Mapping the Dominant Clay Minerals in the Soils of Isfahan Province and Their Relationship with Climate and Parent Materials

Understanding the abundance of clay minerals in soil and also, their spatial variability can provide more comprehensive information about soil properties, behavior and functions. The objectives of this research were: (i) to map the spatial distribution of  the dominant clay minerals in the soils of Isfahan Province and its relationship with climate and parent materials, and (ii) to determine the quantity of  the dominant clay minerals in different climatic classes of Isfahan Province. The amount of palygorskite, illite, expanded minerals and chlorite were semi-quantitatively determined for 100 soil samples collected from Isfahan Province. Maps of the dominant clay minerals were prepared by the Inverse Distance Weighting method. The results showed that palygorskite mostly occurred in the soils of dry areas with higher temperature throughout the province. This mineral was not present in the more humid areas of the province. Besides, palygoskite was found to be dominant in the soils derived from the Qom Formation, as well as Lower and Upper Red Formations belonging to Miocene and Pliocene. It seems, therefore, that the parent material plays a major role in entering palygoskite to the soil system, while the dry climate mostly guarantees the stability of this clay minerals and, to some extent, its limited neoformation in such soils. Both illite and chlorite occur in all soils throughout the province, regardless of their climate, following no particular trend. This may indicate that parent materials play a major role in the occurrence of these minerals. Both climate and parent material appear to have affected the distribution of expandable clays in the soils. In more humid areas of the province (west and southwest), climate plays a larger role in the distribution of this mineral. In other areas of the study region, especially in the eastern parts of the province with a much drier climate, the role of the parent material on the dominant soil clay minerals is more pronounced.