High-purity silica (HPS) is an integral component in technology such as semiconductors and solar photovoltaic cells. It is sourced from a limited number of locations around the world, with only one operational mine in Australia producing metallurgical grade silica (>98% SiO2). Globally, HPS is found in a wide range of geological settings, with known deposits being relatively sparse. This presents a challenge for future exploration efforts, as the conditions that produce HPS are not well understood.
The report discusses various components of silica mineral systems and their prospectivity for HPS using the mineral systems framework. This framework defines the criteria necessary to produce silica. Five components are evaluated: 1) the sources of metals, fluids and ligands, 2) energy sources and fluid flow drivers, 3) fluid-flow pathways and architecture, 4) ore depositional gradients/traps and 5) preservation. The main criteria identified for these components include (1) pegmatites, granites, cherts and turbidites as potential silica sources; (2) granites, partial melting, convergent margins and the fluid pressure gradients triggered by resulting metamorphism as potential energy sources; (3) deep marine basins, shear zones/highly fractured or faulted crust, and competency contrasts as fluid-flow pathways and architecture; (4) deformation partitioning, contact aureoles and occurrences of known mineral associations as evidence of ore depositional gradients; and (5) source outcrop occurs at or near-surface to demonstrate preservation through uplift and erosion preferentially preserving the quartz-rich lithologies in economically viable conditions. In reviewing the components of HPS mineral systems, this report has identified key criteria that are present across a range of silica mineral systems. Greenschist to amphibolite metamorphic facies, and the presence of granitic plutons, appear to be a favourable criterion across a range of HPS targets.
In defining the criteria that govern the formation and emplacement of HPS, this report aims to equip mineral explorers with the mineral systems knowledge needed to motivate and de-risk exploration for HPS in Australia. This information is compiled to act as a foundation for future mineral potential assessments, with the goal of helping to identify new HPS targets in Australia. Integrating the various silica mineral systems into a single framework will create a tool for mineral explorers to effectively identify, discover and define HPS targets, leading to the diversification of silicon supply chains in Australia. This work is undertaken as part of the Australian Critical Minerals Research and Development Hub.
