Project highlights
- Training & hands-on experience in cutting edge geochemical analysis
- Develop protocols for representative analysis of trace elements in heterogeneous magmatic and metamorphic rocks
- Fieldwork in the Lake District & Scotland
Overview
The chemical compositions of rocks provide key geological information that underpins geochemical modelling, allowing geoscientists to make critical interpretations of metamorphic, magmatic and hydrothermal processes. However, determining the whole rock major and trace element compositions of certain heterogeneous rocks such as migmatites, pegmatites, phenocrystic or enclave-rich igneous rocks or layered metamorphic rocks (Fig.1) is not trivial, both in terms of what to sample, and what these values mean in terms of unravelling the rock formation processes.
The most common traditional analytical strategy is to crush and powder large (>10 kg) samples, and then take a homogenised aliquot for analysis. This approach is labour intensive, requires the removal of large quantities of outcrop (causing conservation issues), and the aliquot may not actually be representative of the part of the rock that was reactive or reacting during the formation of the rock anyway.
The development of secondary electron microscopy (SEM) (1) and electron microprobe (EMP) mapping techniques has provided an effective tool for determining major (rock-forming) element compositions through analysing individual mineral domains or distinct layers and calculating whole rock compositions using software tools such as X-MapTools (2). However, the techniques are not sensitive enough for low abundance trace element analysis, including many economically interesting
elements (such as Li, Cs, Ta, W). This leaves large gaps in our understanding of the behaviour, mobility and transport of such elements during metamorphism, partial melting, melt transport and final crystallisation.
This project will investigate how best to approach determining the trace element compositions of such heterogeneous rocks, focussing on elements that are usually not analysed – either due to sample preparation, contamination, interferences or low abundance – but provide useful information about rock petrogenesis. The ultimate goal is to build a framework of how to best sample, separate and analyse trace elements in complex and challenging rocks and to use this framework to constrain the evolution of some key geological areas.
(1) https://doi.org/10.5194/egusphere-egu2020-14000
(2) https://doi.org/10.1088/1757-899X/891/1/012016
Figure. 1 Heterogeneous rocks may be formed during metamorphism and partial melting, like the migmatite on the left, or by magmatic processes such as assimilation and magma mingling, like the granite on the right
Host
The Open UniversityTheme
- Dynamic Earth
Supervisors
Project investigator
Dr Barbara Kunz, The Open University ([email protected])
Co-investigators
Dr Sam Hammond, The Open University ([email protected])
Prof Clare Warren, The Open University ([email protected])
Dr Tom Argles, The Open University ([email protected])
How to apply
- Each host has a slightly different application process.
Find out how to apply for this studentship. - All applications must include the CENTA application form. Choose your application route
Methodology
The project will be based on samples from well-exposed and well-documented continuous metamorphic sequences such as Barrow Zones (Scotland), Connemara (Ireland) and igneous outcrops such as the classical Shap granite in the Lake District. Different methods for sample preparation, sample digestion and analysis via XRF, dissolution chemistry and LA-ICP-MS trace element mapping will be tested, developed and compared in order to create a best-practice framework.
Training and skills
Students will be awarded CENTA2 Training Credits (CTCs) for participation in CENTA2-provided and ‘free choice’ external training. One CTC equates to 1⁄2 day session and students must accrue 100 CTCs across the three years of their PhD.
In the first year, students will be trained as a single cohort on environmental science, research methods and core skills. Throughout the PhD, training will progress from core skills sets to master classes specific to CENTA research themes
You will receive specific scientific training including safe fieldwork planning, first aid, rock preparation, lab safety training, data collection using a variety of cutting-edge geochemical instruments, and interpretation using a variety of chemical and statistical plotting methods.
The School of Environment, Earth and Ecosystem Sciences has a thriving postgraduate community. Additionally, our students can gain excellent skills in science communication by contributing to outreach activities at local schools, science festivals or to CENTA or OU social media communications. The OU is a centre of excellence for public engagement with research.
Further details
Much of the emphasis of this project is on developing and using cutting edge analytical techniques. We are looking for a diligent and methodical applicant who is interested in developing these skills, and would be happy to spend a large proportion of their project working in the laboratory environment (both chemistry and analytical labs).
You should have a background in geochemistry and petrology. Fieldwork experience is desirable but not a requirement. You will join a well‐established team of Earth scientists studying petrology and geochemistry at the Open University (https://www.open.ac.uk/stem/environment-earth-ecosystem-sciences/research/dynamic-earth; https://www.open.ac.uk/stem/environment-earth-ecosystem-sciences/research/analytical-facilities/earth-science-laboratories)
Please contact Barbara Kunz ([email protected]) for further information.
If you wish to apply to the project, applications should include:
- A CENTA application form, downloadable from: CENTA application
- A CV with the names of at least two referees (preferably three and who can comment on your academic abilities)
- An Open University application form, downloadable from: Home OU application form (if you are resident in the UK) or an Overseas OU application form (if you are an international applicant). Please quote CENTA23_OU7 when completing the application form.
- Please send your completed application to: [email protected]
Applications to be received by the end of the day on Wednesday 11th January 2023.
Possible timeline
Year 1
Induction and literature review; Fieldwork Lake District & Scotland (10 days); Sample preparation; Geochemical method development
Year 2
Continued method development; Data collection & interpretation; Presentation at national conference; Work placement (2 weeks).
Year 3
Finish data collation and interpretation; Preparation of manuscripts for publication; Presentation at an international conference. Writing and submission of thesis.
Further reading
Bea, F., Pereira, M. and Stroh, A., 1994. Mineral/leucosome trace-element partitioning in a peraluminous migmatite (a laser ablation-ICP-MS study). Chemical Geology, 117(1-4), 291-312, doi:10.1016/0009-2541(94)90133-3.
Lanari, P. and Piccoli, F., 2020. New horizons in quantitative compositional mapping–Analytical conditions and data reduction using XMapTools. In: IOP Conference Series: Materials Science and Engineering, 891(1), 012016, doi:10.1088/1757-899X/891/1/012016.
Kunz, B.E.; Warren, C.J.; Jenner, F.E.; Harris, N.B.W.; Argles T.W., 2022. Critical metal enrichment in crustal melts: The role of metamorphic mica. Geology, doi:10.1130/G50284.1
Magaldi, T.T., Navarro, M.S., and Enzweiler, J., 2019. Assessment of Dissolution of Silicate Rock Reference Materials with Ammonium Bifluoride and Nitric Acid in a Microwave Oven. Geostandards and Geoanalytical Research, 43, 189–208, doi:10.1111/ggr.12242.
Woodhead, J.D., Hellstrom, J., Hergt, J.M., Greig, A. and Maas, R., 2007. Isotopic and elemental imaging of geological materials by laser ablation inductively coupled plasma‐mass spectrometry. Geostandards and Geoanalytical Research, 31(4), 331-343, doi:10.1111/j.1751-908X.2007.00104.x.
Zhang, W. and Hu, Z., 2019. Recent advances in sample preparation methods for elemental and isotopic analysis of geological samples. Spectrochimica Acta Part B: Atomic Spectroscopy, 160, 105690, doi:10.1016/j.sab.2019.105690.
COVID-19
Pandemic-related risks to this project are low. The proposed fieldwork is UK and Ireland-based, and there are significant collections of suitable rocks in OU and UK colleague collections if travel becomes restricted again in the future. All the relevant labs at the OU have remote access options for training and data collection should the need arise.