Physicochemical properties, Micromorphology and clay mineralogy of soils containing zeolite in Rafsanjan Area, Iran

Zeolite is a group of anionic hydrated aluminosilicates with a tridimensional structure which has great implications in remediation of water, sediment and soil resources. The present research aims at physicochemical investigation, clay mineralogy and micromorphology of soils along Rafsanjan-Sarcheshmeh lithotoposequence, southeastern Iran.
The study area starts from mantled pediments, southern west of Rafsanjan and extends to Sarcheshmeh town. Soil moisture and temperature regimes of the area were aridic and mesic, respectively. Topography and geology maps together with Google Earth images were used to investigate different landforms and geological formations in the area. Mantled pediment (pedon 1), rock pediment (pedons 2 and 3) and mountain (pedons 4, 5, 6 and 7) were among dominant landforms recognized in the area under study. Mantled pediment is composed of younger gravel sediments. On the other hand, arkose and tuff are dominant in rock pediment. Besides, mountain geomorphic surface show high proportion of tracky basaltic and doloritic rocks. Seven pedons affected by geological formations on different landforms were described and sampled. Physicochemical analyses together with clay mineralogy and micromorphological observations performed and Soil Taxonomy and WRB were used for soil classification.
Calcic, gypsic, argillic and cambic diagnostic horizons were identified according to field and laboratory investigations. Soils were classified as Typic Haplocalcids, Typic Calciargids, Typic Torriorthents and Typic Haplocambids using Soil Taxonomy. Cambisols, Calcisols, and Regosols were also found according to WRB classification system. Presence of Btk horizon in pedons 4 and 5 was attributed to more available humidity of paleoclimate. Micromorphological observations showed grey radial (fan shape) zeolite crystals with parallel extinction. Calcite coatings, hypocoatings and nodules were among calcium carbonate pedofeatures identified. Lenticular and interlocked plates of gypsum and clay coatings were also observed during micromorphological investigations. Kaolinite, illite, palygorskite and smectite clay minerals were determined. Chabazite with first, second, and third order peaks of 0.64, 0.59, and 0.29 nm and natrolite with first and second order peaks of 0.42 and 0.3 nm together with calcite and quartz impurities were investigated in zeolitic geological formations of the area using X-ray diffractometers. Natrolite was the only zeolite found in soils under study and showed a decreasing trend with distance from zeolitic geological formations. Zeolite in soils of the area seems to be inherited from parent material.
Results of the study showed role of topography and parent material on variability of soil properties in the area.