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The challenge

A challenge and an opportunity for the mineral explorers

Junior minerals explorer, Sahul Exploration Pty Ltd, has over six years of exploration experience in the relatively understudied Nullagine region in the eastern part of ~3.8 billion years old Pilbara Craton of Western Australia. The coincident occurrence of gold (Au), copper (Cu), lead (Pb), and zinc (Zn) on Sahul’s tenements represent important componentry in new technology used in the renewable energy, space, and medical sectors, piquing both economic and scientific interest.

Scenic landscapes in the east Pilbara with Exploration Manager, Arno Delahaye carrying out field mapping.

Given its unique and ancient geological history, the Archean Pilbara Craton provides insight into the geological and tectonic processes controlling the development of mineral systems and economic mineralisation of the early Earth. Compared to its western counterpart, the structural and metallogenic history of the East Pilbara Granite-Greenstone Terrane has remained understudied, representing both a challenge and an opportunity for the mineral explorers.

Located in the McPhee Dome of the Nullagine area, Sahul’s tenements have previously been considered prospective for porphyry and VMS style mineralisation. During the initial stages of exploration, Sahul identified anomalous Au, Cu, Pb and Zn from soil surveys, historic workings, and RC drilling campaigns. Company geologists noted that a deeper understanding of hydrothermal alteration footprint and the structural controls for these anomalies would greatly assist their geological understanding and targeting. After learning about the Kick-Start program, the Sahul Exploration Manager, Arno Delahaye (MSc, BSc) connected with CSIRO scientists.

Through consultation and collaborative planning, Sahul and CSIRO developed a research project utilising the technology and geological expertise in the CSIRO Mineral Resources Discovery Program. The fruitful partnership was facilitated through the Kick-Start Program, providing valuable cost-matched funding to support the collaboration, ultimately spanning two separate research projects.

Our response

A new understanding of the architecture and mineral footprint

To maximise the value of existing company data and drilling efforts, the focus of the first Kick-Start project was to investigate the hydrothermal alteration zonation from hyperspectral mineralogy in key RC drillholes and to interrogate the existing soil geochemical data. This multi-pronged approach aimed to establish a better understanding of the potential vectors towards mineralisation and characteristics for the mineral system(s) spanning the tenement, guiding future targeting.

During this project, CSIRO collected hyperspectral data from RC drillhole chip trays using the HyLogger-3 system in the ARRC Kensington Drill Core Laboratory. The hyperspectral data analysis revealed interesting mineral compositional vectors, such as white mica crystallinity, and the presence of pyrophyllite that were spatially coincident with anomalous metal trends, hinting a strong structural control on both Au and Cu mineralisation.

Structures observed from rock outcrop during field mapping.

Building on these new findings, the second Kick-Start project was designed to investigate the structural controls on hydrothermal activity and the mineral system footprint. This project incorporated a new diamond drillhole commissioned through the Western Australian government-funded, Exploration Incentive Scheme (EIS), as well as new company RC and diamond drilling.

This project combined a multi-scale structural and paragenetic study of the Sahul prospect, including drillhole-to-microscopic scale characterisation revealing a polyphase mineralisation history.

These observations were integrated with camp-scale structural mapping and airborne hyperspectral image data to develop a new understanding of the architecture and mineral footprint of the early magmatic-hydrothermal base metal system and the overprinting orogenic gold mineralisation.

The results

Research collaboration facilitated by the Kick-Start Program

The research collaboration facilitated by the Kick-Start Program yielded a cohesive structural and mineralogical understanding of the targeted geological area. Working closely with the Sahul geologists, the two Kick-Start projects rapidly advanced the geological and metallogenic understanding of the Sahul prospect, providing greater context of anomalous metal occurrences.

The project outputs provide a strong foundation to guide future exploration by Sahul Exploration and enhance their exploration targeting and mapping success.

“Over the last six years, we conducted systematic exploration work that led to a fantastic gold discovery, in a geological unit that had never seen a drill hole.

In 2021, we drilled our first holes at the Heart prospect under the EIS scheme, a wonderful State Government initiative. In 2022, we confirmed our discovery with additional drilling.

It took a couple of years from discovery to put together a coherent geological model. This was only possible with Sahul entering into a [Kick-Start] research agreement with the CSIRO. Dr Heta Lampinen and Dr Helen McFarlane went beyond all expectations with their work and interpretations. Our brainstorming sessions have been very educational, and I certainly hope we will have the opportunity to work together again.”

— Arno Delahaye, Exploration Manager, Sahul Exploration.

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