GEMOC ARC National Key Centre
Funded basic research projects for 2010-2011
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. In addition to these projects, funding for the ARC Centre of Excellence for Core to Crust Fluid Systems will commence in 2011. Summaries of funded GEMOC projects are given here.
The effective strength of oceanic plate bounding faults
Craig O'Neill, Juan-Carlos Afonso: Supported by ARC Discovery Project Grant and MQ (commencing 2011)
Summary: The strength of the ocean faults surrounding the Australian plate controls the long-term fault motions, stress partitioning across the plate boundary and, ultimately, the seismicity of such fault systems. Numerous lines of evidence suggest such faults are far weaker than previous models predict, possibly due to the alteration of crustal and lithospheric rocks into hydrous phases. This is a critical gap in our understanding of such fault systems, and this project will ultimately constrain the weakening mechanisms acting on such faults, and produce a geodynamic-scale model for their effective strength. This project addresses the anomalously weak behaviour of the seismically active faults on the boundary of the Australian plate, in three key geodynamic areas. This will constrain the mechanisms which weaken such faults, and produce a model for their effective strength and evolution over geological timescales.
Origin of silicic magmas in a primitive island arc: the first integrated experimental and short-lived-isotope study of the Tongan Kermadec system
Tracy Rushmer, Simon Turner: Supported by ARC Discovery Project Grant (commencing 2011)
Summary: Silicic magmas are the building blocks of the continental crust and constitute the most hazardous of volcanic eruptions. Silica-rich magmas are found in the Tonga-Kermadec arc, which extends for several thousand km north of New Zealand. Application of a novel combination of experiments and short-lived isotopes to selected magma samples from the primitive Tonga arc will explain the origin of these magmas. The combined technique will also allow us to estimate water content, rates of melting and magma migration at depth, which are critical factors for understanding volcanic hazards. This approach can then be expanded to other parental magma types here and to other arc systems. The Tongan arc forms a large portion of the Australian plate boundary and is one of the most chemically primitive systems known. Oddly, it produces volumes of more evolved, dangerous silicic magmas. The results of this project will establish the source of these magmas and rates of migration, which are fundamental for understanding volcanic hazards.
Lithospheric Architecture Mapping in Phanerozoic Orogens
Bill Griffin, Sue O'Reilly, Norman Pearson, Elena Belousova: Supported by MQ Enterprise Partnerships Pilot Research Grant (commencing 2011)
Summary: The GEMOC Key Centre has developed the conceptual and technological tools required to map the architecture and evolution of the upper lithosphere (0-250 km depth) of cratons (the ancient nuclei of continents). Through two industry-funded programmes we have mapped most of the world's cratons, making up ca 70% of Earth's surface. The remaining 30% consists of younger mobile belts, which hold many major ore deposits, but are much more complex and difficult to map. This pilot project will develop the additional tools required to map the mobile belts, and will lead to an application for an ARC Linkage Project.
Nature of the lower continental crust
Nathan Dazcko: Supported by MQSN grant (commencing 2011)
Summary: Despite its importance to the study of crustal evolution and geodynamics, the composition of the lower part of the Earth's crust remains poorly known. This project utilises rare exposures of omphacite granulite in the natural laboratories of Fiordland, New Zealand and Hengshan Mountains, China to explore its influence on the composition, mineralogy and physical properties of the lower crust. The outcomes include characterisation of the rock types formed, their history and depth-temperature field of stability, and the determination of how omphacite granulite affects the strength of the crust and provides a fertile lower crustal source for magma.
Strength and resistance along oceanic megathrust faults: implications for subduction initiation
Craig O'Neill: Supported by ARC Future Fellowship and MQ (commencing 2010)
Summary: Plate tectonics is enabled by the sinking of dense oceanic lithosphere at ocean trenches - a process known as subduction, but how this process initiates is poorly understood. The development of an incipient subduction zone involves a major evolution of the plate boundary, into an oceanic megathrust fault system, capable of generating devastating earthquakes. An example is the Hjorta Trench, at the Australian-Pacific plate boundary south of Macquarie Island. This project will explore the evolution of this plate-boundary fault system during subduction initiation. Recent advances in our understanding of physical processes along plate-bounding faults will be incorporated into regional geodynamic simulations of this evolving fault system.
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).
Planetary differentiation of early solar system materials: an integrated isotopic and experimental approach
Bruce Schaefer: Supported by MQSN grant (commenced 2010)
Summary: This project aims to use meteorites of a variety of compositions to investigate how, and how rapidly, planetesimals differentiate and start to form planetary bodies. Physical processes, such as the formation of metallic cores at the centres of small planets (<100 km diameter) and their corresponding rocky exteriors, can be simulated by conducting experiments on specific types of meteorites, which were the starting material for solar system formation. Sophisticated isotopic techniques, such as Os isotopes, will be used, allowing a time dimension on the rate of differentiation to be measured. Such processes can then be applied to the formation of the Earth.
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.
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.