Chemical composition andmetallogenic significance of biotite from the Liwu copper deposit, western Sichuan Province

In order to ascertain the genetic type, physicochemical conditions and metallogenic significance, electron probe analysis of biotite in alteration zone of the Liwu copper deposit is carried out in this paper. The results show that these biotite grains: (1) have high SiO₂ (average 34.67%), Al₂O₃ (average 19.20%), FeO (average 22.45%), MgO (average 7.96%) and K₂O (average 9.37%) contents, and are primary iron biotite; (2) were formed in low oxygen fugacity conditions, medium to high temperature environment (average 531℃) and high pressure (average 3.99 kbar). Combined with previous data, it is believed that biotite in the Liwu copper deposit is probably formed by recrystallization of primary biotite, and the Liwu-type high-grade copper deposit is most likely related to the deformation-metamorphism during the doming process of the Jianglang dome.