TY - JOUR

T1 - Phase relations of a F-enriched peraluminous granite

T2 - An experimental study of the Kymi topaz granite stock, southern Finland

AU - Lukkari, Sari

AU - Holtz, Francois

N1 - Funding Information: Acknowledgments We are grateful to Ilmari Haapala for initiating this project and for his experienced views during the research. We thank O. Dietrich for preparing the thin sections, M. Hahn and J. Koepke for instructions in operating the electron microprobe. Tapani Rämö and Arto Luttinen are greatly appreciated for their comments and suggestions of an earlier version of the manuscript. Constructive and valuable reviews by Bruno Scaillet and an anonymous reviewer are gratefully acknowledged. This study was funded by the University’s Research Funds (project 2105005), by Academy of Finland (bilateral project with DAAD, project 164931), by Foundation for Research of Natural Resources in Finland (projects: 1599/01 and 1628/02) and by the German Research Foundation (DFG 436 TSE 113/48/0-1). Copyright: Copyright 2009 Elsevier B.V., All rights reserved.

PY - 2006/11/17

Y1 - 2006/11/17

N2 - Phase relations of F-rich Kymi equigranular topaz granite have been investigated experimentally at 100-500 MPa as a function of water activity and F content. Fluorite and topaz can crystallize as liquidus phases in F-rich peraluminous systems, but the F content of the melt should exceed 2.5-3.0 wt% for the crystallization of topaz. In peraluminous F-bearing melts containing more than 1 wt% F, topaz and muscovite are expected to be the first F-bearing phases to crystallize at high pressure, whereas fluorite and topaz should crystallize first at low pressure. Following reaction models the saturation of fluorite and topaz: CaAl2Si2O8 (plagioclase) + 2[AlF3]melt = CaF2 (fluorite) + 2Al2SiO4F2 (topaz). The obtained partition coefficient for F between biotite and glass D(F)Bt/glass ranges from 1.89 to 0.80 (average value 1.29) and can be used as an empirical fluormeter to determine the F content of coexisting melts. Combined petrological and experimental studies of the Kymi equigranular topaz granite indicate that plagioclase was the liquidus phase at nearly water-saturated (fluid-saturated) conditions and that the F content of the melt was at least 2 wt%. The mean F content of natural biotite (3.92 wt%) suggests that the late-stage crystallization of biotite occurred in melts containing about 3 wt% F. The early crystallization of biotite and the presence of muscovite in our experiments at 200 MPa contrasts with the late-stage crystallization of biotite and the absence of muscovite in the natural assemblage, indicating that crystallization pressure may have been lower than 200 MPa for the granite.

AB - Phase relations of F-rich Kymi equigranular topaz granite have been investigated experimentally at 100-500 MPa as a function of water activity and F content. Fluorite and topaz can crystallize as liquidus phases in F-rich peraluminous systems, but the F content of the melt should exceed 2.5-3.0 wt% for the crystallization of topaz. In peraluminous F-bearing melts containing more than 1 wt% F, topaz and muscovite are expected to be the first F-bearing phases to crystallize at high pressure, whereas fluorite and topaz should crystallize first at low pressure. Following reaction models the saturation of fluorite and topaz: CaAl2Si2O8 (plagioclase) + 2[AlF3]melt = CaF2 (fluorite) + 2Al2SiO4F2 (topaz). The obtained partition coefficient for F between biotite and glass D(F)Bt/glass ranges from 1.89 to 0.80 (average value 1.29) and can be used as an empirical fluormeter to determine the F content of coexisting melts. Combined petrological and experimental studies of the Kymi equigranular topaz granite indicate that plagioclase was the liquidus phase at nearly water-saturated (fluid-saturated) conditions and that the F content of the melt was at least 2 wt%. The mean F content of natural biotite (3.92 wt%) suggests that the late-stage crystallization of biotite occurred in melts containing about 3 wt% F. The early crystallization of biotite and the presence of muscovite in our experiments at 200 MPa contrasts with the late-stage crystallization of biotite and the absence of muscovite in the natural assemblage, indicating that crystallization pressure may have been lower than 200 MPa for the granite.

UR - http://www.scopus.com/inward/record.url?scp=37549007041&partnerID=8YFLogxK

U2 - 10.1007/s00410-006-0146-8

DO - 10.1007/s00410-006-0146-8

M3 - Article

AN - SCOPUS:37549007041

VL - 153

SP - 273

EP - 288

JO - Contributions to Mineralogy and Petrology

JF - Contributions to Mineralogy and Petrology

SN - 0010-7999

IS - 3

ER -