GEMOC ARC National Key Centre

GEMOC's research program

 

index

• the research aims
• scientific context
• research program
• summary of major strands
• activities 1996
  • description of major new projects
• action 1996
  • for the Tasmanide project
  • for the Western Pacific Lithosphere Project
  • new research appointments
• research projects initiated 1996
• projects from 1995 with major new initiatives in 1996
• projects ongoing from 1995
• GEMOC small seeding grants initiated 1996
• GEMOC small seeding grants planned for 1997
• research outcomes 1996

the research aims

 

• to understand the processes that control the generation and modification of the crust-mantle system and to define the tectonic and geochemical processes that create different crustal and mantle domains
• to map the spatial and temporal distribution of elements, rock types and physical and chemical conditions within this system
• to define the systematics of element redistribution in the mantle and crust during the critical liquid-crystal and vapour-liquid separation events
• to advance the modelling of the crust and lithospheric mantle from geophysical datasets, through integration of geophysical, petrological and geochemical information
• to provide a new framework for area selection for a wide spectrum of economic deposits, by linking these models and processes to the formation of metallogenic provinces
• to develop collaborative links with international institutions and researchers relevant to GEMOC's goals

scientific context

Thermal energy transmitted through the mantle provides the energy to drive lithosphere processes. Mantle-derived fluids and tectonic environment control element transfer across the crust-mantle boundary and the 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 focus of GEMOC's research programs is the driving role of the mantle in Earth processes and its control of element and commodity distribution in the accessible crust.
This bottom-up approach involves

• Understanding the location of different types of metallogenic provinces by understanding the links between:
  • mantle processes
  • crustal generation
  • large-scale tectonics
  • heat and fluid transport
• Integration of information across discipline boundaries, especially petrology, geochemistry, geophysics and tectonics.

research program

The research program comprises four strands:

• Lithosphere Mapping
• Geotectonics
• Crustal Generation Processes
• Metallogenic Provinces

• These strands are conceptual units, not administrative units. They represent thematic foci required for solving the overall problem of the nature of the geochemical evolution and metallogeny of continents.
• Because they are not set up as management entities, overall integration and coordination is facilitated and there are no boundaries to inhibit interdisciplinary interfacing.
• Our research strategy is twofold: (i) set up large-scale goals and (ii) focus on individual, clearly-defined, short- to medium-term projects that fill in pieces of the larger-scale jigsaw puzzle.
• The research program incorporates relevant funded projects existing at the time the Key Centre was awarded, as well as new initiatives.
• Program strands illustrate major directions and framework. The emphasis on each strand varies from time to time.

summary of major strands

The Lithosphere Mapping strand provides the fundamental data for defining mantle domains in terms of composition, structure and thermal state; relating these domains to a better understanding of tectonic evolution will help to define the large-scale evolution of mantle processes through time, and their influence on the development of crustal material and metallogenic provinces.

The Crustal Generation strand 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 (eg Au, Cu, C).

The Geotectonics strand uses stratigraphic, tectonic, and geophysical data to study the history and causes of continental assembly and disruption, with a special focus on Australia and East Asia. It provides the fundamental framework to link the research on crustal and mantle processes with the localisation and development of metallogenic provinces.

The Metallogenic Provinces strand 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.

activities 1996

Research Workshops through 1996 shaped and consolidated the two major umbrella research initiatives foreshadowed in the first report. These will fulfil part of GEMOC's research and training brief and involve significant collaboration between the GEMOC nodes and new cooperative linkages with other researchers. New postgraduate programs for 1997 have been set up as subset strands.

description of major new projects

1. Timing and distribution of lithosphere formation and modification in the Tasmanide Belt

The Tasman Orogen is a natural laboratory for the study of Phanerozoic crust-mantle interaction. The geological and geophysical coverage is excellent. A very large database on the geochemistry and metallogeny of the abundant granitic rocks gives a reflection of variations in middle to lower crustal composition across the region. Abundant mantle-derived xenoliths occur in widespread Mesozoic-Tertiary basalts, making it possible to study regional variations in lithosphere and asthenosphere composition and relate these to crustal domains defined by structural relations, granitoid chemistry, and geophysics.

The Tasmanide project will focus and integrate GEMOC's expertise in mantle studies (basalts and xenoliths) with its expertise in granite genesis/emplacement and metallogenesis. It will interface with the Seismic Tomography Consortium, in the first studies concentrated on the New England Region. Macquarie University is a partner in this Consortium, led by Prof. Stewart Greenhalgh at Flinders University. This interaction will promote GEMOC's goal of integrating geological and geophysical datasets.

Xenoliths of lower crustal origin occur in several localities scattered across the region; a traverse from Mt. Gambier in the west to the Monaro Province in the east provides mantle samples from several crustal domains defined by geophysics, granite chemistry and structural/stratigraphic data, and the traverse also crosses the I-S granite line, which is believed to represent a major discontinuity in the nature of the lower to middle crust. Xenolith-bearing basalts were erupted through Proterozoic basement in western Tasmania, and through the Paleozoic fold belt in the eastern part of the island. Because of this variety of materials and data, this region provides an excellent opportunity to investigate crust-mantle relationships in a major Phanerozoic orogen, and to relate these to tectonics, geophysics and metallogeny.

2. Western Pacific Lithosphere Project

The region provides a natural laboratory to study the evolution of several types of "oceanic" mantle, which may be analogues to the mantle beneath accreted continental margins such as eastern Australia and China. Some of the world's youngest ophiolite sequences outcrop in the Solomon Islands and different tectonic units represent samples of mantle formed in different settings: beneath Cretaceous ocean ridges, in a forearc setting, and during the plume-induced eruption of the basalts of the Ontong-Java Plateau (OJP). Mantle xenoliths from volcanic rocks on Malaita and near Lihir Island provide samples of deep OJP mantle and of relatively shallow forearc mantle, respectively. The Lihir samples have been affected by fluids that may be related to gold deposits in the overlying crust. Regional gravity and seismic data are available. Field, petrological and geochemical studies of the different types of mantle will be integrated with work on the overlying cumulate and volcanic rocks to understand the processes that have produced the spectrum of compositions in each mantle type. Comparisons with similar studies in eastern Australia (the Tasmanide Project) will enable us to construct a broad picture of the processes involved in the creation and modification of lithosphere at convergent margins, and to relate these to ore-forming processes.

action 1996

Workshops of research groups across nodes set up a strategic plan to address these projects. As a result:

for the Tasmanide project

• a project on the geochemical signatures of basalts and lithospheric mantle across the Tasman Line in Tasmania was initiated in collaboration with the Tasmanian Geological Survey.
• four projects, collaborative across GEMOC and representing distinct strands, were formulated and submitted for ARC funding for 1998.
• a collaborative ARC/industry project on new aspects of the metallogeny of granite terrains in the Tasmanides has been crafted and negotiated with AMIRA assistance.
• integration of geophysical information on the lithospheric structure of specific Tasmanide terrains is being initiated with specific emphasis on new seismic data and combined gravity and thermal modelling.
• three Honours projects relevant to this project were set up in 1996 and four new postgraduate and three Honours projects have been planned for 1997.

for the Western Pacific Lithosphere Project

New findings in 1996 have revealed there is secular and apparently irreversible geochemical evolution of newly-formed lithospheric mantle. This has led to the modification of this project to include work relevant to defining the nature of lithosphere formed by identifiable processes. Initiatives in 1996 include:

• ARC project funded including a component on the geochemistry of the ophiolitic sequence on Solomon Islands
• Attendance by two GEMOC representatives at ODP-InterRidge-IAVCEI Workshop "The Oceanic Lithosphere & Scientific Drilling into the 21st Century" (May 26-28, 1996, Woods Hole)
• Agreement between Macquarie and CSIRO for collaborative project on the mantle xenoliths from Lihir Island
• Initiation of analogue study of oceanic lithosphere in the Kerguelen Archipelago
• Initiation of a study of "the roots of an arc" - the Greenhills Ultramafic-mafic complex, New Zealand
• Formulation of analogue study to define plume-type mantle using mantle xenoliths in post-Deccan alkaline basalts from India
• A project with a component relevant to unravelling geochemical discriminants of mantle of different origins (including that of the Ontong-Java Plateau) was submitted to ARC for 1998 funding

new research appointments

Dr Michel Gregoire arrived in May, 1996 as a Macquarie University Research Fellow (MURF) but shortly after was granted an ARC International Australia-France Research Fellowship. His main research focus is the nature of the lower crust and upper mantle of oceanic plateaus, specifically using xenoliths in basalts from the Kerguelen Archipelago collected during DSDP cruises. An important part of this work is determining the acoustic velocity of specific rock types from the Kerguelen lithospheric column in collaboration with Dr Ian Jackson at ANU, to interpret the seismic and gravity datasets for that area. He has applied for a shipboard place on the ODP Kerguelen Leg in 1998.

Dr Yvette Poudjom-Djomani has been appointed as a GEMOC Postdoctoral Research Fellow and will arrive as soon as her visa is processed. Her expertise is potential field (gravity, thermal, magnetic modelling).

Dr Pram Chopra has been appointed as a Reader (on Part 4 Mobility Transfer from AGSO) supported 50% by GEMOC and 50% by a grant from the ERDC (Hot Dry Rock Project)

Ms Esme van Achterbergh has been appointed as an ARC Research Associate to commence in 1997 on mantle geochemistry.

research projects initiated 1996

1. 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.

2. 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.

3. 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.

4. 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.

5. 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.

6. Composition of the oceanic mantle beneath Hawaii (Norman, M. Garcia (U. 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.

7. 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.

8. 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.

9. Depositonal 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.

10. 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.

11. 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.

12. The stability of zirconolite in the crust (Ellis, Allen). The project will review the stability of zirconolite and undertake experiments on the stability of various polymorphs, to characterise one of the important phases in nuclear waste disposal ceramic - Synroc. Funded by ANSTO.

13. Magmatic roots of an island arc system - Green Hills - Pahia Point, South Island of New Zealand (Arculus). 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.

14. Phase relations of extreme-composition xenolith glasses (Draper). 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.

15. 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.

16. 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.

17. 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.

18. 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.

19. 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.

projects from 1995 with major new initiatives in 1996

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.

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).

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).

projects ongoing from 1995

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.

2. 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.

3. 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.

4. 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.

5. 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.

6. 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.

7. 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.

8. 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.

9. 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.

10. 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.

11. 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.

12. 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.

13. 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.

14. 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.

15. 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.

16. The stability of titanite in the crust (Ellis, Allen). 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.

17. 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.

18. 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.

19. 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.

20. 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 3 and 4 GPa. At 6 GPa gnt was confined to the tholeiite only. Analyses by ion microprobe at Edinburgh University and resulting partition coefficients are under evaluation. Funded by MURG.

GEMOC small seeding grants initiated 1996

• Lihir Mantle Xenoliths
  • Fingerprinting fluid types and fluid processes in the mantle beneath a young mineralised area (gold deposit)
• Southeast Asia Diamonds
  • Burmese diamonds in collaboration with Geological Survey of Burma
  • Thailand diamonds in collaboration with Dr Pornsawat Wathanakul (Kasetsart University, Bangkok)

GEMOC small seeding grants planned for 1997 include:

• Deccan Mantle Xenoliths
  • A study of the geochemical fingerprints of mantle xenoliths from alkali basalts erupted through the Deccan plume-derived flood basalts: in collaboration with Dr Nitin Karmalkar from Pune University.
• Siberian diamonds from the Zarnitsa and Dalnaya pipes
  • Morphology, nitrogen aggregation state, carbon isotopic compositions and inclusions of these rare samples in collaboration with Dr Felix Kaminsky and Dr Galina Bulanova. (Partly funded by a DIST grant to N. Fisher and W. Griffin).

research outcomes 1996

There has been a continuing high level of activity within GEMOC's research program as evidenced by the papers published in peer-reviewed journals (appendix 3) and international collaborations: the breadth is also shown by the selection of abstract titles of conference papers presented in 1996 (or submitted for presentation in 1997) since January, 1996 (appendix 5).

Other performance indicators include:

• increased collaboration between nodes and other participants: new collaboration with the University of Sydney and LaTrobe. This includes four new ARC applications based on strong cross-institution collaboration
• development of research strategic plan to address the two major umbrella project initiatives: implementation of the first stage with seeding grants, postgraduate projects and new ARC applications for 1998 funding
• two new Large ARC grants successful for 1997 funding
• formal new interaction with the Tasmanian Geological Survey for the Tasmanian strand of the Tasmanide umbrella New Initiative
• new interaction with La Trobe University through Professor A. Gleadow's Fission Track Group and the zircon/apatite trace element geochemistry project (Elena Belousova PhD)
• interaction with CSIRO increased: joint postgraduates, technology development and collaborative research (resistate minerals project, mantle petrology, stable and radiogenic isotopic applications and interaction with the Geodynamics CRC)
• interaction with AGSO increased principally in seismology and through the Seismic Tomography Consortium. This involves ongoing interaction with Professor Brian Kennett's Group at RSES, ANU
• new collaboration through joint project with Dr V Bennett (RSES at ANU) for Re/Os mantle studies
• new collaboration with Dr I. Jackson (RSES at ANU) for acoustic velocity studies on Kerguelen xenoliths
• new collaboration with Professor M. McCulloch (RSES at ANU) on Pb isotopic composition of basaltic rocks
• collaboration with Prof I MacDougall and Mr Takuya Matsumoto (RSES at ANU) on noble gases in mantle xenoliths
• Funding (see last section for details)