| Supergene enriched, low-grade oxidized porphyry copper deposits are of great economic value. Oxidized porphyry sections are economic targets because even low-grade prospects have the potential to produce low-cost copper in an environmentally friendly fashion due to easy leachability and high recovery rates of the oxide mineralization. The MacArthur Mine, in the historic Yerington mining district of Nevada, is the focus of this study. The MacArthur is a tilted oxidized porphyry deposit, partially mined by open pit methods, hosted in the Jurassic Bear Quartz Monzonite of the Yerington batholith. The objective of the study is to define controls of copper oxide mineralization within the open-pit mine. The objective is investigated through a multi-data study including rock descriptions, geochemistry, spectral radiometry, and fracture density. Multivariate factor score analysis of geochemical data defined potassic and sodic-calcic alteration as well as multiple elements (Co, Ni, Zn, As, Mo, Ag, Cd, U) absorbed in the mineral neotocite (Mn, Cu, Fe)SiO2 x H2O. Finally, high geochemical associations where found in two groups 1 - Cu, Fe, Co, Mo, Ni, U, and 2 - Al, K, Rb, Na, Mn. The high correlations found in the groups represent the hydrothermal event at the MacArthur. Chlorite and epidote identified in spectra using Spectral Analyst tool in ENVI RTM demonstrate a propylitic alteration signature. Spectral Analysts identified several secondary iron and copper minerals produced in oxide zone geology. Fracture density studies defined 98.3% of all fractures in the MacArthur pit are associated with oxide zone produced copper and iron at a close to even distribution amongst fracture families. |
