Further study on deep penetrating geochemistry over the Spence porphyry copper deposit, Chile

A study of deep penetrating geochemistry—the surface exploration techniques for finding concealed mineral deposits—was carried out over the Spence porphyry copper deposit in Chile by Australian, Canadian and Chinese laboratories using selective weak leach methods and is briefly reviewed here. Erratic and weak copper anomalies were obtained above the Spence deposit, which is concealed below a thick piedmont gravel cover. In the literature, such patterns are common in most of the weak selective leach studies carried out over known buried deposits. During exploration in unknown area, such weak leach techniques lead to some success and many dry holes. In this paper, stronger selective leaching methods are developed for oxides and sulfides, which may be the stable end products transformed and accumulated by a mobile precursor phase carried upward through the overburden by gas or water through long spans of geological time. The data obtained by the methods developed in this paper produced more significant and consistent anomalous data than previous efforts. Consequently, the leach approaches described here may increase the effectiveness of deep penetrating geochemistry in exploration for concealed ore deposits.