龙门山构造带早寒武世毛家山锰矿床Ⅲ号矿体含矿岩系沉积环境与锰成矿机制  

The depositional environment and manganese mineralization mechanism of the ore-bearing rock series from the No.Ⅲore body of the early Cambrian Maojiashan manganese deposit,Longmenshan tectonic belt

作　　者：万平益 程文斌[2] 蔡姬敏 吴春章 陈浩 郎兴海[2] 王川 叶小春 彭建华 刘清强 WAN Pingyi;CHENG Wenbin;CAI Jimin;WU Chunzhang;CHEN Hao;LANG Xinghai;WANG Chuan;YE Xiaochun;PENG Jianhua;LIU Qingqiang(The 5th Geological Brigade of Sichuan,Chengdu 610081,China;College of Earth and Planetary Sciences,Chengdu University of Technology,Chengdu 610059,China)

机构地区：[1]四川省第五地质大队,四川成都610081 [2]成都理工大学地球与行星科学学院,四川成都610059

出　　处：《沉积与特提斯地质》2025年第1期134-151,共18页Sedimentary Geology and Tethyan Geology

基　　金：四川省地质矿产勘查开发局局专项项目(SCDZ-KJXM202407);四川省政府性投资地质勘查项目(DZ202312);中国科技部“十四五”国家重点研发计划(2022YFC2905002-4);国家自然科学基金委员会重点项目(42230311);自然资源部新一轮找矿突破战略行动科技支撑项目(ZKKJ202427);四川省自然科学基金重点项目(2024NSFSC1954)。

摘　　要：针对龙门山构造带早寒武世锰矿床锰的富集沉淀机理不明这一科学问题,本文以该构造带毛家山锰矿床Ⅲ号矿体为研究对象,在详细的野外地质调查和室内光薄片鉴定的基础上,对含矿岩系开展了系统的总有机碳(TOC)和元素地球化学测试,初步探讨了锰的来源、沉积环境与富集机制。研究表明:(1)毛家山锰矿床Ⅲ号矿体含矿岩系为下寒武统邱家河组五段,主要由锰矿层(Ⅲ号锰矿体)、黄铁矿层、含锰硅质白云岩、碳泥质板岩、硅质岩和白云岩组成。锰矿层由厘米至毫米级多旋回富锰硫化物层和富锰碳酸盐层组成,矿石矿物主要为硫锰矿和锰白云石,脉石矿物主要为草莓状黄铁矿和石英,含少量有机质。(2)含矿岩系CIA值主要介于65~85,指示中等陆源风化条件,有利于陆源锰的迁出,但Al_(2)O_(3)与MnO之间大致呈现负相关关系,推测陆源风化很可能并非锰的主要来源;在(Cu+Co+Ni)×10–Fe–Mn、(Zr+Y+Ce)×100–(Cu+Ni)×15–(Fe+Mn)/4、Ce/Ce^(*)–(Y/Ho)_(PAAS)、Ce/Ce^(*)–Nd和Fe/Ti–Al/(Al+Fe+Mn)系列判别图解中,含矿岩系各岩/矿石样品投点主要落入热液成因区或水成–热液混合区,指示锰很可能来自海底热液输入。(3)含矿岩系草莓状黄铁矿粒径、EF_(Mo)/EF_U比值、V/Cr比值、V/(V+Ni)比值等氧化还原指标指示其形成于次氧化–缺氧–硫化波动变化的底层水环境;古海洋生产力指标P和Cd指示较高的古海洋生产力条件;Mo–TOC图解和Cd–Mo图解则显示,含矿岩系主体形成于弱局限上升洋流环境。(4)Mn的富集沉淀机制很可能受微生物诱导成矿作用和细菌还原硫酸盐作用(BSR)综合控制。Addressing the scientific question of the unclear mechanism of manganese enrichment and precipitation in the early Cambrian manganese deposits of the Longmenshan tectonic belt,this paper focuses on the No.Ⅲore body of the Maojiashan manganese deposit in this belt as the research object.Based on detailed field geological surveys and thin-section identification,a systematic total organic carbon(TOC)and elemental geochemical test was conducted to preliminarily explore the source of manganese,depositional environment,and enrichment mechanism.The study shows:(1)The ore-bearing rock series from the No.Ⅲore body of the Maojiashan manganese deposit belongs to the fifth member of the lower Cambrian Qiujiahe Formation,primarily composed of manganese ore layers(No.Ⅲmanganese ore body),pyrite layers,manganese-bearing siliceous dolostone,carbonaceous mudstone,siliceous rock,and dolostone.The manganese ore layer is composed of centimeter-to millimeter-scale multicycle manganese-rich sulfide layers and manganese-rich carbonate layers.The main ore minerals are alabandite and kutnahorite,and the main gangue minerals are pyrite framboids and quartz,with a small amount of organic matter.(2)The CIA value of the orebearing rock series mainly ranges from 65 to 85,indicating moderate continental weathering conditions,favorable for the migration of terrigenous manganese.However,there is a negative correlation between Al2O3 and MnO,suggesting that continental weathering is likely not the main source of manganese.In the(Cu+Co+Ni)×10–Fe–Mn,(Zr+Y+Ce)×100–(Cu+Ni)×15–(Fe+Mn)/4,Ce/Ce^(*)vs.(Y/Ho)PAAS,Ce/Ce^(*)vs.Nd,and Fe/Ti vs.Al/(Al+Fe+Mn)discriminant diagrams,the data pertaining to rocks and ores of the orebearing rock series are mainly plotted on the hydrothermal origin area or the aqueous-hydrothermal mixed area,indicating that manganese is likely derived from submarine hydrothermal input.(3)The size of pyrite framboids,as well as redox indicators such as the EFMo/EFU ratio,V/Cr ratio,and V/(V+Ni)ratio,indicate that the o

关 键 词：毛家山锰矿床 早寒武世 物源分析 沉积环境 沉淀机制 

分 类 号：P62[天文地球—地质矿产勘探]