Geochemical anomalies in the igneous wall rock at Mayflower Mine, Park City District, Utah

Approximately 500 samples were collected from the igneous wall rock of the Mayflower Mine, Park City District, Utah. The mine is the sixth largest gold producer in the United States. The samples were analyzed for copper lead, zinc silver, manganese, sodium, potassium, calcium, magnesium and iron by atomic absorption spectrophotometry. Gold was determined by neutron activation analysis, silicon and sulfur by x-ray fluorescence spectrometery. The calculation of the mineral norm from the chemical analysis showed the wall rock to be of granodioritic composition. A study of selected vein samples indicates that the copper, silver and gold content in the veins increases to the eastern and northern part of the mine while lead and zinc show the opposite pattern. The trace element distribution in the wall rock was found to reflect this distribution. The lead and zinc aureoles were found to be confined to the immediate vein area. This indicates low mobility of the two elements. Copper, gold and silver show narrow aureoles in the western part of the mine. The aureoles become much wider in the eastern part where the concentrations in the veins are higher. The manganese aureole is most extensive in the western part where the manganese content of the vein is highest. High anomalous values of copper, lead and zinc in the wall rock coincide with the presence of the minerals chalcopyrite, galena and sphalerite respectively. The results indicate that the size of the trace element aureoles is affected mainly by the mobility of these elements and their concentration in the ore forming solution. Analysis of the wall rock for major elements shows addition of silica in the vein area and some leaching in the immediate wall rock. Aluminum and potassium are enriched in a zone extending 20 to 60 feet away from the vein. In this zone, calcium and sodium are leached. Magnesium and iron show an enrichment zone at some distance from the vein. In the eastern part of the mine alumino-silicate minerals are to some extent replaced by anhydrite, an observation which is also indicated by the very high sulfur values in the eastern wall rock traverses. Factor analysis of the major elements shows clearly the grouping of major elements into two major alteration zones, a potassium rich sericitic zone and a magnesium-iron rich chloritic zone --Abstract, pages ii-iii