Skip to Main content Skip to Navigation
New interface
Journal articles

Multistage growth of Fe-Mg-carpholite and Fe-Mg-chloritoid, from field evidence to thermodynamic modelling

Abstract : We provide new insights into the prograde evolution of H P/L T metasedimentary rocks on the basis of detailed petrologic examination, element-partitioning analysis, and thermodynamic modelling of well-preserved Fe-Mg-carpholite- and Fe-Mg-chloritoid-bearing rocks from the Afyon Zone (Anatolia). We document continuous and discontinuous compositional (ferromagnesian substitution) zoning of carpholite (overall X Mg = 0.27-0.73) and chloritoid (overall X Mg = 0.07-0.30), as well as clear equilibrium and disequilibrium (i.e., reaction-related) textures involving carpholite and chloritoid, which consistently account for the consistent enrichment in Mg of both minerals through time, and the progressive replacement of carpholite by chloritoid. Mg/Fe distribution coefficients calculated between carpholite and chloritoid vary widely within samples (2.2-20.0). Among this range, only values of 7-11 correlate with equilibrium textures, in agreement with data from the literature. Equilibrium phase diagrams for metapelitic compositions are calculated using a newly modified thermodynamic dataset, including most recent data for carpholite, chloritoid, chlorite, and white mica, as well as further refinements for Fe-carpholite, and both chloritoid end-members, as required to reproduce accurately petrologic observations (phase relations, experimental constraints, Mg/Fe partitioning). Modelling reveals that Mg/Fe partitioning between carpholite and chloritoid is greatly sensitive to temperature and calls for a future evaluation of possible use as a thermometer. In addition, calculations show significant effective bulk composition changes during prograde metamorphism due to the fractionation of chloritoid formed at the expense of carpholite. We retrieve P- T conditions for several carpholite and chloritoid growth stages (1) during prograde stages using unfractionated, bulk-rock XRF analyses, and (2) at peak conditions using compositions fractionated for chloritoid. The P- T paths reconstructed for the Kütahya and Afyon areas shed light on contrasting temperature conditions for these areas during prograde and peak stages.
Document type :
Journal articles
Complete list of metadata

https://hal-insu.archives-ouvertes.fr/insu-03641620
Contributor : Nathalie POTHIER Connect in order to contact the contributor
Submitted on : Thursday, April 14, 2022 - 1:53:00 PM
Last modification on : Saturday, April 16, 2022 - 3:39:33 AM

Identifiers

Citation

Amaury Pourteau, Romain Bousquet, Olivier Vidal, Alexis Plunder, Erik Duesterhoeft, et al.. Multistage growth of Fe-Mg-carpholite and Fe-Mg-chloritoid, from field evidence to thermodynamic modelling. Contributions to Mineralogy and Petrology, 2014, 168, ⟨10.1007/s00410-014-1090-7⟩. ⟨insu-03641620⟩

Share

Metrics

Record views

10