摘要
贵州黔东南铁厂沟铝土矿目前已探明矿石量约298万吨,属大型矿床,其含矿岩系为二叠系下统梁山组,矿体常呈似层状、透镜状、漏斗状覆于上泥盆统高坡场组白云岩古侵蚀面上,矿体底部通常含菱铁矿结核。矿体顶板通常为碳质页岩或煤带,部分地区的顶板为二叠系栖霞组灰岩,由此组成了凯里—黄平地区典型的煤-铝-铁结构。对铁厂沟铝土矿成铝盆地中心的1个钻孔中的高岭岩系样品进行元素地球化学特征分析,解剖该成铝盆地中心的沉积风化成岩过程,主要结论包括:1)稳定元素特征如Zr-Ta、Zr-Nb、Cr-Ni图解及Al_(2)O_(3)/TiO_(2)比值等综合表明基底的志留系地层是铁厂沟矿床主要的物源;2)二叠系该区域的第1次抬升剥蚀,致使盆地周缘出露并发生剥蚀去顶作用,风化产物向盆地中心运移,初次沉积以高岭石为主、富集锐钛矿、锆石等副矿物的原始高岭岩系,与志留系页岩相比较,具有低K、Mn、Cs、Rb、Sr、Ba,高Al、Sr、Th、Nb、Zr、Y和REE等特征,δCe异常总体为弱负异常,表明其沉积环境总体以弱还原环境为主;3)第2次抬升作用使得盆地中心剖面也发生了一定程度的风化淋滤改造,但剖面整体Al/Si比值变化较小,表明仅发生了一定的去铁淋滤,上部高岭岩中V/Cr(平均1.96)、Th/U(平均3.40)和Co/Ni(平均0.39)均体现出弱氧化的风化特征,风化淋滤导致上层高岭岩系轻稀土元素的迁移及总稀土元素含量下降,并最终改变了上、下层高岭岩的稀土配分模式,下层高岭岩系以富含菱铁矿结核为特征,风化过程中从上部及盆地周缘成铝部位淋滤的铁在剖面下部富集,推测原始形态为铁结核,在后期成岩过程中与周围的有机碳反应形成菱铁矿结核。
The large-scale Tiechanggou Bauxite deposit,located in the southeastern Guizhou,hosts 2.98 million tons of proved ores.Its ore bodies,hosted in the Middle Permian Liangshan Formation(Fm.),occurred as layered,lenticular and funnel-shaped on the paleo-eroded surface of dolomite in the Upper Devonian Gaopochang Fm.,with usual siderite nodules in the bottom part of the ore bodies.The overlying strata of the ore body is usually carbonaceous shale or coal seams,with limestone of the Permian Qixia Fm.Locally.They consist of a typical coal-bauxite-iron structure in the Kaili-Huangping area.In this paper,we have collected samples of kaolinite rocks from cores of a drill hole in the center of the aluminum-forming basin of the Tiechanggou bauxite deposit for analyzing their elemental geochemical characteristics,then have discussed the weathering,sedimentation,and diagenesis processes of the center of the aluminum-forming basin.The main conclusions are given below.(1)The characteristics of immobile elements(e.g.,Al_(2)O_(3)/TiO_(2)ratios,and Zr-Ta,Zr-Nb,and lgCr-lgNi diagrams)indicate that the ore-forming materials of the Tiechanggou bauxite deposit could be mainly sourced from the Silurian strata in the basement.(2)The first elevation of this area occurred in the Permian,caused the outcropping and denudation of the basin and its periphery area.The weathering products were migrated to and deposited in the central part of the basin with initially deposited kaolinite rock(consisting of dominant kaolinite and enriched accessory minerals such as anatase and zircon).Compared with the Silurian shale,the initial kaolinite rock was characterized with low contents of K,Mn,Cs,Rb,Sr,and Ba,and high contents of Al,Sr,Th,Nb,Zr,Y,and REE,withgeneral negative Ce anomalies in the profile,indicating that its sedimentary environment is general weakly reduced environment.(3)The second elevation caused a certain degree weathering and leaching transformation of sediments in the central part of the basin,but the overall Al/Si ratios of samples in the section are changed relatively slight,indicating that only a certain amount of iron was leached away.The ratios of V/Cr(average 1.96),Th/U(average 3.40),and Co/Ni(average 0.39),of samples from the upper kaolinite rock layer all reflect characteristics of their weathering occurred under weakly oxidized condition.Weathering and leaching caused the migration of the rare earth elements(REE)especially the light rare earth elements away from the upper kaolinite rock layer.This finally changed the REE distribution patterns of samples in the upper and lower kaolinite rock layers.The lower kaolinite rock layer is characterized by rich siderite nodules.The iron leached from the upper part and the periphery of the basin during the weathering process was migrated to and enriched in the lower part of the section.It is believed that siderite nodules were formed by the reaction of initial iron nodules with organic carbon surrounding those iron nodules in the diagenesis process.
作者
陈健
向震中
严琦
席瑶伟
王兴伟
陈军
陈轶平
尹祺
吴涛
谷静
CHEN Jian;XIANG Zhen-zhong;YAN Qi;XI Wei-yao;WANG Xing-wei;CHEN Jun;CHEN Yi-ping;YIN Qi;WU Tao;GU Jing(The Sixth Geological Team,Guizhou Province Bureau of Nonferrous Metals and Nuclear Industry Geological Exploration,Kaili 556000,China;The State Key Laboratory of Ore Deposit Geochemistry,Chinese Academy of Science,Guiyang 550081,China;University of Chinese Academy of Sciences,Beijing 100049,China)
出处
《矿物学报》
CAS
CSCD
北大核心
2021年第4期494-508,共15页
Acta Mineralogica Sinica
基金
贵州省科技支撑项目(编号:黔科合支撑[2019]2859号)
矿床地球化学国家重点实验室领域前沿项目(编号:SKLODG-2018-01)。
关键词
高岭岩系
地质地球化学特征
矿床成因
铁厂沟矿床
贵州
kaolinite rock series
geological and geochemical characteristics
ore genesis
Tiechanggou deposit
Guizhou
