Overview

Rocks of basaltic composition dominate the Earth’s oceanic crust, they dominated the Early Earth’s surface and they are ubiquitous on Mars and even Venus. This PhD project will investigate a focused problem of basaltic magma–sediment–water interaction on Earth and extrapolate the findings to the Early Earth and potentially other planetary environments.

This project is designed to investigate a focused aspect of water–magma–sediment interaction: what are the effects of magma intrusion into sulfate bearing soils? For this, the NASA funded consortium team (see ‘Partners’ below) will carry out fieldwork at the San Rafael Swell on the Colorado Plateau, where we have previously identified the interaction of magmatic intrusions with such sulfate veins1. The overall project will thereby cover all aspects of mineralogy and petrology, reaction pathways of magma-water-sediment interaction and the effect on the habitability of the site. The main hypothesis that the consortium study will be testing is that the subsurface was a habitable environment that would have contained both the water and the energy necessary to support microbial life, and that the introduction of magma might have briefly sterilized metamorphic aureoles, but the introduction of fluids would have stimulated habitability by introducing new nutrient and energy sources. The OU team thereby focuses on two aspects: 1) thermochemical modelling of the reaction pathways between the original host rock and the resulting alteration phases, and 2) assessing the habitability potential of the resulting environments. The successful candidate will be able to take part in the consortium fieldwork and assist with the in-situ investigations.

The main task of the PhD will focus on thermochemical modelling of the reaction pathways at the San Rafael Swell. This work will be based on expertise gained from previous modelling of Ca-sulfate transport in martian environments2,3, but will be unique in the accuracy achievable when working with detailed ground truth data. The results from the modelling will be the basis of the habitability assessment of this planetary analogue, which can - depending on the interests of the student - include testing of the modelled conditions through microbiological experiments.

Image of one outcrop of the field site. Consortium member Crandall for scale. This image is taken from the work by Crandall et al. (2017)

Methodology

Field work, including the use of in-situ instrumentation will be carried out.

Optical microscopy and electron microprobe analysis will be used to study mineralogy and alteration at the site. Electron beam instruments (SEM; Electron Microprobe) will be used to investigate the geochemistry of selected samples.

Thermochemical modelling, using industry standard and research software (Geochemist workbench, CHIM-XPT), will be employed to model reaction pathways, element mobility and secondary mineral precipitation using data collated from the entire consortium as ground truth. This will be the main focus of the PhD project.

Depending on their interests, the student could be trained in microbiological culturing techniques, which could be used to test the newly modelled environments for potential habitability.

Training and Skills

Specifically to this project, the student will be trained in optical microscopy and electron beam instrumentation, but the main skills developed will be in thermochemical modelling. Further, field work will require the development of skills in field methods, including field descriptions and note taking, field analyses, logistics, and sampling strategies. The student may also choose to take advantage of optional training in microbiological techniques. With the international nature of the project, team work and collaboration will be essential aspects of the work. Special emphasis will be on oral and written communications skills, ranging from e-mail and phone negotiations, e.g., in the planning of the field work, conference presentations, report writing and publications in peer reviewed journals.

Timeline

Year 1: Oct to March: Literature work, familiarizing with mineralogy, petrology, geochemistry of the Utah site, familiarizing with thermochemical modelling, and initial models based on estimated temperature values and rock compositions from the literature, preparation of the field trip; March-July: Field trip, orientation to the site, sampling in the framework of the field trips of the consortium. Initial petrological characterisation. July to October: Project report writing, summarizing field and petrological data in preparation for the thesis, and more detailed geochemical work.

Year 2: Detailed modelling of the Utah reaction pathways and potentially microbiological culturing. Depending on the student’s interest the focus of this PhD can be on either modelling or microbiology, with members of the consortium focusing on the other aspect. Prepare a conference presentation.

Year 3: Thermochemical modelling to transfer the results from Utah to Early Earth and potentially other planetary surface’s conditions. Prepare a second conference presentation and initial publication. Write up and submit thesis.

Partners and collaboration (including CASE)

This PhD is embedded in a NASA PSTAR funded international consortium study between the Lunar and Planetary Institute in Houston, USA (project lead), Southern Illinois University in Carbondale, USA, Jet Propulsion Laboratory, USA, Space Research Centre at University of Leicester, UK, and the Open University, which investigates sulfate veins and their habitability on Mars and Earth.

Further Details

Students should have a strong background in Earth sciences or biology and enthusiasm for data analysis and thermochemical modelling (alternatively microbiological work). Experience of thermochemical modeling or microbiological culturing is desirable. The student will join a well-established team researching into fluid rock interaction on Earth and Mars and will be working within an international consortium. Please contact Dr. Susanne P. Schwenzer (susanne.schwenzer@open.ac.uk) for further information.

 

Applications must include: