The effects of parent material on soils tend to be stronger than those of temporal and environmental conditions that interfere with weathering and pedogenesis. The main objective of the present study was to characterize and evaluate rock weathering and pedogenesis in the toposequence of gabbro-derived soils using geochemical and micromorphological data. Four profiles were sampled from a toposequence in the highlands of the Atlantic Forest region of Rio de Janeiro, Brazil. We carried out chemical and physical characterization of samples from disturbed soil horizons, followed by soil classification. Samples from undisturbed soil horizons were subjected to mineral weathering and micromorphological analyses, and scanning electron microscopy was used for microanalyses. We determined the total content of elements (SiO₂, Al₂O₃, Fe₂O₃, TiO₂, CaO, MgO, Na₂O, K₂O, Mn, P₂O₅, and Zr) and calculated the following weathering indices: chemical alteration index, chemical weathering index, and weathering index scale. We observed the progressive alteration of olivine into chlorite, weathering of clinopyroxenes and plagioclase, and neoformation of clay minerals such as kaolinite and iron oxyhydroxides such as goethite and hematite. The weathering of magnetite and ilmenite resulted in hematite and leucoxene, respectively. The high quantities of Si and Al in the soil matrix and the presence of iron oxyhydroxides and nodules indicated that fersialitization was the predominant pedogenetic activity associated with soil formation. Moreover, partial hydrolysis favored the formation of 2:1 clay minerals. Other processes included eluviation and illuviation, evidenced by the micromorphological analysis that indicates clay coating on pores, cavities, and aggregates.

母质对土壤的影响往往强于干扰风化和成土作用的时间和环境条件。本研究的主要目的是利用地球化学和微形态数据表征和评估辉长岩衍生土壤地形序列中的岩石风化和成土作用。从巴西里约热内卢大西洋森林地区高地的一个地形序列中采样了四个剖面。我们对来自扰动土壤层的样品进行了化学和物理表征，然后进行了土壤分类。来自未受干扰的土壤层的样品进行矿物风化和微形态分析，并使用扫描电子显微镜进行微分析。我们确定了元素的总含量（SiO ₂, Al ₂ O ₃ , Fe ₂ O ₃ , TiO ₂ , CaO, MgO, Na ₂ O, K ₂ O, Mn, P ₂ O ₅, 和 Zr) 并计算以下风化指数：化学蚀变指数、化学风化指数和风化指数尺度。我们观察到橄榄石逐渐变成绿泥石，单斜辉石和斜长石的风化，以及粘土矿物（如高岭石）和羟基氧化铁（如针铁矿和赤铁矿）的新形成。磁铁矿和钛铁矿的风化作用分别产生了赤铁矿和白二烯。土壤基质中大量的硅和铝以及氢氧化铁和结核的存在表明铁盐化是与土壤形成相关的主要成土活动。此外，部分水解有利于形成 2:1 的粘土矿物。其他过程包括euviation和illuviation，