Overview

Project Highlights:

  • Training in advanced geochemical techniques
  • Work with an internationally-renowned team at the cutting edge of the new field of petrochronology
  • Fieldwork in metamorphic terranes

Precise and accurate geological ages underpin the entire field of Earth Sciences: defining not only precisely when an event in the geological past happened, but also the rate at which a process operated and the timescales over which different events took place.

Geological time is recorded in minerals that incorporate radioactive elements, such as zircon, monazite, rutile and titanite. The latter three are particularly important for determining metamorphic rates and timescales as they are chemically and physically robust, common across a wide range of rock types and at different metamorphic grades, and are resistant to re-setting. However the reactions responsible for their crystallisation are not well known. Despite being able to date these minerals to increasingly high precision and accuracy, their ages are of limited use if we can’t link them to the pressure-temperature conditions at which they grew with similar accuracy and precision.
This project aims to:

  1. develop new trace element fingerprinting methods to link the growth of the accessory phases to the growth of the main rock-forming minerals,
  2. explore the main controls on trace element partitioning behaviour, for example pressure, temperature and bulk rock composition.

The research findings expected from this project will have important implications for understanding how trace elements move between, and concentrate into, different minerals during metamorphic evolution. As well as helping us improve our determination of the rates and timescales of tectonic processes, the findings from this project are likely to be of interest and use to organisations investigating new sources of rare elements of critical interest.

Y zoning in monazite, major and trace element zoning in garnet and cryptic crystallisation zoning in zircon provide clues about equilibrium.

Methodology

A variety of accessory-phase-bearing rocks from different tectonic settings will be analysed initially, to gain an overview of the broad controls on trace element concentration and partitioning. These samples are immediately available in the Open University collections. Once specific tectonic or metamorphic settings of interest have been identified, there will be opportunities for fieldwork to collect further samples as needed.
Major element concentrations of mineral phases will be determined on the Open University electron microprobe. Trace element concentrations will be acquired by in-situ laser ablation mass spectrometry also at the OU. U-Th-Pb isotope data (for determining ages of accessory phases) will be acquired at the NERC Isotope Geoscience Laboratories (NIGL) at the British Geological Survey, Keyworth.

Training and Skills

CENTA students are required to complete 45 days training throughout their PhD including a 10 day placement. 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. 

Specific training in metamorphic petrology, thermodynamic modelling, analytical techniques and date reduction methods will be provided at the Open University and via external courses.  In addition to scientific skills, the student will be trained in a variety of transferrable skills including public speaking, writing for a variety of audiences and dealing with large and incomplete datasets.

The School of Environment, Earth and Ecosystem Sciences has a thriving postgraduate community, where online teaching opportunities via the Open University Virtual Learning Environment are available, including teaching on the new Massive Open Online Courses (MOOCs).

Timeline

Year 1: Petrographic analysis of available samples. Initial major and trace element analyses. Preliminary pressure-temperature (pseudosection) modelling. Attendance at the Metamorphic Studies group annual research in progress meeting. Fieldwork to collect samples as required. Write a proposal for funding from NIGL to carry out U-Pb analyses.

Year 2: Processing and selection of collected samples as necessary for further specific and in-depth analyses of samples, with the aim of completing the bulk of the analytical work during this year. Trace element partition modelling and thermodynamic modelling of PT conditions. Preparation of first manuscript for publication.

Year 3: Attendance at an international conference. Completion of data collection and synthesis. Preparation/revision of further paper manuscripts and thesis writing.

Partners and collaboration (including CASE)

Nick Roberts (BGS) is a collaborator on this project and will be involved with any U-Th-Pb geochronology data collection at NIGL.

Further Details

Students should have a strong background in metamorphic geology or mineral geochemistry and enthusiasm for petrography and detailed lab work. Experience of working in a geochemical lab or evidence of careful and detailed work in another similar setting is highly desirable. The student will join a well-established Dynamic Earth team researching tectonic processes at the Open University.

Please contact Clare Warren, clare.warren@open.ac.uk for further information.

Applications should include:

Apologies that some bits of information are requested multiple times on different forms. Please fill in everything requested.

Applications should be sent to

STEM-EEES-PhD-Student-Recruitment@open.ac.uk  

by 5 pm on 25th January 2017