1Geological Survey Of New South Wales, Londonderry, Australia
The RoXplorer® coiled tube drilling system is scheduled to be used for MinEx CRC drilling activities in New South Wales (NSW) from 2022 for National Drilling Initiative (NDI) areas South Cobar, North Cobar, Mundi, Forbes and Dubbo. This recently developed system provides a faster and more cost-effective alternative to conventional diamond and reverse circulation drilling, while also offering safety advantages and reduced environmental impacts (Hillis et al. 2014). Ongoing technology development within MinEx CRC will maximise RoXplorer® production during MinEx CRC drilling campaigns, with 5 km spaced holes planned throughout NDI areas to better understand basement and cover sequence geology and the potential for undiscovered ore deposits buried beneath cover.
In this pilot study, two trial drillholes from the RoXplorer® system were scanned using the HyLogger-3TM instrument to determine the best method for scanning RoXplorer® chips and to assess the quality of visible-near infrared to shortwave infrared (VNIR-SWIR) and thermal infrared (TIR) spectra for routine interpretation. Downhole chip samples produced by the RoXplorer® range in size from ~10 µm to ~4 mm (Tiddy et al. 2019), however a separated coarse fraction with sizes ranging from ~1 mm to ~4 mm was used for both drillholes. Outcomes from this study included:
- VNIR‒SWIR and TIR spectra were found to be reliable for routine mineral identification, tracking mineral chemistry and identifying lithological variations downhole.
- Black plastic chip trays produced better spectral results than clear or white trays.
- Larger 50 mm x 50 mm chip compartments produced better spectral results than standard 25 mm x 50 mm chip compartments.
- Regular linescan mode produced spectra with higher reflectance and therefore better sensitivity, than chip scanning mode.
- Rinsing chips with water to remove clinging fines increased TIR reflectance by up to 40% and reduced volume scattering effects.
The findings of this work will be used to help develop a consistent approach to scanning future RoXplorer® drillholes across the state and territory Geological Survey HyLoggerTM nodes.
Hillis R. R., Giles D., Van Der Wielen S. E., Baensch A., Cleverley J. S., Fabris A., Uvarova Y. (2014). Coiled tubing drilling and real time sensing – enabling prospecting drilling in the 21st Century? Society of Economic Geologists Special Publications, 18, 243–259.
Tiddy C. J., Hill S. M., Giles D., van der Hoek, B. G., Normington V. J., Anand R. R., Baudet E., Custance K., Hill R., Johnson A., McLennan S., Mitchell C., Zivak D., Salama W., Stoate K. Wolff K. (2019). Utilising geochemical data for the identification and characterisation of mineral exploration sample media within cover sequence materials, Australian Journal of Earth Sciences, DOI: 10.1080/08120099.2019.1673484
Jake completed undergraduate studies at Curtin University and honours at the University of Tasmania before spending 4 years working for Mineral Resources Tasmania with the HyLoggerTM team. He is currently employed as a spectral geologist with the Geological Survey of NSW to oversee the delivery of the NVCL project.