Electrical and transient electromagnetic modelling of a copper prospect near Cobar, NSW

Abstract

The electrically conductive nature of deeply weathered overburden is a significant hindrance to electrical and electromagnetic exploration. These difficulties can be greatly reduced through well-designed surveys and with modern processing and modelling techniques. Drilling and geochemical sampling in the Cobar Basin encountered a 995 ppm copper anomaly coincident with an abnormally deep weathered zone. Inverted resistivity data reveals a weakly conductive zone below the observed copper anomaly. Modelling of transient electromagnetics shows a narrow conductor with a 0.45 millisecond time constant underlying the overburden. A 60 m wide fault with a 250 Ω-m resistivity below a 40 m deep weathering trough is interpreted to be the cause of the resistivity, transient electromagnetic and coper anomalies.