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花岗岩物质成分的差异,是区分不同成因类型花岗岩最本质的因素。参照B·W·Chappell和J·R·White对S型和I型花岗岩的分类方法,通过对滇西地区494件花岗岩类岩石化学分析资料的计算与统计,获得了该区S型和I型岩类的主要岩石化学指数:A1_2O_3/(K_2O+Na-2O+CaO)S型>1,I型<1;K_2O/Na_2O S型>1.2—1.3,I型<1.2—1.3;Fe~(3+)/(Fe~(3+)+Fe~(2+)) S型0.1—0.6,I型0.2—0.75;SiO_2 S型65—77％,I型56—69％。据以上标准,在已有分析资料的112个岩体中,可分出S型岩体77个,I型岩体30个。上述划分经ACF及Al—K—Na,Ca和Fe~(2+)+Mg(原子数)图解判别,其结果均基本一致。滇西地区含锡及具锡、钨矿化的岩体,都具有S型岩类固有的特征。
The difference of granite matter composition is the most essential factor to distinguish granite of different genetic types. According to the classification methods of S-type and I-type granites by B. W. Chappell and J.R. White, by means of calculation and statistics of chemical analysis data of 494 granitic rocks in western Yunnan, the S-type and I- The major petrochemical indices of rocks are: A1_2O_3 / (K_2O + Na-2O + CaO) S> 1, I <1; K_2O / Na_2O S> 1.2-1.3, I <1.2-1.3; +) / (Fe ~ (3 +) + Fe 2+) S type 0.1-0.6, type I 0.2-0.75; SiO 2 S type 65-77%, type I 56-69%. According to the above criteria, among the 112 rock mass that have been analyzed, 77 S-type rock mass and 30 I-type rock mass can be divided. The above classification by ACF and Al-K-Na, Ca and Fe ~ (2 +) + Mg (atomic number) diagram to determine, the results are basically the same. The tin-bearing and tin- and tungsten-bearing rock masses in western Yunnan have the inherent characteristics of S-type rocks.