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

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P595; P611

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    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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  • Received:May 15,2023
  • Revised:September 26,2023
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  • Online: January 18,2024
  • Published: January 25,2024