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PreSolar Dust

Ashes to ashes, dust to solar system
Contact Trevor Ireland

Early Solar System

Chronology of events in the early solar system
Contact Trevor Ireland

Trace element behaviour in the early solar nebula
Contact Trevor Ireland

Trace elements in refractory inclusions record extremely high-temperature fractionations indicating many otherwise refractory elements were in the gaseous state. Such temperatures can only be attained close to the Sun and yet these objects are now found in meteorites whose parent bodies accumulated in the asteroid belt. Understanding of refractory inclusions is limited by models for their formation particularly with respect to how such high temperatures can be maintained at high levels for sufficient time to fractionate the elements. We would like to experimentally model the fractionations in a high temperature furnace and determine the setting for formation of refractory inclusions in the early solar system.

Early Earth Evolution

Mass Spectrometry

SHRIMP Nuts and Bolts
Contact Trevor Ireland

Mass spectrometers are designed to separate isotopes of elements for measurement of isotopic ratios. RSES has a large number of mass spectrometers covering a variety of fields, but we are continually adjusting the hardware to get enhanced capabilities. Previous projects have ranged from ion optical design of mass spectrometers through to design of specific items of hardware within one of the mass spectrometers. The SHRIMPs are a result of taking a theoretical ion optical design and transforming this into hard steel. This type of work requires interests in one or several of hardware design, ion optical modeling (electrostatic and electromagnetic fields), computer simulations, and computer control of instrumentation. Currently we are modelling the operation of the extraction optics of the SHRIMPs with a view to understanding how the extracted ions are transferred into the mass spectrometers. This involves the construction of a test bench with SHRIMP components and the use of a channel plate to view the ion distributions at various points.

Geochronology

Dating Detrital Zircons by Laser ICP-MS
Contact Ian Campbell

The laser ICP-MS can date over 300 detrital zircons per day by the U-Pb method. We have been using this method to date zircons from the World's major rivers. We have also been working with Peter Reiners of Yale University to develop a new method to date the same zircons by the (Th-U)/He (double dating) and with Malcolm McCulloch (ANU) to measure Hf isotopes in zircons. The U-Pb age of the zircon gives us the crystallization age of the zircon (normally a crustal melting event), Hf isotopes the age of the crust that melted to form the zircons, and the Th-U/He date is the age of the crustal exhumation event that released the zircons into the river. This combination is a powerful new approach to study the evolution of the crust on a global scale, which should appeal to an ambitious young scientist. It can answer questions such as the rate of growth of the continental crust, whether crustal melting events are periodic and global or local and random, time scales for crustal exhumation and orogenic events etc. Double dating will revolutionize sediment provenance studies and will allow us to quantify the percentage of recycling in sediments,

Isotope Geochemistry

Noble Gas Isotopes

The RSES noble gas laboratory is one of the few in the world capable of analysing the isotopic compositions of all the noble gases. Our current research in noble gas geochemistry is focused upon the origin and evolution of planetary volatiles as the main underlying theme. Better characterisation of the present-day and also ancient noble gas reservoirs in the Earth's mantle, and the evolution of these reservoirs, remains a major subtheme. In addition, noble gases generated in surface rocks by cosmic ray interactions are used to provide a measure of exposure ages and erosion rates.

The following is a list of research topics we are currently undertaking or plan to do in the near future:

Combined studies of noble gases, nitrogen and carbon in mantle-derived samples (mid ocean ridge basalts, oceanic island basalts and mantle xenoliths) - in relation to the origin and evolution of planetary atmospheres.

Noble gas studies of diamond.

Noble gas studies on samples derived from the Archaean mantle (e.g. komatiites, old magmatic zircons).

Studies of nucleogenic noble gas production in the Earth.
Experimental studies of noble gas partitioning and diffusion at high pressure.

Cosmogenic noble gases (exposure dating, erosion rates etc), in association with the Environmental Geochemistry Group.

Studies of noble gases trapped in fluid inclusions in ore-forming minerals to deduce the source of the fluids, in association with the Ore Genesis Group.

Contact Mashahiko Honda

Thermochronology

SHRIMP

The raw prawn…
Contact Trevor Ireland

Stable isotope methodologies are being explored on SHRIMP II with the added prospect of dedicated stable isotope analysis on SHRIMP SI. There is a need for postgraduate students interested in technological developments as applied to the SHRIMP stable isotope capability and using these methods for examining geological materials. Examples include oxygen isotopes in zircons for indicators of environment, provenance, etc., sulfur isotopes in ore minerals, C (and N) isotopes in diamonds, and in situ analysis of carbonates as indicators of paleoclimate

Australian Tectonics

In search of the sources of southeastern Australian granites: a Hf, O and U-Pb isotopic study of single zircons.

Contact Ian Williams

New micro-analytical techniques are now being applied to help resolve the long-standing controversy over how and why granitic magmas form. The opportunity is available to undertake a case study of a classic Australian granite terrane, using in situ isotopic micro-analyses of U-Pb, Hf and O in zoned zircon crystals from granites to try to determine (1) the shifts in granite magmatism in space and time, and hence the geometry and nature of the heat sources; (2) the relative contributions to the granite magmas of mantle-derived magma and older, pre-existing crust; and (3) the regional differences in the composition of the lower crust. The work will focus on the Berridale and Kosciuszko Batholiths of SE Australia.

Too late, the Berridale/Kosciuszko project is taken, but if you are interested in working on other SE Australian granites, funds are still available.

Archean Tectonics

Archaean gneisses in the Kapisillit area
Contact Allen Nutman

There are two places (2005-2007) for PhD students to undertake research on Archaean gneisses in the Kapisillit area in the eastern part of the Nuuk region of West Greenland. The area is deeply-incised by fjords from the west and by glaciers from the Inland Ice to the east – it contains superb exposures of Archaean basement geology, including some of the world's oldest rocks (3600-3850 Ma). The successful applicants will spend 2 field seasons (July-August 2005 and 2006) doing fieldwork in the area. This aspect of the work will be fully supported by the Geological Survey of Denmark and Greenland, and the students must produce a geological map of their study area as part of the Survey's regional mapping programme. Possible RSES-based laboratory research projects stemming from the Greenland fieldwork include study of early crustal evolution using the >3600 Ma rocks in the Kapisillit area, late Archaean tectonothermal evolution (terrane assembly) and evolution of Archaean shear zones and their relationships to mineralisation.

Himalayan Tectonics

Alpine Tectonics

Contact Daniela Rubatto

Time (duration and rates) is a crucial information for the understanding of geological and tectonic processes that build mountains. How fast can a rock be exhumed to the surface? How long does deformation last? Is metamorphism continuous or episodic? The timing of these processes can be best studied in young, active mountain belts such as the Alps-Himalayan system, which extend from Spain to New Caledonia across Europe and Asia. The young age of the Alps-Himalayan system (less than 100 Ma) allows resolving the age of the different stages of mountain building. In order to do so we need to date in detail (mainly through the U-Pb system) accessory minerals found in rocks from this mountain system.

Gondwana Tectonics

New Zealand on the edge
Contact Trevor Ireland

New Zealand represents the edge of the Gondwana continent from Cambro-Ordovician through to Cretaceous. The tectonic structure of New Zealand is dominated by apparently accreted slices of arcs of varying dispositions. The western Province of New Zealand represents the Gondwana margin with rocks of continental affinity. The eastern Province of New Zealand comprises a number of Permo-Triassic terranes of predominantly arc origin, although the Torlesse terrane has a quartzofeldspathic composition indicating continental derivation. In between the two provinces is a median belt of rocks of enigmatic origin. How does New Zealand fit together over Phanerozoic time? Even though it’s only 100 Myr since the break up of Gondwana and the opening of the Tasman Sea, the provenance of New Zealand terranes is very hard to get a handle on. The best prospect is through detrital mineral studies (especially zircon) allowing the tracing of distinct components through geological events. SHRIMP work is a must, but development of new techniques for provenance analysis would be highly encouraged

Geochemistry

Diamonds

Noble gas compositions of mantle diamonds
Contact Mashahiko Honda

Diamonds are sampling bottles of ancient mantle. The project will investigate the noble gas compositions of a systematic selection of diamonds of different ages and from different parts of the mantle. Together with carbon and nitrogen isotope systematics, this information will be used to better constrain models of Earth outgassing and the evolution of the Earth's atmosphere and mantle. The project will provide a better understanding of the mantle source regions of diamonds and, in particular, homogeneity/heterogeneity of the source regions as a function of space and time - potentially of economic significance for diamond exploration.

Ore Genesis

The Evolution of Ore-associated Felsic System with Time.
Contact Ian Campbell

The ANU laser ICP-MS can be used to date zircons from felsic rocks with a precision of +-1%. The project would involve determining major and trace elements (also by ICP-MS),and radiogenic isotopes (including Hf in zircon and Sr in plagioclase by laser sector probe) and showing how they evolve with time. The aim of the project would be to document how the chemistry of the system and show how it evolves with time and to establish the relationship between evolution of the felsic system and ore formation. ANU students have successfully applied this approach to the giant Chuquicamata Cu porphyry copper deposit in Chile and we would like to apply this apptoach to other giant felsic ore systems. Hf in zircon and Sr in plagioclase by laser sector probe were not available when the Chuquicamata study was carried out and can be expected to provide exciting new constrains on the evolution of felsic systems.

Regolith

Contact Mashahiko Honda

The project addresses basic questions concerning soil and regolith resources through measurement of nuclides produced by cosmic rays in near-surface minerals. Cosmogenic 21Ne, together with 10Be and 26Al, are used to determine (i) natural rates of soil production from rock weathering across different climatic regions, (ii) rates of sediment dispersion, transport and mixing in regolith mantles, and (iii) residence times of sediment in river and floodplain systems. The research has strong implications for the usage and conservation of soil, sediments and weathered deposits, and sedimentary waste disposal.