An internally consistent pressure calibration of geobarometers applicable to the Earth's upper mantle using in situ XRD

Christopher Beyer*, Anja Rosenthal, Robert Myhill, Wilson A. Crichton, Tony Yu, Yanbin Wang, Daniel Frost

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

3 Citations (Scopus)
146 Downloads (Pure)

Abstract

We have performed an experimental cross calibration of a suite of mineral equilibria within mantle rock bulk compositions that are commonly used in geobarometry to determine the equilibration depths of upper mantle assemblages. Multiple barometers were compared simultaneously in experimental runs, where the pressure was determined using in-situ measurements of the unit cell volumes of MgO, NaCl, Re and h-BN between 3.6 and 10.4 GPa, and 1250 and 1500 °C. The experiments were performed in a large volume press (LVPs) in combination with synchrotron X-ray diffraction. Noble metal capsules drilled with multiple sample chambers were loaded with a range of bulk compositions representative of peridotite, eclogite and pyroxenite lithologies. By this approach, we simultaneously calibrated the geobarometers applicable to different mantle lithologies under identical and well determined pressure and temperature conditions. We identified discrepancies between the calculated and experimental pressures for which we propose simple linear or constant correction factors to some of the previously published barometric equations. As a result, we establish internally-consistent cross-calibrations for a number of garnet-orthopyroxene, garnet-clinopyroxene, Ca-Tschermaks-in-clinopyroxene and majorite geobarometers.

Original languageEnglish
Pages (from-to)421-435
Number of pages15
JournalGeochimica et Cosmochimica Acta
Volume222
Early online date1 Nov 2017
DOIs
Publication statusPublished - 1 Feb 2018

Keywords

  • Calibration
  • Eclogite
  • Geobarometry
  • Mantle
  • Multi-anvil
  • Peridotite
  • Synchrotron

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