Probabilistic evaluation model of an electromagnetic target with a given gravity anomaly

Abstract

An exploration strategy for base metals (sulfides) frequently involves electromagnetic (EM) surveys followed by detailed gravity surveys over the areas of EM anomalies to define clearly drilling targets. Since drilling costs are high, an objective and accurate quantitative target evaluation is necessary. The expected sulfide content of a target is the only evaluation parameter available from geophysics which may have some correlation with the target economic value. The depth, dip angle, and strike‐length of a dipping lenticular electrically conductive body can be evaluated from EM data. Then, the expected sulfide content is evaluated from the gravity data by excess mass calculation. However, there is always some geologic noise in the gravity data which tends to cause an overestimation of the sulfide content. We find that statistical properties of the gravity noise and sulfide content statistical histograms of EM anomalies must be taken into account to make an accurate evaluation of the expected sulfide content of EM anomalies.