MBGS recently used downhole geophysical logs to correlate stratigraphic units throughout an iron ore deposit in Australia. The foresight of the client’s geologist to run geophysical logs in their exploration drill holes across the magnetite deposit proved to be of extraordinary benefit. Through utilizing the geophysical logs, MBGS were able to assist the client to improve the recognition and classification of the ore and stratigraphic boundaries to refine the geological model, and to assess different scenarios for selective mining of the ore-rich layers reducing internal dilution by waste.

MBGS reviewed geochemical analysis, assessed geophysical log quality and confirmed that magnetic susceptibility with other geophysical logs could successfully demonstrate the strata-bound nature of the mineralisation occurring within discrete layers. Magnetic and non-magnetic stratigraphic units were identified and correlated between drill holes across the deposit. Accurate layer thickness and depths could be measured from the geophysical logs and re-interpretation of faulting was undertaken.

Another valuable addition to the geological knowledge of the deposit was through the downhole Acoustic Scanner / Televiewer (ATV). The geotechnical information derived from core logging was limited (many holes drilled were RC), so MBGS’ branch of geophysical interpretation (ASIMS – Acoustic Scanner/Optical Televiewer & Sonic Log Interpretation) used the ATV logs to provide orientation data for identified geotechnically significant features such as joints, possible fault zones and dip of the strata.

Other benefits of utilising geophysical logs in metal deposits include the ability to have a targeted approach to the sampling process, improved exploration planning and potential to reduce exploration costs primarily by reducing the amount of coring and assays.

The added value to this project was significant through the combination of downhole geophysical data with experienced geologists able to process, interpret and integrate different types of data into a more robust understanding of the deposit, improving future planning and potentially reducing costs.