PROJECT BACKGROUND:
Magma compositions at subduction zones control eruptive behaviour and provide critical insight into global geochemical cycles. However, erupted subduction zone magmas represent the integrated result of both source heterogeneity and an array of processes operating throughout the sub-arc crust, such as differentiation, mixing, homogenisation and assimilation. Disentangling these different controls and their relative importance has proven challenging. This is because traditional methods of targeting lava compositions only provide the end result of complex compositional pathways. This project will use a new approach of targeting plutonic xenoliths which represent different parts of the whole trans-crustal plumbing system – crystal mush, cumulate residues, crystallised portions of melt-dominated bodies or older igneous rock. Therefore, allowing processes from the deep to shallow crust to be traced.
Preliminary CSI work from the Lesser Antilles revealed that assimilation largely occurs in the shallow crust, highlighting the significance of incorporating the deeper plutonic record in subduction zone studies (Brown et al, 2021). In addition, whole-rock Fe and Sr-Pb isotope data (Cooper and Inglis, 2022) and melt inclusions (Cooper et al., 2016) from plutonic xenoliths display a surprisingly large degree of chemical variability suggesting that the complexity of subduction zone plumbing systems has been missed by focussing on lavas in isolation.
PROJECT AIMS AND METHODS:
This project aims to develop a new crystal scale isotope (CSI) approach targeting paired plutonic (xenoliths) and volcanic samples from the Lesser Antilles volcanic arc to determine:
• The extent and depths at which crustal and/or sediment assimilation occurs within the crust to establish the true contribution of the overriding crust to magmatic evolution.
• The true compositional and isotopic heterogeneity of melts generated by the sub-arc mantle source.
These objectives will be achieved by using a novel combination of petrology and crystal scale isotope analyses (such as Sr, Nd and Pb) of paired plutonic and volcanic samples from the Lesser Antilles volcanic arc. These data will be the first crystal scale Pb isotope measurements from a subduction zone and will allow for a systematic re-evaluation of geochemical and isotopic cycling in subduction zones and a rigorous reconstruction of the compositional pathways of magmas from source to surface in the Lesser Antilles.
CANDIDATE REQUIREMENTS:
This project would suit a student with a degree in Earth Sciences, Chemistry (or a related field) and strong interests in igneous processes, petrology, trace element and isotope geochemistry.
Excellent time management skills coupled with strong numerical, verbal, and written communication are important. Previous analytical experience would be an advantage but is not essential.
TRAINING:
Training will cover a wide range of petrological and geochemical methods, including: i) SEM mapping ii) Laser ablation ICP-MS ii) Ultra-clean laboratory sample processing methods and iv) Thermal Ionisation Mass Spectrometry (TIMS).
The student will attend national and international conferences, networking events and outreach activities, developing an important network for feedback and future employment. This project will also include fieldwork to the Lesser Antilles including a visit to the Seismic Research Centre, Trinidad to discuss research with local scientists.
The student will have access to the full suite of training and developments offered to Cardiff postgraduate students by the Cardiff Doctoral Academy as well as the expert support of the supervisory team and laboratory support staff within the School of Earth and Environmental Sciences.
ENTRY REQUIREMENTS:
Graduates in appropriate science subject such as Geology or Environmental Science, with at least a First Class or 2:1 Honours degree, or a master's.
English language requirements
IELTS with an overall score of 6.5 with 5.5 in all subskills, or equivalent. Please see our English Language Requirements guidance for more details. See our English language requirements for further information.
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 or Part Time
- 1st October 2023 (or relevant start date)
- Click on ‘Apply now’
Please ensure that you include the ‘Project Title’ you are applying for and supervisor, and that you add ‘source of funding’ under source of funding.
The application deadline is 10/04/2023.
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