Interpretation of a Sub-Audio Magnetic survey over the Lena Shear near Cue, Western Australia

Abstract

The Lena Shear is a gold-anomalous structure that sits in an Archaean greenstone belt and extends for more than 7 km. It is partially obscured by regolith and an extensive salt lake system over its length. Identification of the shear under cover is hampered by the poor magnetic susceptibility contrasts of the host lithologies. A Sub-Audio Magnetic (SAM) survey over an exposed section of the Lena Shear recorded anomalous equivalent magnetometric resistivity (EQMMR) values proximal to the shear, but not directly associated with the geologically mapped location of the shear as expected. An interpretation of the Sub-Audio Magnetic survey highlights current channelling in structural and geological elements that were previously unknown. The relationship between the shear zone and the anomalous EQMMR response is unresolved because of the stronger response of an adjacent ultramafic unit. It is likely that deep weathering of rock units, contacts and shears has combined to produce the observed anomalies.