GEMOC ARC National Key Centre
Funded basic research projects for 2009-2010
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.
Probing the composition of the early Solar System and planetary evolution processes
Sue O'Reilly, Bill Griffin, Norman Pearson, Olivier Alard, Benoît Ildefonse, Sylvie Demouchy: Supported by ARC DIISR French-Australian Science and Technology Program (commencing 2010)
Summary: The aim of this project is to understand the origins and history of chondritic meteorites, the most primitive rocks in the solar system, and the stuff from which planets are made. An ongoing controversy about the relative ages and relationships between the different components of these primitive meteorites goes to the heart of models for the evolution of the Solar nebula and the generation of planets, including Earth. This controversy turns on the question of whether the various components of chrondritic meteorites have been formed separately in space and time, or have shared a common high-temperature history. To provide new constraints on this problem, we will focus on the chemical and micro-structural relationships between the chondrules and the very fine-grained matrix in which they are embedded. We will use both established and recently developed in-situ microanalytical techniques, to measure the abundances and isotopic compositions of critical elements in the fine-grained minerals of chondrules and their matrix, and to determine the degree of structural alignment between the minerals in the two components. The data will be used to evaluate the degree of high-temperature interaction between chondrules and their matrix, and to assess different models for the formation of chondrites. The results will be compared with equivalent information on samples of the Earth's deep interior brought to the surface in volcanoes or tectonic uplift; such samples can provide analogues for the differentiation of meteoritic parent materials. The project will use complementary equipment in France and Australia (laser-ablation (LA) inductively coupled mass spectrometry (ICPMS) at GEMOC (Macquarie University); ion microprobe and electron backscatter diffraction (EBSD) at GM (Geosciences Montpellier, UMR 5342).
The evolution of the oceanic lithosphere and upper mantle: a novel petrological-geophysical approach
Juan Carlos Afonso: Supported by MQNS grant (commenced 2010)
Summary: Understanding the evolution of the oceanic mantle, from the creation of oceanic lithosphere at mid-ocean ridges to its destruction at subduction zones, is a cornerstone in Earth Sciences. However, a complete model capable of reconciling all its geophysical and geochemical characteristics is still lacking. The proposed research program will combine novel interdisciplinary methods and powerful computer software to obtain a robust thermo-chemical-mechanical model for the evolution of the Earth's mantle beneath the oceans. This project will advance our knowledge of the evolution of ocean basins and continental margins, and thus it is directly translatable into predictive exploration methodologies for Australia's energy sector.
Nature, antiquity and length scales of compositional anomalies in the convecting Earth
Bruce Schaefer: Supported by MQNS (commenced 2010)
Summary: The convecting Earth is sampled by volcanic rocks and some ocean island basalts, such those erupted as the Azores, preserve evidence of anomalously ancient material which is chemically and possibly also mineralogically distinct from the rest of the mantle. This project aims to evaluate the nature and role of heterogeneities in the mantle beneath the Azores and how these may influence melting dynamics. Through application of novel isotopic techniques we aim to further constrain geodynamic models for the Azores and inform the current vigorous debate surrounding the age, origin and indeed fundamental nature of the Earth's convecting interior.
Resurrecting Rodinia? The role of east Antarctica in supercontinent assembly
Nathan Daczko: Supported by ARC MQRDG (commenced 2010)
Summary:This project will determine the role of east Antarctica in the Rodinian supercontinent that assembled 1300-900 million years ago. Controversy exists regarding the timing of geological events in east Antarctica and how these relate to the architecture of the Rodinian supercontinent. This project will characterise the age and geochemical signature of key Precambrian rocks in Kemp and MacRobertson lands, which outcrop as islands, isolated nunataks and mountain ranges, and compare their evolution with proposed conjugate regions in India, Australia and broader Antarctica. These rocks will provide a missing link between disparate terranes in recent tectonic reconstructions of Rodinia.
Developing permeability in the Earth's crust: A coupled experimental and numerical study of geologically important fluids in a dynamic environment
Tracy Rushmer: Supported by MQRDG (commenced 2009)
Summary: The development of permeability in host rocks is key to understanding fluid flow and ore formation. However, we have yet to build into fluid transport models realistic evolutionary paths of porosity and permeability with time. While the controls on fluid flow and focusing in the Earth's crust are conceptually understood, we still need a quantitative approach to their evolution. This project uses a coupled approach between numerical modelling and dynamic experiments on natural crustal rocks to gain quantitative information on the physical and chemical mechanisms of generating enriched mineral zones. The results will seed a CSIRO MDU Collaboration Cluster application.
A novel approach for economic uranium deposit exploration and environmental studies
Simon Turner, Bruce Schaefer, Geoffrey McConachy: Supported by ARC Linkage and Quasar Resources (commenced 2009)
Summary:The project proposes the use of a novel approach to prospect for economic uranium ore deposits. The measurement of radioactive decay products of Uranium in waters (streams and aquifers) and sediments will allow us to (i) identify and locate economic uranium ore deposits, and (ii) quantify the rate of release of uranium and decay products during weathering and hence the evolution of the landscape over time. In addition, this project will improve our knowledge on the mobility of radioactive elements during rock-water interaction, which can be used to assess the safety of radioactive waste disposal. Outcomes of this project will be: (i) the discovery of new economic uranium deposits; (ii) development of a new exploration technology allowing for improved ore deposit targeting. Information gained on the behaviour of radioactive elements at the Earth's surface will be critical for the study of safety issues related to radioactive waste storage and obtaining reliable time constraints on the evolution of the Australian landscape.
Did obesity kill the arc? A model from the Fiordland Arc, New Zealand
Nathan Dazcko: Supported by MQNS grant (commenced 2009)
Summary: This project explores crustal growth in a magmatic arc flare up event, immediately before rapid crustal growth (obesity) and death of the arc. Rare exposures of deep arc crust (>60 km), in the natural laboratory of Fiordland, New Zealand, offer unique insight into crustal growth mechanisms. Our approach is to incorporate field-, petrographic- and isotope-based analysis for a fully integrated model of the evolution-extinction of this arc. We will quantify mantle versus crustal recycling sources and variations in magmatic flux rates, and document the rock types formed at the base of the thickest exposed continental arc, and their petrogenesis.
Diamond genesis: cracking the code for Deep-Earth processes
Bill Griffin, Sue O'Reilly, Norman Pearson, Thomas Stachel, Oded Navon, Jeff Harris: Supported by ARC Discovery (commenced 2009)
Summary: Diamonds carry unique, but cryptic, information on Deep-Earth processes. We will take a new approach to the question of how diamond forms deep in the Earth. We will integrate our recently developed techniques for trace-element analysis and new types of compositional imaging with in situ analysis of the isotopic composition of C, O, H and N in a range of diamond types, and in genetically related silicate, sulfide and oxide minerals. This innovative approach will provide new insights into the nature and origin of the fluids that precipitate diamond in the Earth's lithosphere, the transition zone and the lower mantle. These data and insights will become the basis for new geochemical approaches to diamond exploration and target evaluation.
Partial melting in natural metal-silicate and silicate systems: rheological and geochemical implications for the Earth and other planets
Tracy Rushmer: Supported by ARC Discovery (commenced 2009)
Summary: Differentiation is the separation of a melt or fluid from its host. It is the fundamental mechanism by which the terrestrial planets have evolved both chemically and physically through time and central to how the crust has evolved from mantle, how metallic cores are formed from undifferentiated planetary bodies and how economic elements can be concentrated. This proposal tackles this primary process by using the true (observed) rock textures and compositions as templates uniquely constrained by experiment so that numerical modelling can quantify flow processes and deformation regimes. It provides a basis for understanding fluid migration in dynamically evolving permeable networks.
Application of very short-lived Uranium-series isotopes to constraining Earth system processes
Simon Turner, Tony Dosseto, Mark Reagan: Supported by ARC Discovery (commenced 2009)
Summary: Precise information on time scales is fundamental to understanding natural processes. 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 will establish new procedures at the recently founded world-class Uranium-series research facility at Macquarie University for analysing very short-lived isotopes (22 years). These new abilities will be utilised to determine the mechanisms of melt/fluid migration and volcano degassing and to ascertain rates of soil production and erosion over time. The methodologies developed will also have application to Uranium exploration and nuclear safeguarding.
Composition, structure and evolution of the lithospheric mantle beneath Southern Africa: improving area selection criteria for diamond exploration
Bill Griffin, Sue O'Reilly, Norman Pearson: Supported by ARC Linkage and De Beers Group Services (commenced 2008)
Summary:Trace-element analyses of garnet and chromite grains from kimberlites distributed across the Kaapvaal craton and the adjacent mobile belts will be used to construct 2D and 3D models of compositional and thermal variation in the lithospheric mantle (to ~250km depth), in several time slices. Regional and high-resolution geophysical datasets (e.g. seismic, magnetotelluric, gravity) will be used to test and refine this model. Links between changes in the compositional structure of the lithospheric mantle and far-field tectonic events will be investigated using 4-D plate reconstructions. The results will identify factors that localise the timing and distribution of diamondiferous kimberlites, leading to new exploration targeting strategies.
Basin development in Proterozoic South Australia: developing a time-integrated, compositional framework to assist mineral exploration
Elena Belousova, Bill Griffin, Anthony Reid (PIRSA), Alsa Schwarz (PIRSA) (commenced 2008)
Summary: This project will generate new geochemical and age information to improve the existing geochronological framework for geologically ancient regions of South Australia. These chemical "fingerprints" and age data will be obtained for zircon (collected from river sands and rocks), that acts as a time capsule allowing us to determine the nature and sources of individual magmatic rocks and also sedimentary sequences. This will provide an integrated understanding of the geological history of the region to aid mineral exploration, and will also add to knowledge of the composition, metallogeny and assembly of this region of the Australian continent.
The role of supercontinents in Earth's dynamic evolution
Craig O'Neill: Supported by ARC Discovery (commenced 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, Craig O'Neill: Supported by ARC Linkage and BHP Billiton (commenced 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.
Forming Earth's first silicic crust
Tracy Rushmer: Supported by MQNS (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, Klaus Regenauer-Lieb (with 8 partner investigators): Supported by ARC Discovery (commenced 2007, ended 2009)
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, 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.