Mineral and Petroleum Resources

This group covers nearly all aspects of resource exploration, including coal, petroleum and mineral resources. Research encompasses fundamental processes which ultimately drive the formation and accumulation of ore deposits and hydrocarbons.

Archaean Diamonds

Archaean diamonds

The world’s oldest in situ diamond deposits have been discovered in rocks that contain upper mantle fragments, or xenoliths, brought to surface as the early continents were stabilised. The xenoliths provide a unique record of continent-forming events and can be compared with younger examples to accurately establish the evolution of the continental lithosphere. Chemical and isotopic evidence indicates that some xenoliths were permeated by hydrous fluids before emplacement. In northern Ontario and Quebec (Canada), and 1000’s of km away in the Northwest Territiores, these old diamond deposits are closely associated with some of the world’s largest vein-gold deposits. Therefore, understanding the origin and distribution of the deep-fluid plumbing systems preserved in the xenoliths will also help to resolve the mechanisms responsible for the formation of gold-rich vein deposits that accompanied continent formation. For more information contact Associate Professor Derek Wyman.

The Australian palaeo-stress map project

Palaeostress Australia

Petroleum exploration is expensive and risky, particularly in Australia where structural reactivation and loss of oil and gas is common. Understanding tectonic reactivation through time is crucial to avoid dry wells. Present-day stresses for Australia are well understood, but their evolution through the geological past is unknown. The Australian palaeo-stress map project's aim is to link numerical models of intraplate stress fields through time to predictive tools for evaluating fault reactivation. In order to understand the effect of time-dependent geometries of mid-ocean ridges, subduction zones and collisional plate boundaries on basin evolution and reactivation through time, we reconstruct tectonic plates, including ocean floor which has now entirely vanished, restore plate boundary configurations, and model the effect of time-dependent plate driving forces on the intraplate stress field. We have created a digital model of the (Indo-) Australian Plate that distinguishes cratons, fold belts, basins, and ocean crust in terms of their relative differences in mechanical stiffness. We model intraplate palaeo-stresses since the Early Cretaceous and use mapped fault reactivation histories for model validation via time-dependent fault slip/rupture analysis. Our approach employs Coulomb-Navier criteria to determine the risk of strain in a body of rock being accommodated by sliding along pre-existing planes of weakness instead of slip along newly developed fractures. We apply this methodology reconstruct the dominant stress regime (reverse, normal or strike-slip) for particular basins through time. Our approach provides a powerful predictive framework for evaluating fault reactivation through time in structural traps. For more information contact Prof. Dietmar Müller.

Early Precambrian petroleum and ore deposits

Hydrocarbons are a crucial component of mineral systems of many world-class sedimentary-basin-hosted hydrothermal ore deposits. Although the maturation and generation of hydrocarbons are well-understood processes, their role in the genesis of ores and ore-forming systems is not. We are using the relatively recent discovery of oil inclusions in early Precambrian basins to establish the role that hydrocarbons played in the genesis of some of the world’s most significant early Precambrian ore deposits. Work to date has included uranium deposits at Elliot Lake in Canada and natural fission reactors at Oklo in Gabon. For more information contact Dr Adriana Dutkiewicz.

Oil inclusions

High-P partial melting and melt escape from the lower crust

Partial melting, melt segregation and magma transport are the main processes controlling change on Earth. Though there is clear evidence that even small melt fractions can segregate into large igneous bodies, our inability to directly observe active magma ascent means that there is not agreement on the mechanisms by which melt initially segregates, pools and ascends. This Australian Research Council and National Science Foundation (USA)-funded project has studied well-exposed lower crustal rocks from the root of a long-lived Mesozoic island arc to resolve the mechanisms that controlled melt escape from, and extensive magma transport through deep crustal environments. Recent discoveries of transitional high-P granulite to eclogite facies rocks are presenting exciting new assemblages and a rare insight to dynamic processes at the crust-mantle transition. In collaboration with Mr Matthew DePaoli (PhD student, University of Sydney), Dr Keith Klepeis (University of Vermont, USA), and Dr Mo Turnball and Dr Andrew Allibone (IGNS, Dunedin, New Zealand).

Work on the project was showcased to an international audience in the 2003 Field Forum sponsored by the Geological Society of America, Structural Controls on Magma Transport and Vertical Coupling in the Continental Lithosphere. For more information contact Prof. Geoff Clarke.

Crustal growth at non-collisional orogens

Patagonia field work

One of the most important but least understood issues in convergent tectonics centers on the mechanisms by which orogenesis initiates ,and crustal growth occurs, at noncollisional margins. The type example for this process is the western Andean margin, where intraplate shortening, crustal thickening and uplift resulted from the westward acceleration of the South American plate and strong interplate coupling during ocean-continent convergence. Strong disagreement over how and why certain structural patterns develop stems from inadequate information on how processes operating deep within the back arc environment influence the growth and mechanical behavior of orogens. Uncertainties over the age, kinematic significance and P-T conditions of deep crustal fabrics especially obscure our understanding of back arc processes and their role in orogenesis. The Darwin Complex, located on Tierra del Fuego in southernmost Patagonia, contains one of the largest exposures of Mesozoic high-P (8-10 kbar) metamorphic rocks in the Andes south of Ecuador. These exposures record the thermal and structural evolution of the middle and lower crust as orogenesis initated during the Cretaceous closure of the early Mesozoic Rocas Verdes extensional basin.

Through funding from the National Science Foundation (USA), this project will involve a coordinated structural, metamorphic and geochronologic investigation of the deep crust in an unusually well preserved, ancient back arc setting located in southernmost Patagonia. The composite Rocas Verdes-Magallanes basin south of 54° S latitude is a key locality in the Andes because it provides a nearly complete record of back arc processes during the initial rise and growth of the cordillera from below sea level during early Mesozoic-Cenozoic time. Unlike other areas in the Andes, this region escaped most of the effects of Neogene orogenesis and volcanism that obscures early Andean processes elsewhere. In addition, the basin is unique because its southernmost rim contains >5000 km2 of the only high-P (7-9 kbar) Mesozoic rocks south of Ecuador. These exceptional elements will allow us to address questions that are critical to our understanding of how the early Andean orogen formed and grew in a back arc setting.

The project is lead by Prof. Keith Klepeis (University of Vermont) and is in collaboration with Dr Mark Fanning (Australian National University), Prof. Suzanne Baldwin (University of Syracruse) and Prof. Stuart Thomson (Yale). For more information contact Prof. Geoff Clarke.