Mount Anak Krakatau erupted on 22nd December 2018, resulting in a large deposit of fresh volcanoclastic materials on the island's surface. As the age of these new soil materials is known precisely, and the island is isolated from human activities, studying the ash and pyroclastic materials of Anak Krakatau will provide insights on the first stages of pedogenesis in tropical volcanic regions. This paper reports for the first time the chemical and geochemical characteristics of the fresh volcanic materials of Mt. Anak Krakatau. Samples were collected at 63 days and 82 days after the eruption. Remobilization of newly deposit volcanic materials occurred immediately after the eruption. Rill and gully erosion were observed on the surface of the island. Two types of samples were collected and analysed: volcanic ash (< 2 mm) and lapilli (2–64 mm). The pH_H2O of the samples had a mean value of 5.9 (std. dev. 0.6). The CEC of the materials was very low but variable (3.11 ± 2.3 cmol_c kg⁻¹) and the cations were easily leached (Mg > Ca > K > Na). Microscopic analysis and XRD patterns showed that the materials were dominated by plagioclases, with labradorite being the dominant species. XRF analysis indicated that there were two types of volcanic materials: the first group had lower SiO₂ concentration (mean 39%) and lower Al₂O₃ (mean 10%) but a higher concentration of Fe₂O₃ (mean 18.9%), CaO (15.6%), K₂O (1.7%), SO₄ (2.9%), P₂O₅ (2.8%), and heavier elements (Mn, Zn, Cu, Ti, Sr, Zr, Cr) and Ag₂O (0.76%). The second group was more common with basaltic-andesitic composition with a mean concentration of 54.9% SiO₂, 17.2% Al₂O₃, and 8.5% Fe₂O₃. Anak Krakatau eruptions and volcanic deposits are rare events; basic information provided in this report offers valuable information on the initial stage of pedogenesis and can be used as a baseline for future pedogenesis study.

阿纳克·克拉卡托山（Mount Anak Krakatau）于2018年12月22日爆发，导致该岛表面大量沉积了新鲜的火山碎屑物质。由于这些新土壤材料的年龄已被精确地知道，并且该岛与人类活动隔绝了，因此研究Anak Krakatau的火山灰和火山碎屑材料将为热带火山区成岩作用的第一阶段提供见识。本文首次报道了新鲜的火山山的化学和地球化学特征。Anak Krakatau。喷发后第63天和第82天收集样品。喷发后立即进行了新沉积火山材料的移动。在岛的表面上观察到沟壑和沟壑侵蚀。收集并分析了两种类型的样本：火山灰（<2毫米）和青金石（2-64毫米）。样品的_H2O平均值为5.9（标准差0.6）。材料的CEC非常低，但变化很大（3.11±2.3 cmol _c kg ^-1），阳离子易于浸出（Mg> Ca> K> Na）。显微分析和X射线衍射图谱表明，材料主要由斜方晶石为主，拉长石为主要物质。XRF分析表明，有两种类型的火山物质：第一类具有较低的SiO ₂浓度（平均39％）和较低的Al ₂ O ₃（平均10％），但具有较高的Fe ₂ O ₃浓度（平均18.9％）。 ，CaO（15.6％），K ₂ O（1.7％），SO ₄（2.9％），P ₂O ₅（2.8％）和较重的元素（Mn，Zn，Cu，Ti，Sr，Zr，Cr）和Ag ₂ O（0.76％）。第二组是更常见玄武安山岩组合物与二氧化硅的54.9％的平均浓度₂，17.2％的Al ₂ ö ₃，和8.5％的Fe ₂ ö ₃。Anak Krakatau火山喷发和火山沉积是罕见的事件。本报告中提供的基本信息提供了有关成岩初期的有价值的信息，并且可以用作将来进行成岩研究的基准。