The Application of Geologic Mapping, Core Logging, and 3-D Geoscientific Data Integration in the Exploration and Resource Expansion of Porphyry Copper-(Gold) Deposits: Examples from Recent Discoveries in Ecuador and Chile

Abstract

The collection of accurate geologic data is critical in minerals exploration. The successful visualization, integration, and interpretation of quantitative vein abundance data, associated selvages of wall-rock alteration mineralogy, sulfide mineral proportions, and metal zoning facilitate the path to discovery and orebody delineation. The application of the Anaconda method, developed by the Anaconda Copper Mining Company geologists in the 1960s, to geologic mapping and drill core logging has facilitated the discovery and resource expansion in the giant Alpala porphyry Cu-Au-Ag deposit in northern Ecuador and the Cortadera porphyry Cu-Au-Mo deposit cluster in northern Chile. In both porphyry systems, high-grade zones have been targeted through the delineation of an intrusion and vein chronology that allows for the recognition of early-stage causal intrusions, zones of abundant porphyry-style quartz veins, and elevated chalcopyrite to pyrite ratios. Increased amounts of molybdenum, as molybdenite along fractures and in quartz veins, as well as anhydrite veins and disseminations, correlate with proximity to the deposit cores. The field-based methods presented in this article have proven useful in porphyry exploration for decades. The application of the Anaconda method of geologic mapping and core logging by geologists can assist in the targeting of high-grade cores of deposits and improved estimation of metal resources.