矿床地质2024，Vol.43Issue(2)：289-303,15.DOI:10.16111/j.0258-7106.2024.02.004
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
摘要
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分类
天文与地球科学引用本文复制引用
廖凤初,王勇,刘湘华,徐军伟,熊伊曲,李斌,赖健清,骆检兰,陈雨林,罗益周..湘南地区东湘桥沉积型锰矿床地球化学特征及成矿机理[J].矿床地质,2024,43(2):289-303,15.基金项目
本文得到湖南省地质院科研项目(编号:HNGSTP202402)和国家自然科学基金项目(编号:42073001、42372105)联合资助 （编号:HNGSTP202402）
