Funded basic research projects for 2004

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

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.

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.

Melt escape and trace element partitioning during high-pressure partial melting in the lower crust, northern Fiordland, New Zealand

Nathan Daczko: Supported by Macquarie University Early Career Research Grant

Summary: This project aims to derive new constraints on processes of lower crustal (>30 km depth) melting and melt escape.  It will test and expand upon the proposed hypothesis that the efficient segregation and transport of magma from the lower crust is controlled by fracture propagation, not just slow upwelling.  It is impossible to directly observe active ascent mechanisms at such depths. This, as well as the heterogeneity and structural complexity of lower crustal source regions, has led to controversy.  Integration of field relationships, petrological and geochemical analyses will define the parameters of lower crustal melting and improve our understanding of deep-Earth processes.

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Annual Report 2003