Mineralogy of In Situ Soils Developed from Basalt Weathering in an Arid-Semiarid-Semihumid Climosequence of Middle Alborz

Basalt is among igneous rocks that contains susceptible minerals to weathering minerals, and their weathering products are deposited as secondary minerals and different cations in the soil. Soils derived from basalt bedrock have many distinctive properties that are rarely found in other soils. Clay minerals constitute an important component of the soil system, and knowledge of their role in soil fertility is imperative for sustainable soil management and productivity. Therefore, the objective of the current study was to evaluate clay minerals formation of in situ soil derived from basalt in three different climate conditions. In the present study, physicochemical properties of 24 soil profiles, which formed on basalt rocks, were investigated in the arid, semi-arid, and semi-humid regions of middle Alborz and also mineralogical properties were studied in 6 profiles. X-ray diffraction analysis indicated that illite and smectite were the dominant minerals in the arid and semi-arid soils, respectively. Results revealed that the neosynthesis mechanism and deformation process of other minerals (especially illite) confirm the pedogenic formation of smectite soils in semi-arid regions. Evidence suggested that the illite in the studied soils had a pedogenic origin. Also, the vermiculite origin was to affected by the weathering of mica and chlorite within the three study areas.