Kaolinite (Kt) is the most studied mineral, being widely used in the ceramic, pharmaceutical and cellulose industries, in addition to being the main soil mineral in the world. Found in different parts of the planet, it differs in genesis and may be formed as a result of local weathering of the rocks, occurring in the silt fraction; and also due to the mineral's neogenesis with a predominance of clay-sized particles. The plain of upper Iguaçu river has the largest kaolinitic deposit in the south of Brazil and it’s formation raised doubts if this kaolin was transported or formed in situ due the high organic matter in the alluvial plain. To elucidate the origin of kaolin deposits, we sampled a possible font of the mineral, in the mountains of Serra do Mar and sampled two tubes that reach 4 m depth in the upper Iguaçu plain. We performed textural analysis, organic carbon, X-ray diffraction, Kt crystallography in silt and clay fractions, thermal analysis (TDA/TG) to quantify Kt and Gb in the clay fraction and scanning electron microscopy (SEM) with dispersive energy spectroscopy (EDS). The TDA/TG analysis demonstrated that saprolite has 66% of the kaolinite found in the plain. The XRD analysis shows a significant presence of mica (Mc) in all samples of the silt fraction, both in Serra do Mar and in the plain. In SEM/EDS, crystals with planar growth are observed, and the presence of pseudomorphic Mc-Kt in the silt fraction of all analyzed samples, with emphasis on the tubes sample with the crystal having almost twice the size of that observed in the saprolite sample from Serra do Mar, allowing to infer that the Kt of the silt fraction of the wetland soils were formed on site by the diagenesis of mica particles. The results obtained in this work indicate that the kaolinitic material found in the wetland of the upper Iguaçu plain is the result of weathering processes in the wetland itself, evidenced by the large pseudomorphs found, even greater than those observed in Serra do Mar.

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巴西伊瓜苏河上游的高岭石矿床：地层和矿物学特征

高岭石（Kt）是研究最多的矿物，除是世界上主要的土壤矿物外，还广泛用于陶瓷，制药和纤维素工业。它发现于地球的不同部分，其成因也不同，可能是由于淤泥部分中发生的岩石局部风化而形成的。也是由于矿物的新生，主要是黏土大小的颗粒。伊瓜苏河上游平原是巴西南部最大的高岭土矿床，由于冲积平原中有机质含量高，它的形成使人们怀疑这种高岭土是否是原位运输或形成的。为了阐明高岭土矿床的起源，我们在Serra do Mar山区采样了一种可能的矿物字体，并采样了两个在伊瓜苏平原上部深度达4 m的试管。我们进行了结构分析，有机碳，X射线衍射，粉砂和粘土馏分中的Kt晶体学，热分析（TDA / TG）来量化粘土馏分中的Kt和Gb以及具有分散能谱（EDS）的扫描电子显微镜（SEM） ）。TDA / TG分析表明，腐殖土占平原地区发现的高岭土的66％。XRD分析表明，在塞拉杜马尔和平原的所有淤泥部分样品中均存在大量云母（Mc）。在SEM / EDS中，观察到具有平面生长的晶体，并且在所有分析样品的粉砂级分中均存在假晶Mc-Kt，重点是试管样品，其晶体大小几乎是腐泥土样品中观察到的晶体大小的两倍。从塞拉杜马尔出发，可以推断出，湿地土壤粉粒级分的Kt是通过云母颗粒的成岩作用在现场形成的。这项工作获得的结果表明，在伊瓜苏平原上游的湿地中发现的高岭土物质是湿地自身的风化过程的结果，发现的大型假晶形物证明了这一点，甚至比在塞拉多马尔地区观察到的还要大。