GEMOC ARC National Key CentreGEMOC's research program
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Scientific context Thermal energy transmitted through the mantle provides the energy to drive lithosphere processes. Mantle-derived fluids and the tectonic environment control element transfer across the crust-mantle boundary and control commodity distribution in the accessible crust. The nature of mantle heat transmission reveals information on fundamental deep Earth processes from the core-mantle boundary to the surface. The Earth's interior can be mapped for rock types and their relationships using fragments of deep materials such as mantle rocks and diamonds, and the compositions of mantle-derived magmas. The focus of GEMOC's research programs is the driving role of the mantle in Earth processes and its control of element concentration and distribution in the accessible crust. This bottom-up approach involves:
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| "The focus of GEMOC's research programs is the driving role of the mantle in Earth processes" |
The research aims
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advances in the Geochemical Analysis Unit, relevant to in situ trace and isotopic analysis, are allowing us to exceed our original goals in ... tracking the degree of crust-mantle interaction” |
Research Program The Research Highlights section gives an overview of major progress in 2002. The Research Program for 2003 follows the topics of the funded projects listed in Appendix 5. The ARC Discovery Program Grant (O'Reilly and Griffin) incorporates some of the new research directions in the GEMOC continuation. Some of the industry projects are summarised in the section on Industry Interaction. The progress of the SPIRT Project with WMC for 2001 to 2003 (Lithospheric Architecture of Australia: Relevance to Location of Giant Ore Bodies) is an excellent example of the delivery of one of GEMOC's main original Research Aims. This research project is testing the concept that giant magmatic and hydrothermal ore bodies are localised by major structural discontinuities that extend through the Earth's lithosphere. The original scope of the project has been extended to modelling global lithospheric domains and their boundaries. Tectonic analysis and geochemical data on crustal and mantle rocks are being integrated with large-scale datsets (including geophysical data) to understand the relationship between lithosphere domains and large-scale mineralisation. The new methodologies of using mantle sulfides to date mantle events, and of characterising crustal terrane development using U-Pb dating and Hf isotopic compositions of zircons (see Research Highlights) provides more information for integration with the geophysical modelling. Technology developments in GEMOC are driven by the needs of
the research (including industry collaborative) programs. The
2002 advances in the Geochemical Analysis Unit, relevant to in
situ trace and isotopic analysis, are allowing us to exceed
our original goals in the areas of tracking the degree of crust-mantle
interaction and recognising the timing of different generations
of major lithospheric events. Foremost in these new methods are
the refining of in situ PGE and Re/Os analysis of sulfides;
U/Pb, Lu/Hf and trace-element spectrum in zircon; and Rb/Sr and
Nd/Sm analyses in a range of minerals (see Technology
Development). The research program for the first six years focused on four strands: the current Research Program is pushing new conceptual and technology frontiers, building on our intellectual capital from the first phase of GEMOC. |
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Lithosphere Mapping provides the fundamental data for defining mantle domains in terms of composition, structure and thermal state. Lithosphere profiles built up by this information are interpreted in the context of geophysical datsets (especially seismic tomography) to extrapolate laterally. Relating lithospheric domains to refined models of tectonic evolution will help to define the large-scale evolution of mantle processes through time, and their influence on the development of the crust and metallogenic provinces. The nature of mantle fluids and the mantle residence and abundances of siderophile, chalcophile and noble elements and sulfur, carbon, oxygen and nitrogen are keys to understanding the transfer of mineralising elements into the crust. Geotectonics uses stratigraphic, tectonic, and geophysical data to interpret the history and causes of continental assembly and disruption, with a special focus on Australia, East Asia and major cratons (Siberia, Kaapvaal, Canada, South America). It provides the fundamental framework to link the research on crustal and mantle processes with the localisation and development of metallogenic provinces. Crustal Generation Processes seeks to understand: the large-scale processes that have created and modified continental crust; how these processes may have changed through time; and how crustal processes influence the concentration and localisation of economically important elements. The role of crust-mantle interaction in granite genesis, coupled crust-mantle formation and its influence on tectonism, and transport of elements across the crust-mantle boundary link to the Lithosphere Mapping and Metallogenesis strands. Metallogenic Provinces seeks to define the mantle and crustal reservoirs of economically important elements, the mechanisms by which elements can be extracted from the mantle and transported into the crust, and the mechanisms of fluid transfer in the crust and mantle. The emphasis is on understanding processes of regional scale, and relating these processes to the tectonic framework and the processes of mantle and crustal generation. |
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Tectonic analysis and geochemical data on crustal and mantle rocks are being integrated with large-scale datsets (including geophysical) to understand the relationship between lithosphere domains and large-scale mineralisation.” |
strengthening Geophysics
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Lithosphere Mapping Geochemical structure and evolution of continental lithosphere and interpretation of geophysical data Research Highlights Mantle terranes and cratonic roots: Canada, USA, southern Africa, Siberia, eastern China, Australia, Brazil Gravity modelling of lithosphere terranes (regional elastic thickness) Evolution of oceanic lithosphere: Kerguelen Plateau, Hawaii, Crozet Islands Diamonds: origin and clues to lithosphere evolution and structure; Canada, Siberia, South Africa Research Highlights Seismic imaging of Moho structure and integration with petrological data: Indian Ocean, Kerguelen Plateau Basalts as lithosphere/asthenosphere probes Thermal framework of the lithosphere: paleogeotherms, heat production, conductivity, thermal evolution Experimental studies of mantle minerals: high pressure partition coefficients; role of accessory minerals in controlling mantle fluid compositions Research Highlights Lithosphere extension processes and consequences in East Asia: Taiwan and eastern China regions Constraints on the timing of depletion and fluid movements in lithospheric mantle of different ages, using a range of isotopic and trace-element methods, including Re-Os in mantle sulfides Research Highlights The nature of lithospheric mantle in arc regions (Japan, Kamchatka, Philippines, Solomon Islands) Tracking mantle plumes through time Crustal Evolution Role of oceanic plateaus in oceanic and continental crustal formation: Kerguelen Crustal evolution and metallogenesis, southeastern China Evolution of continental crust: central Queensland; San Francisco Volcanic Field, Arizona; Peninsular Ranges batholith of Baja California, Mexico Origin of granites and crustal genesis at continental margins: eastern Australia, southeastern China Metamorphic reactions and mineral growth; microstructural processes in metamorphic rocks Tracers of magmatic processes; trace elements in accessory minerals Integrated U-Pb, Hf-isotope and trace-element in situ analysis of detrital zircons to characterise the magmatic history of major crustal terrains ( Event Signatures”): applications of TerranechronTM, South America, South Africa, Australia, India Research Highlights Timescales of magmatic and erosional processes Hf-isotopic signatures of zircons (in situ LAM-ICPMS) as tracers of crust-mantle interaction in granites Metallogenesis Geochemistry of mantle sulfides Chromite chemistry in mantle-derived magmas and residues Resistate minerals and mineral exploration Area selection and evaluation for diamond exploration Lithosphere domains through time and location of ore deposits Crust-mantle interaction, granites and metallogenesis through time Sulfide and PGE budget of the mantle Re-Os dating of mantle sulfides in situ and timing of mantle processes Research Highlights Highly siderophile element (including platinum group element) concentrations in sulfides (LAM-ICPMS) Zircon composition in mineral exploration Groundwater geochemistry and aquifer lithology Stable-isotope ratios of some important commodity elements (eg Cu, Fe, Zn, Mo) in a range of ore minerals and deposit types Research Highlights Trace elements in diamonds - possible genetic indicators? Geotectonics Influence of mantle processes on crustal geology and topography: regional geotectonic analysis: Slave Craton (Canada), Siberia, eastern China, Australia, Kaapvaal Craton Research Highlights Neoproterozoic earth history of Australia: Tectonics, isotope-, volcanic- and bio-stratigraphy Tasman Fold Belt tectonism and regional volcanology: Tumut-Gundagai region; Louth area; central western NSW; central Queensland Paleomagnetic studies of the northern New England Orogen Geodynamic modelling of large-scale processes using constraints from 4-D Lithosphere Mapping results Research Highlights Evolution of lithospheric composition and Earth geodynamics through time Research Highlights |
