GEMOC ARC National Key Centre
GEMOC Research Projects listed by strands and
years
Research Projects initiated 1997
Lithosphere Mapping
L97-1. 4-D Lithosphere Mapping III: fingerprinting the nature
and mechanisms of secular evolution of the Earths' 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. (SEE Case Histories)
L97-2. 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)
L97-3. 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)
L97-4. 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.
L97-5. 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
L97-6. 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
L97-7 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.
L97-8. 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.
L97-9. 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.
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.