Little gold diggers

There’s gold in them thar termite mounds! Termites can bring up buried gold, making their mounds a potentially valuable indicator of the presence of subterranean gold deposits.

CSIRO entomologist Aaron Stewart made the discovery by studying sites in the West Australian goldfields region. His findings could improve the identification of potentially valuable gold deposits, which are often buried deep under eroded or weathered material in the Australian landscape.

Part of Aaron’s research involves working out where ingested elements end up in insects. He is investigating how termites accumulate and excrete elements that may subsequently build up in nest structures and be used for mining exploration. Aaron used x-ray fluorescence microscopy (XFM) at the Australian Synchrotron because XFM has the ability to map a range of elements of interest at low concentrations and at high resolution.

In a recent examination of two different concretion types defined by the mutually exclusive presence of calcium and zinc, XFM was particularly useful because of the difficulty of using SEM EDX (scanning electron microscopy and energy-dispersive x-ray spectroscopy) methods to detect minor amounts of zinc in the presence of significant amounts of sodium.

“Insects could provide new, cost-effective and environmentally friendly ways of exploring for new mineral deposits,” Aaron says. “Traditional drilling methods are often prohibitively expensive.”

Aaron and CSIRO colleagues are working with exploration companies to further develop his methods.

Photo above right: Aaron Stewart collecting insects and mound material samples for analysis from an ant mound North of Kalgoorlie, WA. Credit: Nathan Reid.

Photo above: Synchrotron XFM images of Malpighian tubule concretions.
Scan size 8.0×8.0 µm2, 80×80 pixels, 1 s dwell per pixel. A: Composite image map of Zn and Ca (red and green). B: Zn map (red), C: Ca map (green). Image A demonstrates that high concentrations of Zn and Ca occur in mutually exclusive concretions. Credit: Aaron Stewart

Little gold diggers could help find more gold

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