Probing the water content of the Earth's mantle: an experimental study of hydrogen mobility under extreme conditions
dc.contributor.advisor
Bromiley, Geoffrey
en
dc.contributor.advisor
Graham, Colin
en
dc.contributor.advisor
Whaler, Kathy
en
dc.contributor.author
Brooke, Jennifer Christine
en
dc.contributor.sponsor
Natural Environment Research Council (NERC)
en
dc.date.accessioned
2018-03-26T13:12:32Z
dc.date.available
2018-03-26T13:12:32Z
dc.date.issued
2017-07-03
dc.description.abstract
Previous research has established that the majority of nominally anhydrous
minerals (NAMs) in Earth’s mantle can incorporate water in the form of structurally
bound hydrogen and, correspondingly, the mantle is thought to contain a substantial
volume of water. Water has been shown to play a key role in the geodynamics of the
Earth’s interior and quantifying the amount, and distribution, of water in the mantle is
an important step in understanding many deep-Earth processes. One of the parameters
highly sensitive to the incorporation of water in the mantle is electrical conductivity, as
hydrogen is highly mobile and acts as the dominant charge-carrying species. In theory,
this relationship can be used in conjunction with geophysical techniques that measure
mantle-scale electrical conductivity to ‘map-out’ the deep Earth’s water content – but
accurate interpretation of such data requires full understanding of hydrogen mobility
in NAMs under extreme conditions, which remains poorly constrained.
The aim of this project is to contribute to the reconciliation of geophysical
observations with laboratory measurements of electrical conductivity, by considering
hydrogen-deuterium exchange in single crystals. In a novel experimental design,
hydrogen in crystals synthesised under mantle conditions (such that the hydrogen
defects present correspond to the conditions being studied) exchanges with deuterium
from a liquid source under controlled (mantle) pressure and temperature conditions for
a specified time period. This results in hydrogen-deuterium exchange profiles that can
be characterised by SIMS and subsequently fitted to Fick’s law to calculate hydrogen
diffusion coefficients – which in turn can be related to electrical conductivity through
the Nernst-Einstein equation.
Analysis of the experimental results underlines the complexity of the influence
of hydrogen on electrical conductivity in NAMs, and emphasises the need for
careful consideration when interpreting and applying the results of diffusion studies.
Ultimately, the data obtained in this study provides a useful contribution to
understanding hydrogen diffusion in mantle minerals, but the non-trivial nature of both
the experimental and analytical aspects mean that the method cannot easily be applied
to other mantle phases.
en
dc.identifier.uri
http://hdl.handle.net/1842/28994
dc.language.iso
en
dc.publisher
The University of Edinburgh
en
dc.relation.haspart
The University of Edinburgh. College of Science and Engineering
en
dc.subject
mantle
en
dc.subject
water
en
dc.subject
deuterium
en
dc.subject
hydrogen
en
dc.subject
mineral conductivity
en
dc.subject
electrical conductivity
en
dc.subject
hydrogen-deuterium exchange
en
dc.title
Probing the water content of the Earth's mantle: an experimental study of hydrogen mobility under extreme conditions
en
dc.type
Thesis or Dissertation
en
dc.type.qualificationlevel
Doctoral
en
dc.type.qualificationname
PhD Doctor of Philosophy
en
Files
Original bundle
1 - 1 of 1
- Name:
- Brooke2017.pdf
- Size:
- 165.79 MB
- Format:
- Adobe Portable Document Format
This item appears in the following Collection(s)