Genesis and Timing of Gold Mineralization at Mineral Ridge, Esmeralda County, Nevada, and Implications for Future Exploration and Discovery

摘要

After more than 100 years of exploration and exploitation in the Mineral Ridge area there has never been a comprehensive study or determining of the nature of the gold mineralization, controls, or appropriate and effective exploration tools. Scorpio Gold has been the first operator to employ many of the common tools used today for exploration. Some of the surveys conducted and compiled by Scorpio are satellite imagery of various band widths, Airborne VTEM surveys, geochemical surveys including multi-element analyses, regional and detailed geological/structural mapping, and drilling outwards from known mineralization. The poorly understood Mineral Ridge area is now revealing its secrets, some of which are as follows: ? Genetically, gold occurs in an Eocene, sulfur-poor, base-metal skarn system related to a metamorphic core complex. ? Gold is most closely associated with younger pegmatite-alaskite-quartz sills, and it appears to be concentrated along NW-striking axes of open folds developed during the metamorphic event. These sills occur within a "carapace" of Wyman formation metasediments above the core intrusive. ? Miocene and later, extension features are commonly occupied by mafic dikes. This extension, along with related rotation, has offset gold bearing strata, but these post-mineral events neither introduced more gold nor significantly "remobilized" gold. * Due to the relative lack of sulfide content and absence of epithermal alteration associated with the gold event, typical geophysical exploration methods are less effective in directly identifying favorable exploration areas at Mineral Ridge. Magnetic (basement) highs remain potential targets. ? Given the nature of mineralization, relatively shallow depths, and general lack of cover over the favorable carapace package, drilling remains the best and most efficient exploration tool. Interpretation of drilled areas is now commonly done in the framework of the 3D lithology model for maximum efficiency. ? Past assumptions about favored hosts such as the "Mary Limestone", are now shown to be without merit in guiding future exploration.