By the team at SPH Engineering, with input from Dr Janis Karuss, Lead Geophysicist at SPH Engineering, and Trevor Grace, Director at AEROPHYSX

The use of drones in the mining industry has been taking off over the last few years, with an array of drone-based technologies being utilised to streamline mining operations, as well as for asset management and monitoring. Drone-based magnetometry is one of the technologies gaining traction in the mineral exploration sphere overseas and is under rapid development in Australia.

In the world of mineral exploration, searching for valuable deposits requires advanced techniques and tools. One such tool is magnetometry, which utilises the Earth’s magnetic field to identify potential mineral resources.

Magnetometry, in simple terms, involves measuring the strength of the Earth’s magnetic field at various locations. The magnetic field is not uniform globally; it exhibits variations and anomalies. These anomalies can be attributed to objects with magnetic properties beneath the Earth’s surface. For instance, underground large ore bodies or metallic structures can alter the nearby magnetic field.

Mapping these magnetic anomalies meticulously can offer insight into geological properties and potential mineral deposits.

Choosing the right survey methods

When it comes to mineral exploration, magnetometry has proven itself highly useful. Certain minerals, like iron or nickel, exhibit strong magnetic properties, making them detectable through magnetometry surveys. Minerals withoutinherent magnetic properties can still be identified indirectly by the changes they cause in the surrounding magnetic field.

Creating an exhaustive list of minerals that can be discovered using this method is challenging, as the focus is on identifying magnetic signatures that deviate from the norm, indicating potential areas of interest.

Mr Grace said that magnetometry does not actually directly detect minerals but instead maps out the geological structures that influence the magnetic field.

Mineral exploration teams can strategically plan future drilling locations along these paths by understanding the magnetic response of specific geological formations or fault lines. The information provided by magnetometry assists geologists in making informed decisions and optimising exploration projects.

Over the years, methods of magnetic surveying have evolved and advanced to meet the demands of mineral exploration.

Mr Grace said close collaboration between clients and geologists is an essential key to establishing clear objectives and realistic expectations. While magnetic surveying cannot directly pinpoint minerals, it can isolate areas of interest within the magnetic structure.

Factors such as line spacing resolution, linear versus nonlinear structures, and flying height in airborne surveys all come into play in magnetometry. Additionally, designing an effective survey strategy requires careful consideration of budget constraints, target identification and the desired level of detail.

In recent years, drone-based magnetometry has been used increasingly in mineral exploration. The process involves using drones equipped with magnetometers to map the Earth’s magnetic field.

Drone-based magnetometry offers unique advantages and limitations compared to other methods, such as ground-based surveys or satellite- based measurements.

Dr Karuss said the drone-based magnetometry provides a cost-effective solution for covering medium-sized areas that are otherwise challenging to access on foot or by larger aircraft. The method offers a middle ground between ground-based and standard airborne magnetometry, providing better resolution and lower costs than the latter.

In terms of the size of areas that can be effectively surveyed using drone-based magnetometry, Dr Karuss said that a few square kilometres are within a reasonable range. Larger areas – such as country- sized regions – may require alternative approaches due to budget considerations and constraints.

However, the ability to access remote and inaccessible locations makes drone- based magnetometry an invaluable tool in mineral exploration.

Example of how drone-based magnetometry can improve the accuracy of magnetic data. Image credit_ AeroPhysx

Mr Grace highlighted the significance of resolution in drone-based surveys, due to the fact that drones can capture data with unmatched precision by flying at lower altitudes..

With modern technology, high sample rates of up to 1,000Hz can be achieved, resulting in quality data that surpass regional surveys. This level of resolution is particularly advantageous in mountainous terrains, where conventional aircraft face limitations due to safety concerns.

Despite its benefits, drone-based magnetometry also has its limitations. Mr. Grace said there are obstacles when operating in large and inaccessible areas or when simultaneous gamma- ray surveys are required. Weight limitations constrain endurance, making it logistically challenging to cover extensive regions. Moreover, risks, such as encounters with dangerous animals, rugged terrains, or hostile locals, require careful planning and emergency procedures. These challenges may prove especially difficult for monitoring in the extensive, remote expanses of Australia where the country’s mineral resources are largely located.

Dr Karuss said that climate and weather conditions can also impact drone operations, particularly in polar regions where sudden strong winds and adverse weather changes can jeopardise the equipment. In addition, extreme heat – such as that found in certain parts of Australia – can have an impact on drone batteries as they can lose capacity and efficiency in high temperatures.

Although certain drones are more resilient to such conditions, it remains a limitation when choosing the right approach.

Magnetometry mastery

Mr Grace has 40 years of experience in exploration and magnetics, and he placed emphasis on the importance of skilled personnel for data acquisition and processing, ensuring the delivery of accurate and reliable results.

“It takes more than just flying a drone. A professional approach is necessary to analyse and utilise the acquired data effectively,” Mr Grace said.

Mr Grace also referenced the crucial steps in the workflow when embarking on a magnetic surveying project for mineral exploration.

The process begins with obtaining the area information from the client as a file, allowing for a comprehensive evaluation of the terrain characteristics. Factors such as topography, accessibility, and potential obstacles like power lines or cell phone towers are carefully considered during the project design phase.

Drone-based magnetometry merged with regional data. Image credit_ AeroPhysx.

Photogrammetry is often employed as a preliminary step to optimise data collection, providing a high-resolution base for flight planning. At this point in the process, the need for adaptability and client input in defining project goals and budgetary considerations is essential.

“The geological structure plays a significant role in determining the flight line direction. Aiming for a 90-degree approach angle allows for accurate correlation between survey lines,” Mr Grace said.

Addressing logistical and technical considerations

Addressing the challenges of remote areas, Mr Grace said logistical support, such as accommodation and vehicles, is extremely important.

In certain instances, preliminary reconnaissance or local support is required to ensure a smooth operation. Additionally, crew fatigue, communication with the field team, and safety protocols must be meticulously managed to uphold data quality and personnel wellbeing.

Dr Karuss said that acquiring high-quality data and understanding the measurements obtained is key, and also echoed Mr Grace’s sentiments about the need for proper training and knowledge in the field.

“It’s not just about collecting data; it’s about collecting accurate and reliable data,” Dr Karuss said.

Case study: Gold exploration in Guinea. The gold sits in quartzsite veins, which are non-magnetic but are associated with slightly more magnetic surrounding material. Image credit_ AeroPhysx.

Investing in training programs and seeking guidance from experienced professional is vital to ensure a strong foundation in geophysical surveying.

Both experts agreed that the reputation of drone-based magnetometry in mineral exploration has suffered due to subpar data collection and misinterpretation. Mr Grace said that businesses should approach this technology seriously andinvest the necessary resources to deliver reliable results.

“Mag has gotten a bad name due to the prevalence of low-quality data,” Mr Grace said.

“To regain trust, it’s essential to conduct surveys properly and implement compensation techniques to minimise noise and oscillation distortions.”

Drone technology, when utilised effectively, has the potential to revolutionise the mining industry. By adhering to a well-structured workflow, employing skilled professionals, and prioritising data accuracy, businesses can harness the full potential of drone-based magnetometry.

As technology advances and further improves, the mining sector can capitalise on drone based magnetometry’s potential in enhancing exploration, resource allocation, and decision-making.

Although the method is not without its challenges, possessing a broad understanding of its capabilities and constraints can help mining professionals judiciously integrate drone-based magnetometry into their practices, fostering advancements in mineral exploration.

The success of any drone-based magnetometry project relies on meticulous planning, skilled execution, and accurate data processing. As the mining industry continues to embrace technological advancements, especially in Australia, it is essential to prioritise expertise and quality to unlock the true benefits of drone technology in mineral exploration.

To learn more about SPH Engineering and applications for drones in the mining industry, visit www.sphengineering.com/applications/mining

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