摘要
为确定小西南岔铜金矿床的成矿时代,对北山矿段新发现的含辉钼矿石英脉进行了系统研究和同位素测年.空间上,含辉钼矿石英脉与相邻铜金矿体平行,它们受相同的构造体系控制;钼矿石中金属矿物以辉钼矿为主,并明显被黄铜矿和黄铁矿沿裂隙、晶隙充填交代,根据不同矿物间的交生关系,结合前人研究资料认为,该辉钼矿石英脉是该区大规模铜金矿化的早期阶段产物.在此基础上,对6件辉钼矿样品进行了Re-Os同位素分析,获得的模式年龄为109.2±3.4 Ma^110.8±4.0 Ma,平均年龄为109.9±3.9 Ma,等时线年龄为111.1±3.1 Ma,与该区燕山晚期花岗岩类最新测年结果具明显的耦合关系,为小西南岔矿床提供了一个准确的形成时限.综合辉钼矿中低的Re含量、成矿岩体岩石学、地球化学特征以及精细的同位素年代学研究认为,该区大规模铜金矿化主要发生于燕山晚期,成矿构造环境为伊泽奈崎板块向古亚洲大陆边缘俯冲造成的岩石圈伸展背景下的活动陆缘环境,成岩成矿物质具深源特征,主要来自上地幔.
To obtain the exact metallogenic age of Xiaoxi＇nancha copper-gold deposit, the quartz-molybdenite vein newly discovered in the Beishan ore block is studied and dated by Re-Os isotopic dating of molybdenite. The quartz-molybdenite vein is parallel to adjacent lode copper-gold ore bodies, which indicates that both are controlled by the common structure system The dominant metal minerals in molybdenum ore is molybdenite which is occasionally cut by later pyrite and chalcopyrit. Due to the intergmwth of different metal minerals, the lode molybdenum mineralization in Xiaoxi＇nancha deposit is clearly earlier than major copper-gold metallogenic stage. Accordingly, it can be concluded that the lode molybdenum mineralization belongs to early metallogenic stage of copper-gold mineralization. Six samples of molybdenite for Re-Os isotopic dating are analyzed. The model ages vary from 109. 2±3. 4 Ma to 110. 8±4. 0 Ma, average 109. 9±3. 9 Ma, and a good isochron age of 111.1±3. 1 Ma. These results are consistent with new isotopic dating of granitic intrusions related to copper-gold mineralization in this deposit. It indicates that the large copper-gold mineralization took place in late Yanshanian periods and both the granites and copper-gold mineralization were generated under extensive active continental margin resulted from the obliquely subduction of Pacific Ocean slab. Moreover, petrological ＆ geochemical characters, isotopic dating of ore-forming intrusions as well as low content of Re in molybdenite demonstrate that granitic intrusions and copper-gold mineralization were derived from deep source, mainly upper mantle.
出处
《地球科学（中国地质大学学报）》
EI
CAS
CSCD
北大核心
2011年第4期721-728,共8页
Earth Science-Journal of China University of Geosciences
基金
中国地质调查局项目(Nos.1212010913026
资[2010]矿评01-20-06)
中国科学院地球化学研究所矿床地球化学国家重点实验室开放研究基金(No.200910)
