湘西北古丈地区大塘坡组锰矿沉积地球化学特征与沉积环境分析  

Geochemical Characteristics and Sedimentary Environment Analysis of Manganese Ore from the Datangpo Formation in the Guzhang Area,Northwest Hunan Province

作　　者：付文念 李凤杰[1,2] FU WenNian;LI FengJie(Key Laboratory of Deep-time Geography and Environment Reconstruction and Applications,MNR&Institute of Sedimentary Geology,Chengdu University of Technology,Chengdu 610059,China;State Key Laboratory of Oil&Gas Reservoir Geology and Exploitation,Chengdu University of Technology,Chengdu 610059,China)

机构地区：[1]自然资源部深时地理环境重建与应用重点实验室/沉积地质研究院,成都理工大学,成都610059 [2]油气藏地质及开发工程国家重点实验室(成都理工大学),成都610059

出　　处：《沉积学报》2025年第1期50-62,共13页Acta Sedimentologica Sinica

基　　金：中国地质调查局公益性基础地质调查项目(DD20160032)。

摘　　要：【目的】分析湘西北古丈地区南华系大塘坡组锰矿沉积环境,探讨古丈地区大塘坡组锰成矿环境和成矿物质来源,可为该区大塘坡组锰矿的勘探提供理论依据。【方法】以主、微量元素、稀土元素和碳氧同位素等地球化学分析为基础,对大塘坡组锰矿沉积时的氧化—还原环境、成矿物质来源等进行研究。【结果】(1)古丈地区锰矿床的主量元素Al_(2)O_(3)与SiO_(2)、TiO_(2)、K_(2)O均具有良好的正相关性,与MgO、CaO呈弱的负相关,而与MnO、Na_(2)O、TFe、P_(2)O_(5)的相关性不强,这种相关关系与湖北古城锰矿、湖南湘潭锰矿及湖南照洞锰矿具有一定相似性,整体表现为高Si、低Fe、含P锰矿;(2)Fe/Mn<1、20.57、Ni/Co<5、U/Th<0.75等多种沉积环境氧化—还原敏感元素指标显示古丈地区大塘坡组锰矿形成时处于常氧—贫氧环境,“帽式”稀土元素分配模式和弱的Ce正异常表明Mn先以锰的氧化物或氢氧化物形式沉淀,然后在成岩过程中转化为菱锰矿;(3)SiO_(2)/Al_(2)O_(3)>3.6、Y/Ho比值接近海底热流体比值、Fe-Mn-(Ni+Cu+Co)×10三角图解和Co/Zn-(Cu+Ni+Co)图解投点结果等多种成矿物质来源判别指标均显示古丈地区大塘坡组锰矿Mn元素的形成具有热水沉积的特征,与海底热液作用关系密切。【结论】湘西北古丈地区大塘坡组锰矿形成时处于常氧—贫氧环境,锰质形成与海底热液作用密切相关。[Objective]We analyzed the sedimentary environment of manganese ore in the Datangpo Formation of the Nanhua System in the Guzhang area,northwest Hunan province.[Methods]Based on the geochemical analysis of major and trace elements,rare earth elements and carbon and oxygen isotopes,the oxidation-reduction environment and the source of ore-forming materials during the deposition of manganese ore in the Datangpo Formation were stud-ied.[Results](1)There is a positive correlation between SiO_(2),TiO_(2),K_(2)O,and Al_(2)O_(3),weak negative correlation with MgO and CaO,and weak correlation with MnO,Na_(2)O,TFe,and P_(2)O_(5) for the main elements of manganese ore in the Guzhang area.The deposit is similar to the Gucheng manganese ore in Hubei,Xiangtan manganese ore in Hu-nan,and Zhaodong manganese ore in Hunan,with an overall high Si,low Fe,and P-bearing manganese ore.(2)The redox-sensitive elemental indicators,Fe/Mn<1,2<V/Cr<4.5,V/(V+Ni)>0.57,Ni/Co<5,and U/Th<0.75,of the depositional environment indicate that the water column was in a normoxic-poor environment when the manga-nese ore was formed in the Datangpo Formation.The enrichment pattern of the medium rare earth elements,depletion of light and heavy rare earth elements,and the weak positive Ce anomaly indicate that Mn was first precipitated in the form of manganese oxides or hydroxides and then changed into Mn carbonate during digenesis.(3)A variety of metal-logenic material source identification indicators,SiO_(2)/Al_(2)O_(3)>3.6,Y/Ho close to that of the hydrothermal fluid on the seafloor,results of Fe-Mn-(Ni+Cu+Co)×10 triangulation,and Co/Zn-(Cu+Ni+Co)diagrammatic show that the for-mation of Mn elements from the manganese ores in the Datangpo Formation in the Guzhang area is closely related to submarine hydrothermal action and has characteristics of hot-water deposition.[Conclusions]The manganese ore of the Datangpo Formation was formed in a normoxic-poor environment in the Guzhang area,northwest Hunan province.The formation of manganese is closely related t

关 键 词：大塘坡组 古丈地区 地球化学 沉积环境 热水沉积 

分 类 号：P512.2[天文地球—地质学]