滇东南中三叠统法郎组锰矿床成因的新认识  

A new recognition about genesis of manganese ore deposits in the Falang Formation of Middle Triassic,Southeastern Yunnan

作　　者：杜秋定[1] 伊海生[2] 惠博[2] 武向峰[2] 陈三运[2] 陈广义[2] 

机构地区：[1]中国地质调查局成都地质矿产研究所,成都610082 [2]成都理工大学沉积研究院,成都610059

出　　处：《地质论评》2010年第5期673-682,共10页Geological Review

基　　金："十一五"国家科技支撑计划项目(编号2006BAB01A12-5)的成果

摘　　要：产于滇东南中三叠世拉丁期法郎组地层中的锰矿床,锰矿石出现氧化锰矿与碳酸盐锰矿混合存在现象,没有明显的变质现象,为沉积成因。矿石中一般都含有生物碎屑。我们对采自这一地区的斗南、岩子脚、老乌,土基冲等典型矿床的锰矿石样品,进行了系统的薄片显微镜和扫描电镜观察,同时应用X射线衍射对矿石矿物成份作了相应分析。观察到这些矿石中的鲕、豆状结构是由蓝绿藻类微生物凝聚作用形成的显微叠层构造,具有核形石特有的核心和包壳,其明—暗纹层相间的显微结构特征可以与现代深海大洋铁锰结核相类比。本文通过对核形石显微结构特征的观察和对锰矿物生成时介质环境的讨论,初步研究结果表明,锰矿形成可能位于古氧化还原界面附近,该区锰的富集可能与微生物活动密切相关。The manganese deposit in the Ladinian Falang Formation of the Middle Triassic,produced in the Southeast of Yunnan.In research areas both have Mn oxide and Mn carbonates,which is sedmentry no obviously metamorphism and most of them have bioclast. Concentric rings structure are obviously observed in oolitic and pisolitic manganese ores. The thin sections from manganese ore samples are systematically observated from typical deposits in Dounan,Yanzijiao,Laowu and Tujichong. The microstructures of oolitic and pisolitic ores are detailed described on the observation of microscope. It is suggested that these concentric laminar structures in manganese deposits are origin of blue-green algae micro-organism and similar to common oncolitic structures. They have nucleus and encrustation fabric that can be compared with present Fe—Mn nodule in modern deep ocean environment. The preliminary study results show that Mn enrichment in this region probably relative to micro-organism activity,also finding biodetritus in the manganese ore,which means manganese ore close to the redox level.

关 键 词：锰质核形石 微生物成因 氧化还原界面 中三叠统法郎组 滇东南地区 

分 类 号：P618.32[天文地球—矿床学]