Article from resourceful: Issue 12
Recent developments in mineral characterisation and analysis technologies have been some of the most significant advances for decades in exploration – opening up entirely new approaches and a wealth of valuable new data.
An example of such innovation is the ability to rapidly analyse mineralogy and texture of rock chips generated from low cost work such as rotary air blast (RAB) drilling.
Rock chip analysis
Rock chips do not necessarily contain the mineral being sought by an explorer, but can contain indicator minerals associated with the formation of mineral systems. These help narrow down the area to be searched.
The TESCAN integrated mineral analyser (TIMA) has this ability – it analyses rock chips, and then stores the data, to form the basis of an increasingly valuable “library” to help identify potential mineralised systems.
Importantly, the information extracted from minerals in the chip samples can assist in significantly expanding the footprint of a potential system. It can also reveal the timing of a geological event, which helps with understanding geological structures by integrating the data with geochemical and geophysical information.
CSIRO, through its Advanced Resource Characterisation Facility, plays a critical role in providing the industry with access and expertise to use TIMA and other cutting edge technologies.
Fortunately for small- to medium-sized companies – who make a significant proportion of Australia’s exploration industry – access is also made much easier and affordable through federal government programs.
Initiatives like Innovation Connections support collaboration between industry and research organisations, by providing funding and access to technology, as well as the geoscience experts who can provide enormous value to the data analysis.
Sipa Resources case study
Australian company, Sipa Resources, recently engaged CSIRO through this program to apply the latest mineral analysis technologies, including TIMA. The company found the work to be particularly useful in narrowing down its search for copper and other minerals in the remote Paterson region of north-west Western Australia. Paterson is home of the giant Telfer goldmine and a number of other substantial deposits of gold, copper and tungsten.
Sipa chief executive, Lynda Burnett, says thanks to the collaboration, the team was able to collect a vast amount of data that an exploration company would not normally acquire because of the cost.
"The analyses gave us quantitative petrology (the composition, texture and structure of rocks) from all our fresh rock drill chip samples. It tells us exactly what minerals are there, and what percentage in every sample," Ms Burnett says.
"As you interpret the data you build a strong picture of the regional geology and the paragenetic history (the sequence of rock formation and subsequent alteration and deformation). It's a real breakthrough for working under surficial cover.
"In particular, the alteration paragenesis and its spatial zonation is helping us to make decisions about where exploration should focus, whether we’re looking at a mineral system capable of hosting a large deposit and what type of mineral system it is."
A core focus of CSIRO’s integrated research programs using a range of analytical characterisation capabilities, is to extend the detectable “distal” footprint (mineral signature) for a range of different deposits under cover.
CSIRO group leader in mineral system science, John Miller, says mineral analysis and characterisation also helps to answer basic questions about the type of mineralised system being explored – an early but important question to determine the best exploration techniques.
"By analysing the chips, you can tell what type of system you're in," Dr Miller says.
"That’s huge for a mineral explorer, because it answers a question of whether it’s something that’s worth pursuing. It means an early decision in the exploration process because it can be tuned to different deposit types."
Dr Miller says a lot of analysis had been conducted on core produced from diamond drilling, but the ability to analyse chip samples enables engagement during the first pass stage of drilling favoured by the exploration sector (e.g. air core, RAB or reverse circulation drilling).
"It's those chips which give an explorer a good look at what is underneath surface cover."
The CSIRO team is currently working with nine other companies on mineral systems analysis projects through government supported industry research collaborations.These projects enable smaller companies to double the value of their research dollars.
The benefits go both ways, with the CSIRO researchers getting access to real data that helps build their knowledge base on mineral systems around Australia.
CSIRO research scientist, Adam Bath, says the team discovered the importance of more alkaline fluids in the formation of some ore deposits where slightly acidic and near neutral fluids have previously been favoured.
"This has implications for gold deposit formation, because gold nanoparticles are known to be more stable in alkaline fluids and these types of fluids may be more efficient at transporting the gold," Dr Bath says.
Understanding mineral systems
In addition to gold, the team is gaining insight into polymetallic, copper and tungsten systems.
"A lot of the work we’ve done is based on the understanding of mineral systems," Dr Bath says.
"We learn a lot about those systems, we learn about their patterns and we apply that knowledge to greenfield exploration."
Dr Bath says that in the case of using TIMA, the data being generated often comes from rocks that are not actually mineralised.
"Those non-mineralised rocks still show hydrothermal alteration that’s part of the broader mineralised system, because the fluids at the heart of the system don't just stay where the metals are deposited, they move into outlying rocks.
"Often when you get further away from a deposit, the alteration assemblage that's related to the mineralisation is very subtle. Having bulk rock mineralogy doesn’t always help.
"It's important to see the textures, and say, that's the alteration event because I can see it over-printing another event. You get a timing relationship that you won't see in other datasets."
Peering deeply into the mineralogy and texture of a chip sample is a microscopic version of one of the oldest forms of exploration, looking for indicator minerals in stream samples such as the garnets used as pointers to potential diamond deposits