GEMOC ARC National Key CentreFunded basic research projects for 2007-2008
Funded research projects within gemoc are formulated to contribute to the long-term, large-scale strategic goals and determine the short-term Research Plan. Research goals for each year are linked to the aims of funded projects. Summaries of these projects are given here.
Episodicity in mantle convection: effects on continent formation and metallogenesis
Craig O’Neill: Supported by ARC Discovery (commences 2008)
Summary: The formation and destruction of supercontinents has far-reaching consequences for the evolution of life, the distribution of Earth’s resources, and the shaping of the Earth’s crust and surface that support human society. Tools to investigate these supercontinent processes have only recently been developed to the stage where they can be used to investigate the complex interactions of the continent-mantle system. Mantle convection simulations will be used to assess the thermal and dynamic impact the aggregation and dispersal of supercontinents has on the mantle, with a view to understanding the origin of anomalous volcanism often associated with supercontinent breakup.
Global lithospheric architecture mapping II
Sue O’Reilly, Bill Griffin and Craig O’Neill: Supported by ARC Linkage and BHP Billiton (awarded June 2007, commences 2008)
Summary: Domains of different composition in the deep part of Earth’s rigid outer shell (the lithosphere) reflect processes of continent formation and breakup through Earth’s history. The boundaries of domains focus the fluid flows from the deeper convecting mantle that may produce giant ore deposits. We will integrate mantle petrology, tectonic syntheses, and geophysics to image the 3-D architecture of the continental lithosphere, and provide a basis for realistic dynamic modelling of the behaviour of these deep continental roots and their response to geodynamic forces through time. This will provide a new approach to identifying predictive relationships between different types of lithosphere domains and structures, and large-scale mineralisation.
Tomorrow’s TerraneChron®: new developments, new deliverables and new destinations
Elena Belousova: Supported by Macquarie University Innovation Fellowship Program (commenced 2007)
Summary: TerraneChron® is a unique methodology for studying the evolution of Earth’s crust on which we live, and evaluating the metallogenic potential of target terranes. It capitalises on the erosion-resistant properties of zircon, a common mineral in most crustal rocks and easily collected from surface drainages. Zircon is a robust time-capsule; high-technology analytical procedures can yield its crystallisation age, the nature of its source region deep in the Earth’s crust or mantle, and the nature of the actual rock it was eroded from. TerraneChron® is thus a cost-effective tool for mineral exploration in remote, inaccessible or complex terranes, and can be extended to sophisticated basin analysis applications relevant to petroleum reserves. This project will carry TerraneChron® methodology and delivery to a significantly higher level, and will develop a robust predictive framework for recognising prospective mineralised terranes using data-mining and advanced statistical analysis.
Forming Earth’s first silicic crust
Tracy Rushmer: Supported by Macquarie University MQNS program (Awarded September 2007)
Summary: Earth’s earliest history (the Hadean eon) was a different world, yet we have recently discovered that in this unusual environment Earth’s first silicic crust, the portion that forms the continents, began to grow and set the stage for the planet we know today. This experimental project aims to address fundamental issues concerning planetary evolution, early Earth and origin of the Hadean magmatism. The approach combines melting experiments performed on rocks with numerical modelling. The results will help allow us to assess the nature of earliest Earth and conditions necessary to produce crust during the Hadean eon.
Earth’s internal system: deep processes and crustal consequences
Sue O’Reilly, Bill Griffin, Norman Pearson, Olivier Alard and Klaus Regenauer-Lieb (with 8 partner investigators): Supported by ARC Discovery (commenced 2007)
Summary: New ways of imaging Earth’s interior are providing remarkable insights into its structure and opening the way to a new synthesis linking tectonics, mantle structure and the internal transport of material and energy. We will harness the resources of an interdisciplinary, international team with leading expertise in geochemistry, seismic imagery and numerical modelling, and capitalise on new developments in these fields, to explore the internal dynamics of the Earth to understand how these produced the present structure of our planet. The resulting new conceptual framework for the evolution of the continents and their deep roots will be directly translatable into predictive exploration methodologies for Australia’s mineral and energy sector.
Outcomes will include significant new information about the structure and formation of the Earth’s crust and the underlying mantle. An improved framework for interpreting the architecture of Australia and other continents will be directly relevant to exploration for world-class economic deposits, the Earth resources on which society depends.
Trace element analysis of diamond: new applications to diamond fingerprinting and genesis
Sue O’Reilly, Bill Griffin and Norman Pearson: Supported by ARC Linkage and Rio Tinto (commenced 2007)
Summary: As diamond crystals grow, deep in the Earth’s mantle, they trap minute inclusions of the fluids from which they crystallise. We will use recently developed laser-ablation microprobe techniques to analyse the trace-element patterns of diamond crystals from the Argyle, Diavik and Murowa mines (Australia, Canada and Zimbabwe). The results will define the nature and evolution of the parental fluids of the diamonds, and thus shed new light on the processes of diamond formation and the nature of fluids in the deep Earth. A better understanding of these processes can lead to improved models and techniques for diamond exploration, enhancing the prospect of finding new deposits in Australia and abroad. The project will test the potential of trace-element microanalysis to fingerprint diamonds by source. If successful, this technology will provide economic benefits by reducing theft and illegal mining, which represent significant losses to legitimate companies. Application of this Australian development could reduce the circulation of “conflict diamonds”, which would have real social benefits worldwide, especially in some developing countries.
Spreading ridge sedimentation processes: a novel approach using Macquarie Island as a natural laboratory
Nathan Daczko and Julie Dickinson (University of Sydney): Supported by ARC Discovery (ends 2008)
Summary: This project is the first that aims to understand the generation, deposition and lithification of sedimentary rocks at mid-ocean spreading ridges. It will improve our understanding of the construction of significant volumes of oceanic crust that commonly host important economic resources such as cupriferous sulfides. The project will examine spreading-related sedimentary rocks, including processes relating to their depositional system, utilising unique exposures on Macquarie Island, where in situ oceanic crust still lies within the basin in which it formed. This research will examine the south eastern tectonic plate boundary of Australia, providing analogues for seafloor-spreading-related crustal processes at present plate boundaries and ancient examples now joined to the Australian continent. The scientific innovation represented by this project will help Australian scientists to better understand an important part of the plate tectonic cycle. This project will be of direct relevance to the Australian minerals exploration industry and will provide better constraints on rift-related metallogenesis.
Toward the use of metal stable isotopes in geosciences
Olivier Alard: Supported by ARC Discovery (ended 2007)
Summary: Metal stable isotopes (MSI: Mg, Fe, Cu, Zn, Ga) have enormous potential applications (basic and applied) in Geosciences and beyond. However, the use of these elements as geochemical tracers and petrogenetic tools requires: (i) the definition of their isotopic composition in Earth’s key reservoirs and in reference materials such as the chondritic meteorites; (ii) understanding and quantification of the causes of MSI fractionations during geological processes. By a unique combination of in situ and solution geochemical analytical techniques, available now through frontier technology and method development, we aim to establish a conceptual and theoretical framework for the use of metal stable isotopes in Geosciences.
Isotopic fractionation of the ore minerals (Cu, Fe, Zn): A new window on ore-forming processes
Simon Jackson and Bruce Mountain: Supported by ARC Discovery (ended 2007)
Summary: Stable isotopes of common ore metals (e.g. copper and iron) are new tools for investigating ore deposits. Our data suggest that metal isotopic variations can provide new insights into mechanisms operative during formation of ore deposits. Stable metal isotopes also show promise as a new exploration tool for identifying the location of economic mineralisation within large prospective terrains; e.g. weakly vs strongly mineralised zones in a volcanic belt.
This project will provide fundamental baseline data that will help elucidate the processes that cause metal isotope variations. This will allow stable metal isotopes to be used much more effectively by the mining and exploration industries.
Episodicity in mantle convection: effects on continent formation and metallogenesis
Craig O’Neill: Supported by Macquarie University Research Fellowship (ended 2007)
Summary: Quantitative numerical modelling will be used to evaluate the links between episodes of intense mantle convection and the production of the continental crust that we live on. These models will assess the degree of melt production and crustal generation resulting from different styles of episodic mantle convection, and will determine which types of mantle evolution through time could produce the age distribution observed in the continental crust worldwide. The research addresses a critical shortcoming in our understanding of the formation and evolution of continents, with important implications for the distribution of major mineral and energy resources.
Mantle melting dynamics and the influence of recycled components
Simon Turner: Supported by ARC Discovery (ends 2008)
Summary: Precise information on time scales and rates of change is fundamental to understanding natural processes and central to developing and testing physical models in the earth sciences. Uranium series isotopes have revolutionised the way we think about time scales because they can date processes which occurred in the last 10-350 000 years. This proposal aims to use U-series isotopes to constrain the rates of mantle melting and residual porosity beneath the Manus basin, Papua New Guinea and the East Pacific Rise. By contrasting normal and enriched basalts we aim to constrain the effect of heterogeneities, including volatiles, on mantle melting. This will radically improve our understanding of mantle melting, which powers the Earth's dynamics. This proposal is directly concerned with the continuing aim of building a sustainable Australia through knowledge of deep earth resources. The more we know about the processes of melting and melt and fluid migration the better we will be able to inform models for resource exploration and volcanic hazard mitigation. Uranium series isotopes are relevant to the very recent history of the planet (< 350 000 years) - time scales which are often overlooked. Application to mantle melting may also have direct application to gold exploration in the Manus basin and elsewhere. It is to these techniques we must look if we are to understand the immediate past as a clue to the immediate future of our planet.
The behaviour of geochemical tracers during differentiation of the Earth
Bernard Wood: Supported by ARC Discovery (ends 2008)
Summary: The aims of this project are to understand the processes by which the Earth separated its metallic core, to test models of how it developed ‘enriched’ and ‘depleted’ mantle components and to constrain the nature of continuing interactions between near-surface geochemical reservoirs and Earth’s deep interior. These processes have traditionally been followed using chemical tracers, but lack of understanding of chemical behaviour under the conditions of the deep Earth limits their application. This project is aimed at filling the gap, by determining experimentally, at high pressures and temperatures, the chemical behaviour of those trace elements which are central to our understanding of geochemical processes in Earth’s interior. The project is aimed at providing fundamental data which Earth Scientists will use to understand the processes by which Earth separated into its chemically-distinct layers (core, mantle, crust, atmosphere, oceans) and to determine the nature of the continuing interactions between the surface environment in which we live and the deep interior.
Discovering the deep mantle: experimental petrology at very high pressures
Bernard Wood (CI on project based at ANU with H.S. O’Neill and T. Irifune): Supported by ARC Discovery (ends 2008)
Summary: A novel super-hard diamond composite material will be used to double the pressures accessible to experimental investigation under carefully controlled conditions in the ‘multi-anvil’ apparatus, in order to study the Earth’s lower mantle (below 670 km depth). Anticipated results include a better understanding of how the Earth’s core formed, how the mineralogy of the lower mantle changes with depth and with redox state, and what controls the strength of the lower mantle, and thus how the mantle convects and how long-lived geochemical heterogeneities might be preserved. The great processes that shape the Earth at its surface, including plate tectonics and continental drift, can only be understood by appreciating how the interior of the Earth works. However, studying the deep Earth is difficult because of the enormous pressures and temperatures involved. This research proposes to simulate conditions in the Earth’s lower mantle (that is, below 670 km in depth) by making use of an Australian invented diamond-based ceramic, to double the pressure at which experiments can be performed.