新疆包古图斑岩铜矿成矿流体演化

西安科技大学 地质与环境学院,陕西 西安 710054

矿产普查与勘探; 斑岩矿床; 电子探针分析; 成矿流体演化; 硫化物成分; 蚀变矿化

Ore-forming fluid evolution of Baogutu porphyry copper deposit,Xinjiang
WEI Shao-ni,Yang Yu-xin

(College of Geology and Enviroment,Xi'an University of Science and Technology,Xi'an 710054,China)

mineral resource prospecting and exploration; porphyry copper deposit; electron probe microanalysis; ore-forming fluid evolution; sulfides compositions; alteration and mineralization

DOI: 10.13800/j.cnki.xakjdxxb.2018.0313文章编号: 1672-9315(2018)03-0435-08

备注

通过岩石学和矿床学研究,探讨了新疆包古图斑岩铜矿各矿化岩体的岩石学特征和蚀变矿化程度。通过金属矿物组合和成分对比,探讨了成矿流体演化相关信息。研究发现,包古图矿化岩体以石英闪长岩和花岗闪长岩为主,各岩体蚀变矿化特征差别明显。Ⅰ,Ⅱ,Ⅳ号岩体蚀变较弱,表现为斜长石局部蚀变为绢云母,黑云母和角闪石部分蚀变为绿泥石; 矿化作用表现为少量浸染状黄铜矿和黄铁矿。Ⅲ号岩体蚀变矿化中等,除绢云母化和绿泥石化外,还发育黑云母化、绿帘石化、白云母化、碳酸盐化和黝帘石化; 具有全岩矿化的特征,黄铜矿、黄铁矿和磁黄铁矿呈浸染状分布于岩体中,但品位较低。Ⅴ号岩体蚀变矿化作用发育,黑云母化、绢云母化、硅化等多种蚀变类型相互叠加。金属矿物以黄铁矿、黄铜矿和辉钼矿为主。Ⅲ号和Ⅴ号岩体硫化物成分对比研究表明,成矿早期阶段,流体高温富硫(T = 431~574 ℃,logf S2=-6~-4),形成的硫化物具有富S贫As的特征,矿化较弱。随着流体向低温方向演化(363 ~ 491 ℃),体系硫逸度降低(logf S2=-7.8~-4.7),金属矿物As含量升高,矿化作用广泛发育。

Based on petrology and metallogenic study,we investigated the petrologic characteristics and the alteration and mineralization features of mineralized intrusions in Baogutu porphyry copper deposits,Xinjiang.The metallogenic evolution was discussed through the sulfide mineral assemblage and compositions.It is pointed that the mineralized intrusions in Baogutu area are mainly quartz diorite and granodiorite.Large differences of alteration and mineralization features exist among these intrusions.Intrusion I,Ⅱ and Ⅳ experienced a weakly degree of alteration,represented by sericitization of plagioclase,chloritization of biotite and amphibole.These intrusions developed only small amounts of disseminated chalcopyrite and pyrite.Intrusion Ⅲ has a medium-level of alteration,including sericitization,chloritization,biotitization,epidotization,muscovitization,carbonatation and zoisitization.The whole intrusive body is mineralized with disseminated chalcopyrite,pyrite and pyrrhotite in low grade ores.Intrusion Ⅴ developed intensively alteration and mineralization,biotitization overlapped with sericitization and silicification.Sulfides in this intrusion are mainly chalcopyrite,pyrite and molybdenite.Comparison of sulfides compositions from intrusion Ⅲ and Ⅴ indicate that temperature and sulfur fugacity(log f S2)of the ore-forming fluid during the early stage are 431~574 ℃ and -6~-4,accounting for weakly mineralization.Sulfides precipitates during this stage are rich in S and poor in As.As the mineralization keep going,the temperature and sulfur fugacity of the ore-forming fluid are lowered to 363~491℃ and -7.8~-4.7,accounting for strongly mineralization and sulfides with higher As contents.