TY  - JOUR
A1  - Pourteau, Amaury
A1  - Bousquet, Romain
A1  - Vidal, Olivier
A1  - Plunder, Alexis
A1  - Duesterhoeft, Erik
A1  - Candan, Osman
A1  - Oberhänsli, Roland
T1  - Multistage growth of Fe-Mg-carpholite and Fe-Mg-chloritoid, from field evidence to thermodynamic modelling
JF  - Contributions to mineralogy and petrology
N2  - We provide new insights into the prograde evolution of HP/LT 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 Kutahya and Afyon areas shed light on contrasting temperature conditions for these areas during prograde and peak stages.
KW  - HP/LT metamorphism
KW  - Carpholite
KW  - Chloritoid
KW  - Growth zoning
KW  - Element partitioning
KW  - Chemical fractionation
Y1  - 2014
U6  - https://doi.org/10.1007/s00410-014-1090-7
SN  - 0010-7999
SN  - 1432-0967
VL  - 168
IS  - 6
PB  - Springer
CY  - New York
ER  -