Controlled-Source Audio-Frequency Magnetotellurics (CSAMT) is a low-impact, non-intrusive, ground geophysical surveying method, used extensively in minerals and ground water exploration. The main factors affecting the measured resistivity are like AEM and include the rock porosity, moisture variations and the presence of certain mineral assemblages. CSAMT data in mineral, mining and hydrological surveys can provide critical information about geological structure, lithology, water-table trends, pore fluid salinity and certain mineral concentrations.
CSAMT works by transmitting a controlled signal using a series of frequencies from one location into the ground using a grounded electrical source. The response of the subsurface is then measured through electric and magnetic field receivers placed at various distances, providing consistent, variable signals for the precise imaging of geological structures. The ratios of orthogonal, horizontal electric and magnetic field magnitudes are then used to calculate the resistivity structure of the earth.
By measuring resistivity contrasts in the subsurface, CSAMT identifies key indicators of mineralisation such as variations in rock type, structure, and alteration. Worldwide, the technology has been used to delineate epithermal gold systems, massive sulphide deposits, and porphyry copper targets.
One of the significant advantages of CSAMT is its ability to penetrate deep into the Earth’s crust, often to depths of several kilometres or more, while maintaining high resolution readings. This allows explorers to detect buried ore bodies, alteration zones, and structural features.
Kavango is pioneering the use of CSAMT in the KCB to map subsurface geology, identify significant trap-site architecture and identify potential mineralised zones beneath the Kalahari sands. By generating detailed resistivity profiles down to depths exceeding 4,000m, our optimised CSAMT technique allows us to “slice” through the earth and detect key geological structures like folds, faults and trap-site structures that controls copper-silver mineralisation associated with the D’Kar/Ngwako Pan Formation contact zone across the region.
If validated, Kavango’s approach could transform mineral exploration in Botswana, enabling more efficient target generation and significantly reducing reliance on early-stage drilling.
