Contamination rate of granitic rocks and metamorphic grade of metamorphic rocks by using ammonium content in biotite

在变质岩中，麻粒岩黑云母的铵含量低于角闪石-黑云母片麻岩黑云母的铵含量。从角闪岩相到麻粒岩相，黑云母中铵含量有系统降低的趋势。麻粒岩中的黑云母可能会释放出铵，黑云母的铵含量不能记录原岩中氮的存在。所研究的花岗质岩石中黑云母的铵含量与花岗岩类型和产状密切相关。在变质成因花岗岩中，其黑云母的高铵含量是由于变质液富含铵。黑云母的铵含量在M型花岗岩中很低，在I型花岗岩中稍低，在A型花岗岩中稍高，在S型花岗岩中较高。

In the metamorphic rocks, ammonium content of biotites from granulite is low compared with those of biotites from hornblende-biotite gneiss. Systematic decreasing tendency of ammonium content was recognized in biotite from amphibolite facies to granulite facies. Ammonium might be liberated from biotite in the granulite and the ammonium content of the biotites would not record the existence of nitrogen in the original rocks.Ammonium content of biotites in the granitic rocks studied is closely related to the granite type and the occurrence. In the metamorphic origin granitic rocks, the high ammonium content of their biotites is due to to the metamorphic fluid enriched in ammonium. The ammonium content of biotites is very low low in M-type granite, slightly low in I-type granite, somewhat higher in A-type granite and higher in S-type granite.