Overview

Project Highlights:

  • Training in, and becoming an independent user of, analytical methods (optical microscopy, electron microprobe, noble gas mass spectrometry)
  • Training in thermochemical and hydrocode modeling to become an independent modeler
  • Understanding processes on the Early Earth at a time life first emerged – with potential applications to other celestial bodies

Manicouagan Crater is one of the largest impact craters on Earth (diameter of ~ 100 km) and is well-exposed, non-metamorphosed and nearly pristine. Large hypervelocity impacts cause a visible crater in the Earth’s crust and also deposit a lot of heat into the target.  It is this heat energy that may also have provided new habitats for microbial life on Earth, especially in its very early history. Unfortunately, plate tectonics and other geologic processes have erased these early potential habitats and so our knowledge of them is derived from models that have little ground truth. This project will investigate one of the largest terrestrial impact craters that was not eradicated by plate tectonic processes, and will quantify the following key processes: (1) the dissipation of heat and the duration of the cooling, derived from the hypervelocity impact (2) the generation of a hydrothermal system, with heat from the impact and ground- and surface-waters in the immediate environment and (3) the mobility of elements within the shattered rocks. Among the population of preserved impact structures on Earth, Manicouagan provides a well studied and accessible site. Most importantly for this project, exploration work has provided ~18 km of drill core from 38 separate holes, the deepest of which reaches a depth of 1.8 km (see Spray et al. 2010; Fig. 1). The extensive drill core collection and the surface sample suite available to this project through collaborator Spray, who has been the leading expert at Manicouagan for decades, will ensure comprehensive sampling for the thermal work and extensive coverage of the hydrothermal systems.  This crater will allow the temperature evolution and water availability in a terrestrial crater to be determined, thus allowing the significance of impact craters to life on the early Earth to be determined.

In order to test the hypothesis that early life was sustained and shielded beneath and within large impact craters, the successful candidate will investigate the time/temperature, volatile, fluid flow and associated bio-geo-chemical history of Manicouagan impact crater to assess the effects of such cratering events on the habitability of the Early Earth’s surface.

Drill core locations on the central island of Manicouagan crater, i.e., into its central uplift (from Spray et al. 2010) and beyond to the radial limit of melt sheet. Coring penetrated the impact melt into the underlying host rocks, making them especially valuable for this study.

Methodology

  1. Optical microscopy and electron microprobe analysis will be used to study mineralogy and geochemistry of the alteration in the different crater settings and to understand the alteration mineralogy.
  2. Noble gas mass spectrometry will be used to measure Ar-Ar- ages of minerals from detailed profiles below the Manicouagan crater floor along traverses from the melt/impactite sequences into the country rock, to learn about its cooling history.
  3. Thermochemical modeling will be used to add the information that cannot be measured, e.g., fluid temperature and chemistry, and numerical modeling will be used to understand the distribution of impact heating and the subsequent cooling timescale.
  4. The new data and heating models will be used to test and refine existing hydrothermal models and to quantify the concentrations of elements acting as nutrients in the hydrothermal fluid and the environmental conditions for microbial life.

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. 

The student will be trained in optical microscopy, electron microprobe and noble gas mass spectrometry, to the level of independent user. In addition, field work will provide planning and sampling skills. With the international nature of the project, team work and collaboration is an essential aspect of the work. Special emphasis will be on the oral and written communications skills, ranging from e-mail and phone negotiations, e.g., in the planning of the core sampling, to conference presentations, report writing and publication in peer reviewed papers.

Timeline

Year 1: Oct to March: Literature work, familiarizing with mineralogy, petrology, geochemistry of the Manicouagan site, familiarizing with cooling and thermochemical modelling, and initial models based on estimated temperature values and rock composi-tions from the literature, preparation of the core sampling trip; March-July: core sampling trip, samp-ling of cores, sample preparation; petrologic charac-terization. July to October: Project report writing, summarizing petrological data in writing, preparation for Ar-analytics and more detailed geochemical work.

Year 2: Detailed petrological and geochemical work and Ar-Ar analysis, understanding the cooling history from data obtained from the rock samples studied. Prepare a conference presentation and publication.

Year 3: Thermochemical modelling to find out about fluid conditions upon formation of the minerals formed and using the thermal history deduced from the samples and models. Prepare a second conference presentation and initial publication. Write up and submit thesis.

Partners and collaboration (including CASE)

This project will be in collaboration with two project partners: Dr. Gareth Collins at Imperial College, London and an expert in impact cratering processes. Prof. John Spray, who is Director of the Planetary and Space Science Centre and High-speed Impact Research and Technology Facility at New Brunswick University. 

Further Details

Students should have a strong background in Earth sciences and enthusiasm for laboratory work and data analysis. Experience of thermochemical modeling is desirable. The student will join a well-established team researching into fluid rock interaction on Earth and Mars and working within the world leading Ar-laboratory at the Open University. Please contact Dr. Susanne P. Schwenzer for further information (susanne.schwenzer@open.ac.uk).

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