钠长花岗岩-H_2O-HF体系中流体/熔体间氟的分配实验研究

EXPERIMENT ON THE FLUID/MELT PARTITION OF FLUORINE IN THE SYSTEM ALBITE GRANITE-H_2O-HF

在p＝100MPa，770℃≤t≤800℃和W_F＝2％-6％条件下进行了钠长花岗岩－H_2O－HF体系液相线附近流体／熔体间氟的分配实验。对淬火玻璃的主要元素和氟含量进行了电子探针测定，用质量平衡法计算了流体中的氟含量，所获得的氟的流体／熔体分配系数D_F均小于1．0，随体系氟含量的增加，D_F有所增大。表明在花岗岩岩浆－热液体系中，氟优先进入熔体相，含氟花岗岩结晶晚期流体释放阶段残余熔体仍可保持富氟特征，同时表明氟作为流体相搬运金属成矿元素的配合剂作用是有限的。

The fluid/melt partitioning experiments for fluorine were carried out in the systemalbite granite-H_2O-HF at p = 100MPa, 770℃≤t≤800℃ and W_F = 2%-6% conditions.The concentrations of major elements and fluorine in quenched glasses (melt) weredetermined by electron microprobe and fluorine concentrations in coexisting aqueousfluid were calculated by mass balance method. The result shows that fluorineconcentrates in granitic melt relative to coexisting fluid at our experimental conditions.The partition coefficient D_F(W^(Fl)/W^(Mt)) ranges from 0.35 to 0.89, but it increases withincreasing fluorine content in the system. This means that there is not just one singlevalue of partition coefficient for fluorine in granitic melt-flind system. The partitionbehavior of fluorine in such a system depends critically on fluorine and proton (H^+)concentration. Our data suggest that F-rich granitic melt exist in nature and thatfluorine may not be important in the mass transport of ore-forming elements inF-bearing granitic melt-fluid system.