Skip Navigation



Journal of Petrology Advance Access published online on October 12, 2009
Journal of Petrology, doi:10.1093/petrology/egp068
This Article
Right arrow Full Text
Right arrow Full Text (PDF)
Right arrow Supplementary Data
Right arrow All Versions of this Article:
50/11/2043    most recent
egp068v1
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Alert me to new issues of the journal
Right arrow Add to My Personal Archive
Right arrow Download to citation manager
Right arrowRequest Permissions
Google Scholar
Right arrow Articles by Konzett, J.
Right arrow Articles by Frost, D. J.
Social Bookmarking
Add to CiteULike   Add to Connotea   Add to Del.icio.us  
What's this?

© The Author 2009. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oxfordjournals.org

The High P–T Stability of Hydroxyl-apatite in Natural and Simplified MORB—an Experimental Study to 15 GPa with Implications for Transport and Storage of Phosphorus and Halogens in Subduction Zones

Jürgen Konzett1,* and Daniel J. Frost2

1Institut Für MINERALOGIE Und Petrographie, Universität Innsbruck, Innrain 52, A-6020 Innsbruck, Austria
2Bayerisches Geoinstitut, Universität Bayreuth, D-95440 Bayreuth, Germany

Received October 16, 2008; Revised typescript accepted September 15, 2009


  Abstract

Experiments have been conducted in the range 3–15 GPa and 850–1800°C to investigate the P–T stability field of OH-apatite in an average mid-ocean ridge basalt (MORB) and a model Mg-basalt, to study the compositional evolution of apatite and its breakdown products and the partitioning of P between phosphates and silicates. In the bulk compositions investigated OH-apatite is stable to <7·5 GPa at 950°C in a typical eclogite assemblage garnet + omphacite + SiO2 + TiO2. This is ~5 GPa below the breakdown P of pure OH-apatite. The high-P breakdown product is tuite [{gamma}-Ca3(PO4)2]. Both apatite and tuite are stable in a wide range of subduction zone T regimes but not along an average mantle adiabat. This precludes apatite or tuite stability in the asthenospheric mantle. Apatite may be stable in cold continental lithosphere (40 mW/m2) but is restricted to P < ~4–5 GPa. The apatite breakdown reaction is an important limit for the crust–mantle transport of Cl in subduction zones and can contribute to the Cl depletion of subducted cust. Both apatite and tuite are important storage sites for large ion lithophile elements (LILE) and rare earth elements (REE), therefore apatite breakdown does not greatly affect LILE or REE transport in subduction zones. In an eclogite assemblage only garnet can accommodate significant P. In the presence of apatite or tuite, P2O5 contents in garnet range from ~0·2 to 0·6 wt % between 3 and 11 GPa and increase to ~0·8 wt % at 15 GPa in the absence of a detectable phosphate phase. The P-storage capacity of clinopyroxene is limited to ~250 ppm. Because of the extreme preference of P for the garnet structure, virtually the entire P budget of subducted MORB will be locked up in garnet well into the lower mantle provided fO2 is high enough to prevent the stability of a metal phase.

KEY WORDS: apatite; MORB; tuite; phosphorus; high P–T stability

*Corresponding author. Telephone: +43-(0)512-507-5506. Fax: +43-(0)512-507-2926. E-mail: juergen.konzett{at}uibk.ac.at


Add to CiteULike CiteULike   Add to Connotea Connotea   Add to Del.icio.us Del.icio.us    What's this?




Disclaimer: Please note that abstracts for content published before 1996 were created through digital scanning and may therefore not exactly replicate the text of the original print issues. All efforts have been made to ensure accuracy, but the Publisher will not be held responsible for any remaining inaccuracies. If you require any further clarification, please contact our Customer Services Department.