GEMOC ARC National Key CentreFunded basic research projects for 2005
Funded research projects within GEMOC are formulated to contribute to the long-term large-scale strategic goals and determine the short-term Research Plan. Summaries of these projects for 2004 are given here
Isotopic fractionation of the ore minerals (Cu, Fe, Zn): A new window on ore-forming processes
Simon Jackson and B. Mountain: Supported by ARC Discovery (awarded in 2004 for 2005-7)
Summary: Stable isotopes of common ore metals (eg 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; eg 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.
A new approach to understanding the mechanism and deep crustal controls of continental rifting
Nathan Daczko: Supported by ARC Discovery
Summary: The Papuan Peninsula region of Papua New Guinea represents an active plate boundary on the northern Australian margin that is presently rifting. This project will develop models that detail how the rifting is accommodated in continental rocks and compare and contrast this with oceanic rocks. The project aims to understand the tectonics of rifting by examining this active tectonic region, thus investigating a fundamental plate tectonic process that is critical to understanding Earth evolution. Expected outcomes include a deeper understanding of plate tectonics, with special focus on deep Earth processes.
Global lithosphere architecture mapping
Sue O’Reilly and Bill Griffin: Supported by ARC Linkage Project and WMC Resources
Summary: Compositional domains in the subcontinental lithospheric mantle reflect the processes of continental assembly and breakup through Earth’s history. Their boundaries may focus the fluid movements that produce giant ore deposits. Mapping these boundaries will provide fundamental insights into Earth processes and a basis for the targeting of mineral exploration. We will integrate mantle petrology, tectonic synthesis and geophysical analysis to produce the first maps of the architecture of the continental lithosphere, to depths of ca 250 km. These maps will provide a unique perspective on global dynamics and continental evolution, and on the relationships between lithosphere domains and large-scale mineralisation.
Toward the use of metal stable isotopes in geosciences
Olivier Alard: Supported by ARC Discovery
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.
Crustal Evolution in Australia: Ancient and Young Terrains
Elena Belousova: Supported by ARC Discovery
Summary: The mechanisms of crustal growth and the processes of crust-mantle interaction will be studied in selected Archean, Proterozoic and Phanerozoic terrains in Australia, using a newly developed approach: the integrated, in situ microanalysis of Hf and Pb isotopic composition and trace-element patterns in zircons from sediments and selected igneous bodies. The results will provide new information on the evolution of the Australian crust, with wider implications for the development of global crust and mantle reservoirs. The outcomes will define crustal evolution signatures related to regional-scale mineralisation, and thus will be highly relevant to mineral exploration in Australia and offshore.
How has continental lithosphere evolved? Processes of assembly, growth, transformation and destruction
Sue O’Reilly and Bill Griffin (with 5 partner investigators): Supported by ARC Discovery and Linkage International
Summary: We will use new in situ analytical techniques, developed in-house, to date the formation and modification of specific volumes of the subcontinental lithospheric mantle, and to define the temporal and genetic relationships between mantle events and crustal formation. Quantitative modelling will investigate the geodynamic consequences of spatial and temporal variations in lithosphere composition and thermal state. Magmatic products will be used to assess the roles of mantle plumes and delamination in construction of the lithosphere, and xenolith studies will investigate the evolution of oceanic plateaus. The results will provide a framework for interpreting the architecture of lithospheric terranes and their boundaries.
The timescales of magmatic and erosional cycles
Simon Turner (with 4 partner investigators): Supported by ARC Discovery
Summary: Precise information on time scales and rates of change is fundamental to understanding natural processes and the development and testing of quantitative physical models in the Earth Sciences. Uranium decay-series isotope studies are revolutionising this field by providing time information in the range 100-100,000 years, similar to that of many important Earth processes. This project is to establish a dedicated Uranium-series research laboratory and to investigate (1) the processes and time scales of magma formation, transport and differentiation beneath western Pacific island arc volcanoes, (2) the time scales and relative roles of physical and chemical erosion in Australian river basins.
Isotopic fractionation of the ore metals (Cu, Zn, Fe): Mechanisms and significance
Simon Jackson: Supported by Macquarie University Research Development Grant
Summary: Utilising recent advances in laser and mass spectrometric technologies, it has been determined that the stable isotope ratios of important metals (eg Cu) exhibit significant variations in ore systems. However, little is known of the fractionating processes. The proposed project will determine the mechanisms that fractionate isotopes of Cu, Fe and Zn by: (a) building a data-base of isotopic signatures for rock types commonly associated with mineralisation, (b) study of selected active and ancient hydrothermal systems, (c) experimental studies. This information will allow metal isotopes to be applied to determining the genesis of, and, potentially, exploration for, ore deposits.
The oxidation state of the early Earth mantle: new clues from iron isotopes
Helen Williams: Supported by Macquarie University New Staff Grant and Industry (Nu Instruments)
Summary: This project’s goal is to understand how the Earth’s atmosphere became oxygen-rich. Oxygen stored in the Earth’s deep interior (the mantle) was probably released to the surface as water and CO2, allowing the growth of free oxygen in the atmosphere to a significant level by ~2.4 Ga (billion years ago). These processes, and the distribution of oxygen in the mantle, are poorly understood. This project will use iron and chromium isotopes as oxygen tracers in 3.3-2.1 Ga mantle rocks to understand the evolution of oxygen in the mantle and how this is linked to the development of the Earth’s atmosphere.
Thallium isotopes: a novel geochemical tracer to map recycling in Earth’s mantle
Sune Nielsen: Supported by a fellowship from the Danish Research Council
Summary: The recycling of crustal material back into the mantle at subduction zones is one of the most fundamental Earth processes, but its effect on the evolution of the geochemistry of the mantle, and the ultimate fate of the subducted material, are poorly understood. This project will use the stable isotope geochemistry of thallium as a novel and sensitive tracer to follow subducted oceanic crust through the subduction process, and test for its reappearance in hot-spot volcanoes and the continental lithosphere. The results will provide firm constraints on models of mantle convection, Earth evolution and the generation of continents
Evolution of the upper mantle beneath the Siberian Craton and the southern margin of the Siberian Platform
Vladimir Malkovets: Supported by Macquarie University Research Fellowship
Summary: This project will contribute new information and concepts about the formation of Earth’s continents over the last 4 billion years. It will use geochemical techniques recently developed with state-of-the-art instrumentation in the GEMOC laboratories, and apply these techniques to unique suites of mantle-derived samples (xenoliths) from volcanic rocks across Siberia to investigate differences between mantle domains of different age and tectonic setting. The results will provide direct analogues for better understanding of mantle structure and mantle evolution beneath Australia, and will contribute to development of tectonic models relevant to the area selection process in mineral exploration.
Lithosphere extension in East Asia: tectonic mechanisms and geochemical consequences
Kuo-Lung Wang: Supported by Macquarie University Research Development Grant
Summary: This project seeks to better understand how continents pull apart (extend) and how the mantle part of the lithosphere (~200 km depth) responds. Novel Re-Os techniques will date mantle samples delivered to the surface in magmas; geochemical fingerprints of processes related to extension will be established. Integration of new geophysical data with geochemical results will constrain the lithosphere architecture. The East Asia region is an ideal natural laboratory and the results will be applicable to analogous tectonic scenarios globally and throughout geological time. The results will have particular relevance for unravelling the geological evolution of Phanerozoic eastern Australian lithosphere.
Zircon analysis of Cretaceous and Eocene sediments of Lambert Graben -Prydz Bay, Antarctica
John Veevers: Supported by Macquarie University Research Development Grant
Summary: Five samples from Prydz Bay, East Antarctica, have become available recently. (a) Ocean Drilling Program (ODP) Leg 188, Site 1166, encountered an Upper Eocene (35 Ma) 100-m-thick coarse sand interpreted as deposited on an alluvial plain. 'Prydz Bay is at the downstream end of a drainage system that originates in the Gamburtsev Mountains of central East Antarctica' (ODP Initial Report 188) so that zircons from this sand may reflect the Gamburtsev provenance. Two samples have been supplied by the ODP. (b) ODP Leg 119 Sites 740 and 741 encountered an Early Cretaceous (middle to late Albian, 105-99 Ma) coal-bearing fluvial sediment 100 m thick. It is part of a subhorizontal sequence 2-3 km thick, that probably overlies Precambrian basement. Again, zircons from this sand are expected to reflect the Gamburtsev provenance. Three samples have been supplied by the ODP. Zircons from the five samples have been separated and mounted. Combined with those from Beaver Lake immediately upstream and the Mahanadi Basin (India) downstream, the Prydz Bay zircons will provide crucial data about the age and composition of the Gamburtsev provenance.
3D shape of the Mole Granite and the thickness of the Torrington Pendant
Mark Lackie and Dick Flood: Supported by Macquarie University Research Development Grant
Summary: The aim of this project is to undertake a gravity survey of the Mole Granite to quantify the 3D shape of the granite. As well, a seismic section utilising national seismic facility equipment will be undertaken across a contact of the granite to assist in the modelling of the shape of the granite. A secondary aim of this project will be to undertake a seismic survey across a roof pendant of the granite to delineate the pendant’s thickness and shape. Understanding the shape of the Mole Granite is important in unravelling the geological history of the western New England region.
Timing and mechanisms of melt migration and interaction at mantle, lithospheric and crustal levels
Rhiannon George: Supported by Macquarie University Research Development Grant
Summary: A tantalising window into crust and mantle processes is opened up if we can link them to the key variable of time. A key initiative of this proposal is to provide a unique, quantitative way of constraining the physical mechanisms by which the Earth differentiates. It does so by strategically targeting two key areas: (1) Testing models of the movement of small melt fractions in the lithospheric mantle beneath island arcs, ocean islands and the continents; (2) The time scales of lower and upper crustal melting and the effect of such processes on the interpretation of Uranium-series isotope systematics.