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中国贵州西部地区晚二叠世峨眉山玄武岩组上覆地层宣威组和龙潭组中具有明显的Nb、Ta、Zr、Hf、REE等元素的矿化现象。宣威组和龙潭组地层中岩性变化较大，包括砂岩、粉砂岩、泥岩、页岩及粘土岩均有产出，但富铌钽元素地层以粘土岩和页岩为主，其次为泥岩。矿物学分析揭示富铌钽元素地层的主要矿物为高岭石，其次是绿泥石、金红石、锐钛矿，部分样品含少量的钠长石、石膏、伊利石、绢云母、方解石、白云石和含铁矿物，长石和石英晶屑也占了一定比例。地球化学特征分析显示Al2O3和Fe2O3相对富集，而CaO、Na2O、MgO、K2O出现强烈亏损；Ga、Cu、Nb、Ta、Zr、Hf等微量元素强烈富集。宣威组和龙潭组地层样品中Nb/Ta比值变化较大，与大陆地壳的Nb/Ta比值相似，但却远小于大陆玄武岩的Nb/Ta比值。是因为在表生作用过程中Nb的活动性要大于Ta，导致在峨眉山玄武岩风化过程中Nb的流失量要大于Ta，所以在风化产物所形成的沉积岩中展现出相对于母岩贫Nb而富Ta的特征，使得宣威组和龙潭组沉积岩中的Nb/Ta比值降低。铌钽元素含量与金红石和锐钛矿的含量具有显著的相关性，且相对于峨眉山玄武岩，铌钽元素的变化率与钛元素变化率呈现较高的相关性，所以，宣威组和龙潭组地层中铌钽元素极有可能赋存在金红石或锐钛矿等含钛矿物中。宣威组和龙潭组地层的形成及铌钽元素的矿化过程大体为：晚二叠世早期，峨眉山玄武岩大面积喷发后，大量的峨眉山玄武岩暴露地表。加之该时期扬子板块处于低纬度地区，在长期高温湿热的大气条件下，特别是受火山气体污染的酸性雨水淋滤下，Ca2+、Na+、K+等阳离子从硅酸盐矿物中释放出来，而Al、Fe、Ga、Hf、Nb、Ta、Th等稳定元素保留在残留物中，因此部分铌钽元素仍保留在玄武岩中抗风化能力强的矿物中，如金红石、锐钛矿等。风化剥蚀后形成的富集铌钽元素的玄武岩风化碎屑物在地形差的作用下，自西向东经过短距离的搬运，汇聚到地势低洼处，分别形成陆相的宣威组地层和滨海相的龙潭组地层，金红石和锐钛矿等副矿物在分选作用下富集，从而导致宣威组和龙潭组地层中铌钽元素的富集。后期快速的海侵，使得超常富集铌钽元素的沉积粘土-粉砂岩层被晚期的沉积地层所覆盖。

The overlying strata of the Emeishan basalt group in the western Guizhou, China, is the Xuanwei and Longtan Formation, which has obvious mineralization phenomena such as Nb, Ta, Zr, Hf and REE. The lithology of the Xuanwei and Longtan Formation varies greatly, including sandstone, siltstone, mudstone, shale and clay rock, but the rich Nb and Ta layer is dominated by clay rock and shale rock, followed by mudstone. Detailed mineralogical analysis reveals that the main minerals in the rich Nb and Ta layer are kaolinite, followed by chlorite, rutile, anatase, and some samples contain a small amount of albite, gypsum, illite, sericite, calcite, dolomite and iron-bearing minerals, feldspar and quartz crystal also account for a certain proportion. Geochemical characteristics show that Al2O3 and Fe2O3 are relatively enriched, while CaO, Na2O, MgO and K2O are strongly depleted; trace elements such as Ga, Cu, Nb, Ta, Zr and Hf are strongly enriched. The Nb/Ta ratio in the Xuanwei and Longtan Formation samples varies greatly, similar to the Nb/Ta ratio of the continental crust, but much smaller than the Nb/Ta ratio of the continental basalt.It is because the activity of Nb is greater than Ta in the process of epigenetic action, resulting in the loss of Nb is greater than Ta in the process of Emeishan basalt weathering, so it shows the characteristics of Ta-rich in sedimentary rock formed by weathering products relative to the parent rock, resulting in a decrease in the Nb/Ta ratio in the sedimentary rocks of the Xuanwei and Longtan Formation. The content of Nb and Ta has a significant correlation with the content of rutile and anatase, therefore, The content of Nb and Ta have a significant correlation with the content of rutile and anatase, and the rate of change of Nb and Ta have a higher correlation with the rate of change of Nb and Ta relative to that of Emeishan basalt, so Nb and Ta are most likely to be hosted in titanium-bearing minerals such as rutile or anatase in the Xuanwei and Longtan Formation. The formation and mineralization process of the Nb and Ta are generally in the Xuanwei and Longtan Formation: In the early Late Permian, after the large-scale eruption of the Emeishan basalt, a large number of Emeishan basalts exposed in the surface. In addition, the Yangtze plate is in a low latitude area during this period. Under long-term high-temperature hot and humid atmospheric conditions, especially leaching by acidic rainwater polluted by volcanic gases, cations such as Ca2+, Na+ and K+ were released from silicate minerals, while Stabilizing elements such as Al, Fe, Ga, Hf, Nb, Ta, and Th remained in the residue, so some of the lanthanum remains in the minerals with strong weathering resistance in basalt, such as rutile and anatase. The basal weathered clastics which enriched Nb and Ta by weathering and denudation are transported from west to east by short distances and concentrated to the low-lying areas, the Xuanwei Formation was formed in the continental facies and the Longtan Formation was formed in the coastal phase, the secondary minerals such as rutile and anatase are enriched under the sorting, resulting in the enrichment of Nb and Ta in the Xuanwei and Longtan Formation. The rapid transgression in the later period makes the superimposed enriched elemental sedimentary clay-siltstone layer covered by the late sedimentary strata.