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 paper. The 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 (C ^Fl-sat_{F in melt} ). The modeling indicates that the compositional effect of melt cations on the variation in C ^Fl-sat_{F in melt} can be expressed quantitatively as one parameter FSI (fluorite saturation index): FSI=(3Al^NM+Fe²⁺+6Mg+Ca+1.5Na-K)/(Si+Ti+Al^NF+Fe³⁺), in which all cations are in mole, and Al^NF and Al^NM are Al as network-forming and network-modifying cations, respectively. The dependence of C ^Fl-sat_{F in melt} on FSI is regressed as: C ^Fl-sat_{F in melt} =1.130−2.014·exp (1 000/T)+2.747·exp (P/T)+0.111·C ^H2O_melt +17.641·FSI, in which T is temperature in Kelvin, P is pressure in MPa, C ^H2O_melt is melt H₂O content in wt.%, and C ^Fl-sat_{F in melt} is in wt.% (normalized to anhydrous basis). The reference dataset used to establish the expression for conditions within 540–1 010 °C, 50–500 MPa, 0–7 wt.% melt H₂O content, 0.4 to 1.7 for A/CNK, 0.3 wt.%–7.0 wt.% for C ^Fl-sat_{F in melt} . The discrepancy of C ^Fl-sat_{F in melt} 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 C ^Fl-sat_{F in melt} indicate that fluorine incorporation in silicate melts is largely controlled by bonding with network-modifying cations, favorably with Mg, Al^NM, Na, Ca and Fe²⁺ in a decreasing order. The proposed model for predicting C ^Fl-sat_{F in melt} is also supported by our new experiments saturated with magmatic fluorite performed at 100–200 MPa and 800–900 °C. 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.

中文翻译：

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岩浆系统中萤石饱和度的实验：对硅酸盐熔体中最大F浓度和氟阳离子键的影响

本文总结了熔体组成，温度和压力对萤石（CaF ₂）溶解度的影响，即硅酸盐熔体中的氟浓度与萤石平衡。作者基于文献中的实验数据进行了统计研究，并提出了一种预测模型，用于估算萤石饱和度（熔体中的C ^Fl-sat _F）中熔体中的F浓度。该模型表明，熔体阳离子对熔体中C ^Fl-sat _F变化的组成效应可以定量表示为一个参数FSI（萤石饱和指数）：FSI =（3Al ^NM + Fe ²⁺ + 6Mg + Ca + 1.5 Na-K）/（Si + Ti + Al ^NF + Fe ³⁺），其中所有阳离子均以摩尔计，Al ^NF和Al ^NM分别为Al，它们分别作为网络形成阳离子和网络修饰阳离子。_熔体中的C ^Fl-sat _F对FSI的依赖性回归为：_熔体中的C ^Fl-sat _F = 1.130-2.014·exp（1000 / T）+ 2.747·exp（P / T）+ 0.111· C ^H2O_熔体+ 17.641·FSI，其中T为开尔文温度，P为MPa压力，C ^H2O_熔体为H ₂ O含量（wt。％），C ^Fl-sat _F 以wt。％（以无水为基准）。参考数据集用于建立540–01010°C，50–500 MPa，0–7 wt。％熔体H ₂ O含量，A / CNK的0.4至1.7、0.3 wt。％– 7.0 wt。_熔体中C ^Fl-sat _F的。％。计算值和测量值之间的_熔体C ^Fl-sat _F差异小于±0.62 wt。％，置信区间为95％。FSI的表达及其对_熔体中C ^Fl-sat _F的影响表明，氟在硅酸盐熔体中的掺入很大程度上受与网络修饰阳离子的键合控制，最好与Mg，Al ^NM，Na，Ca和Fe ^2+结合。 以降序排列。我们_在熔融岩浆萤石中在100-200 MPa和800-900°C下进行的新实验也支持所提出的预测_熔体中C ^Fl-sat _F的模型。岩浆分级结晶的模型强调，萤石的饱和度取决于原生岩浆的成分及其初始F含量。