Determining the precise age of ore deposition in many mining districts has been an elusive geochronologic problem. Paleontologic and isotopic determination of the ages of pre- and postore units commonly provide only broad limits, and in many deposits suitable materials for dating are unavailable. Especially promising is the possibility of direct radiometric dating of gangue and alteration minerals such as alunite, adularia, and coarse sericite, but in most previous attempts independent age control on the host rock and postore rocks has been lacking. However, a study on alunite (Silberman and Ashley, 1970) from the Goldfield district, Nevada, has demonstrated that K-Ar ages from hypogenea lunite can give reliable ages in comparison [...]
