Among the useful tools in characterizing weathering degrees are chemical indices, which combines bulk major elemental oxides into a single metric value and commonly presented along a vertical profile. However, characterizing geomaterials of diverse nature using chemical indices may be problematic. In this study, chemical indices were evaluated to characterize weathering degrees in decomposed volcanic rocks from different depths, locations and formations. This was achieved by conducting comprehensive geochemical tests and statistical analyses. A good index must give appropriate trends, provide meaningful statistics and varies greatly with weathering degrees irrespective of the approach employed. Correlations were made between chemical indices and specific volume, depth, weathering degree as well as geological formation using tentative numerical value. The extent of weathering is best characterized by relating chemical indices with in-situ specific volume rather than depth, which is commonly used. The weathering potential index (WPI), hydration coefficient (Hc), leaching coefficient (Lc) and weathering index of Parker (WIP) are the most appropriate indices that could be used to characterize weathering in decomposed volcanic rocks. The chemical indices that have many mobile elements or cations and water content in their formulations are most useful. The chemical indices that are relating few oxides to each other should be avoided. The influence of formation on using chemical indices to characterize weathering degree is insignificant and the effect of weathering grade is very significant. This approach can be applied to similar geomaterials.

化学指数是表征风化程度的有用工具，该化学指数将大量的主要元素氧化物结合成一个度量值，并通常沿垂直剖面显示。但是，使用化学指标表征多种性质的土工材料可能会遇到问题。在这项研究中，评估了化学指数以表征来自不同深度，位置和地层的分解火山岩的风化程度。这是通过进行全面的地球化学测试和统计分析来实现的。一个好的指数必须给出适当的趋势，提供有意义的统计数据，并且随风化程度的不同而变化很大，而与采用的方法无关。化学指标与比容，深度，使用暂定数值计算风化程度和地质构造。风化程度的最佳体现是将化学指标与通常使用的原位比容而不是深度相关联。风化潜力指数（WPI），水合系数（Hc），浸出系数（Lc）和帕克的风化指数（WIP）是最合适的指数，可用于表征分解后的火山岩中的风化。在配方中具有许多可移动元素或阳离子和水含量的化学指标最有用。应避免将很少的氧化物相互关联的化学指标。地层对使用化学指标表征风化程度的影响微不足道，风化等级的影响非常显着。