Source of Palygorskite in Gypsiferous Aridisols and Associated Sediments from Central Iran

Abstract

Arid soils in central Iran that evolved from the weathering of post-Tethyan sediments contain palygorskite. Clay fractions of gypsiferous soils and their associated sediments from different landforms from central Iran were investigated. Palygorskite was the dominant silicate clay mineral in clay fractions of the soils, and of Oligo-Miocene limestone, a less common parent rock. The Jurassic shale and Cretaceous limestone contain illite and chlorite with a trace amount of palygorskite. Association of large amounts of palygorskite bundles with gypsum in the gypsiferous soils studied, supports the hypothesis that palygorskite was probably formed after the initial precipitation of gypsum, that created a high pH and Mg/Ca ratio. The major portion of the palygorskite present in colluvial and plateau soils was probably formed authigenically when central Iran was covered by post Tethyan shallow hyper-saline lagoons. Palygorskite in alluvial soils appeared to be essentially detrital.

Pedogenesis and clay mineralogical investigation of soils formed on gypsiferous and calcareous materials, on a transect, southwestern Iran

“…The association of smectite and palygorskite in the Oligo-Miocene limestone and marl is consistent with the results of others (Gindy et al, 1985;Shadfan et al, 1985a,b,c;Shadfan and Mashhady, 1985;Ingles and Anadon, 1991;Pletsch et al, 1996;Khormali and Abtahi, 2003). Khademi and Mermut (1998) found palygorskite and sepiolite and appreciable amounts of mica and smectite in the clay fraction of the Oligo-Miocene limestone of central Iran. All formations contained small quantities of interstratified minerals, but only the youngest contained measurable amounts of quartz.…”

“…Khademi and Mermut (1998) discussed three ideal conditions for palygorskite formation in soils and sediments of central Iran: (1) Increase in Mg/Ca ratio due to gypsum crystallization in the shallow water bodies; (2) Increasing environmental pH due to warm climate; and (3) Increasing soluble Si due to enriched hydrothermal solutions. Eswaran and Barzanji (1974) showed that neoformed palygorskite fibers coat gypsum and hornblende crystals.…”

“…Both inherited and pedogenic sources of palygorskite in Iranian soils were mentioned by Toomanian et al (2001), Farpoor et al (2002) as well as Owliaie and Abtahi (2003). Fibrous clay minerals (sepiolite and palygorskite) were found to be widespread in late Cenozoic sediments of arid and semi-arid regions of Iran (Khademi and Mermut, 1998). Khormali and Abtahi (2003) concluded that the percentage of palygorskite in soils is related to the gypsum content and the ratio of mean annual precipitation to mean annual reference crop evapotranspiration (P/ET8).…”

Palygorskite in the Late Miocene Red Clay Sediment from the Chinese Loess Plateau and Its Paleoclimatic Implications

“…In many soils from semiarid regions of the world, palygorskite has been reported with increasing frequency. In these environments, two main mechanisms have been proposed to explain the presence of palygorskite: (1) a detrital origin [48,49], i.e., the occurrence of palygorskite is attributed to palygorskite-bearing rocks, sediments, or soils, allochthonous or inheritance, and (2) an in situ pedogenic origin [24,50,51]. Allochthonous or inherited palygorskite provides insight into the evolution of the paleoclimate of the source area, whereas in situ authigenic palygorskite documents information on the paleoclimate of the depositional region.…”

Nanostructure of palygorskite/sepiolite in Texas caliche: Possible bacterial origin

“…1993;Molinaroli and Irba 1995;Singer et aI. 1995;Verreechia and Le Coustumer 1996;Khademi and Mermut 1998). In general, the two clay minerals occur in the lower parts of caliche profiles, having been dissolved nearer to the surface, and they are precipitated during the dry season but dissolve during the humid part of the year (van den Heuvel 1966;Newman 1987;Gauthier-Lafaye et aI.…”