******************************************************************** Fully-funded PhD opportunity - Ar-Ar dating of young volcanic rocks ******************************************************************** From: Dave McGarvie <d.mcgarvie@xxxxxxxxxx> Ar-Ar dating of young volcanic rocks: Arcane isotopes and how to unravel them Supervisors - Sarah Sherlock, Tiffany Barry, Simon Kelley and Dave McGarvie (all Open University) 1. Training in cutting-edge laserprobe Ar-Ar dating techniques in a world-class laboratory; 2. Fieldwork in Tenerife; 3. The opportunity to develop our understanding of the Ar-system in volcanic materials through detailed sample characterisation, laserprobe Ar-Ar analysis, and technique refinement. 4. The opportunity to work within a cross-disciplinary team of geochronologists, volcanologists and geochemists in a RAE Grade 5 department. Crucial to our understanding of the interaction between volcanoes and the environment is establishing the lifespan and evolution of recent volcanoes. This requires a geochronological tool that can accurately and precisely measure the ages of eruptions, and Ar-Ar dating holds the greatest potential. Despite success in dating sanidine crystals from young volcanoes (< 500 kyr), attempts to date glasses have been thwarted by disturbances to the argon system, a consequence of the very hot, volatile-rich and dynamic environment of a volcano. However, if these disturbances can be fully characterised then high-precision Ar-Ar dating will become the most powerful tool for unravelling the evolution of young volcanoes. Young active volcanoes, inevitably, are the ones that need high-quality age data for use in hazard mapping and civil protection schemes - yet these sorts of volcanoes also present the greatest challenges for high-precision Ar dating. Not only is high resolution data necessary for hazard mitigation, but it is also crucial in the study of rates of magmatic processes and correlative studies attempting to link volcanic eruptions with climate change models. The objectives of this project and how they will be achieved are : 1. Sampling different types of volcanic materials to compare and contrast the behaviour of the Ar-system: magmatic and phreatomagmatic fall deposits and lavas collected from Tenerife, along with sub-glacial and sub-aerial Icelandic rhyolites, and calc-alkaline rhyolites from Mexico, which will be selected from pre-existing archive material. 2. The factors that are likely to affect the Ar-system in volcanic materials are their potassium content, whether they are altered or devitrified, the presence of phenocrysts or xenocrysts and their microtextures, and compositions. To test these, samples will be characterised by electron microprobe and SEM. 3. One of the key problems associated with dating young volcanic material is the often extensive volatile component, and how to 'clean' the samples so that the measured isotopes are free from this interference. Water and CO2 content of volcanic glasses will be measured using FTIR microscope spectrometry to see how their presence affects the Ar system. The project will involve a significant component of technical development - how can the samples be physically cleaned before analysis, how can we modify the analytical equipment to clean the gases that are extracted during laserprobe analysis? 4. Atmospheric, excess and inherited argon play a large part in obscuring the age in many cases , and detailed laserprobe Ar-Ar analyses of well-characterised samples should help us to understand how, and to what extent. This project is a laboratory-based project with a small fieldwork component. The emphasis is on how we can improve on current analytical processes, and establishing the factors that control the Ar-Ar system in volcanic rocks. The studentship will provide the opportunity to be at the forefront of advances in dating young volcanic material, and has the potential to lead to further research in volcano geochronology, for which there is currently massive interest. The project will offer training in laserprobe Ar-Ar dating and sample preparation, mass spectrometry and ultra-high vacuum equipment, electron microscopy and FTIR microscopy. The Department has a thriving postgraduate community and the postgraduate training programme provides a full range of courses covering: research techniques, scientific methods, information technology, communication and interpersonal skills, which are tailored to the needs of each student. For further information on the Ar-Ar and Noble Gas Research Laboratory go to: www.Ar-Ar.co.uk. Please note that this project is fully funded and we would like it to start as soon as possible. If you have any queries about this project please contact Sarah Sherlock (s.sherlock@xxxxxxxxxx). If you would like to apply either send a full CV and the names and addresses of three academic referees in an e-mail to Sarah, or to the following address: Dr Sarah Sherlock, Department of Earth Sciences, The Open University, Milton Keynes, England, MK7 6AA ============================================================== To unsubscribe from the volcano list, send the message: signoff volcano to: listserv@xxxxxxx, or write to: volcano-request@xxxxxxxx To contribute to the volcano list, send your message to: volcano@xxxxxxxx Please do not send attachments. ==============================================================
