Near real-time drillhole data analysis using non-destructive mineral exploration tools

Field-based data acquired from drillholes by pXRF, spectrometer, and wireline loggings can provide prompt, relatively inexpensive and precise information about the geochemistry, mineralogy and petrophysical properties of geological units. When on-site data capture is followed by proper visualisation and statistical analyses, these non-destructive methods can assist in rapid interpretations and decision makings.

Identification of distinctive units and critical zones in exploration under cover can be challenging for even experienced geologists when dealing with drilling chips. This study presents a data-driven framework for rapid boundary detection from drillhole cuttings through a combination of geochemical, mineralogical, and geophysical data. The workflow was tested on two drillholes during a drilling campaign conducted by Mineral Exploration Cooperative Research Centre (MinEx CRC) for Geoscience Australia's Exploring for the Future program in the Delamerian orogeny located in far western New South Wales, Australia.

A multivariate change point detection technique was applied to the 30 effective attributes retained from various geochemical variables, spectral scalars, and petrophysical parameters obtained through field-based instruments. These include major (e.g., Al, K, Ca, Fe etc.), conserved (Ti and Zr), and trace elements (e.g., Cu, Pb, and Zn), as well as spectral features associated with ferric oxides, kaolinite, micas, smectite, chlorites, and epidote. Natural gamma, electrical conductivity and resistivity, and magnetic susceptibility were also used as petrophysical parameters. Various interfaces between the weathered profile and basement rocks were detected at two scales providing useful insights into the stratigraphy and detailed geochemical logs previously carried out by the field geologists. Using different data types resulted in more reliable boundary detection compared to the limitations of using each data type on its own. This approach was also able to delineate a critical zone in the saprock zone above the fresh basement where elevated concentrations of lead and zinc are accumulated, providing guidance for more detailed sampling and analysis.

This framework can be utilised for data-driven stratigraphy/lithology logging, regolith characterisation, identification of the key horizons for further sampling and studies and can facilitate decision-making during exploration drilling campaigns.