Michael Agnew - Ultramafic rocks in volcanic arc terrains – their formation, tectonic significance

Ultramafic rocks in volcanic arc terrains – their formation, tectonic significance and role in hosting porphyry and epithermal deposits Ultramafic volcanic and intrusive rocks make up a small but not insignificant proportion of exposed, modern and ancient volcanic arcs. They are characterised by high Magnesium, Chromium, Nickel and Copper concentrations and other critical minerals. Due to their olivine and pyroxene content, ultramafic rocks are highly susceptible to alteration, metamorphism and deformation, often leading to the formation of regional-scale, highly magnetic, fault-bound serpentinite belts, that may react with hydrothermal fluids. In modern and ancient arcs, the emplacement of picrites (high-Mg basalt) has been linked to slab tears or slab windows and mantle mixing processes. In this week's session with Michael Agnew from Stavely Minerals Limited we'll be presented four field examples from Australia and around the World of porphyry and epithermal deposits located within, or adjacent to high-Mg, high-Cr igneous rocks and highlight their significance.