Representative, High-Spatial Resolution Geochemistry from Diamond Drill Fines (powders): an Example from Brukunga, Adelaide, South Australia

The analysis of drill powders (drill fines) extracted from fluid that is returned during drilling can provide a sampling media that records cm-scale changes in the geochemistry of the rock being drilled through. In addition to being an ideal sample media (~78% of particles are <38μm; cf. conventionally pulverised samples where ~42% of particles are <38μm) that is ready for analysis once dried, diamond drill fines may produce a larger sample per meter drilled than recovered by the core itself, and thus be a better representation of the rock that has been drilled through. For an HQ hole size (for rocks with specific gravity=3100kg/m3), the mass of drill fines produced in 1m of drilling is 12.5kg, whereas, the mass of the 1m in length of core for the same interval is 9.7kg. In this contribution we compare high-spatial resolution geochemistry collected by portable X-ray fluorescence (pXRF) and mineralogy collected by portable X-ray diffraction (pXRD) from 12m of diamond drill core to the corresponding interval of drill fines to highlight the depth fidelity (at the cm-scale) that this sample source may record. We also demonstrate that the drill fines that were previously discarded show high potential to act as a representative sample media of the lithology intersected by the drill hole and can be successfully used for analysis in real time. The integrated pXRF-pXRD data can be used to constrain lithologies and contacts between various units, hydrothermal alteration and ore types.