桂西二叠系铝土矿含矿岩系沉积相特征及其演化  

Characteristics and evolution of sedimentary facies of bauxite-bearing rocks series of Permianbauxite deposits in western Guangxi

作　　者：张启连 黄光琼 韦访 黄文芳 邓军 李活松 韦良喜 蒙家锋 覃良朝 杨海 黄宝宁 吴含志 辛晓卫 马坚高 黎家龙 吴向宇 ZHANG Qilian;HUANG Guangqiong;WEI Fang;HUANG Wenfang;DENG Jun;LI Huosong;WEI Liangxi;MENG Jiafeng;QIN Liangchao;YANG Hai;HUANG Baoning;WU Hanzhi;XIN Xiaowei;MA Jiangao;LI Jialong;WU Xiangyu(Guangxi Institute of Geological Survey,Nanning 530023,Guangxi,China;4th Team of Guangxi Bureau of Geology,Nanning 530031,Guangxi,China;274 Team of Guangxi Bureau of Geology,Beihai 536005,Guangxi,China;3th Team of Guangxi Bureau of Geology,Qinzhou 535000,Guangxi,China)

机构地区：[1]广西壮族自治区地质调查院,广西南宁530023 [2]广西壮族自治区第四地质队,广西南宁530031 [3]广西壮族自治区二七四地质队,广西北海536005 [4]广西壮族自治区第三地质队,广西钦州535000

出　　处：《地质通报》2024年第10期1734-1755,共22页Geological Bulletin of China

基　　金：广西壮族自治区地质矿产勘查局项目《广西关键矿产资源深部勘查人才小高地》(编号:桂组通字[2019]85号);《广西沉积型铝土矿成矿理论研究和找矿突破关键技术研发与示范》(编号:桂科AB21196028号);《广西矿产地质志续编与产品服务》(编号:KD-[2023]-XZ-050)。

摘　　要：桂西二叠系铝土矿含矿岩系沉积相研究薄弱,长期未能建立沉积层序。通过线路调查和剖面研究,将桂西二叠系铝土矿含矿岩系厘定为4个沉积相8个亚相,即顶部为沼泽炭泥相,上部为滨海平原泥岩相,中部为准平原铝土岩(矿)相,下部为滨湖-平原湖泊铁铝质岩相。中部准平原相可分为凹地铝土岩夹泥岩亚相、缓坡残坡积铝土矿亚相、凹地沉积铝土矿亚相、斜坡铝土岩亚相。下部滨湖平原湖泊铁铝质岩相可分为滨浅湖铝土质泥岩-铁质泥岩-铁铝岩亚相和滨湖平原古土壤亚相。陆相火山灰在各相中均有残存。含矿岩系中泥岩成分变异指数ICV在1左右,表明存在沉积再循环,泥岩中化学蚀变指数CIA均大于97,显示风化程度高;亲硫元素(Cu、Zn、Co、Ni)和亲铁元素(V)在下部铁铝质岩相中普遍高于中上部铝土岩(矿)-泥岩相,亲氧元素(Th、U、Nb、Ta、Sn、W)则相反;铝土矿相稀土元素总量最高,中上部铝土岩(矿)-泥岩相中的δCe和LREE/HREE均明显高于铁铝质岩相。Fe2O3-Al2O3-SiO2投影表明,季风气候贯穿整个含矿岩系沉积,铝土矿相中的泥岩元素特征值在所有泥岩中均为极值,指示了极端红土化的存在,砾屑及元素地球化学显示含矿岩系具有继承性;对应4个沉积相,可推断3个演化阶段,第一阶段为红土聚集,第二阶段为准平原化(即铝土矿化),第三阶段为平原化;含矿岩系发育期间火山灰持续沉降。铝土矿是第二次风化壳的产物。The study on sedimentary facies of Permian bauxite−bearing rock series in western Guangxi has been rare so that a sedimentsequence has not been set up yet.Based on line survey and section study,adding microscopic observation and elemental analysis ofrocks and ores,this paper has determined four sedimentary facies and eight subfacies of ore−bearing rock series,the four faces areswamp carbonaceous mud facies on the top,the coastal plain mudstone facies in the upper,the peneplain bauxite facies in the middleand the lakeshore−lake ferric−aluminous rocks facies in the lower,and the peneplain bauxite facies can be divided into subfacies suchas valley bauxite laminated mudstone,gentle−slope residual bauxite,valley sedimentary bauxite and slope bauxite subfacies,and thelakeshore−lake ferric−aluminous rocks can be divided into the aluminous mudstone−ferro mudstone−ferroaluminite of theshore−shallow lake and the paleosoil of lakeshore plain.The continental volcanic ash remains in all facies.In bauxite−bearing rockseries,the composition variations(ICV)of mudstone fluctuates around 1,indicating the existence of recycling sediments,and chemicalindex alteration(CIA)of mudstone is greater than 97,indicating a high degree of weathering.The contents of sulfurophilic elements(Cu,Zn,Co,Ni)and ferriophilic elements(V)are generally higher in the lower ferric−aluminous rocks than ones in the bauxite andmudstone,while oxygenophilic elements(Th,U,Nb,Ta,Sn,W)are on the contrary.The values of REE in bauxite phases are thehighest,and theδCe and LREE/HREE of bauxite and mudstone are significantly higher than those of ferro−aluminous rocks.TheFe2O3−Al2O3−SiO2 projection shows that monsoon climate persist all the time when the ore−bearing rock series developed,and thespecial element values of the mudstones in bauxite facies are the extreme ones in all mudstones that mean a period of extremelaterization produced by peneplain,and the gravel and element geochemistry show that the ore−bearing rock series are of

关 键 词：铝土矿 含矿岩系 沉积相 古气候 古地理 火山灰 桂西 

分 类 号：P531[天文地球—古生物学与地层学] P595[天文地球—地质学] P618.45