GEOPHYSICAL AND GEOCHEMICAL LOGS FROM A COPPER-OXIDE DEPOSIT, SANTA-CRUZ PROJECT, CASA-GRANDE, ARIZONA

In support of an in-situ leaching experiment, five holes drilled into a copper oxide deposit have been logged with geophysical and geochemic al tools developed for use in the petroleum industry. When combined wi th geological description, chemical analyses, and mineralogical data f rom core and cuttings, the logs provide information regarding the alte ration, fracturing, copper distribution, porosity, and permeable zones . Correlations among sonic velocity, rock strength from mechanical tes ts on core, and alteration indicators from neutron and potassium logs demonstrate a close link between the state of alteration and the mecha nical state of the rock. Neutron activation, natural gamma-ray, and de nsity logs, in combination, correlate so well with copper assays that log-based prediction of copper content is possible; in addition, an es timate of whole-rock mineralogy is presented in log format. Based on c omparisons of flow logs and acoustic logs obtained in the same holes, reductions in acoustic velocity appear to be the best indicators of pe rmeability increases.