Mineral systems of Australia: An overview of resources, settings and processes

Abstract

Australia produces more than 22 mineral commodities from a wide variety of deposit types, but >90% of the value of mine production is obtained from just 10 commodities. Both production and resources are underpinned by a few major deposit classes and a small number of world‐class deposits. Most major deposits lie in highly endowed metallogenic provinces and formed at discrete intervals during major metallogenic epochs, notably: 2.7–2.6 Ga, 2.4–2.2 Ga, 1.7–1.6 Ga, 1.2 Ga, 500–480 Ma, 440–420 Ma, 380–350 Ma, 320–280 Ma, 240–220 Ma and 100–0 Ma. These lie within the global metallogenic epochs that have previously been shown to coincide with the accretion and breakup of the major continents. Many of the major metallogenic provinces formed by accretion during convergent tectonic regimes and can be linked to particular orogenic events and/or changes in the apparent polar wander path. Giant deposits appear to have formed from large systems commonly located at major crustal structures. The interplay of source, transport and trap is critical. Formation of ore bodies occurs when hydrothermal fluids are released in a focused manner, migrate along ‘open’ transport zones, and interact with suitable traps to deposit metals. Typically this occurs late in the tectonic evolution of the province or basin and may be associated with uplift and/or basin inversion. The efficiency of the trap site is a key factor in determining ore‐deposit size, and is enhanced by major physical and chemical contrasts between trap and fluid. Emplacement of mineralised intrusions and migration of mineralising fluids occurs in response to geodynamic triggers involving changes to the stress regime that may include far‐field stresses propagated across the Australian continent. With the exception of supergene deposits, mineralisation typically appears to have occurred within short time frames (<1 million years) in response to the geodynamic triggers. Formulation of the next generation of predictive, geologically credible models requires an integrated, holistic mineral systems approach with a strong focus on crustal architecture and the relative timing of critical events.

Basin-related uranium mineral systems in Australia: A review of critical features

“…However, it is not clear if the above-mentioned ingredients on their own can assist in assessing the size (tonnage of contained uranium) of deposits resulting from fertile mineral systems. The challenges of identifying unique features that characterise world-class or giant mineral systems are involved and complex, and only in recent years has some significant progress been made in defining these features for some minerals systems (e.g., Laznicka, 2014;Richards, 2013;Jaireth and Huston, 2010;McCuaig et al, 2010;Jaques et al, 2002). Unfortunately, little progress has been made to understand critical features of world-class and giant uranium mineral systems.…”

The fracture permeability of Hard Rock Aquifers is due neither to tectonics, nor to unloading, but to weathering processes

“…In a hydrothermal context, several scales correlated in space and time are hierarchized (Jaques et al, 2002) as listed below: the geodynamic event, lasting from 20 to 200 Ma, the building-up of a volcanic edifice, comprising several successive intrusions with a time-scale up to a few million years, the intrusion and cooling of a single magmatic intrusion with a duration from 10 to 200 ka (Cathles et al, 1997), and the fracture giving birth to a mineral vein, the active lifespan of which must be less than or at least equal to the one described above, especially when one takes into account the fact that such veins have a polyphased functioning and a smaller spatial scale. If one considers that one intrusion is at the origin of ten successive mineralization episodes (which must be a default estimate), and that the process of fracturing and sealing is cyclic, then the lifespan of a permeable fracture would be from 20 to 1 ka.…”

Applying regional airborne electromagnetic (AEM) surveying to understand the architecture of sandstone-hosted uranium mineral systems in the Callabonna Sub-basin, Lake Frome region, South Australia

“…Hence, the description focuses on important constituent features of these systems. A mineral system (Wyborn et al 1994;Knox-Robinson & Wyborn 1997;Jaques et al 2002) is generally defined by the following constituent elements: geological setting; sources of energy driving the system; sources of fluids, metals and ligands; pathways along which melt or fluid move; chemical and/or physical traps/gradients in proximity to pathways; outflow zones for discharge of residual fluids; and preservation. High-resolution, small area data validation and mapping, geo-electrical modelling, system selection and risk reduction Borehole induction conductivity logging AEM system selection, data validation, inversion modelling and interpretation, high-resolution stratigraphic mapping and geo-electrical modelling Other geophysics (e.g.…”