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Research Projects at RSES
Inside isotopic clocks: distribution of parent and daughter nuclides in geochronometer minerals
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Supervisor:Amelin, Yuri Ireland, Trevor
Subject keywords: Geochronology (dating), Planetary studies, Deep Earth/Continent evolution, Petrology, Chemistry, Geochemistry, Laboratory, Analytical
Degree types: Honours, M.Sc, PhD, PhB,
Knowing the distribution of U, Th and radiogenic Pb in chondrules and refractory inclusions is important for accurate interpretation of U-Pb isotopic dates. For example, the distribution of U between primary and secondary minerals can indicate whether the date corresponds to formation or to alteration of a chondrule or a Ca-Al-rich refractory inclusions (CAIs). In the case of dating equilibrated (i.e. metamorphosed) chondrites, we need to know the host mineral of U in order to apply correct diffusion parameters for estimating closure temperatures.


The student will explore and advance the sensitivity limits of modern secondary ionisation mass spectrometry, and will use this technique to measure U, Th and Pb concentrations and isotopic ratios in chondrules, CAIs and their components. Extremely low concentrations of U and Th in chondrites in a low parts per billion range, together with micron-scale heterogeneity of chondrules and CAIs makes this project analytically challenging.


The history of mixing nucleosynthetic components during formation of our Solar System
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Supervisor:Amelin, Yuri Ireland, Trevor
Subject keywords: Geochronology (dating), Planetary studies, Petrology, Chemistry, Geochemistry, Physics, Laboratory, Analytical, Computational
Degree types: M.Sc, PhD, PhB,
All chemical elements heavier than lithium, that comprise the Earth and our Solar System, were produced by nuclear reactions in stars, and mixed during formation of the Solar System. It was once thought that that mixture once existed as a hot and almost homogeneous molecular cloud, and the minerals, planetesimals and planets formed during its cooling and gradual condensation and accretion. That concept was overthrown by discovery of refractory materials (Ca-Al-rich inclusions and hibonite grains) containing isotopic anomalies that are incompatible with condensation from homogeneous 'bulk solar' gas. Existence of presolar grains with extreme isotopic compositions for many elements, and small but systematic differences in isotopic compositions of Mo, Cr, Ni, Ba and other elements between Earth, Mars, and meteorites from various asteroids demonstrates heterogeneity of the Solar System at scales from micron-sized minerals to planets. The pattern of mixing, however, remains poorly understood. The student will explore the timing of mixing nucleosynthetic components and mechanisms of homogenisation by precise isotopic analysis of several elements containing isotopes produced in various stellar environments from selected meteorites, and by comparative modelling of mixing and mass-independent fractionation that can possibly mimic incomplete mixing. The main emphasis can be given to either an analytical or a modelling part, depending on the talents and skills of the student.
The Early Time: towards consistent time scale of the Solar System formation
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Supervisor:Amelin, Yuri Ireland, Trevor
Subject keywords: Geochronology (dating), Planetary studies, Petrology, Geochemistry, Geology, Laboratory, Analytical
Degree types: M.Sc, PhD,
An interstellar molecular cloud transformed into our Solar System through condensation of mineral grains, accretion and growth of planetesimals and planets in a short period of a few million years. Understanding the nature of these events is impossible without their precise sequencing. The aim of this project is to determine the timing and duration of the key events of accretion and planetary growth with precision and accuracy hitherto unattainable.

The student will The student will analyse some of the best preserved meteorites and their components (minerals, chondrules, refractory inclusions) for U-Pb, 26Al-26Mg, 53Mn-53Cr and 182Hf-182W using high-precision and high-resolution analytical techniques: thermal ionisation and plasma ionisation mass spectrometry and SHRIMP ion microprobes. The project involves extensive laboratory development work in order to maximize precision, accuracy and sensitivity of isotopic methods.

Exploring potential and limitations of ultrahigh-precision U-Pb dating
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Supervisor:Amelin, Yuri Williams, Ian Rubatto, Daniela
Subject keywords: Geochronology (dating), Planetary studies, Deep Earth/Continent evolution, Petrology, Chemistry, Geochemistry, Geology, Physics, Laboratory, Analytical
Degree types: M.Sc, PhD,
The goal of this project is to enhance our ability to solve geological problems with more precise and accurate isotopic dating. Geochronology allows us to determine which of the geological events close in time occurred first, and thus to constrain their causal relations. With precision of dating of 0.1-0.2 million years, we can verify the links between mass extinctions and impact events or catastrophic volcanic eruptions, pinpoint geological processes responsible for formation of major ore deposits, and solve other important scientific and practical problems, which cannot be solved reliably with 20-50 times less precise microbeam techniques, currently adopted by the Australian geological community. The student who undertakes this project will comprehensively evaluate the accuracy (and various possible causes of inaccuracy) in U-Pb dating at the new level of precision, in order to establish a procedure for routine dating of Precambrian zircon and other minerals with precision and accuracy of ±0.1-0.2 Ma, or about 3-10 times better than before. This project is most suitable for a student who is interested in both the history of the Earth, and in solid state chemistry and physics.
Archaean granite-greenstone evolution
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Supervisor:Amelin, Yuri Campbell, Ian
Subject keywords: Geochronology (dating), Deep Earth/Continent evolution, Economic and Structural Geology, Petrology, Geochemistry, Geology, Laboratory, Analytical, Fieldwork
Degree types: M.Sc, PhD,
The aims of the project are: (i) to determine the relationship between mafic and felsic volcanism, (ii) to test whether greenstones can be correlated across terrane boundaries, and (iii) to develop a model for the evolution of 2.7 Ga granite-greenstone terranes in the light of the new dates and geochemical data, and if possible, their relationship to gold mineralization.

The centrepiece of the project will be the production of the first ultra-high precision dates of zircons and baddeleyites extracted from Archaean greenstones of the Yilgarn craton, Western Australia. The expected precision is better than ± 0.5 Myr compared with ±5 Myr current available through SHRIMP. The speed at which the crust evolved we can be used to test hypothesis for evolution of granite-greenstone terranes.

The project will also involve Hf isotopes in zircon by LA-ICP-MS, oxygen isotope analysis of zircons by SHRIMP, Nd and Sr isotope analyses of rocks and minerals, and trace element analyses.

The project is funded by ARC and forms part of a larger Monash-ANU project.

The student will carry out ultra-high precision dating and isotopic analyses. This will require high level of laboratory aptitude, and sufficient knowledge of geochemistry for interpretation of geochronological and isotopic data. The project will also involve working in the field at several different mining camps in Western Australia, mainly with diamond drill core, so you will need to be a good observer.

Precise timing of ore formation
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Supervisor:Amelin, Yuri Campbell, Ian
Subject keywords: Tectonics/Earth Deformation/faults, Geochronology (dating), Economic and Structural Geology, Petrology, Geochemistry, Geology, Laboratory, Analytical
Degree types: Honours, M.Sc, PhD,
Precise knowledge of the age relationships between ore formation and related magmatism, metamorphism and fluid migration is necessary for understanding the conditions of ore formation. This project (co-supervised by Y. Amelin and I. Campbell, ANU, and V. Kamenetsky, Uni. Tasmania) is aimed at dating the giant Olympic Dam Cu-Au-REE-U deposit and its host rocks using modern high-precision geochronology. The age of the Olympic Dam deposit is currently known with precision of ca. ±10 million years, which is insufficient for resolving the ages of individual components in the Olympic Dam Breccia Complex. The student will date zircon and other uranium-bearing accessory minerals from the key rocks in the Olympic Dam Breccia Complex, with precision by 10-30 times higher than before, using high-precision U-Pb isotopic analyses. The project will involve developing better constrained models of formation of this unique deposit, using the determined isotopic ages.
Diffusion as a limiting factor in isotopic dating and tracing
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Supervisor:Amelin, Yuri ONeill, Hugh
Subject keywords: Geochronology (dating), Planetary studies, Deep Earth/Continent evolution, Petrology, Chemistry, Geochemistry, Laboratory, Analytical, Experimental
Degree types: M.Sc, PhD,
If a rock has been affected by thermal metamorphism, aqueous alteration or shock metamorphism some time after crystallization, it is likely that uranium and radiogenic lead accumulated since crystallization moved between the minerals, or at a larger scale, in that process. The date calculated from the radiogenic 207Pb/206Pb ratio assuming closed system evolution could yield an erroneous date. Knowing the nature of element mobility in the secondary process is important for accurate interpretation of isotopic dates. For example, if we try to apply diffusion formalism to a rock in which the isotopic systems were reset by mineral recrystallization, then we are likely to get a meaningless date.

The student will study the distribution of U and Pb isotopes in a variety of rocks, minerals and meteorites, and search for characteristic geochemical and isotopic patterns predicted by diffusion formalism. He or she will also inspect the existing set of experimental data for diffusion of parent and daughter elements in the minerals used in isotopic dating, and plan and perform experiments necessary to obtain the missing data.

What the Earth is made of?
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Supervisor:Amelin, Yuri ONeill, Hugh Ireland, Trevor
Subject keywords: Planetary studies, Deep Earth/Continent evolution, Petrology, Chemistry, Geochemistry, Geology, Laboratory, Analytical, Computational
Degree types: M.Sc, PhD, PhB,
The 176Lu-176Hf isotopic system is an invaluable tool for studying early differentiation in the Earth and other planets. The initial condition of this isotopic system in the Earth, a pre-requisite for its accurate use, remains elusive, despite the growing amount of Lu-Hf data on early Solar System materials. The Lu/Hf ratio, and ratios of other refractory elements, directly measured in chondrites, may not represent the bulk terrestrial and Solar System values, because of chondrite heterogeneity (within a meteorite and between the classes of chondrites), and possible impact erosion or early volcanism. These complications will be addressed in this project.


The student will study the Lu-Hf isotopic system, and U-Pb and Sm-Nd as necessary, in the least metamorphosed chondrites and in chondritic matrices using plasma ionisation mass spectrometry, and explore the correlation between Lu/Hf and the ratios of other refractory lithophile elements in various classes of chondrites and in Solar photosphere. This project will also involve the first direct measurements of the initial 176Hf/177Hf of the Solar System in minerals with low Lu/Hf ratio (such as ilmenite and zircon) from old, well preserved meteorites.

Dating the Permian-Triassic extinction event in Australia
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Supervisor:Amelin, Yuri
Subject keywords: Tectonics/Earth Deformation/faults, Geochronology (dating), Economic and Structural Geology, Palaeontology, Geochemistry, Geology, Biogeosciences, Laboratory, Analytical
Degree types: Honours, M.Sc, PhD, PhB,
The Permian - Triassic (Palaeozoic - Mesozoic) boundary marks the greatest mass extinction in the history of the Earth's biosphere, which is sometimes referred to as Great Dying. Correlation of the Permian - Triassic (P - T) boundary in Australia and Gondwana with global and northern hemisphere marine boundary sequences and the formal GSSP section is limited by the paucity of marine index fossils. Interpretation of non - biostratigraphic proxies for the P - T boundary in Australia is also difficult. In this project, the student (co-supervised by Ian Metcalfe, University of New England, and Bob Nicoll, Geoscience Australia), will perform time calibration of the P - T boundary by U-Pb analysis of zircons from volcanic rocks bracketing the boundary, using the modern high-precision analytical techniques and the methods of zircon treatment that eliminate the influence of inheritance and Pb loss, such as mechanical and chemical abrasion.
Early Earth: the zircon tale continues.
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Supervisor:Amelin, Yuri
Subject keywords: Geochronology (dating), Planetary studies, Deep Earth/Continent evolution, Petrology, Geochemistry, Geology, Laboratory, Analytical
Degree types: Honours, M.Sc, PhD, PhB,
Zircon is a unique, although not exactly perfect, chronometer mineral and "time capsule" that preserves information about the earliest history of the Earth. The set of tools for extracting this information includes U-Pb dating, Lu-Hf isotopic tracing, trace element concentrations, oxygen isotope composition, Ti concentrations thermometry, and imaging of the internal grain structure. Veracity of this information, however, deteriorates, if the grain is internally heterogeneous, and various isotopic and chemical analyses sample domains of different age, origin, and degree of alteration. The goal of this project is developing methodology for extracting comprehensive and accurate information about the origin of the zircon's host rock while circumventing the effects of heterogeneity. The student will use a combination of ion microprobe techniques, imaging, and precise isotopic analysis of U, Pb and other elements separated from zircon grain fragments, to refine the ways of getting a comprehensive genetic information from zircon. This methodology will be applied to the earliest terrestrial zircons, and, after optimisation, to other important detrital zircon populations throughout the Earth's history.
How old are the planets?
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Supervisor:Amelin, Yuri
Subject keywords: Geochronology (dating), Planetary studies, Petrology, Geochemistry, Geology, Laboratory, Analytical
Degree types: M.Sc, PhD, PhB,
The geological history of differentiated asteroids - small "terrestrial planets", is recorded in achondrites - eucrites, angrites, ureilites, and in iron and stony-iron meteorites. Achondrites are igneous rocks of basaltic or ultramafic composition from asteroids that underwent melting and subsequent magma differentiation and crystallisation. The purpose of this project is to determine precise timing of formation of achondrite parent asteroids using isotopic systems that record fractionation between volatile and refractory elements (e.g., initial Sr isotopic composition). The student will study early geological history of asteroids: magmatism, thermal and impact-induced metamorphism, using U-Pb, 26Al-26Mg and 53Mn-53Cr isotope chronometers and a selection of high-precision and high-resolution mass spectrometry techniques. Precise and consistent dates obtained using a variety of isotopic chronometers on the best preserved meteorites will serve as the reference points for building a consistent time scale of our Solar System.