陕南镇巴地区中-晚三叠世界线富锂黏土岩的发现及找矿意义
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P595; P611

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中陕核工业集团公司科技攻关项目(61210103)


The discovery and prospecting significance of lithium-enriched claystone in the Middle-Late Triassic boundary in Zhenba area, southern Shaanxi
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    摘要:

    首次报道了扬子板块北缘镇巴地区中-晚三叠世界线黏土岩锂的超常富集,黏土岩产于关岭组(T2g)/须家河组(T3x)平行不整合界面,为古风化壳沉积物,Li2O品位0.08%~0.11%,最高达0.22%,超过了该类型矿产的边界品位(0.06%),界线黏土岩的岩石学特征、矿物组成及岩石成因亟待查明。本文通过XRD分析、TIMA分析以及详细的地球化学研究,查明了界线黏土岩的矿物组成,探讨了黏土岩形成的沉积环境及物质来源,提出了不整合面黏土岩类关键金属矿产的综合找矿方向。研究表明,镇巴地区T2/T3界线黏土岩主要由石英、伊利石、高岭石组成,并含有极少量绿泥石、蒙脱石和铝绿泥石。主量元素(SiO2、Al2O3TFe2O3、TiO2)特征表明界线黏土岩属于铝土质泥岩,黏土岩CIA值(化学蚀变指数)为85~93,ICV值(成分变异指数)为0.22~0.46,说明其沉积母岩经历了强烈的化学风化作用。微量元素(V、Ni、Sr、Ba)显示黏土岩形成于氧化-还原过渡的陆相淡水沉积环境。我国目前在不整合面发现的黏土岩有铁-铝质黏土岩、铝质黏土岩、铝土岩,代表了古风化壳沉积,并产有锂、镓、稀土、铌等关键金属矿产,形成时代主要为石炭纪-二叠纪,具有多元素综合成矿的特点,建议后期加强不整合面黏土岩类的综合找矿工作,助力新一轮找矿突破。

    Abstract:

    It is the first time that the super abnormal enrichment of lithium has been reported in the claystone at the bottom of the Middle-Late Triassic Xujiahe Formation in the Zhenba area, located on the northern margin of the Yangtze plate. The claystone, which contains Li2O ranging from 0.08% to 0.11% (up to 0.22%), develops in the parallel unconformity interface of Guanling Formation (T2g)/Xujiahe Formation (T3x), representing ancient weathering crust sediments. The Li2O content exceeds the boundary grade (0.06%) of this type of deposit. To further understand the petrological characteristics, mineral composition, and petrogenesis of the boundary claystone, this paper aims to identify the minerals composition, discuss the sedimentary environment and sediment source, and propose a comprehensive prospecting direction for key metal minerals using XRD analysis, TIMA analysis, and detailed geochemical research. The results demonstrate that the T2/T3 boundary claystone in the Zhenba area is mainly composed of quartz, illite, and kaolinite, with small amounts of chlorite, montmorillonite, and sudoite. The major elemental characteristics (SiO2, Al2O3, TFe2O3, TiO2) indicate that the boundary claystone belongs to bauxite mudstone. The CIA (chemical index of alteration) and ICV (index of compositional variability) values range from 85 to 93 and 0.22 to 0.46, respectively, indicating that the sedimentary parent rock has undergone significant chemical weathering processes. Currently, the claystone found in unconformities in China includes iron-aluminum claystone, aluminum claystone, and bauxite rock. These represent ancient weathering crust sediments, and important metal minerals such as lithium (Li), gallium (Ga), rare earth elements (REE), and niobium (Nb) are produced. The formation age is primarily Carboniferous-Permian, exhibiting characteristics of multi-element comprehensive mineralization. This paper suggests that comprehensive exploration of claystone on unconformity surfaces should be strengthened in the future to facilitate new breakthroughs in prospecting.

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周伟,祁晓鹏,张嘉升,徐磊,杨杰,高景民,2024,陕南镇巴地区中-晚三叠世界线富锂黏土岩的发现及找矿意义[J].岩石矿物学杂志,43(1):47~62. ZHOU Wei, QI Xiao-peng, ZHANG Jia-sheng, XU Lei, YANG Jie, GAO Jing-min,2024,The discovery and prospecting significance of lithium-enriched claystone in the Middle-Late Triassic boundary in Zhenba area, southern Shaanxi[J]. Acta Petrologica et Mineralogica,43(1):47~62.

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  • 收稿日期:2023-05-15
  • 最后修改日期:2023-09-26
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  • 在线发布日期: 2024-01-18
  • 出版日期: 2024-01-25