Prospecting with the Synchrotron – from hunting for rare minerals to exploring for new nickel deposits [Video]

Louise Schoneveld was invited by ANSTO to give this talk at the Australian Synchrotron Microscopy Beamlines workshop (online) in 2024. For more info go to https://events01.synchrotron.org.au/event/184/

Abstract

Nickel, copper and the platinum group elements (PGEs; i.e. Ru, Rh, Pd, Pt, Os, Ir, Pt) are all critical metals and using the synchrotron XFM beamline we can understand how these metals form in mineral deposits and how to explore for them. Platinum group elements (PGEs; i.e. Ru, Rh, Pd, Pt, Os, Ir, Pt) are very rare elements that are usually found in distinctive micro-minerals known as platinum group minerals (PGMs). These minerals are impossible to see in rock samples and even when using the scanning electron microscope, these tiny minerals are difficult to spot and are often hidden beneath the sample surface even in a 30µm thin rock section. Using the Australian Synchrotron, we not only observe the surface of the sample at the micron scale but can penetrate the custom made “thick” (100µm) sections of rock to detect these very rare minerals below the surface and observe what minerals they are associated with. From this information we can understand how these critical micro-minerals form. We have also used the Synchrotron to measure the chemical variation within pyroxene crystals. These minerals trap information in their crystal structure as they grow; like the rings of a tree. Using the Synchrotron XFM beamline we can visualise these chemical changes at a 1µm scale and within multiple grains, to understand not only the chemical variation but how these changes are affected by crystal orientation. In doing so, we show that the most complicated zoning in Cr and Ti in pyroxene are correlated to nickel and copper mineralisation. This is due to cycling and recharge of the magma chamber which causes both the pyroxene chemistry to change and the sulfide minerals to become enriched in precious metals. We can now use these intra-grain zonations to explore for intrusions that may contain nickel or copper using just a desktop XRF mapper. The Synchrotron XFM beamline has countless geological applications and can be used to understand our earth and explore for critical metals across scales.