Expressions of interest are now invited for prospective PhD candidates commencing in late-2011 or 2012. Below is a list of research opportunities currently available in the Department of Earth and Planetary Sciences and contacts for further information. Some projects below are fully funded. You are also welcome to contact a possible supervisor directly about your own ideas for research or projects that may not have made it here yet. Prospective candidates should first discuss the research opportunity with the academic contact listed before preparing a brief research proposal to accompany a HDR Applicaiton form. For further details on applicaiton, enrolment and scholarship opportunities please go to: HDR Home

 

Research Opportunities

Fully funded PhD project : Fundamental link between deformation, fluids and the rates of reactions in minerals: Nature and Experiments.

Co-supervised by Dr Sandra Piazolo (Macquarie University) and A/Prof. Nathan Daczko (Macquarie University)

This exciting project investigates the influence of differential stress rates of reactions during fluid present conditions. Within the project the student will investigate a “natural laboratory” of well exposed high strain zones in Fiordland, New Zealand. The student will analyse samples from the field in detail. In addition, the student will perform experiments using a unique see through pressure and deformation cell at the department. During experiments the fluid composition, fluid pressure and temperature is controlled while deforming the samples at different strain rates. The student will not only observe and quantify the replacement mechanisms but also investigate the sites of change relative to stress concentrations. In addition, the student will record and quantify precisely the formation and evolution of porosity development during the replacement reaction.  Depending on the background and interest of the student, the project can also involve numerical simulations using the numerical modelling system ELLE (http://www.microstructure.info/) as well as work together with experts to improve large scale modeling systems such as Underworld (http://www.underworldproject.org/models.html). The project outcomes will enhance our understanding of many fundamental geological processes, including metamorphic phase transformations and ore-body formation.

Enquiries: Dr. Sandra Piazolo (+61 2 9850 4407, e-mail: sandra.piazolo(AT)mq.edu.au).

 

Fully funded PhD project : Flow characteristics of lower crustal rocks: Field studies and numerical modelling.

Co-supervised by Dr Sandra Piazolo (Macquarie University) and Dr. Craig O'Neill (Macquarie University)

This varied project aims to improve our knowledge of the flow behaviour, or "rheology", of rocks consisting of different mineral phases. This behaviour controls large scale processes, such as plate tectonics and mountain building. In this project, the student will perform detailed field studies in a selected “natural laboratory” in Fiordland New Zealand, analyse in detail the rocks and geometric relationships and implement results into the numerical modelling system ELLE (http://www.microstructure.info/) as well as work together with experts to improve large scale modeling systems such as Underworld (http://www.underworldproject.org/models.html). In the course of the project the student will gain expertise in field work in high grade rocks, chemical and crystallographic analysis and numerical modeling techniques. Depending on the background and interest of the student, the project may also involve some physical experiments. The outcomes have a profound significance, as the accuracy of the latest large-scale geodynamic models is dependent on the correct rheological constants.

Enquiries: Dr. Sandra Piazolo (+61 2 9850 4407, e-mail: sandra.piazolo(AT)mq.edu.au).

 

Fully funded PhD project : Flow characteristics of lower crustal rocks: In-depth analysis of Xenoliths and experimental studies.

Co-supervised by Dr Sandra Piazolo (Macquarie University) and Dr. Juan-Carlos Afonso (Macquarie University)

This varied project aims to improve our knowledge of the flow behaviour, or "rheology", of rocks consisting of different mineral phases. This behaviour controls large scale processes, such as plate tectonics and mountain building. In this project, the student will perform detailed analysis of two suites of lower crustal xenoliths and perform experiments on polymineralic materials. Experiments will be focused on uniaxial deformation experiments using both samples from the field as well as analogue materials such as ice. The student will work together with experts to implement results into large scale modeling systems such as Underworld (http://www.underworldproject.org/models.html). In the course of the project the students will gain expertise in chemical and crystallographic analysis, numerical techniques and different experimental techniques. The outcomes have a profound significance, as the accuracy of the latest large-scale geodynamic models is dependent on the correct rheological constants.

Enquiries: Dr. Sandra Piazolo (+61 2 9850 4407, e-mail: sandra.piazolo(AT)mq.edu.au)

 

PhD project : The eclogite-granulite transition exposed in the exhumed Gondwana continental arc margin, Fiordland New Zealand.

Co-supervised by Dr Nathan Daczko (Macquarie University) and Prof. Geoff Clarke (The University of Sydney)

Fiordland New Zealand exposes high-P granulite and eclogite facies rocks that form a deeply exhumed crustal profile through a Cretaceous Gondwana margin continental arc system. Spectacular exposures of omphacite-plagioclase-bearing rocks and eclogite were recently discovered in Breaksea Sound; these represent Earth’s most extensive and best-preserved exposures of lower crustal high-T omphacite-bearing rocks. This project will establish and distinguish which igneous versus metamorphic processes form omphacite granulite, and ascertain what processes allow the preservation of omphacite granulite during its return to the surface. It will use thermodynamic modeling and experimental studies to quantify the P-T stability fields of high-T omphacite-bearing equilibria relevant to both igneous and metamorphic assemblages.

Suitable students should enjoy the outdoors and have interests in igneous and metamorphic petrology, geochemistry, geochronology and field-based research. The field sites will be accessed via helicopter and inflatable rubber boat.

Enquiries: Nathan Daczko (ndaczko(AT)els.mq.edu.au) and Geoff Clarke (geoffrey.clarke(AT)sydney.edu.au)

 

PhD project: The behaviour of isotopes in migmatites and granite production; a case study from Mt Stafford, central Australia

Co-supervised by Prof. Geoff Clarke (University of Sydney) and Dr Nathan Daczko (Macquarie University)

Earth’s distinctive continental crust reflects its unique, on-going process of planetary differentiation and is perhaps most profoundly expressed in large granitic batholiths that dominate most continental landmasses. Interpretations of granitic magma sources have recently changed from them having involved just the remelting of ancient igneous and metasedimentary rocks to new models involving the interaction of mantle-derived and crust-derived magma, largely based on complex Nd, Hf and O isotope records in mineral assemblages forming granite bodies. However, as parallel isotopic studies of sedimentary rocks show that turbidite mud-sand whole-rock pairs may include isotopic variations of the same magnitude used to interpret crustal and mantle sources for granite plutons, there is a need to validate models for isotope behaviour during crustal melting.
This project will study the behaviour of Hf and Nd isotopes at all stages of granite production, utilising a rare field site in central Australia where the unmelted protoliths to a suite of migmatites and granite can be studied. It will characterise Hf and Nd isotopic values and reservoirs in a suite of migmatised turbidites and lower grade equivalents to resolve the relative contribution of pelite, semi-pelite and psammite in local granite production. It will establish, for this representative example, the dispersion of Hf isotopic values that may result from the partial melting of such composite crust, and whether these processes could be misinterpreted as mixing between crustal and mantle sources of magma.

Candidates should be interested in igneous and metamorphic petrology, isotope geochemistry, geochronology and field-based research. Fieldwork will focus on Mt Stafford 200km NW of Alice Springs in the outback of central Australia. It is accessed via 4WD only; interested students should enjoy the outdoors.

Enquiries: Geoffrey Clarke (geoffrey.clarke(AT)sydney.edu.au and Nathan Daczko (ndaczko(AT)els.mq.edu.au)

 

PhD project: Melt-rock interactions and granite models in the eastern Lachlan Orogen, southeastern Australia

Co-supervised by Dr Nathan Daczko (Macquarie University), Dr Cameron Quinn (Geological Survey of NSW) and Prof. Geoff Clarke (The University of Sydney)

Studies of open system melt-rock interactions in the Earth’s crust are commonly restricted to examining the loss of melt. This project will examine how granite magmas interact with upper crustal material during their ascent and emplacement.

This project will focus on mapping well exposed transects across unmelted metasedimentary protoliths to a suite of migmatites and granite plutons in the Wagga-Omeo-Mt Hotham region. Specifically, we will examine the metamorphic history, thermochronology and isotopic characterisation of the interaction between metasedimentary and granitic components to determine the interdependencies of granite development and metamorphism of the country rock and the influence of the upper crust on granite compositions. The project will characterise Hf and Nd isotopic values and reservoirs in a suite of migmatised turbidites and lower grade equivalents to resolve the relative contribution of local versus distal melts in granite production.

Candidates should be interested in remote fieldwork in the Australian Alps, igneous and metamorphic petrology, isotope geochemistry, geochronology and field-based research. Field sites will be accessed via 4WD, mountain bike, and/or foot.

Enquiries: Nathan Daczko (ndaczko(AT)els.mq.edu.au), Cameron Quinn (cameron.quinn(AT)industry.nsw.gov.au) and Geoff Clarke (geoffrey.clarke(AT)sydney.edu.au)

 

PhD project: The Role of Amphibole in Island Arc Magmatism: Generating Earth's Continental Crust

Co-supervised by Prof Jon Davidson (Durham University UK) and Dr Tracy Rushmer (Macquarie University)

Aims and Objectives — Planet Earth is unique in the solar system in having both a silica-rich (continental crust) and in having abundant water. The connection between these factors has been the subject of a number of investigations and speculations. A widespread belief was held that wet melting of Earth’s mantle produced siliceous andesites, which roughly approximated the composition of the continental crust. Subsequent research has shown this not to be the case - magmas derived from the mantle are fundamentally basaltic. Generating an andesitic crust may therefore have more to do with the way the basaltic flux from the mantle is processed as it moves into and through the lithosphere, usually in island arc settings. The presence of water during this processing may be critical in generating a silica-rich product, and it has been suggested that water might stabilise minerals such as magnetite or amphibole, or influence the phase proportions fractionating during differentiation, such that liquid compositions are silica rich. Recently new work at Durham University and Macquarie University have discovered compelling evidence that amphibole plays a major role in magma processing at arcs, and therefore in the origin of the continental crust [1]. It now appears that amphibole plays a major role in the differentiation of arc magmas and is therefore an important component of geochemical reservoirs in the mid-deep arc crust. This implication has very important consequences, such as determining the geochemical nature of the continental crust.

Scientific Training: The project will be run as a co-tutelle between Durham (UK) and Macquarie Universities (Sydney, Australia). The student will carry out research at both institutions and will be awarded the PhD from both. The opportunity to travel between the campuses and to be embedded in two different research groups is regarded as a significant opportunity. The proposed research will be using a combined petrology and experimental approach to: (1) study the relationship between arc lavas, their crystal cargo and their included cumulates to develop quantitative differentiation models, distinguishing whether cumulate assemblages or “phenocrysts” are more important in controlling geochemical evolution, (2) measure the distribution of REE and, most importantly water, between amphibole and host liquids, and (3) use melt inclusions and other geobarometry/ geothermometry approaches to try and establish conditions of crystallisation for the cumulate and “phenocryst” phases; and (4) to carry out melting experiments on selected amphibole cumulates. We plan to use a suite of samples from the Lesser Antilles. A published study of cumulate compositions along the arc has emphasised the important role of amphibole. The collection of cumulate samples used in this study (Arculus and Wills) is available to us at Durham, and is complemented by a wealth of published geochemical data. The experimental results will allow us to establish the melt compositions in equilibrium with amphibole and the stability range of amphibole in island arc settings [2].

Theses at both Universities are now written in a manuscript format so the student will be assured of journal publications. We also expect the student to attend national (VMSG) and international (AGU/ IAVCEI/ Goldschmidt) conferences to present their work.

References:.
[1] Davidson et al., Geology
[2] Rushmer, 1991

Enquiries: Jon Davidson (j.p.davidson(AT)durham.ac.uk) and Tracy Rushmer (trushmer(AT)els.mq.edu.au)

 

PhD project: Evolution of the Qualibou Volcanic Complex, St Lucia, Lesser Antilles

Co-supervised by Prof Jon Davidson (Durham University UK), Prof Simon Turner (Macquarie University) Dr Colin Macpherson (Durham) and Dr Kurt Knesel (University of Queensland)

Aims and Objectives — The Qualibou Volcano is the most recently active volcanic edifice on St Lucia [1]. The island is one of the southernmost along the Lesser Antilles, an island arc which is the result of westward subduction of the Atlantic Plate beneath the Caribbean. This arc, one of only two in the Atlantic, is characterised by extreme ranges in geochemistry. Some of the magmatic rocks have isotopic ratios consistent with derivation from the continental crust. Given the oceanic provenance of the arc, these geochemical features can be inherited either from subducted sediments, or from crustal contamination by continental sediments intercalated in the arc crust. There are some along-arc systematics to the geochemical variations. They are more restricted in the northern part of the arc, and become more diverse towards the central and southern islands. In this context, St Lucia is second only to Martinique in its isotopic diversity, yet it is poorly studied. The rocks from The Qualibou Complex are dominated by porphyritic dacite domes, but include less evolved compositions. Isotopic compositions are crust-like and these data have been used to argue for wholescale contamination by subducted sediment [2]. On the other hand oxygen isotope data and correlations with differentiation indices are consistent with crustal contamination [3]. These contrasting hypotheses need to be tested by mineral scale isotopic investigations which are now possible with technologies available at Durham. In principle, if the isotopic compositions are inherited from source then subsequent crystallisation would result in isotopically homogeneous phases. On the other hand, if crystallisation occurs during crustal contamination (AFC) then we would expect to see core-rim isotopic zoning in crystals [4].
 

Scientific Training — The proposed research will consist of collecting rocks within a well-constrained stratigraphic and volcanological context. This will involve careful fieldwork, and a program of Ar dating in collaboration with the University of Queensland. Petrographic examination will be succeeded by a full geochemical analysis to include major and trace elements, (at Macquarie) along with Sr, Nd, Pb, Hf (Durham) and O isotopes (which will be accessed through a proposal to the NERC facility). Microsampling of the crystals for isotopic compositions will make use of the microsampling facility at Durham, and will ensure that the student is trained in cutting edge small sample isotope approaches. Theses at Durham are now written in a 3-manuscript format so the student will be assured of journal publications. We also expect the student to attend national (VMSG) and international (AGU/ IAVCEI/ Goldschmidt) conferences to present their work.

References:.
[1] Wohletz, K., Heiken, G., Ander, M., Goff, F., Vuataz, F-D and Wadge, G., 1986. The Qualibou Caldera, St Lucia, West Indies. J. Volcanol. Geotherm. Res., 27, 77-115.
[2] Vidal, P., Le Guen de Kerneizon, M., Maury, R. C., Dupré, B. & White, W. M. (1991). Large role of sediments in the genesis of some Lesser Antilles andesites and dacites (Soufrière, St. Lucia): isotopic constraints. Bulletin de la Societé Géologique de France 162, 993–1002.
White, W. M. & Dupre, B. (1986). Sediment subduction and magma genesis in the Lesser Antilles: isotopic and trace element constraints. Journal of Geophysical Research 91, 5927–5941
[3] Davidson, J.P., 1987, Crustal contamination versus subduction zone enrichment: Examples from the Lesser Antilles and implications for mantle source compositions of island arc volcanics." Geochim. et Cosmochim. Acta, 51, 2185-2198
[4] Davidson, J.P., Morgan, D.J., Charlier, B.L.A., Harlou, R. and Hora, J.M., 2007. Microsampling and Isotopic Analysis of Igneous Rocks: Implications for the Study of Magmatic Systems. Ann. Rev. Earth Planet. Sci. 35, 273–311

Enquiries: Jon Davidson (j.p.davidson(AT)durham.ac.uk) and Simon Turner (sturner(AT)els.mq.edu.au)

 

PhD project: Origin of high-temperature rhyolitic magma - a study of interstitial glass in continental flood basalts

Co-supervised by Prof Jon Davidson (Durham University UK) and Prof Simon Turner (Macquarie University)

Aims and Objectives — Whether silicic magmatic rocks are largely derived by partial melting or crystal fractionation is a much debated question in Earth sciences and one closely linked to debates over the origin of the continental crust. One of the striking observations is that many silica-rich magmatic rocks occur in bimodal associations. In particular, many continental flood basalt provinces contain voluminous rhyolites and many studies have concluded that these higher silica rocks are crustal melts from metapelitic or tonalitic country rock. However, although many continental flood basalt sequences exhibit a marked a silica gap from ~55-65 wt % SiO2, many incompatible element ratios, and the calculated eruption temperatures (950-1100°C) are strikingly similar between the rhyolites and associated basalts [1]. This suggests a close relationship between the mafic and silicic rocks and there are two alternatives. Either the silicic rocks formed by fractional crystallisation of parental mafic magmas or else they formed by partial melting of solidificed equivalents. To date distinguishing between these two hypothesis has proved difficult. One of the objections to the fractional crystallization model is the lack of intermediate compositions. However, Marsh [2] has suggested that silicic melts could before formed as interstitial melt within mafic magma that becomes physically squeezed out by gravitational compaction forces. An important question therefore, is how such a model might be tested. In the Columbia River flood basalts, Lambert et al. [2] observed interstitial glass of rhyolitic composition which constitutes some 10% of the samples and which, if segregated, could form 10,000 km3 of rhyolite. Thus, thus project is to analyze interstitial glass from selected flood basalts for major and trace element compositions and radiogenic isotopes in order that these can be compared with associated rhyolites.

 

Scientific Training — The project will be run as a cotutelle between Durham and Macquarie Universities (Sydney, Australia). The student will carry out research at both institutions and will be awarded the PhD from both. The opportunity to travel between the campuses and to be embedded in two different research groups is regarded as a significant opportunity. The proposed research will consist of compiling mafic and silicic rocks within a well-constrained stratigraphic and volcanological context from a number of flood basalt provinces. This will involve careful fieldwork in at least one province. Petrographic examination will be succeeded by a full in-situ geochemical analysis to include major and trace elements, (at Macquarie) along with Sr, Nd, Pb, Hf (Durham), and will ensure that the student is trained in cutting edge small sample isotope approaches.
Theses at both Universities are now written in a manuscript format so the student will be assured of journal publications. We also expect the student to attend national (VMSG) and international (AGU/ IAVCEI/ Goldschmidt) conferences to present their work.

 

References:
[1] Turner, S., & Rushmer, T. 2009. Similarities between mantle-derived A-type granites and voluminous rhyolites in continental flood basalt provinces. Earth and Environmental Science Transactions of the Royal Society of Edinburgh, 100, 1-10.
[2] Marsh, B.D. 2002. On bimodal differentiation by solidification front instability in basaltic magmas, part 1: Basic mechanics. Geochimica et Cosmochimica Acta 66, 2211-2229.
[3] Lambert, R. St. J., Marsh, I. K. & Chamberlain, V. E. 1989. The occurrence of interstitial granite-glass in all formations of the Columbia River Basalt Group and its petrogenetic implications. Geological Society of America Special Paper 239, 321-332.
 

Enquiries: Jon Davidson (j.p.davidson(AT)durham.ac.uk) and Simon Turner (sturner(AT)els.mq.edu.au)

 

PhD project topics available under the supervision of Dr Juan Carlos Afonso

Inversion of multiple geophysical data for composition and thermal structure of the Earth's upper mantle

Global lithospheric models

Initiation of subduction

Detection of small-scale chemical anomalies within the lithospheric mantle

Evolution of the oceanic lithosphere from thermodynamic-thermomechanical approaches

 

FURTHER GENERAL ENQUIRIES

A/prof Tracy Rushmer
Postgraduate Reserach Coordinator
Department of Earth & Planetary Sciences
Macquarie University  NSW  2109
Phone: (02) 9850 8366
Fax:  (02) 9850 6904
E-mail: Tracy.Rushmer@mq.edu.au

Dr Mark Lackie 
Head of Department
Phone: (02) 9850 8377
Fax:  (02) 9850 6904
E-mail: mark.lackie@mq.edu.au