News & Stories

Reading rocks to find mineral trace elements

Josh’s research examines rocks’ “halo” of trace elements to see if there’s ore deposits worth digging for.


When you’re holding a rock in your hand, you’re holding a piece of history millions of years old.

Josh Phillips is a postgraduate in CODES, studying the trace element chemistry of hydrothermal minerals around ore deposits.

Every rock tells a story, you just have to speak the language.

“When an ore deposit forms, the fluid that it’s carried in will deposit the metals of interest. Those fluids, even though the metal is no longer in them, continue moving through the rocks, altering them and forming different minerals.

“Often these alteration minerals are confused with what we might refer to as background, or metamorphic, minerals,” he said

However these alteration minerals can also form in non-ore forming metamorphic environments and the trick is to be able to tell the difference

By looking at their trace element chemistry, we hope to see a halo of trace elements around ore deposits.

Josh said it’s becoming harder to find new ore deposits, so different approaches are needed.

We’re looking for enrichments in specific trace elements within those target minerals. We’re testing this approach at a site in Arizona.

Josh takes samples from the site, and analyses them back at UTAS.

“We cut the rocks into special mounts which we can analyse on a variety of instruments.

“First we go to the scanning electron microscope to make sure the minerals we want to analyse are there. Then we take them to the laser ablation lab, and analyse our target minerals.

“The idea is that when you plot the results on a map you’ll see a systematic change away from the centre of the deposit that you wouldn’t see if they were metamorphic minerals.

That will help inform exploration in the future, so when geologists are out sampling rocks containing these minerals, and they’re not sure whether it is an undiscovered ore deposit or if it is just metamorphic fluids, you can use this method see its trace element composition and help guide the decision process.

“It’s really an early stage tool to help either prioritise prospects, better target drill holes,and streamline the exploration process.

“In Arizona, the deposit is very deeply buried, so drill holes can cost millions of dollars. So if you only have to drill two or three holes to find the deposit rather than 10 plus, that’s a huge saving.

“The other benefit is environmental. In order to drill holes, you need to clear large areas of land and pump drilling fluid into the ground. Minimising environmental impact is also key to the work that we do.”

Originally from the UK, Josh came to Australia for work.

“Having worked in exploration for a number of years,I realised my geology credentials weren’t up to scratch so I enrolled in the CODES Master of Economic Geology course, which is a great, part-time course. Everyone was really friendly. The department was just a really appealing place to be.

“The clincher for me was my PhD project, which allows me to work very closely with industry.

Travel is a great aspect of studying geology here at UTAS. A lot of students are working on projects overseas and this allows exposure to a great diversity of world class geology. Not only that, but Tassie is also a great place for getting out and looking at rocks, with all kinds of unsolved mysteries.

Josh’s research is part of the ARC Industrial Transformation Research Hub for Transforming the Mining Value Chain (TMVC). The TMVC is funded by the Australia Research Council (ARC), AMIRA International, Newcrest Mining, BHP Billiton & Corescan (Partner Organisations), Laurin Technic & RWTH Aachen University (Other Organisations) and various other Additional Funder Organisations.

Keen to make your own impact? Find out about starting your research degree here.