摘要
本文利用作者首次设计改进的固液制样术、金管处理术及测试分析程序完成了铅、锌在花岗质硅酸盐熔体和共存含水流体间的分配实验,确定了一系列铅锌流-熔分配系数;并从分配模型和熔体地球化学等方面探讨了铅锌的流-熔分配规律和机理。实验结果和理论分析均表明,在含水花岗质岩浆体系中,氯(钠)有利于铅、锌的流-熔分离,而氟(钾)则相对地阻碍了这种分离。
Three new experimental techniques9 i.e. the solid-liquid preparing teehnique, the treatment technique of gold capsules and the measurement procedure, have been designed and used for finishing three series of experiments of Pb and Zn partitioning between granitie silicate melts and aqueous fluids. A series of partitioning coefficients (D_(Me)^(V/L)),defined as the ratio of the concentration of metal elements (Me)in fluids(V) to that in melts(L), have been determined, It is clear in the experimental results that D_(Me)^(V/L) is proportional to less than or near 1 power of the NaCl mole coneentration[m_(NaCl)], and thatD_(Me)^(V/L) increases with the Cl(Na)fractions in the system, but reduces with the increasing F(K) fractions instead.
On the other hand, it is shown in our theoretical analysis that under the magmatie parameters, Pb and Zn might exist in the form of hydroxyl-chloride, [Me(OH)Cl_3], in the fluids phase. In the melt phase, however, Pb and Zn might dominantly be fitted in the lattice of aluminosilieate tetrahedron by non-bridging oxygen. The cations could be replaced by H^+ ions derived from hydrolysis through the proton-cation exchange reactions. If the partition reaction is as follows. _LMe^(2+)+_VNaCl+_VH_2O=_VMe(OH)Cl+_LNa^++_LH^+, D_(Me)^(V/L) would be proportional to less than 1 power. When there is a host of chlorine in the system, Pb and Zn would associate with a large number of Cl^- ions favourable for partition into the fluids and OH^- ions derived from hydrolysis to form stable hydroxyl-chlorides because of the distinctive differences in the polymerization and the partition coefficient between fluorine and chlorine. When fluorine is rich, however, Pb and Zn would tend to hold in the melt because of the polymerization of luorine favourable for partition into the melt phase. When fluorine is rich the D_(Me)^(V/L) would therefore be much less than that when chlorine is rich. In addition, when potassium is rich the D_(Me)^(V/L) would be slightly less than that when sodium is rich, because of slight differences in the polymerization and the partition coefficients between potassium and sodium.
The partitioning regularity and mechanism of Pb and Zn have been discussed based on the experimental results and theoretical, analysis in the paper.
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
1990年第2期12-19,T001,共9页
Acta Petrologica Sinica
关键词
铅
锌
硅酸盐
熔体
流体
分配
Pb and Zn partitioning between melts and fluids
Experimental methods
Mechanism
