Project background
Mantle plumes are one of the most spectacular geological features on Earth. They form from the buoyant rise, and subsequent melting, of deep-seated mantle components. Compositionally, they carry the signatures of the plate recycling process; hence, their study provides significant insights into the long-term geodynamic evolution of the Earth. Radiogenic isotope (e.g., Sr-Nd-Pb) analyses of ocean island lavas have been the traditional way of assessing plume compositions, and have revealed a wealth of information on the origin of mantle plumes and the nature of the underlying mantle (e.g., Hofmann, 1997; White, 2010). However, lavas are mixed in crustal magma reservoirs prior to eruption, and hence do not record the full isotopic composition of their mantle source. Recent work from our group in Cardiff, aimed at mid-ocean ridges, has demonstrated that plutonic rocks, crystallised upon initial emplacement of mantle melts into the crust, provide a way to get around this problem, and reveal the true extent of mantle heterogeneity (Lambart et al., Nature Geoscience, 2019). This project will apply this approach to mantle plumes.
Project aims and methods
This project will make mineral-scale isotopic measurements on plutonic xenoliths preserved in erupted plume-derived basalts from Hawaii and the Canaries, with the objective of establishing the true heterogeneity of the mantle plume source. This will be achieved by detailed petrological-geochemical studies of the plutonic xenoliths. First, full-sample element maps will be produced in Cardiff’s state-of-the-art Electron Microbeam Facility. This approach, which is being pioneered at Cardiff, will reveal the different compositional domains that minerals in plutonic rocks frequently preserve. Combined with mineral trace element measurements (to be measured on the newly installed qqq ICP-MS at Cardiff), this will enable isotopic analyses to be targeted to span the full compositional range preserved in the plutonic rocks (Lambart et al., 2019). Isotopic analyses will be done at the CELTIC labs at Cardiff (MC ICP-MS) and at Bristol (TIMS). The coupled trace element-isotopic dataset thus obtained will place new constraints on the heterogeneity of the Hawaii and Canaries mantle source, and inform on the long-term evolution of the solid Earth and the origin of deep-mantle superstructures such as large low-shear-velocity provinces (LLSVPs; e.g., Weis et al., 2011).
Candidate requirements
This project would appeal to students interested in using geochemistry to improve understanding of the large-scale evolution of the Earth. An interest in igneous processes and an affinity for geochemical analytical techniques would be required.
Project partners
Highlight the exciting research collaborations, resources and student opportunities provided by the GW4+ Research Organisations, GW4 Universities, CASE partners and Collaborative Partners on the project
Training
The student will receive an extensive training programme in petrology and geochemistry. This comprises a wide range of techniques, with a particular focus on in-situ mineral analysis. Field sampling in the Canary Islands and/or Azores will be a key component of the project. In addition to project-specific training and the DTP training courses, the student will have access to the large range of Cardiff University Student Development courses, to maximise transferable skills. The student is also expected to present project results to national and international conferences. Finally, the student will have the opportunity to demonstrate both in the classroom and in the field. Combined, the training package of the project will give the student an excellent basis for a career in academia or industry.
Entry requirements
In order to be accepted you would need to have a first-class BSc degree or a second-class degree plus an MSc or good MSci. However, for international students, you would need to have a relevant degree in the subject area and have evidence of an English Language qualification. Further information on the English Language can be found here: https://www.cardiff.ac.uk/study/international/english-language-requirements/postgraduate
How to apply
In order to formally apply for the PhD you will need to go to the following web page: https://www.cardiff.ac.uk/study/postgraduate/research/programmes/programme/earth-sciences
In the black box on the right of the page please select the following options:
·Doctor of Philosophy
·Full Time
·1st October 2022
Click on ‘Apply now’.
Please ensure that you include the ‘Project Title’ you are applying for and supervisor and that you add ‘NERC DTP’ under the source of funding.
The application deadline is Monday 10 January 2022 at 2359 GMT. Interviews will take place from 23rd February to 9th March 2022. For more information about the NERC GW4+ Doctoral Training Partnership please visit https://www.nercgw4plus.ac.uk.
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