To shore up Australia’s future economy and prepare us for the ongoing effects of climate change, researchers are decoding ancient mineral messages in Earth’s crust and tracking movements of the Antarctic Ice Sheet.
Over the past decade, the University of Tasmania’s Centre for Ore Deposit and Earth Sciences (CODES) has become a magnet for global mining companies eager to break new ground.
Geoanalytical technologies developed by CODES are enabling cheaper and faster ‘eureka moments’ of new mineral deposits, and the industry is seeing major impacts.
National and local governments feeling the pressure of rising sea levels are also partnering with the University, where Matt King, Professor of Polar Geodesy, directs a multidisciplinary team of researchers with expertise in surveying and spatial sciences, ice sheet dynamics, and the effects of sea-level change.
“We continue to try to understand how the ice sheet is changing and contributing to sea-level changes,” says Professor King.
“We’re also trying to understand how rising sea levels vary in their interaction with the coastline at different points, and what effects that has on our economy, on how people live, and on people’s sense of place.”
In July 2018, Professor King’s team submitted a proposal to develop a national centre of excellence in sea-level rise and coasts.
The centre meets CODES’s established discovery network at the point of sampling Antarctic bedrock to determine how much heat is exuded from Earth’s interface of ice and land, and how that will affect the melting and flow of ice into the sea.
“Our work in terms of impact is just beginning,” says Professor King.
The new drill
Some of the world’s biggest mining companies, plus geological surveys in 15 countries, use techniques developed by CODES to analyse core samples for signs of valuable minerals and ores nearby.
Although undiscovered and potentially lucrative deposits are still abundant in Australia and other mineral-rich territories, they are buried deeper, and are more difficult to detect than the ore bodies that are currently being mined.
The genius of CODES has been to apply geochemical analysis to samples, and to modify existing Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICPMS) to achieve reliable signals of ore bodies and mineral deposits up to a kilometre away from the sampled earth.
The result is fewer, smarter test holes, that can deliver better intelligence to support currently employed geophysical and bulk rock geochemistry – previously the most common prospecting methods – and an estimated $4.66 million in savings between 2011 and 2016.
In LA-ICPMS, “A laser drills a little hole, measuring only 50 microns [1 micron equals one-millionth of a metre], into a mineral sample and ablates – or vaporises – it,” says Professor Ross Large, an internationally renowned expert in ore deposit geology at CODES.
“That vapour is directed into a machine that can measure all the elements it contains, and our software then identifies and quantifies those elements.”
The super-halo effect
Pyrite is one of the most frequently analysed minerals, because it’s common in Earth’s crust, and retains trace elements of fluids that flowed through an area where ore bodies form.
At any given site, CODES’s technology uses marker minerals such as pyrite, chlorite, and epidote (known as ‘green rocks’) for generating a series of geochemical ‘halos’ that point towards the bullseye of a hidden deposit.
“A halo is a three-dimensional volume around an ore deposit, from which you get a signal of that deposit in nearby marker minerals,” explains Professor Large. “Halos around big copper deposits can go out to 10 to 15 kilometres.”
In December 2017, Rio Tinto’s chief geochemist indicated that the impact of CODES’s green-rock technology on the success of the company’s global copper-exploration teams had been substantial.
“This technology,” he said, “has demonstrated potential to assess the fertility of a system before it has been discovered, as well as offering explorers the opportunity to vector towards the deposit from significant distances away, where traditional tools and techniques are largely ineffective.”
The CODES team works with industry in different ways. Rio Tinto has licensed CODES protocols for use in its own laboratories, while BHP funds one of its chief scientist’s work within the CODES research hub.
Many organisations send samples to be analysed on a fee-for-service basis, and some support the University’s PhD students with opportunities to work at their premises, or on site, for longer-term projects.
The CODES laboratory – the most sophisticated of its kind in the world – is now home to six LA-ICPMS machines, and operates on a financially independent basis, attracting the majority of its funding from industry.
Companies such as South Africa’s AngloGold Ashanti, US-based miners Newmont and Barrick, and Thailand’s Assara Mining have collaborated with CODES on developing new methods to identify concentrations of invisible gold and free gold in deposits.
Although both kinds of gold are signalled by the presence of pyrite, invisible gold is chemically locked inside pyrite, and is often characterised by the presence of arsenic. These two factors make it expensive – often prohibitively so – and dangerous to process.
Protocols developed by CODES and its partners now allow miners to distinguish between deposits with high percentages of free gold and invisible gold, enabling fast, evidence-based decisions for ongoing exploration.
“We’re always developing our techniques,” says Professor Large. “We’ve just signed up seven companies to work with us on a research project in northern Australia using pyrite technology to assist in finding lead-zinc deposits.”
Australia is the world’s largest producer and exporter of zinc, which is primarily used for galvanising (or rust-proofing) steel, but Professor Large says the industry hasn’t found a new zinc deposit for almost 20 years.
Improving discovery rates, he says, is critical, because not only is the mining industry crucial to Australia in terms of revenue, but it can also maintain employment in zinc mining and processing, which underpins the prosperity of several regional communities.
According to Professor Large, no private laboratory can offer the combination of fundamental research capability and world-leading services to mining that CODES does. And partnerships with industry ensure that the University’s work in earth sciences continues to be relevant in the Australian economic context.
Key facts about CODES:
- $4.66 million in savings over five years for age dating rocks.
- Up to $200,000 in savings per drill hole that was avoided in deep porphyry copper exploration.
- $35 million in industry funding to CODES from 2002 to 2016.
About the researchers
Matt King is Professor of Polar Geodesy at the University of Tasmania, Australia. He works within the Surveying and Spatial Sciences group, forming a part of University researchers working on solid earth geophysics and geodesy. In particular, his work focuses on the use of geodetic tools to solve problems related to Earth geophysics, notably sea-level change, polar ice mass balance and Earth deformation. He also seeks to advance the accuracy and precision of those geodetic tools (e.g., Global Navigation Satellite Systems (GNSS/GPS), GRACE and SLR).
Distinguished Professor Ross Large is internationally renowned in ore deposit geology. His research has focused on understanding how mineral deposits form and using this knowledge to help industry find deposits of ore like gold. But he has now turned his geological skills to answering the most fundamental question of all – what controlled the evolution of life?
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