GEMOC ARC National Key CentreGEMOC Research Projects listed by strands and years
Research Projects initiated 1998
Lithosphere Mapping
L98-1. 4-D Lithosphere Mapping III: fingerprinting the nature and mechanisms of secular evolution of the Earth's lithosphere (O'Reilly). Methodologies developed and refined in previous work will be used to produce 4-D pictures (with time) of the thermal and compositional structure of the upper mantle, including a traverse through China, Mongolia and Siberia along about one-third of the Earth's circumference. Mantle samples from regions of contrasting age (ancient to modern) and tectonic environment will be used to define the nature of irreversible changes with time in the composition of the upper mantle and the mechanisms that cause formation of new, and destruction of old, continental mantle. The results will provide new information about the large-scale controls on tectonics and magmatism in space and time within Australia and Asia and can be applied to the selection of areas prospective for diamonds and other magma-related economic deposits (eg nickel, base metals, platinum group and rare-earth elements, copper and gold). Funded by ARC large grant from 1998 and previously by ARC, Industry, Macquarie University.
L98-2. Basaltic magmas: clues to large-scale mantle processes (O'Reilly, Zhang). Chemical compositions of primitive basaltic magmas record the nature and evolutionary history of various mantle source reservoirs. In this project, basalts that erupted through different tectonic regions or at different times in the same region in eastern Australia and eastern China will be targeted to trace the locus with time of the "Indian" and "Pacific" Ocean upper mantle convective domains beneath eastern Gondwanaland and subsequent tectonic domains. New techniques for Pb-isotope analysis will be developed. The project will provide new insights into the history of formation, preservation and destruction of the subcontinental lithospheric mantle and the nature of some large-scale mantle convective domains. Funded by Small ARC for 1999.
L98-3. Lithosphere structure beneath Siberia: an integrated geophysical, petrological and tectonic analysis (Griffin, Poudjom Djomani, O'Reilly). This is an extension (new strand) of a successful project (1998), aimed at exploring the integration of mantle petrology, tectonics and advanced geophysical analysis to understand the large-scale architecture of the continental lithosphere and how it controls the localisation of large ore deposits. This project began in the eastern Siberian Platform, and we now will extend the analysis to a much larger region, which includes the giant Norilsk nickel deposits. Geophysical data will be provided by VSEGEI (St. Petersburg) and the analysis will be carried out at Macquarie. Funded by WMC and Macquarie University for 1999.
L98-4. Structure of the Australian lithosphere from combined geophysical and petrological data (O'Reilly, Poudjom Djomani). The Australian continent is divided into the Precambrian to the West and the Phanerozoic to the East, separated by the Tasman Line. Knowledge about the nature, composition and thermal structure of the Australian lithosphere is important for understanding the formation and current lithospheric structure of this continent and its natural resources. Many large resource concentrations may be related to boundaries of large-scale tectonic domains. Xenolith-based data can be used to study the composition of the lithosphere, while geophysical data analysis can be used to estimate the strength of the lithosphere. A combination of both datasets and other existing data will give an actualistic interpretation of the nature of lithospheric blocks in Australia. Funded by MURG.
L98-5. Trace element characteristics of the Kerguelen ultrabasic and basic xenoliths: a key study to understand the nature and evolution of the lithosphere beneath oceanic plateaux (Gregoire, O'Reilly). This project will provide data on trace element contents of the minerals occurring in high pressure xenoliths from the Kerguelen Islands (Indian Ocean). The laser microprobe ICPMS in GEMOC will enable these analyses to be carried out in situ for Rare Earth Elements and other trace elements such as Zr, Hf, Nb, Ta, Ti, Rb, Sr, Ba, U, Th. These geochemical data will provide a new opportunity to explore and quantify the rates, the depth and the type of partial melting processes, the nature and evolution of the mineral assemblages and compositional fingerprints of the xenoliths, and the role and type of fluid-related processes in the upper mantle relevant to plume-related processes in the oceanic lithosphere. Funded by MURG.
L98-6. Advanced statistical analysis of mantle garnet database (Griffin, O'Reilly, Friedman, Fisher). This travel grant brings together a team of geologists and statisticians to develop and apply new statistical techniques to a large database on the geochemistry of minerals derived from the Earth's mantle. The major aim is to learn how to recognise meaningful natural populations within such a database, and to develop tools for mapping the geology of the Earth's upper mantle in three dimensions. If successful, this approach will provide new insights into the composition, structure and evolution of the mantle beneath different parts of the Earth's crust, an outcome important both for basic science and for mineral exploration. Funded by MURG.
Crustal Evolution
C98-1. Source and evolution of strongly fractionated granites (Chappell). Strongly fractionated granites are a distinctive group of rocks with rather constant major mineral and chemical compositions. However, the abundances of accessory minerals and trace elements vary widely within and between suites of such granites and those variations will be used to establish the mechanisms that produce such rocks. Specific features of different suites of felsic granites will generally relate back to features of source rocks. Since some mineral deposits are related to these granites, this project will have practical outcomes for mineral exploration. It also relates to the possible development of geothermal energy resources in Australia. Funded by ARC.
C98-2. Aluminosilicate mineral reactions in deforming metamorphic rocks. (Vernon). The aluminosilicate (Al2SiO5) minerals, andalusite, kyanite and sillimanite, are excellent indicators of temperature and pressure in Earth's crust. I plan to use these minerals to decipher changes in temperature and pressure in solid rocks at depth in the crust (metamorphism) and to relate their growth to the deformation events responsible for these changes. A major change in pressure-temperature regime has been inferred for the northern Cascade Range, Washington, USA, where all three aluminosilicate minerals are present, so that the rocks exposed in this area are ideal for tracing the changes and relating them to evidence (folds and foliations) of the deformation events. Funded by MURG.
C98-3. Experimental partitioning of Zr and Hf between rutile and silicate liquids at high pressure (Green). A characteristic feature of andesitic volcanism of convergent plate boundary regions is that the magmas are depleted in high field strength elements (Nb, Ta; Zr, Hf) relative to mid-ocean ridge basalts. A commonly held view is that this depletion is due to the preferential retention of these elements in rutile during the magma generation process. It is important to determine the behaviour of these elements between rutile and silicate melt in order to critically assess this view, and to determine the extent to which rutile decouples Zr and Hf from Nb and Ta. Funded by MURG.
C98-4. GIS Mapping of SE Australian Granites (Chopra, D. Wyborn, Chappell). Detailed GIS datasets are being compiled of the known and interpreted distribution of granites in SE Australia. These spatial data are being combined with the ANU's extensive granite geochemistry database to produce an integrated tool for ongoing research into the evolution of the Lachlan Fold Belt. Funded by ANU.
Metallogenesis
M98-1. Application of lithosphere Mapping to diamond exploration models: Slave Craton, Canada (Griffin, Davies, Doyle, O'Reilly, Pearson, Poudjom Djomani, Gohl). We will analyse the composition and structure of the upper mantle beneath the Slave Craton of northern Canada, using mineral and rock samples from newly discovered kimberlites, and relate this structure to the nature and distribution of diamonds across the Craton. Geophysical and tectonic analysis will be used to understand the 3-dimensional structure of the cratonic lithosphere and its evolution. This work will clarify the processes that form and modify cratonic lithosphere, and lead to an integrated model for diamond exploration in the Slave Craton, and to concepts and mineral exploration methodologies that can be exported to other regions. Funded by SPIRT.
M98-2. Sulfur content of the upper mantle (Griffin, Pearson). The content of sulfur in Earth's upper mantle is poorly known, although the mobility of sulfur and the distribution of sulfide minerals are critical factors in understanding the distribution of many economically-important elements and the ultimate generation of many ore deposit types. Measurement of S contents of upper-mantle rocks at the required very low levels is analytically challenging. This proposal seeks funding to build a simple but effective apparatus for carrying out these analyses, in support of a larger program of research into mantle geochemistry, including the development of age-dating methods using the Platinum Group Elements. Funded by MURG.
M98-3. Development of a new technique for in situ trace element determinations in sulphide minerals and its applicability to exploration for sulphide mineral deposits (Jackson). Sulphide minerals are the major ore minerals of many important metals (Cu, Zn, Pb, Mo, As, Sb, Ni, Co, Bi). The aim of this project is to develop a new technique for in situ analysis of these minerals at trace element levels using a laser microprobe. The ability to produce extremely rapid analyses of these economically important minerals is expected to have important significance in: (1) understanding the genesis of mineral deposits, allowing refinement of current models; (2) immediate application to ore processing; (3) potential application to exploration for buried mineralisation using the trace element signatures of peripheral sulphide (pyrite) occurrences. Funded by MURG.
M98-4. Heavy element isotopic fractionation during microbial processes: Implications for the source and genesis of, and exploration for, sulphide ore deposits (Jackson). Microprobial processes involving electrochemical reduction of sulphate results in the fixing of metals as sulphide minerals. This action is known to result in strong isotopic fractionation of carbon and sulphur. Using new technology, the multi collector-ICP-MS, this study proposes to assess, for the first time, isotopic fractionation of a suite of heavier elements of economic interest (Cu, Zn, Fe, Ni, Ag, Sb) during sulphide-forming microbial processes. The technique will further be applied to the study of selected sulphide ore deposits in NSW. It is expected that understanding the isotopic fractionation processes of these elements will provide a tool for assessing the source of metals concentrated in many important ore deposits, with obvious important ramifications for mineral exploration. Funded by MURG.
Geotectonics
Many of the Lithosphere Mapping projects are also relevant to this topic.
GT98-1. Carboniferous magmatism in the Lachlan Fold Belt and New England Fold Belts (Veevers). To find the fundamental connection between uplifted primitive granites (Carboniferous LFB and Permian NEFB) and evolved granites (Silurian and Devonian LFB) without uplift by modelling mechanisms of emplacement and exhumation of mid-Carboniferous plutons and related volcanics. Funded by ARC.
GT98-2. Australian Earth Data On-Line (Chopra). AEDOL (http://aedol.anu.edu.au) provides automated processing facilities for the acquisition, harmonisation, generation and dissemination of commercially valuable spatial products including GIS datasets and geocoded images. Local processing capabilities are provided through cross-platform JavaT applets. These permit the user to make rapid improvements to the images without the need for Internet traffic. At the back-end of AEDOL is a full-featured image processing system based on custom calls to ER MapperT. This brings to the user the ability to perform sophisticated image processing without reliance on specialist software or training. The current AEDOL system requires nothing more than an Internet connection and a standard WWW browser. By automating the processing, delivery and commerce of these products, AEDOL can significantly lower the cost to the user. This will drive technology take-up by eliminating transport costs and minimising delays and importantly, it puts the power of the system directly into the hands of the end-user. Funded by DIST and ACT AusIndustry.
GT98-3. Low-temperature rock magnetic studies of Palaeozoic volcanic rocks from the New England Orogen and the Lachlan Fold Belt (Lackie). The major aim of this project is to undertake low-temperature (4 to 77K) rock magnetic experiments to aid in the rock magnetic interpretation of previously collected late Palaeozoic volcanic rocks from the northern New England Fold Belt and early/mid Palaeozoic rocks from the Lachlan Fold Belt. As well, rock magnetic experiments are to be done on a set of samples both here, utilising current and new equipment, and at the Institute of Rock Magnetism in the USA, using both similar and different equipment with the view to comparing the results. The secondary aim of this project is to report the results of previous and current palaeomagnetic studies at an international conference. Funded by MURG.
GT98-4. Palaeomagnetism of Ordovician eastern Australian alteration systems: implications for the breakup of Rodinia and assembly of Pangaea (Lackie, Schmidt). Our aim is to resolve the apparent polar wander path (APWP) polarity controversy for the early to mid Palaeozoic of Gondwana by undertaking new palaeomagnetic studies of well-dated Siluro-Ordovician mineralisation/alteration systems. Recent palaeomagnetic data from north Queensland from the Silurian suggest that the APWP for the Early Palaeozoic can be much better defined by focussing on alteration systems. Funded by ARC (seeding grant).
Research Projects initiated 1997
Lithosphere Mapping
L97-1. Lithosphere Structure Beneath Siberia: an integrated Geophysical, Petrological and Tectonic Analysis (Griffin, Poudjom Djomani, Natapov, O'Reilly) Kimberlite fields in the eastern Siberian Platform provide mantle samples along a 1000-km traverse across several major terrane boundaries. This project investigates methodologies for mapping large lithospheric blocks by a combination of petrological, geophysical and tectonic analysis of this region. Gravity and magnetic data, provided through a collaboration with VSEGEI (St. Petersburg), are being used to map the regional extent of lithospheric mantle of different types beneath the Siberian Platform and to relate the distribution of lithospheric blocks in this region to the distribution of different types of mineralisation. Funded by ARC and MU collaborative grant with Western Mining Corporation.(SEE Case Histories)
L97-2. Lithosphere structure and origin of diamonds, Slave Craton, Canada (Griffin, O'Reilly, Davies, Pearson). This project is part of a larger program that uses xenoliths, heavy mineral concentrates and diamonds from newly discovered kimberlites in the Slave Craton, to map the structure, composition and thermal state of the lithospheric mantle. In this module, we are studying the nitrogen contents and aggregation state, carbon isotopic composition and mineral inclusions to place the diamonds in their lithospheric context. This is leading to new models for the formation of the cratonic mantle beneath this little-known craton, with implications for the formation of continental roots in general. Funded by MU collaborative grant with Kennecott Canada Inc. (SEE Case Histories)
L97-3. Igneous rocks, mineral deposits and tectonic setting: Southeastern China and eastern Australia (O'Reilly, Griffin, Zhang). This project is providing enhanced collaboration between the National Key Centre for Geochemical Evolution and Metallogeny of Continents (GEMOC) at Macquarie University in Australia and Nanjing University in China. It is a focussed study of the relationships between igneous rocks, metallogeny and geological architecture of southeastern China, capitalising on the Nanjing participants' expertise of the in the field of igneous rocks and associated mineralisation. Southeastern China and Australia have geological similarities and contrasts. Southeastern China, with its more complex geological structure and areas of recent tectonic activity, provides analogues to interpret the geological structure and metallogenic framework of the Australian continent. The "4D lithosphere mapping" project now being carried out at GEMOC has already identified major changes in mantle structure beneath eastern China since Mesozoic time, and this project is specifically designed to study the effects that these changes have had on crustal generation and metallogeny. This project will have practical outcomes in assisting area selection and evaluation for mineral exploration. Funded by AusAID ACILP and reciprocal funding from Chinese sources including China NSF and China Ministry of Education.
L97-4. Basalts as probes to unravel the evolution of the subcontinental lithosphere in East Australia and East China (O'Reilly and Zhang) The chemical compositions of basaltic magmas that erupted through different tectonic regions in eastern Australia and eastern China are being used as probes to understand the composition of the Earth's mantle down to depths of ~100 km. This will help trace the evolution of the mantle beneath the supercontinent of Gondwanaland since it split into small pieces. The project will provide new insights into the genesis of the basalts, the evolution of the mantle and continental crust, the nature of mantle convection at a global scale, and a framework for targeting resources related to volcanic processes. Funded by small ARC
L97-5. Lithospheric architecture of an oceanic plateau with continental affinity: seismic investigation of the Agulhas Plateau, SW Indian Ocean (Gohl). Dredged basalt samples of the southern plateau indicate a Proterozoic age of continental fragments adjacent to overthickened oceanic crust. A deep crustal seismic reflection and wide-angle/refraction transect across the southern plateau was recently acquired to determine its crustal thickness and composition, and to test an hypothesis of an apparent anomalously low density upper mantle. Funded by Macquarie University
L97-6 Nature and evolution of the oceanic upper mantle at a convergent plate boundary: trace elements study of the mantle xenoliths from the Tubaf Volcano (south of Lihir Island, New Ireland, Papua New Guinea) (Grégoire, McInnes (CSIRO) and O'Reilly). Trace element signatures of bulk rocks and minerals in mantle xenoliths from the Tubaf volcano provide a better understanding of the role of fluids derived from a subducted slab in the modification of an oceanic upper mantle showing evidences of early partial melting processes. It gives new insights on the nature and evolution of the deep lithosphere beneath a young gold deposit in the geodynamic setting of an oceanic plateau in a collisional zone. Funded by a GEMOC seeding grant and CSIRO.
L97-7. The nature of the upper mantle beneath the southwestern margin of the Siberian platform (Ionov, Griffin, O'Reilly, Malkovets). Mantle-derived xenoliths from the Minusa region, southern Siberia are used to characterise the nature of the upper mantle beneath a Paleozoic terrain at the southwestern margin of the ancient East Siberian platform. This study will provide analogue data to interpret similar tectonic regions globally, including eastern Australia Funded by MURG and a GEMOC seeding grant.
L97-8. Diamonds and their inclusions, Zarnitsa and Dalnaya pipes, Siberia (Griffin, Davies, Bulanova). Most data on diamonds and their inclusions from the Siberian Platform have come from two major mines (Mir and Udachnaya). This project examines material, made available through a collaboration with TsNIGRI (Moscow), from two small uneconomic kimberlites in the Daldyn field, for comparison with the diamonds from the nearby Udachnaya pipe. An integrated study, it involves analysis of nitrogen content and aggregation state, carbon isotopes, and the composition of mineral inclusions, as well as examination of the internal structure of the diamonds, in an effort to characterise the nucleation and growth environment of the diamonds. Funded by GEMOC seeding and TsNIGRI.
L97-9. Lithosphere structure beneath Siberia: an integrated geophysical, petrological and tectonic analysis (Griffin, Poudjom Djomani, Natapov, O'Reilly). This study aims to investigate methodologies for mapping large lithospheric blocks by a combination of petrological, geophysical and tectonic analysis. The regional extent of lithospheric mantle of different types beneath the Siberian Platform and surrounding areas is being defined with the objective of relating the distribution of large lithospheric blocks in this region to the different types of mineralisation. Funded by WMC and Macquarie University.
L97-10. Mantle environment of diamonds from the Slave Craton, Canada (O'Reilly, Griffin, Pearson, Davies). This study is using the petrography and mineral chemistry (major- and trace elements) of mantle xenoliths from the recently discovered kimberlites of the Slave Craton in the Northwest Territories of Canada to understand the stratigraphy of the lithospheric mantle and lower crust. Data on the chemistry of mineral inclusions in diamonds from these kimberlites are being used to define the relationship of these diamonds to the mantle stratigraphy. Carbon-isotope composition and nitrogen aggregation state of the diamonds are helping to understand their origin and their relationship to the metasomatic history of the mantle section. Funded by Kennecott and Macquarie University for 1998.
Crustal Generation
C97-1. Sulfide partitioning between felsic melts and residues during ultrametamorphism of the deep crust (Ellis, Sheraton, Mavrogenes). A suite of partially melted (migmatitic) deep crustal hornblende granulites is being studied. These rocks were saturated with sulfides during partial melting and thus provide remarkable information for the partitioning of sulfur and chalcophile elements between felsic melts and residues in the deep crust. Whole rock geochemical, mineralogical and trace element data (using the ANU laser ablation equipment for oxides, sulfides and silicates) are being gathered. This will provide valuable information on the role of partial melting and melt extraction in infracrustal differentiation of sulfides. Funded by ARC.
C97-2. Crustal evolution in a Mesozoic Circum-Pacific magmatic arc - the Peninsular Ranges batholith of Baja California, Mexico (Johnson, Vernon, Tate). The project investigates the ways in which large bodies of magmatic rocks (plutons) are emplaced, the timing of their intrusion relative to regional deformation and heating of the crust, the extent to which the plutons are responsible for this deformation and heating, and the relative roles of source and diversification processes in granitoid chemistry. Funded by ARC and Mexican CONACyT.
C97-3. Accessory mineral solubility and experimentally-determined constraints on trace element behaviour in proposed mantle metasomatic melts (Green, Adam). The trace element characteristics of metasomatic melts may be determined by the accessory minerals that they are saturated in at high pressure. Early experiments show that apatite and a Ti-rich phase in high-silica and alkali melts have contrasting solubility behaviour with both increasing pressure and K content. Funded by ARC Small Grant.
C97-4. The ages of mafic underplating in central coastal Queensland (C.M. Allen with I.S. Williams (RSES)). Mafic crustal xenoliths from Cretaceous and younger basalt flows are being dated by SHRIMP analysis of zircon in an effort to tie the ages of mafic underplating to granite production. Initial results suggest that these granulites are good recorders of the major heating events that produced granites. Pilot project funded by ANU; external funding being sought.
C97-5.A major review of the trace-element geochemistry of granitic rocks and implications for petrogenesis (John Sheraton, Lesley Wyborn and John Tarney, University of Leicester). Funded by AGSO.
C97-6. An old method for studying element mobility revised (John Sheraton and Wendelin Himmelheber, University of Gottingen). This research deals with the use of statistical methods for comparing chemical analyses of high-grade gneisses with their retrogressed equivalents, with a view to identifying any geologically significant changes in composition. Funded by ANU.
C97-7. A regional geochemical study of the island-arc and other volcanic rocks of the Papua New Guinea area (John Sheraton and R. W. Johnson). Analyses of about 1600 whole-rock samples have been processed and plotted, and preparation of a summary paper has begun. Funded by AGSO
Metallogenesis
M97-1. Tracing sulfur, chalcophile and precious metals behaviour during differentiation and vapour evolution from subduction zone magmas (Eggins). Metals in magma derived ores, specifically porphyry Cu-Mo and epithermal Au deposits. This research also has implications for understanding the sulfur dioxide yields and atmospheric loading from past and future volcanic eruptions. Funded by ARC, ANU.
M97-2. Metals behaviour in ultramafic-mafic intrusions in southernmost NZ (Arculus, Eggins). This project examines specifically the origin of primary platinoid mineralisation in chromite lenses and their behaviour during magmatic differentiation. Funded by ARC.
Geotectonics
GT97-1. Hot Rock Geothermal Energy: a major new Australian energy source (Chopra, Wyborn). Research has established that Australia has enormous reserves of Hot Rock Energy. The successful utilisation of this environmentally benign energy source could go a long way to solving Australia's current greenhouse gas problems. Current work involves refinement of hot rock resource models and detailed planning for a field trial in the Hunter Valley, NSW. Funded in part by ERDC.
Technology Development
TD97-1. Laser ablation ICP-MS developments at ANU (Eggins). Laser ablation ICP-MS ablation environment and applications development (inductively coupled plasma mass spectrometry): specifically (1) design and testing of a high efficiency ablation cell and transport system, (2) in situ analysis of precious metals (PGE and Au) at ultra trace levels, (3) analysis of trace elements in Li borate fusions prepared for XRF analysis, (4) metals analysis in tiny (<100µm) melt inclusions trapped in phenocrysts. Funded by ARC, ANU.
Research Projects initiated 1996
Lithosphere Mapping
L96-1. The nature of the upper mantle and lower crust in eastern Mongolia and the Siberian Pacific margin (Ionov, O'Reilly). Part of an integrated program to reveal the nature of the upper mantle beneath lithospheric blocks of different age, geological history and tectonic environment in a xenolith-based traverse across the northern Asian continent. It focuses on two localities (Dariganga in eastern Mongolia, and NW Sikhote-Alin near the Pacific margin of Siberia) in the central-SE segment of the transect. This study also characterises mantle heterogeneity on a m-km scale and provides a better insight into mantle processes. Funded by ARC small grant.
L96-2. Geochemical structure of lithospheric mantle: key to interpretation of regional geophysics (Griffin). Uses detailed studies of mineral chemistry in mantle xenoliths to interpret data from mineral concentrates, so these can be used for detailed mapping of mantle composition and structure. Focuses on application of these geochemical/geological data to the interpretation of regional geophysical surveys, for mapping large-scale variations in the nature of the upper mantle. Funded by ARC.
L96-3. Deep structure of the Canadian Shield (Griffin, Pearson, O'Reilly). Mantle xenoliths, xenocrysts and diamonds from kimberlites are being used to map the lithospheric mantle beneath the Slave Province of the Canadian Shield. Funded by Macquarie University Collaborative Grant with Kennecott Canada Inc.
L96-4. Eastern Australian and Indochinese diamonds (Davies, Griffin, O'Reilly, Win, Metcalfe, Wathanakul (Kasetsart Univ)). Morphological and geochemical studies of alluvial diamonds and their inclusions, to determine the nature of the mantle source(s) and to develop new models for exploration in regions without known kimberlite/lamproite source rocks. Funded by CRA Exploration and GEMOC, and in cooperation with the Myanmar Ministry of Mines and Kasetsart University, Bangkok.
L96-5. Seismic imaging of the MOHO and deep crust and upper mantle in SE Australia (Gohl). The depth of the eastern Australian crust as well as the nature of the crust-mantle boundary are not yet well defined. With the new pool of seismic recorders available through the Joint-University Seismic Facility, new data will be recorded using quarry blasts as the seismic source. Seismic models will integrate results from petrology of xenoliths. Funded by MURG and MU Seeding Grant for ARC.
L96-6. Evolution of oceanic lithosphere and crustal growth in the Kerguelen archipelago (Grégoire, O'Reilly). Combined petrological, geochemical and petrophysical analysis of upper mantle and lower crustal xenoliths of the Kerguelen islands provides detailed stratigraphy of rock types in this lithosphere section. This new dataset and its interpretation will have global significance for the understanding of the formation of oceanic plateaus and their possible contribution to the lithosphere beneath continents. Funded by IRF.
L96-7. Abundance, residence and significance of heat-producing and other trace elements in mantle peridotites (O'Reilly, Griffin, Ionov, Norman, Pearson). Laser microprobe ICPMS analyses in situ of rare earth elements and other key trace elements such as U, Th, Rb, Sr will provide baseline data on trace element contents to ppm levels of the main minerals present in the Earth's mantle and for some accessory minerals. These new data will provide heat production values which will have important implications for thermal models of the Earth's lithosphere. Funded by MURG.
Crustal Genesis
C96-1. Evolution of a hotspot volcano: geochemistry of glasses from Mauna Loa (Norman, Garcia (Univ. Hawaii)). Traces the magmatic evolution of Mauna Loa volcano, using laser microprobe trace element analysis of quenched melt inclusions in olivine crystals. Funded by MURG.
C96-2. Composition of the oceanic mantle beneath Hawaii (Norman; M. Garcia (Univ. Hawaii)). Explores the composition and thermal structure of the oceanic crust and mantle beneath the Hawaiian hotspot, the classic example of a mantle plume, through study of xenoliths from a previously inaccessible locality on Kauai. Funded by MURG.
C96-3. Silurian and Early Devonian tectonic development of the Tumut-Gundagai region, southeastern NSW (Dadd). The complex history of extensional and compressional events in the region is being analysed by studies of back-arc lavas intercalated with felsic volcanic rocks and extensive units of serpentinised ultramafic rocks, intruded by Silurian(?) granodiorite.
C96-4. Age, tectonic affinity and economic potential of volcanic rocks in the Louth area, western NSW (Dadd). Volcanic rocks intersected in drill holes in the Louth area of western NSW form the northernmost occurrence of such rocks in the Lachlan Fold Belt. The Louth rocks may correlate with Ordovician volcanic arc rocks in the Mt. Dijou area to the east, or with younger Devonian continental rift sequences to the south near Mt Hope. Both sequences contain significant but distinct mineralisation. Determination of the age and magmatic affinity of the Louth rocks, will give a better understanding of the large-scale tectonic evolution of the region and be better able to establish target areas for mineralisation. Funded by MURG.
C96-5. Depositional style of subaqueous volcanogenic debris deposits, regional facies analysis, metallogenesis and tectonic setting of the Mount Hope group, central western NSW. (Dadd) Very few convincing examples of subaqueously deposited and welded pyroclastic flows exist in the world although references abound in the literature. The Mount Hope Group provides numerous examples of welded and non-welded pyroclastic debris deposits intercalated within a subaqueous sedimentary package. Documentation of these deposits will either prove that flows can maintain their integrity and weld in the subaqueous environment or lead to the development of models for flow transformation from pyroclastic to debris flow. The location of the source areas for these flows will aid in mineral exploration within the area and within similar volcanic terrains. Funded by Macquarie University ARC Large Grants Scheme Seeding Fund.
C96-6. A metamorphic transect through the Himalayan Main Central Thrust (MCT) (Nichols, Pearson, Johnson). The MCT is a significant Himalayan structure, which experienced south-directed movement during the Tertiary. This project aims to understand the kinematics of the MCT by quantifying the associated change in P-T across the thrust zone. Funded by MURG.
C96-7. Proterozoic uplift in East Antarctica (Nichols; F. Fahey (NIST, Washington)). Three generations of mylonites cut ca. 1000 Ma granulite facies rocks in East Antarctica, and are distinguished on the basis of orientation, texture, and associated mineral assemblages. Second generation mylonites are ubiquitous in the northern Prince Charles Mountains, and are granulite-grade ultramylonites associated with a total uplift of ca. 6 km across the region. The ion microprobe is used to date the timing of mylonitic deformation, and thereby place better constraints on the formation and exhumation of this lower crustal segment.
C96-8. The stability of zirconolite in the crust and mantle (Ellis, Allen). Various zirconium- and titanium- rich phases occur in kimberlites, calcareous skarns and form the mineral basis for the synthetic nuclear waste disposal material invented at ANU - Synroc. The project is reviewing the occurrence of zirconolite and carrying out experiments on its stability. These phase relations will lead to a better understanding of Zr-Ti accessory mineral stability fields as an aid to diamond exploration. Funded by ANSTO and ARC.
C96-9. Magmatic roots of an island arc system - Green Hills - Pahia Point, South Island of New Zealand. (Eggins, Arculus, Price (LaTrobe)). The magmatic evolution of island arc systems is fundamental to the growth of continental crust, and global geochemical recycling. Fortuitously excellent exposure of the magmatic roots of a ~250 million year old arc system in New Zealand provides the kind of access which we need to understand the processes of magmatic fractionation, recharge, eruption tapping, and interaction with preexisting crust. A comprehensive analytical effort is planned with colleagues from other Australian and NZ universities. Funded by ARC Small Grant.
C96-10. In search of olivine-saturated arc high-alumina basalt (Draper). Experimental studies testing alternative models for the origins of mafic arc high-alumina basalt : either a derivative magma from a parental high-magnesia basalt, or a direct melt of the subducted lithospheric slab. The two hypotheses have fundamentally different ramifications for the thermal and physical structure the mantle in subduction zones. Funded by Small ARC.
C96-11. Trace element studies of mineral growth and metamorphic reactions (Pearson, Nichols). Development of trace element zonation patterns to interpret growth mechanisms and P-T history of minerals in metamorphic rocks and applications for models for element redistribution in high-grade metamorphism. Funded by MURG.
Metallogenesis
M96-1. Origin of mineralisation in the Browns Creek Gold Mine, NSW (Blevin, Wilkins (Uni of Sydney)). Recent discovery of monzonitic intrusives intimately associated with gold mineralisation at Browns Creek indicates the presence of a previously undescribed igneous suite of economic significance in the eastern Lachlan Fold Belt. The top of this intrusive is aplitic to pegmatitic and shows good textural evidence of the evolution of a volatile phase. Funded by AMIRA.
Geotectonics
GT96-1. Neoproterozoic earth history of Australia: Tectonics, Isotope-, volcanic- and bio-stratigraphy. (Veevers, Walter). Isotopic chemostratigraphy and acritarch biostratigraphy will elucidate the history of the Neoproterozoic in Australia and enable convincing correlation to other regions. This work will provide an effective basis for petroleum exploration of the Neoproterozoic succession of Australia. Funded by ARC.
Research Projects initiated 1995
Lithosphere Mapping
L95-1. Lithosphere evolution in eastern China (O'Reilly, Griffin, Zhang, Guo). Integrates petrological data on basalts, xenoliths and xenocrysts from kimberlites and basalts, and a range of regional geophysical data, to examine the evolution of the continental lithospheric mantle from Archean to present. A large-scale collaborative project involving personnel from several Chinese institutions. Funded by ARC, DEET Targeted Institutional Links, Academia Sinica, China NSF, China Ministry of Geology, China Education Ministry, Macquarie University.
L95-2. Lithosphere mapping in Australia (O'Reilly, Griffin, Zhang, Norman, Gaul, McCarron). Links studies of mantle petrology (using xenoliths and xenocrysts in volcanic rocks) with regional geophysical data, in collaboration with Prof. B. Kennett's tomography group at ANU-RSES. Funded by ARC, Stockdale Prospecting Ltd. (APA-I).
L95-3. Siberia-Mongolia lithosphere traverse (Griffin, O'Reilly, Ionov). Mantle xenoliths and xenocrysts from kimberlites and basalts are being used to map the mantle along a traverse extending from the Arctic sea, south across Siberia into the Baikal Rift and further into Mongolia and the Russian Far East. Funded by ARC, Macquarie University and Almazy Rossii-Sakha (Russian diamond exploration and mining conglomerate).
L95-4. Alkali and heat-producing elements in the lithosphere of eastern Australia (Norman). The distribution of K, Rb, Cs, Th and U in the continental crust and lithospheric mantle of eastern Australia is being studied to determine the composition of the continental crust and the primitive mantle of the Earth, constrain the origin of the Earth and Moon, and measure the contribution of mantle sources to lithospheric heat production. Funded by ARC.
L95-5. Experimentally determined Zr and Hf partition relationships at high pressure (Green, Fujinawa (Ibaraki University)). Partitioning relationships of Zr and Hf between amphibole, clinopyroxene, garnet and basanitic and andesitic melts are being determined at high pressure and temperature. Results show a consistent decrease in partition coefficients (D) with increasing pressure for amphibole, clinopyroxene/ melt pairs, and Hf D values are always greater than Zr values. In contrast, for garnet D (Zr) is greater than D (Hf). Funded by MURG.
L95-6. Garnet-clinopyroxene 2-mineral partition coefficients at high pressure (Green, Blundy (Bristol Univ.), Yaxley (RSES), Adam) . Large (>30um) crystals of coexisting gnt and cpx crystallised from tholeiitic and basanitic compositions at 2, 3 and 4 GPa. At 6 GPa gnt was confined to the tholeiite only. Analyses on initial runs were by ion microprobe at Edinburgh University, but two later runs at 2 and 4 GPa will be analysed by LAM ICPMS at MU. Funded by MURG.
L95-7. Phase relations of extreme-composition xenolith glasses (Draper, Green). Anhydrous and fluid-saturated liquidus phase relations, of melts rich in SiO2, Al2O3, Na2O and K2O and poor in MgO, FeO, and CaO, typical of the extreme range of compositions of glasses found in many mantle xenoliths worldwide, show that such liquids are in equilibrium with a harzburgitic to lherzolitic residue. Such liquids can act as agents of cryptic mantle metasomatism, but will not result in wholesale reaction with mantle minerals. The experiments document the surprisingly large extent of dissolution of major-element components into supercritical hydrous fluids at mantle conditions. Funded by MURG.
Crustal Genesis
C95-1. Evolution of magmas in the Peninsular Ranges Batholith, Baja California (Vernon, Johnson, Tate). 80-140 million years ago, subduction of Pacific Ocean crust beneath the North American plate caused melting of the lower continental crust, forming the Peninsular Ranges batholith. This study of the evolution of these granitic melts provides insights into the chemical evolution of magmatic arcs. Funded by MURG, ARC and AINSE.
C95-2. Microstructural processes in metamorphic rocks (Vernon). This project investigates the microstructures (shapes and arrangements of crystals) of metamorphic rocks in selected parts of Earth's deeper crust, now exposed at the surface, to determine the heating and deformation histories at the time of their formation. Funded by MURG and ARC.
C95-3. Crustal evolution in a Mesozoic Circum-Pacific magmatic arc (Johnson, Vernon). The project investigates the ways in which large bodies of magmatic rocks (plutons) are emplaced, the timing of their intrusion relative to regional deformation and heating of the crust, and the extent to which the plutons are responsible for this deformation and heating. Funded by ARC.
C95-4. High pressure vapour-melt partitioning experiments (Nichols, Green). Models for the genesis of subduction-zone magmas usually require a hydrous fluid component. This experimental project seeks to quantify the trace element attributes of hydrous fluids equilibrated with basanitic melts, using the laser-ablation-microprobe-ICPMS technique. Funded by ARC.
C95-5. P-T studies across the central Nagssugtoqidian Orogen, west Greenland (Nichols, Kriegsman (UNSW). The Nagssugtoqidian is thought to represent a Palaeoproterozoic continental collision zone. This project is aimed at defining P-T-t changes and melting processes across the region in order to elucidate the tectonic processes active during collision. Funded by Danish Lithosphere Centre.
C95-6. Granite emplacement: New England Batholith (Shaw, Flood). Investigation of the emplacement mechanisms of two granite bodies in a well documented batholith. A cross-disciplinary project with structural mapping, geochemistry, geochronology, rock magnetism and geophysical modelling. Funded by MURG.
C95-7. Magma genesis and tectonics in western Pacific island arcs (Arculus). Investigation of the impacts of lithospheric filtering on arc magmatism in the northeast Japan arc, the origin and tectonics of the Ontong Java Plume portion obducted onto Santa Isabel in the Solomon Islands (SI), and the petrogenesis of (multiply sourced) peridotites on Choiseul, Santa Isabel and San Jorge (SI). Funded by ARC.
C95-8. Evolution of continental crust: examples from the San Francisco Volcanic Field, AZ (Arculus). Investigating the evolution of the Proterozoic - Phanerozoic lower crust of the Colorado Plateau through integrated geochemical and petrological studies of volcanic rocks and crustal xenoliths. Funded by ARC.
C95-9. Origin of granites and their role in the production and development of new crust at continental margins (Chappell). Geochemical studies of granites, mainly in eastern Australia, and their importance in crust formation processes. Funded by ARC to end 1995.
C95-10. Geochemistry of granites formed at accreted continental margins (Chappell). This project aims to relate the composition of granitic rocks to the processes occurring at collisional margins. Funded by ARC.
C95-11. The stability of titanite in the crust (Ellis, Troitzsch). The aim of this project is twofold - to calibrate the Al content of titanite as a geobarometer, and to determine the PH2O, fO2 conditions under which titanite is a magmatic phase in I-type, hornblende bearing granites. Funded by ARC.
C95-12. An experimental examination of eclogite partial melting: Liquids, residues and trace element partitioning (Ellis, Gust (Univ. Qld)). Experimental determination of the composition (major and trace element) of the magmas formed by partially melting natural basaltic compositions during subduction. Funded by ARC.
C95-13. An experimental study of the diffusion of lead in zircon (Ellis, Lee (RSES)). Determination of the behaviour of lead during heating and cooling events, to improve the interpretation of U-Pb geochronology data. Funded by ARC.
Metallogenesis
M95-1. Geochemistry of mantle sulfides: probing the Earth's core-mantle-crust system (Guo, Griffin, O'Reilly). Geochemical and petrological studies of sulfides in mantle-derived xenoliths and ophiolites, and included in diamonds, to define the size and nature of the sulfide reservoir for chalcophile elements, and to enhance our understanding of the genesis of base-metal sulfides and platinum-group elements mineralisation in the crust. Funded by ARC and Macquarie University.
M95-2. Volatile, chalcophile, and noble siderophile elements in subduction zone magmas (Arculus, Eggins). Tracking the origin and distribution of the chalcophile and noble siderophile elements in subduction zone systems, with particular reference to volatile associations and episodes of volatile phase loss. Funded by ARC.
M95-3. Magmatic and hydrothermal evolution of intrusive_related gold deposits (Chappell, Blevin). metallogeny of gold deposits in eastern Australia, with particular emphasis on the internal magmatic and hydrothermal evolution of Ordovician copper-gold systems in New South Wales. Funded by AMIRA and ARC.
Geotectonics
GT95-1. Palaeomagnetic studies of the northern New England Orogen Queensland (Lackie). Palaeomagnetic analysis is being used to interpret the tectonic and thermal history of the region, with emphasis on the effects of magnetic overprinting and events leading to the opening of the Tasman Sea. Funded by ARC.
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