study of the use of oxygen isotope ratios as an exploration tool in the Park City District, Utah

The Park City district is located about 20 miles southeast of Salt Lake City, Utah. Exposed in the district are Mississippian to Triassic sediments and Cretaceous to Mid-Tertiary volcanic and intrusive igneous rocks. The structural geology of the district is rather complex. Most of the ore bodies are limestone replacements; others occur as fissure veins. If hydrothermal alteration of limestone significantly changed the 018 composition of carbonates as an inverse function of temperature, the 018 content of limestone wall rock might be expected to decrease as ore is approached, assuming relatively higher temperatures near ore. This principle was tested in the study. Carbonate samples were collected from parts of the Humbug (Miss.) and Morgan (Penn.) formations. The 018 values of about 70 samples were measured. In the Humbug formation, the 018 values of the samples appear to vary as a function of temperature and indicate the presence of ore about as much as 100 feet fro the sample site. In the Morgan formation, the presence of a mineralized fissure was indicated by the 018 values of samples collected as much as 900 feet from ore. The use of oxygen isotope ratios as an exploration tool does show promise in the Park city district and should be investigated further. This tool requires a basic knowledge of the district geology.