Rutile as a pathfinder for mineral exploration
Under the microscope: examining rutile (falsely coloured yellow in this image) as a pathfinder for critical minerals. Image: J. K Porter, et al.
In the hunt for new mineral deposits in Western Australia, researchers at Curtin University have turned their attention to the mineral rutile as a possible indicator.
After analysing rutile grains from across the state, the team found that rutile holds distinct geochemical signatures in different ore-forming and non-ore forming geological environments. This insight will be useful, and even game-changing for explorers looking for new critical mineral deposits around Australia, particularly when it is coupled with the fast data processing capability of machine learning.
At this point in Australia’s history, most at- or near-surface mineral deposits have been discovered. In order to help find new deposits, researchers are developing new techniques to identify mineralisation in fresh rock, which challengingly, is located beneath tens to hundreds of metres of obscuring weathered rock across around 80 percent of the Australian continent.
‘Seeing’ below weathered rock which covers around 80 percent of the Australian continent is the biggest challenge that geologists have in finding new mineral deposits. Image: Dr Jennifer Porter
So researchers look to rutile: a robust mineral that is found in many rock types in small amounts, and can be eroded from parent rock and transported in sediments over long periods of time. Rutile contains trace elements that can give clues about how the mineral formed, as well as its economic mineral association. This trace element geochemistry makes rutile an ideal candidate as a potential exploration tool.
In this recent study on rocks of Western Australia, researchers from Curtin University sourced rutile from as many different ore types as possible in Western Australia including from known gold, gold-copper, lamprophyre, carbonatite, pegmatite, and VHMS deposits, and from most barren rock types. They then analysed the rutile grains’ trace element geochemistry using AuScope enabled instruments at the John De Laeter Centre, and conducted a statistical analysis in order to identify ore system-specific characteristics.
General geological map of Western Australia indicating the location of studied deposits, their respective ore types and GSWA samples for background igneous-metamorphic rocks. Image: J. K Porter, et al.
Their statistical analysis of 3149 samples revealed nine distinct rutile groupings, each giving insight to the formation conditions of the host rock, including temperature, age, source rock type, and ore association.
Lead investigator, Dr Jennifer Porter explains the implications of this study for economic geologists:
“The exploration industry may be able to use this background dataset and classification system as an exploration tool. If the rutile chemistry matches a rutile known to be associated with a gold source, especially from the Kalgoorlie and Big Bell areas, that rutile is likely sourced from a similar system.”
They can also use this database to compare with rutile of unknown source. But most excitingly:
“The results of this study can form a basis upon which a supervised machine learning algorithm can be used to quickly predict formation environments, such as ore association, lithology and metamorphic grade of detrital or unknown rutile, which is beneficial to mineral exploration.”
The research team now look forward to developing the database to include rutile from outside of Western Australia, and from a larger range of mineralised systems to help make rutile classification more precise, and allow it to be used in gold exploratio, in the same way that garnet is used to locate diamond mineralisation.
AUTHORS
By Dr Jennifer Porter,
Curtin University; and
Jo Condon, AuScope
ACKNOWLEDGEMENTS
This research was funded by a
WA industry-government consortium including the Geological Survey of WA, Independence Group and the Mineral Research Institute of WA
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Dr Jennifer Porter