Water in cratonic lithosphere: calibrating laboratory-determined models of electrical conductivity of mantle minerals using geophysical and petrological observations

Alan G. Jones*, Javier Fullea, Rob L. Evans, Mark R. Muller

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

62 Citations (Scopus)

Abstract

Measurements of electrical conductivity of "slightly damp" mantle minerals from different laboratories are inconsistent, requiring geophysicists to make choices between them when interpreting their electrical observations. These choices lead to dramatically different conclusions about the amount of water in the mantle, resulting in conflicting conclusions regarding rheological conditions; this impacts on our understanding of mantle convection, among other processes. To attempt to reconcile these differences, we test the laboratory-derived proton conduction models by choosing the simplest petrological scenario possible - cratonic lithosphere - from two locations in southern Africa where we have the most complete knowledge. We compare and contrast the models with field observations of electrical conductivity and of the amount of water in olivine and show that none of the models for proton conduction in olivine proposed by three laboratories are consistent with the field observations. We derive statistically model parameters of the general proton conduction equation that satisfy the observations. The pre-exponent dry proton conduction term (σ0) and the activation enthalpy (ΔHwet) are derived with tight bounds, and are both within the broader 2σ errors of the different laboratory measurements. The two other terms used by the experimentalists, one to describe proton hopping (exponent r on pre-exponent water content Cw) and the other to describe H 2O concentration-dependent activation enthalpy (term αC w1/3 added to the activation energy), are less well defined and further field geophysical and petrological observations are required, especially in regions of higher temperature and higher water content.copy 2012. American Geophysical Union. All Rights Reserved.

Original languageEnglish
Article numberQ06010
Pages (from-to)1-27
Number of pages27
JournalGeochemistry, Geophysics, Geosystems
Volume13
Issue number6
DOIs
Publication statusPublished - 14 Jun 2012
Externally publishedYes

Keywords

  • Kaapvaal craton
  • mantle water
  • Rehoboth terrane

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