About the Project
Porphyry Copper Deposits (PCDs) are the major source of world’s copper and the focus of heated debate on the relationship between magmas and mineralisation. At the heart of the argument is the timing of magma emplacement relative to when mineralisation occurs and a greater understanding of this relationship is an important tool for future mineral exploration. Uranium-lead dating techniques produce highly precise and accurate ages for individual magma batches and therefore provide a gold standard for an absolute timeframe for magma emplacement. Directly dating the mineralisation is more troublesome, but Re-Os dating of molybdenite, pyrite and chalcopyrite is routinely utilised. Dating of molybdenite provides some unique analytical challenges, because the measured Os isotope ratios are extreme, but are sensitive to common Os and blank corrections. Commonly, only model ages rather than isochrons are determined, which makes an assessment of the veracity of the age difficult.
Aims and Methods
We have developed new miniaturised dissolution techniques, which allow for much lower blanks, but increased throughput of samples, with the aim of generating Re-Os isochrons as well as model age determinations. The aim of the project will be to develop this new technique to provide age constraints on discrete mineralisation events at the level of individual veins sets. Isotope data will be complemented by trace element analyses of molybdenites. The project will also make a concerted attempt to calibrate U-Pb and Re-Os isotope ages by working with our collaborators at the BGS. A critical part of the project is the collaboration with BHP who will provide key samples from PCDs, but will also provide a link to understanding the data in the context of exploration strategy.
Candidate
The successful applicant should have a background in either Earth Sciences or a related physical science such as Chemistry, preferably to MSc/MSci level. An interest in mineral deposits and economic geology would be useful but not essential.
Case Award
BHP Billiton will provide key samples for the student to date. The student will also be hosted either at a nominated BHP Billiton office or at one of their properties for a period of up to 3 months. During this time the student will be introduced to a variety of mineral exploration and extraction activities, enabling them to put their research into a wider context.
Training
Training in clean laboratory techniques and mass spectrometry will be provided during the Ph.D at both Bristol and the BGS. Additionally, the student will learn micro-analytical techniques such as electron microprobe and laser-ablation ICP-MS.
More information on the application process can be found here: http://nercgw4plus.ac.uk/research-themes/prospective-students/
References
Blundy, J, Mavrogenes, J, Tattitch, B, Sparks, S & Gilmer, A, 2015, Generation of porphyry copper deposits by gas-brine reaction in volcanic arcs. Nature Geoscience, 8, 235-240.
Markey, R.J., Hannah, J.L., Morgan, J.W., Stein, H.J., 2003. A double spike for osmium analysis of highly radiogenic samples. Chemical Geology 200, 395-406.
Markey, R., Stein, H.J., Hannah, J.L., Zimmerman, A., Selby, D., Creaser, R.A., 2007. Standardizing Re-Os geochronology: A new molybdenite reference material (Henderson, USA) and the stoichiometry of Os salts. Chemical Geology 244, 74-87.
Sillitoe, R.H., 2010. Porphyry copper systems. Economic Geology 105, 3–41.
Stein, H.J., Markey, R.J., Morgan, J.W., Hannah, J.L., Schersten, A., 2001. The remarkable Re-Os chronometer in molybdenite: how and why it works. Terra Nova 13, 479-486.
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