Matching Magnetic Source Models to Geology ? An Example from the Bendigo 1:250,000 Map Sheet, Victoria

Abstract

Relationships between magnetic field anomalies, inversion models and geology are investigated, using examples from the Bendigo 1:250,000 map sheet. The objective of this study is to develop a methodology for encapsulating these relationships in databases which can then be used in interpretation elsewhere. A magnetic anomaly database distils the magnetic field variations from which quantitative estimates of source bodies can be recovered. A related database of inversion models provides those source parameters and supplies a more direct linkage between geology and magnetic field anomalies than can be achieved simply by spatial correlation of the anomalies and geological mapping. Sensitivity tests are important in evaluating the role of inversion in the process of recovering geological information from magnetic field data. Such tests suggest that to recover depth to a buried source it is generally preferable to treat magnetization as a free variable during inversion rather than risk biasing depth estimates by imposing an incorrect fixed value.