Tschermak's substitution in antigorite and consequences for phase relations and water liberation in high-grade serpentinites

Jose Alberto Padron-Navarta*, Vicente Lopez Sanchez-Vizcaino, Joerg Hermann, James A. D. Connolly, Carlos J. Garrido, Maria Teresa Gomez-Pugnaire, Claudio Marchesi

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

96 Citations (Scopus)

Abstract

A model for the incorporation of alumina in FeO-MgO-Al2O3-SiO2-H2O (FMASH) serpentinites has been developed by considering ideal Tschermak (Al2Mg-1Si-1) solid solution in antigorite. The antigorite model has been calibrated by fitting the experimental conditions for the decomposition of antigorite to chlorite + olivine + orthopyroxene + fluid in the FMASH system. The antigorite Al-contents predicted with this model are in agreement with natural observations and suggest a maximum alumina solubility in antigorite of 3.6 wt.% Al2O3 at 20 kbar-650 degrees C and of 4.5 wt.% Al2O3 at 3 kbar-560 degrees C. In the assemblage antigorite-olivine-chlorite-fluid, the Al-content of antigorite is buffered and temperature sensitive. This temperature sensitivity is the basis for a serpentinite geothermometer at greenschist, amphibolite and eclogite fades conditions. The buffered assemblage is stable in harzburgite compositions for relatively moderate amounts of Al2O3 (>1.8 wt.%) and is widespread in lherzolites, where it occurs together with diopside or, in a narrow temperature field, with tremolite. (C) 2013 Elsevier B.V. All rights reserved.

Original languageEnglish
Pages (from-to)186-196
Number of pages11
JournalLithos
Volume178
DOIs
Publication statusPublished - 15 Sep 2013
Externally publishedYes

Keywords

  • Antigorite
  • Tschermak's exchange
  • Geothermobarometry
  • Serpentinite
  • Dehydration
  • Subduction zones
  • HIGH-PRESSURE SERPENTINITES
  • SYSTEM MGO-SIO2-H2O MSH
  • CERRO DEL ALMIREZ
  • WESTERN ALPS
  • PROGRESSIVE METAMORPHISM
  • CHLORITE HARZBURGITE
  • TITANIAN CLINOHUMITE
  • ULTRAMAFIC COMPLEX
  • SUBDUCTION ZONES
  • EASTERN DESERT

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