Ph.D. Scholarship in Geochemistry / CosmochemistryApplications are invited for an outstanding and enthusiastic student to pursue fully-funded graduate (Ph.D.) research in cosmochemistry and geochemistry in the new Centre for Trace Element Analysis and the Department of Chemistry at the University of Otago. Applicants with a strong background in the geosciences, chemistry, physics, or a related quantitative discipline, with a demonstrated academic excellence at the Bachelor or Master's level, are encouraged to apply. The appointment is supported by the New Zealand Marsden Fund and includes a 3-year stipend of NZ$ 25,000 per year (tax free), travel to national and international conferences, and collaborative research with the University of Oxford and the Australian National University. Student fees will also be paid. The appointment can be started at any time from May 2008. The project will focus on two aspects of uranium isotope geochemistry utilizing (1) meteorites to investigate the sequence of events leading to the formation of our solar system, and (2) terrestrial surface samples to investigate isotope fractionation of the very heavy elements during (bio)geochemical cycling: (1) Our solar system evolved from a giant molecular cloud of dust and gas that collapsed gravitationally more than 4.5 billion years ago. What triggered this collapse is the subject of debate, but one leading theory invokes shock waves from a nearby massive exploding star - a supernova. The project aims to test various competing models describing the formation of our solar system. This objective can be achieved by detecting small variations in the uranium isotopic composition of meteorites, derived from asteroidal-sized objects that formed at the start of the solar system, which in turn, can be related to the abundances of supernovae-produced nuclides in the proto-solar molecular cloud. The measurement of uranium isotopic composition is also of paramount importance for the accuracy of the uranium-lead chronometer (based on the slow decay of uranium to lead), which defines the most precise age of the solar system at 4.5672 ± 0.0006 billion years, but currently assumes no uranium isotopic variations in meteorites. Therefore, the chronometry of the early solar system may need to be drastically revised by up to tens of millions of years if uranium isotopic effects are found. (2) Uranium is the heaviest naturally occurring element and isotope fractionation between its two non-radiogenic isotopes, 235U and 238U, is not normally considered to be significant. However, following the discovery of natural variability in 235U/238U in near-surface terrestrial environments, measurements of uranium isotopes have emerged as a novel potential tracer of reaction pathways activated during biological cycling and redox processing, offering new insight into the processes at work. Natural variability in uranium isotopic composition will also have a direct impact on the accuracy of the uranium-lead chronometer and the uranium decay-series short-lived Quaternary chronometers, which currently assume no uranium isotopic variations in all terrestrial and extraterrestrial environments. Samples will be chemically purified in a Class 10 clean laboratory. Using double-spike protocols, uranium isotopic measurements will be acquired using multiple-collector inductively coupled plasma mass spectrometry (MC-ICPMS). Supporting measurements will be acquired by ICP-MS. The University of Otago is New Zealand's largest and most research-intensive university and is situated on the east coast of New Zealand's South Island. Applicants should submit a cover letter, complete CV, academic transcripts, and the names and contact information of at least two referees to: Dr. Claudine Stirling The position will remain open until filled. Further information about the Department of Chemistry can be found at |
