Experiments on the Saturation of Fluorite in Magmatic Systems: Implications for Maximum F Concentration and Fluorine-Cation Bonding in Silicate Melt

作     者：Xiaoyan Li Chao Zhang Lianxun Wang Harald Behrens Francois Holtz Xiaoyan Li;Chao Zhang;Lianxun Wang;Harald Behrens;Francois Holtz

作者机构：State Key Laboratory of Continental DynamicsDepartment of GeologyNorthwest UniversityXi'an 710069China Institute of MineralogyLeibniz University HannoverHannover 30167Germany State Key Laboratory of Geological Processes and Mineral ResourcesSchool of Earth SciencesChina University of Geosciences Wuhan 430074China 

出 版 物：《Journal of Earth Science》 (地球科学学刊（英文版）)

年 卷 期：2020年第31卷第3期

页      面：456-467页

核心收录：

学科分类：0709[理学-地质学] 070901[理学-矿物学、岩石学、矿床学] 07[理学] 0708[理学-地球物理学] 0704[理学-天文学] 

基　　金：This study was supported by the National Natural Science Foundation of China(No.41902052) the German Research Foundation(DFG)(No.BE 1720/40) 

主　　题：fluorine fluorite solubility silicate melt experimental petrology 

摘      要：The effects of melt composition,temperature and pressure on the solubility of fluorite(CaF2),i.e.,fluorine concentration in silicate melts in equilibrium with fluorite,are summarized in this *** authors present a statistic study based on experimental data in literature and propose a predictive model to estimate F concentration in melt at the saturation of fluorite(CFin melt^Fl-sat).The modeling indicates that the compositional effect of melt cations on the variation in can be expressed quantitatively as one parameter FSI(fluorite saturation index):FSI=(3Al^NM+Fe^2++6Mg+Ca+1.5Na-K)/(Si+Ti+Al^NF+Fe^3+),in which all cations are in mole,and Al^NF and Al^NM are A1 as network-forming and network-modifying cations,*** dependence of CFin melt^Fl-sat on FSI is regressed as:CFin melt^Fl-sat=1.130-2.014·exp(1000/T)+2.747·exp(P/T)+0.111·CmeltH2O+17.641·FSI,in which T is temperature in Kelvin,P is pressure in MPa,CmeltH2O is melt H2O content in wt.%,and CFin melt^Fl-sat is in wt.%(normalized to anhydrous basis).The reference dataset used to establish the expression for conditions within 540-1010℃,50-500 MPa,0-7 wt.%melt H2O content,0.4 to 1.7 for A/CNK,0.3 wt.%-7.0 wt.%for CFin melt^*** discrepancy of CFin melt^Fl-sat between calculated and measured values is less than±0.62 wt.%with a confidence interval of 95%.The expression of FSI and its effect on CFin melt^Fl-sat indicate that fluorine incorporation in silicate melts is largely controlled by bonding with network-modifying cations,favorably with Mg,Al^NM,Na,Ca and Fe^2+in a decreasing *** proposed model for predicting CFin melt^Fl-sat is also supported by our new experiments saturated with magmatic fluorite performed at 100-200 MPa and 800-900℃.The modeling of magma fractional crystallization emphasizes that the saturation of fluorite is dependent on both the compositions of primary magmas and their initial F contents.