湘南地区东湘桥沉积型锰矿床地球化学特征及成矿机理
Geochemical characteristics and metallogenic mechanism of Dongxiangqiao sedimentary manganese deposit in southern Hunan Province
廖凤初 1刘湘华 2徐军伟 3熊伊曲 4李斌 4赖健清 4骆检兰 3陈雨林 3罗益周 3王勇5
作者信息
- 1. 湖南省地球物理地球化学调查所,湖南长沙 410014;广西民族大学建筑工程学院,广西南宁 530006
- 2. 湖南省地球物理地球化学调查所,湖南长沙 410014;广西民族大学建筑工程学院,广西南宁 530006;中南大学地球科学与信息物理学院,湖南长沙 410083
- 3. 湖南省地球物理地球化学调查所,湖南长沙 410014
- 4. 中南大学地球科学与信息物理学院,湖南长沙 410083
- 5. 湖南省地质调查所,湖南长沙 410014
- 折叠
摘要
湘南地区广泛发育二叠纪海相沉积型锰矿,为揭示其成矿过程及机理,文章以湖南永州东湘桥锰矿床沉积剖面为研究对象,对其开展主、微量元素和碳-氧同位素分析.结果表明,富锰岩层富Cr、Ni、Co等元素的地球化学特征,其Co/Zn、Mn/Fe、Y/Ho比值和多判别图解共同指示该矿床为热液沉积,表明成矿物质Mn主要来源于海底热液.Mo和U元素富集因子(MoEF和UEF)、U/Th和V/(V+Ni)比值等沉积氧化还原指标分析结果表明,高品位锰矿石层产于氧化向缺氧转变的背景下,而低品位含锰岩层则主要产于氧化或强烈缺氧环境下.富锰岩层的δ13CPDB(-0.2‰～1.9‰)和δ18OSOMW(18.1‰～23.1‰)与海相碳酸盐岩相似,表明成矿物质的C和O主要来源于海水.基于上述结果,笔者认为东湘桥锰矿床成矿过程受海水CO2-3 浓度和沉积氧化还原条件的双重控制,其成矿过程可以概况为 2 个阶段:①深水盆地的热液Mn在还原条件下以可溶Mn2+向近岸CO2-3 过饱和的浅水台地迁移;②当沉积环境由氧化向缺氧转变时,锰氧化物在沉积/水界面还原释放Mn2+,显著提高水柱中溶解Mn浓度,促进富锰碳酸盐矿物析出,形成高品位锰矿石.
Abstract
The Permian marine sedimentary manganese deposits are widely developed in the southern Hunan region.In order to reveal the ore-forming processes and mechanisms,this study focuses on the sedimentary profile of the Dongxiangqiao manganese deposit in Yongzhou,Hunan Province.Major and trace elements,as well as carbon-oxygen isotopes,were analyzed.The results indicate that the manganese-rich rock layers enrich in elements such as Cr,Ni,Co.The ratios of Co/Zn,Mn/Fe,and Y/Ho,along with interpretations from multiple discriminant dia-grams,collectively indicate that the ore deposit is a hydrothermal deposit,suggesting that the ore-forming materi-al,manganese(Mn),primarily derived from seafloor hydrothermal fluid.The analysis results of sedimentary re-dox indicators,such as the enrichment factor of Mo and U(MoEF and UEF),as well as U/Th and V/(V+Ni)ratios,indicate that the layers of high-grade manganese ores were formed in the context of the transition from oxic to an-oxic conditions.In contrast,low-grade manganese-bearing rock layers were mainly formed in oxic or strongly anoxic conditions.The δ 13 CPDB(-0.2‰～1.9‰)and δ18 OSOMW(18.1‰～23.1‰)values of the manganese-rich rock layers,similar to marine carbonate rocks,suggest that the sources of ore-forming materials C and O are pri-marily derived from seawater.Based on these results,this study proposes that the ore-forming process of the Dongxiangqiao manganese deposit is controlled by both seawater CO 2-3 concentration and sedimentary redox conditions.The ore-forming process can be summarized infollowing two stages:① Hydrothermal Mn in deep-water basins migrates towards nearshore CO 2-3 supersaturated shallow-water platforms under reducing condi-tions;②When the sedimentary environment transitions from oxic to anoxic conditions,manganese oxides at the sediment/water interface are reduced to release Mn2+,significantly increasing the dissolved Mn concentration in the water column,promoting the precipitation of manganese-rich carbonate minerals,and forming high-grade manganese ores.
关键词
二叠纪/孤峰组/沉积型锰矿/地球化学/祁零盆地Key words
Permian/Gufeng Formation/sedimentary-type manganese deposit/geochemistry/Qiling basin引用本文复制引用
基金项目
湖南省地质院科研项目(HNGSTP202402)
国家自然科学基金(42073001)
国家自然科学基金(42372105)
出版年
2024
国家科技期刊平台
NSTL
万方数据