MLA 23-94 - State of Arizona Department of Mines and Mineral ...

MINERAL APPRAISAL OF CORONADO NATIONAL FOREST, ARIZONA, PART 15EXECUTIVE SUMMARYbyMark L. Chatman ~IIIIIiIIIIiiiISUMMARY OF SIGNIFICANT FINDINGSFavorable geologic environments in Coronado National Forest have been mined in thepast for large quantities of base-and-precious metals; one metal mine is currently(1994) active.In the foreseeable future, most major mineral exploration and development will beconcentrated in the western part of the Forest, near the growing Nogales-Tucson, AZ,urban corridor.Future large-scale mining is most likely to ensue in the northern Santa Rita Mountains,south of Tucson, AZ, at a group of near-surface copper-porphyry deposits with over400 million short tons of copper resources.Shallow, low-grade, refractory gold deposits, west of Nogales, AZ, have high potentialfor future development. Gold grades are nearly sufficient to support mining undercurrent gold prices, but known tonnages are insufficient, based on sparse subsurfaceexploration. Geologic indicators suggest additional tonnage may be present but as yetundiscovered.Sporadic future exploration of deep copper-porphyry deposits in the PatagoniaMountains, northeast of Nogales, AZ, is possible, but the possibility of mining themin the foreseeable future is diminished because of deep burial of the combined severalhundred million short tons of copper resources.Air-quality standards in Pima County, which increasingly have become more stringent,may eventually force development of stone and aggregate sources from more distantlocalities, such as Cochise County. If so, aggregate, limestone, marble, decorativestone, rip-rap, and gypsum sources from several localities in the National Forest mayexperience prospecting and development.Exploration for undiscovered copper-porphyry deposits in the northern part of the SantaCatalina Mountains, northeast of Tucson, appears to be warranted, based on limitedgeologic data.1 Geologist, Resource Evaluation Branch, Intermountain Field Operations Center, Denver, CO.