摘要
通过在0.1GPa压力下钠长花岗岩-H_2O-HF体系相关系实验获得,随体系F含量的增加,石英的温度稳定域上限升高,长石的温度稳定域上限降低;石英、碱性长石的晶-液平衡热力学计算表明,F导致花岗质熔体中组分SiO_2的活度增加,组分NaAlSi_3O_8和KAlSi_3O_8的活度减小,且NaAlSi_3O_8活度较KAlSi_3O_8活度减小幅度大。这些结果显示了F在花岗质熔体中与Si以外的阳离子Al、Na、K等产生了结合,且F与Na结合的优先性大于K,破坏了具有电荷平衡离子Na、K的AlO_2^-四面体,使熔体架状网格中Si/(Si+Al)和K/Na比值增大。通过F与H_2O对花岗岩体系相平衡的影响比较,作者认为F不与Si结合是它与OH^-在干扰熔体结构方面的最大区别。
Experiments carried out on the system granite-H_2O-HF at 0.1G Pa show that the upper temperature limite raises for thestability field of quartz and falls for the stability fieldof alkali-feldspar as F contents increase. The calculated results of quartz, alkali-feldspar crystal-liquid equilibriumshow that the activity of SiO_2 in melt increases and the activities of NaAlSi_3O_8 (Ab)and KAlSi_3O_8 (Or) decrease, with a greater decreasing extent for α_(Ab)~L than α_(Or)~L. These systematic changes are believed to be caused by F complexing with A1, Na, K, but not Si in melt, and are consistent with F decomposing AlO_2^- tetrahedra and preferentially forming coplexes with Al, Na rather than K. The comparison between effects of F with that of H_2O on phase equilibrium suggests that the maximum differenceaffectingmelt structure between F and OH is F complexing without Si and OH complexing with Si in granitic melt.
出处
《地质科学》
CAS
CSCD
北大核心
1997年第1期1-10,共10页
Chinese Journal of Geology(Scientia Geologica Sinica)
基金
国家自然科学基金
南京大学成矿作用国家重点实验室开放基金
