Investigation of mineralogical properties of soils developed on pyroclastic deposits; A case study from Karaj region, Iran

ABSTRACT: The study of soils derived from volcanic products because their large extent and unique characteristics are very important and can help us in the management and identification capabilities of them. Clay minerals are among the most important indicators of soil evolution via influencing a widerange of physical and chemical characteristics. Relationships between clay mineralogy suite and soil parent materials are keys to distinguish between inherited and neoformed minerals. Samples from surfacial soils of more than 40 sites at different topographic and climatic positions of the studied area were selected, described and analyzed.Some physical, chemical and mineralogical characteristics of samples were determined using standard methods. The aims of this study are investigation of clay mineralogy of soils formed on Karaj-green-tuff and their physicochemical properties under different topographic and climatic conditions.The results showed that although weathering the pyroclastic parent material has caused to formation of mixed clay minerals, chlorite, illite, vermiculite, smectite and kaolinite, but physicochemical properties of the studied soils including sandy soil texture (regarding to limited dispersion due to the existenec of short-rang-order minerals) with high cation exchange capacity demonstrate that the main properties of the studied soils have originated from pyroclastic materials.