Li-F花岗岩液态分离的微量元素地球化学标志  

Geochemical indicators of trace element in Li-F granite liquid segregation

作　　者：王联魁[1] 王慧芬[1] 黄智龙[2] 

机构地区：[1]中国科学院广州地球化学研究所,广州510640 [2]中国科学院地球化学研究所,贵阳550002

出　　处：《岩石学报》2000年第2期145-152,共8页Acta Petrologica Sinica

基　　金：中国科学院出版基金资助

摘　　要：华南和世界其他国家典型 L i- F花岗岩 195个微量元素分析结果的研究表明 ,随 L i- F花岗岩自下而上不同岩相变化 :Zr/Hf- F、Nb/Ta- F等有负相关变化 ;同样 ,随 F增加 ,Ta(Nb)、Sn、W、Al升高和 Nb/Ta(Zr/Hf)降低 ;在 K/Rb- Rb图中黄英岩成分点位于相关斜线左下方 ;在 K- L i图中有低 L i、K的异常变化 ;在 Rb/Sr- P2 O5 图中有 Rb/Sr的二～三个数量级异常变化等 ,均是 L i- F花岗岩气液分馏为主液态分离的标志。相邻岩相 (香花岭岩和翁岗岩 )的微量元素和主要元素有突变和不均一特点 ,香花岭岩比翁岗岩富主要元素 F、K、Fe、Mn、Mg(或 Ca)和微量元素 Rb(或 Cs)、Zr(或 Hf)、Nb(或 Ta)、Th、W、Sn(或 Mo)、Ba(或 Sr)等。因而富 F、K、Fe与贫 Si、Na的香花岭岩和贫 F、K、Fe与富 Si、Na的翁岗岩属成分共轭和突变的岩性对 ,应为 L i-The results of trace element determination of 195 Li-F granite samples from China and other countries indicate that with the variation of Li-F granite facies from the lower to the upper, there are negative correlations between Zr/Hf and F and Nb/Ta and F; the contents of Ta(Nb), Sn, W and Al increase and the ratios of Nb/Ta(Zr/Hf) decrease with the F content increase. The topazites are plotted in the down-left side of correlative oblique line in the diagram K/Rb-Rb of Li-F granite. The Li-F granites show the lower Li and K anomaly in the diagram Li-K, and Rb/Sr unusual anomaly(2~3 magnitudes) in the diagram Rb/Sr-P 2O 5. All of these facts are the indicators of the liquid segregation mainly with vapour-liquid fractional distillation. The contents of main and trace elements in neighbourhood rock facies(xianghualingite and ongonite) are characterized by variation of a saltation and heterogeneity. The contents of main elements such as F, K, Fe, Mn, Mg(or Ca) and trace elements such as Rb(or Cs), Zr(or Hf), Nb(or Ta), Th, W, Sn(or Mo), Ba(or Sr) etc in xianghualingite are richer than those in ongonite. Therefore, the xianghualingite rich in F, K, Fe and poor in Si, Na, and the ongonite poor in F, K, Fe and rich in Si, Na are conjugate and saltatory in compositions of rock pair. This can be considered as the indicators of liquid segregation mainly with the immiscibility of Li-F granite.

关 键 词：花岗岩微量元素 稀有金属花岗岩 液态分离的岩浆不混溶 岩浆气液分馏 

分 类 号：P588.121[天文地球—岩石学]