鄂西长阳跑马坪锰矿地球化学特征与沉积环境  

Geochemical Characteristics and Sedimentary Environment of Paomaping Manganese Deposit in Changyang, Western Hubei Province

作　　者：刘海 漆双林 范玖琳 郭威 陈爱章 张书杰 Liu Hai;Qi Shuanglin;Fan Jiulin;Guo Wei;Chen Aizhang;Zhang Shujie(Hubei Institute of Metallurgical Geology(Central South Institute of Metallurgical Geology),Yichang 443000,China)

机构地区：[1]湖北冶金地质研究所(中南冶金地质研究所),湖北宜昌443000

出　　处：《地球科学》2025年第1期58-76,共19页Earth Science

基　　金：湖北省国土资源科技攻关计划项目(No.ETZ2014A05);湖北省科技发展专项项目(No.42000022205T000000150);湖北省重点研发项目(No.2024BCB098);湖北省地质联合基金重点项目(No.JCZRLH202501101)。

摘　　要：鄂西长阳背斜南华系锰矿为大塘坡式锰矿,其成矿时代恰处于新元古代“雪球地球”事件中的间冰期.在Rodinia超大陆裂解的背景下,大塘坡期气候环境转变、裂谷盆地作用以及锰矿成矿作用三者间存在成因上的联系.为了详细阐述古气候、沉积环境、锰质来源对大规模锰矿沉积成矿作用的控制,恢复鄂西地区大塘坡式锰矿成矿过程,选取鄂西长阳地区跑马坪锰矿作为研究对象,对其地球化学特征开展了综合研究.测试结果显示碳酸锰矿石Mn/Fe比值较高,沉积过程中Mn、Fe分离十分彻底,氧化-还原敏感元素V、U亏损,Mo富集,揭示大塘坡期为氧化-弱氧化的沉积环境.δU、Uau、Th/U、V/Cr、Co/Ni值也指示大塘坡期为氧化-弱氧化沉积环境.长阳背斜碳酸锰矿石Al、Ti含量略高于湘黔渝地区,说明扬子北缘锰矿石陆源碎屑含量高于扬子东南缘,指示沉积水体深度相对较浅或者距离物源较近.CIA指数研究显示长阳背斜大塘坡期风化强度中等,碳酸锰矿石、碳质泥页岩Al/(Al+Mn+Fe)比值较低,Eu正异常、LREE富集,Nb/Ta、Zr/Hf、Y/Ho比值以及碳酸锰矿石La/Yb-Ce/La、(Co+Ni+Cu)×10-Fe-Mn、Zr-Cr图解分析均认为锰质来源以深部热液来源为主,陆源锰质为辅助来源,且成矿期有明显的热水沉积作用.通过研究CIA指数以及Sr/Cu、Rb/Sr、Sr、Sr/Ba值认为长阳背斜大塘坡期为温暖湿润的气候环境.碳酸锰矿成矿与氧化还原环境、锰质来源、古气候、古盐度耦合明显.The Nanhua manganese deposit in Changyang anticline of western Hubei is a Datangpo-type manganese deposit,and its metallogenic age is precisely in the interglacial period of the Neoproterozoic Snowball Earth event.Under the background of the breakup of the Rodinia supercontinent,there is genetic relationship among the climate change,rift basin and manganese mineralization in the Datangpo period.In order to elaborate the control of paleoclimate,sedimentary environment and manganese source on the sedimentary mineralization of large-scale manganese deposits,restore the metallogenic process of Datangpo-type manganese deposits in western Hubei,this study selected Paomaping manganese deposit in Changyang area of western Hubei as the research object,and carried out a comprehensive study on its geochemical characteristics.The results show that the Mn/Fe ratio of manganese carbonate ore is high,the separation of Mn and Fe was very thorough during the deposition process,the oxidation-reduction sensitive elements V and U are depleted,and Mo is enriched,revealing that the Datangpo period is an oxidation-weak oxidation sedimentary environment.Paleo-oxygenation facies such asδU,Uau,Th/U,V/Cr,and Co/Ni indicate that the Datangpo period was an oxygen and weak oxidation sedimentary environment.The Al and Ti contents of the Changyang anticline rhodochrosite are slightly higher than those in the Hunan,Guizhou and Chongqing areas,indicating that the content of terrigenous debris in the manganese deposits in the northern margin of Yangtze is higher than that in the southeastern margin of Yangtze and the depth of its sedimentary water is relatively shallow or closer to the source.The study of CIA index shows that the weathering intensity of Datangpo period in Changyang anticline is medium,rhodochrosite and carbonaceous mud(shale)rock are characterized by the low Al/(Al+Mn+Fe)ratios,positive Eu anomalies,LREE enrichment,Nb/Ta,Zr/Hf,Y/Ho ratio and La/Yb-Ce/La,(Co+Ni+Cu)×10-Fe-Mn,Zr-Cr diagram analyses of manganese carbonate indicate t

关 键 词：跑马坪锰矿床 地球化学 古气候 沉积环境 锰质来源 

分 类 号：P611[天文地球—矿床学]