Joshi, Ranee1,2, Madaiah, Kavitha1,2, Jessell, Mark1,2 and Lindsay, Mark1,2
1Centre of Exploration Targeting, School of Earth Sciences, University of Western Australia, 35 Stirling Highway, Crawley 6009 Western Australia,2Mineral Exploration Cooperative Research Centre (MinEx CRC), School of Earth Sciences, University of Western Australia, 35 Stirling Highway, Crawley 6009 Western Australia
Exploration and mining companies rely on geological drill core logs to target and obtain initial information on the composition and size of mineralized zones and/or a potential ore deposit. The drilling data is also used as inputs to 3D geological modelling to allow better visualization and understanding of the geology in a local and/or mine scale. With the amount of legacy drilling data available in geological surveys, extraction and processing of these data will allow for better shallow subsurface constraints for semi-regional and regional 3D geological models. These models will be helpful in designing mapping programs and more efficiently targeting sustainable new discoveries.
In this contribution, we focus on the processing and classification of lithological logs from the Geological Survey of Western Australia Mineral Exploration Reports Database in the Yalgoo-Singleton Greenstone Belt (YSGB) region. We refer to lithological logs as the component of a geological log that contains the dominant rock type in a specific downhole interval. Inevitably, lithological drill core logging is subjective and plagued with uncertainty, particularly as at a regional scale it is likely to have been conducted by tens to hundreds geologists, all of whom would have their own personal biases. It can also be difficult to recognize lithology with confidence and to establish subtle variations or boundaries in apparently homogeneous sequences. Given that we are dealing with geological legacy datasets, a large amount of important data are recorded in an unstructured textural form using varying geological drill core logging forms and formats depending on the company, logging geologist, investigation method, investigated materials and/or drilling campaign.
To resolve these challenges and unlock the vast information store in legacy drilling datasets, we developed dh2loop (github.org/Loop3D/dh2loop), an open-source python library that provides the functionality to extract and standardize drill hole data and export it into readily importable interval tables (collar, survey, lithology). dh2loop addresses the subjective nature and variability in nomenclature of lithological descriptions within and across different drilling campaigns by integrating published dictionaries, glossaries and/or thesaurus that were built to improve resolution of poorly defined or highly subjective terminology and idiosyncratic logging methods. Furthermore, lithological data is classified into multi-level groupings that can be used to systematically upscale and downscale drill hole data inputs for multiscale 3D geological modelling. dh2loop also provides drill hole desurveying and log correlation functions so that results can be plotted in 3D for analysis and comparison. dh2loop formats legacy data bridging the gap between utilization and maximization of legacy drill hole data and drill hole analysis functionalities available in existing python libraries (lasio, welly, striplog).
Keywords: drill core logging, legacy data, subsampling, Yalgoo-Singleton Greenstone Belt
We acknowledge the support of the MinEx CRC and the Loop: Enabling Stochastic 3D Geological Modelling (LP170100985) consortia. The work has been supported by the Mineral Exploration Cooperative Research Centre whose activities are funded by the Australian Government’s Cooperative Research Centre Programme. This is MinEx CRC Document 2020/41.
Ranee is a PhD candidate in the Centre for Exploration Targeting working with Mark Jessell, Mark Lindsay, Nicolas Thebaud and Tim Ivanic. She works on developing subsampling workflows to be able to automate multiscale 3D geological modelling. This project is a collaboration between the Loop and MinEx CRC consortium.