This work focuses on the study of the oldest, most complete rock sequences from Southwest Greenland, which range in age from 3.6 to 3.9 Ga and contain a range of lithologies.

We are using these rocks to determine the age and origin of the oldest continents, the early planetary processes that many have affected the Earth and the types of early life environments that may have existed, providing a range of potential research topics depending on the interests of the student.

We combine a variety of approaches to study the ancient rock record including petrology, geochemistry and field observations. A wide range of analytical techniques are used including laser ICP-MS, ion-probe (SHRIMP), and electron microprobe and as well as some innovative isotopic techniques developed in-house.

Projects range from totally laboratory based to those with a combination of laboratory and fieldwork and from the more petrologically oriented to those that are largely geochemistry based. Contact me for more information.

The mantle is a significant part of the total Earth system comprising the vast bulk of the silicate rock fraction of our planet and forming the deep roots of the continents. The chemistry of the mantle has changed throughout geologic time, initially as result of early planetary formation more than 4.5 billion years ago and then throughout geologic history by the extraction of continental crust and the recycling of material in subduction zones. Using new isotopic and chemical methods applied to the study of mantle rocks and minerals ranging in age from more than 3.8 billion years, to just months old, we can track the changing composition revealing ancient and modern global events. From this work we are beginning to unravel the complex chemical linkages between the deep Earth and crustal environments.

There are a number of student projects available as part of this research, most of them based on the direct study of mantle rocks using leading edge analytical methods with three examples listed here. One project is investigating the petrology and geochemistry of our recently discovered ancient mantle samples (3.8 billion year old rocks from southwest Greenland) and related basalts to determine processes of planetary differentiation on the early Earth. A second project (so-supervised with Dr. Honda) is to measure the nitrogen isotopic composition of mantle rocks through time to investigate atmosphere evolution and mantle-crust linkages. A third project (jointly with Dr. Norman) is using the petrology and chemistry of peridotite xenoliths (upper mantle rocks) carried to the surface in modern Hawaiian plume basalts to reveal deep Earth chemistry.

The emphasis of the various projects can be tailored to the background and interests of the student, but all will involve a significant laboratory component using a range of analytical techniques, including leading edge isotopic approaches. We can break the research into suitable size projects for interns, honours, masters and PhD work. This research will appeal to students who want to use the details preserved in the record to look at global questions in Earth evolution and are willing to become experts in some aspects of geochemistry. Contact me for more information or other possible projects, or if you have some ideas of your own to discuss as possible projects.

Have you ever thought about how the oceans overturn, with surface waters sinking to deep in the ocean at high latitudes, drawing warm waters and heat poleward from lowlatitude? Global warming will cause greater freshwater inflow at the sea surface from the melting of ice-caps at high latitude. This might slow, or even shut-down, the ocean overturning. In the geophysical fluid dynamics laboratory we are carrying out experiments with convection and rotation that explore the physics underlying global ocean overturning.

A PhB scholar, research Intern, Summer Scholar or a student looking for a Special Research Topic, and who is studying physics or mathematics will assist with the laboratory fluid dynamics experiments, the computer logging of data, and the analysis of the experimental data. Contact the supervisor directly for more information.

No continuous, high resolution records documenting paleoenvironmental change through the most recent deglaciation period for southern Australia currently exist. An extremely well-laminated stalagmite from the Flinders Ranges , SA, has been identified by U/Th disequilibrium dating to have formed during the period 17.5 - 14 ka. This stalagmite offers a rare opportunity to examine paleoenvironmental change and search for evidence of rapid climate events such as Heinrich event 1 that is well-documented in the northern hemisphere. In addition, dune building in the Strzelecki Desert to the north and east is concentrated in a number of discrete phases during this time. Comparing the dune and speleothem records will lead to a better understanding of the relationships between regional hydrology and environmental response during this period of rapid, high magnitude climate change. An opportunity exists for a Summer Scholar to assist in reconstructing the paleoenvironmental record for this stalagmite.

The student would gain experience in laboratory analyses (O-isotopes, laser ablation trace element analyses, U-series dating) and the interpretation of speleothem and dune paleoclimate records.

Changes in atmospheric pressure cause elastic deformation of the surface of the Earth of up to 15 mm in height. The thermal variations of the atmosphere also cause atmospheric "tides" that produce periodic variations in atmospheric pressure - hence deformation - that are detectable in high-precision GPS analysis.

The plot to the right shows the amplitude (in hPa) of the once/day pressure tide. This project will involve generating new, more accurate models of the atmospheric tides for use in the analysis of GPS data, building upon recent advances of modelling the actual variations in atmospheric pressure. The student will be required to compute surface deformation from observed pressure data sets, integrate the new deformation models into the GPS analysis then (hopefully!) demonstrate from an analysis of GPS data that the new models yield improved results.

The 'solid' Earth actually deforms by up to 40 cm during the day as a result of the gravitational forces of the sun and the moon. Perhaps more surprising is that the continents also deflect because of the changing mass as the ocean tides move water around the surface of the Earth. The movement of the surface of the Earth can be measured by high-precision geodetic measurements of gravity and also position using gravimeters and GPS equipment.

This project will involve using gravity and GPS observations at Mt Stromlo observatory to study the ocean tide loading effects in Canberra. The student/summer scholar will use the measurements to derive independent estimates of the tidal deformation, compare to existing global models and determine which - if any - of the existing models are accurate. The project will involve learning how to compute accurate GPS coordinates, how to reduce gravity measurements and how to model tidal deformation. Computing skills are not required, although would be very useful!

Understanding the processes that enable marine phytoplankton to acquire trace metals are fundamental to discerning primary production in the global ocean. There is compelling evidence to demonstrate that phytoplankton in major regions of the world ocean are limited by the availability of certain trace elements, notably iron.

While much attention has been focused on iron, it is becoming evident that other trace elements, chiefly cobalt, zinc and cadmium, also play fundamental roles regulating phytoplankton growth.

Recent work in our laboratory has focused on understanding the links between the chemical speciation of these metals and phytoplankton growth.

This is multidisciplinary work integrating marine chemistry and biology, and includes a strong fieldwork component. Students involved in the work would help in the collection of samples, making the chemical speciation measurements and the communication of the work.

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. The advantage of the detrital zircon approach is that the history of an entire river basin can be determined from a single sample collected near the mouth of a river. 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 zircon 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. The PhD project would involve applying the methodology to all of the major rivers on one continent.

Improved structural models of the Earth and the knowledge about seismic wave propagation allow seismologists to study earthquake mechanisms. The earthquakes could most generally be divided to tectonic and volcanic. The far-field radiation of most tectonic earthquakes can be conveniently described with the so-called double-couple system of forces. However, a full seismic moment tensor representation is more complete form of the mathematical representation of seismic sources, especially in non-tectonic environments. Of particular interest are seismic events with anomalous seismic radiation and puzzling focal mechanisms, such as volcanic earthquakes, mid-ocean ridge events or explosions.

Different computational methods are used to reveal statistically significant non-double-couple components of the moment tensor and model complex finite sources. A student with maths and physics background and strong analytical skills is invited to join the project and assist with analysis and interpretation of results. Please contact the supervisor directly at hrvoje@rses.anu.edu.au for more information.

We live in a decade of unprecedented quantity and quality of seismic data, which are easily accessible online. Although the quality of seismic records is improving constantly, there are still vast amounts of unanalysed seismic waveforms, which might hold a key to deciphering unresolved geophysical puzzles.

One such puzzle is the inner core structure. The inner core was discovered in 1936, and inner core anisotropy (directional dependence of elastic properties) was hypothesised fifty years later, to explain anomalous travel times of core-sensitive seismic waves. Some recent results suggest the existence of "innermost inner core". However, inadequate spatial sampling of the central inner core by seismic waves makes further advances on this topic very challenging.

This project will focus on finding new ways of sampling the centre of the Earth and interpreting the results in the context of our planet's dynamics and evolution. Interested students with a physics or maths background are invited to contact the supervisor directly at hrvoje@rses.anu.edu.au to discuss possibilities.

Seismologists combine the so-called receiver functions and surface wave data to improve the general understanding of crustal and upper mantle structure in various regions of the world.

An important humanitarian objective of obtaining improved structural models is better understanding of the seismicity and hazard assessment for the region of study. Receiver functions are mostly sensitive to sharp gradients in Earth's elastic properties (such as the Moho discontinuity), while surface wave data contribute to a better understanding of overall seismic wave speeds. We are working to develop a reliable method for the joint modeling of these two types of data, possibly with independent information from seismic "noise".

This project will focus on applying this method to the data collected by the seismic stations at various regions to better constrain crustal and upper mantle structure, including features such as the crustal thickness, upper mantle low-velocity zone and transverse isotropy (polarization anisotropy). Students with a strong computer science, physics or mathematics background including familiarity with Unix are invited to contact the supervisor at hrvoje@rses.anu.edu.au for more information.

This topic is a subject of very active research in the geophysical community and was exploited in a recent science-fiction motion picture 'The Core' (although the scientific facts in the movie were almost entirely wrongly represented). Differential rotation of the inner core with respect to the rest of the planet was first suggested from numerical simulations of the geodynamo in 1995. Since then, seismological studies aiming to detect differential rotation of the inner core using temporal changes in seismic waveforms were mostly controversial, and often subjected to criticism (the title above was taken from a publication in Science). One reason for scrutinising seismological data is a very likely inadequate resolution to resolve small temporal changes in inner core properties.

This project will explore a unique dataset from Australian seismic stations to address the above issue. A highly motivated student with a background in geophysics, physics, astronomy or mathematics will find the project challenging and satisfying. Please contact the supervisor directly at hrvoje@rses.anu.edu.au for more information.

There is now general acceptance of the concept that the earth's mantle is chemically and isotopically heterogeneous on a variety of scales and that much of this heterogeneity relates to reintroduction of crustal material into the mantle via subduction. Recycled oceanic lithosphere may be subducted deep into the convecting mantle and eventually entrained in upwelling mantle where it may melt and contribute components to lavas erupted in a variety of tectonic settings. For example, an important recent contribution (Sobolev et al. 2007, Science 316, 412-417) claims on the basis of minor elements in olivines crystallised from primitive magmas, that the magmas' source regions contained garnet orthopyroxenite, itself a reaction product between normal mantle peridotite (lherzolite or harzburgite) and partial melts of deeply recycled oceanic crust (eclogite).

This project aims to test this model by performing high pressure melting experiments on garnet orthopyroxenite, and analysing run products by electronprobe microanalysis or by laser ablation ICPMS. The summer student would be involved in performing the high-pressure experiments on the RSES' piston-cylinder presses and sophisticated microbeam analysis of the run products. This data can then be used to test models invoking involvement of recycled oceanic crust in magma genesis.

Whether the earth's mantle is oxidising or reducing is of particular importance, because its oxidation state partially controls the nature of fluids present there. For example, in a reduced mantle, fluids may be methane + water dominated, but in a more oxidised mantle they may be carbon dioxide + water dominated. Trace or minor amounts of fluid in the mantle exert a profound influence on the way the mantle partially melts to produce magma and consequently on the nature of the magmas produced and erupted or emplaced into the crust. It is possible to determine the oxidation state of the mantle from fragments of lithospheric material (garnet peridotite xenoliths) transported to the surface in some volcanic eruptions. However, this requires precise measurement of Fe3+/total Fe in the mineral garnet, and this is currently difficult using conventional microbeam analytical techniques.

We are endeavouring to develop a new synchrotron-based technique called Fe K-edge XANES. This requires a series of well-characterised garnet samples for calibration, and the summer student involved in this project would be engaged in synthesising them using high pressure experimental equipment at RSES, and in the full characterisation of the experimental materials using sophisticated analytical techniques such as electronprobe microanalysis and X-ray diffraction. Subsequent involvement in synchrotron measurements may also be possible.

Gordon The aim is examine fault rocks produced in some of the Earth's most famous faults, for example a sample from the EarthScope project that has drilled through the San Andreas fault at some km depth, or samples from some of the most famous so-called "impossible" detachment faults, namely those that appear to form at low-angles over large areas in extensional environments. How can we predict earthquakes if we don't know how the rock in the fault itself is behaving? How can we say that LANFs are impossible if we do not understand the processes that operate within them? Photo adjacent shows the Whipple detachment fault, a low-angle fault that formed when western North America was pulled out from underneath the Colorado Plateau.

We want to understand why such a big fault could be so sharp, for example. Is there evidence for sub-critical propagation of fractures? If we can demonstrate this we come closer to understanding one of the most puzzling riddles that has confronted modern Earth Sciences. There is some room to shape this project differently for a geology major as opposed to a physics or geophysics major (e.g. in respect to fieldwork).

The photo on the right shows two photos of different fluid instability -- the upper one is often called Kelvin-Helmholtz instability, the lower one is called Holmboe's instability. The generation of these two instabilities are both predicted from some simple physics, but as they grow to larger size the physics becomes complicated. These types of instability occur in both the ocean and atmosphere, where they are an important source of turbulence and mixing. The best way of determining what happens in these instabilities is to isolate them in laboratory. This project will involve a series of laboratory experiments making measurements of the flow speed and the generation of instabilities.

The student/intern can expect to conduct a number of experiments, making visual (qualitative) measurements of the flow as well as quantitative measurements of the instabilities as they grow. Contact the supervisor directly for more information.