Characteristics of magnetic sources and guidelines for exploration in the Cobar area N.S.W.

Abstract

Many of the ore deposits in the Cobar area contain sufficient pyrrhotite and/or magnetite to form suitable targets for magnetic exploration methods. Hence, aeromagnetic survey, supported by ground magnetics is a primary method of exploration in this area. However, widespread occurrences of magnetic material (maghemite and other lateritic minerals) at or near the surface commonly produce a magnetic noise which may mask the response of bedrock sources, or produce anomalies which are hard to distinguish from those due to bedrock sources. The characteristics of magnetic orebodies, and surface or near-surface occurrences of maghemite, have been studied by field surveys and laboratory measurements on rock samples. Modelling, data processing, and signal enhancement have been used to study the use of magnetic methods for exploration in the Cobar area. These studies show that the use of magnetics for exploration in the Cobar area requires very careful attention to survey specification, data processing, and interpretation of results, to ensure reasonable effectiveness throughout much of the area.