Palygorskite-Sepiolite Clays of Lebrija, Southern Spain

Abstract

Abstract--The Upper Pliocene sediments near Lebrija in southern Spain contain commercial deposits of palygorskite and sepiolite. These sediments of continental origin consist chiefly of carbonate, marl, and clay resting on marine Pliocene quartzose sand. The lowest unit, the "Marly-Calcareous Bed," consists of sepiolite-rich marl associated with concretions and irregular layers of chert, <0.5 m thick, and local diatomite layers, as well as limestone, sandy limestone, marl, and clayey sandstones. This unit has a maximum thickness of 30 m and contains three clay-mineral suites as follows: (1) bottom--sepiolite ___ palygorskite; (2) center--sepiolite and palygorskite _+ illite; (3) top--palygorskite and illite, _+ sepiolite and smectite. Sepiolite decreases and palygorskite and illite increase toward the top, reflecting the composition of detrital material supplied to the basin. Beds 0.5-1 m thick locally and containing 50 to 60% sepiolite have been called "Tierra del Vino" (wine earth) because the material formerly was used to clarify and purify wine. The sepiolite-rich beds are as much as 15 m thick in the eastern part of the area. The upper unit is called the "Palygorskite Bed" because certain layers, 0.3 to 3 m thick, contain 35 to 75% palygorskite. The palygorskite-rich layers are interbedded with limestone and marl, and the entire unit is 15 m thick. The total resource of palygorskite is estimated at about 9 million tonnes.The sediments are believed to have been deposited in a brackish, lacustrine environment. Originally, tectonic stability and an arid climate favored the formation of sepiolite at about pH 8. Later, after significant weathering of the source rocks, detrital illite was transformed to palygorskite in the Mg-and Si-rich waters. Here, palygorskite was also precipitated directly.

Crystallochemical characterization of the palygorskite and sepiolite from the Allou Kagne deposit, Senegal

“…There are few references in the literature in which sepiolite and palygorskite occur in the same or adjacent localities. For example, they are described together in the following Spanish deposits: Tajo Basin, (Leguey et al" 1995;Galán and Castillo, 1984), Tabladillo (M artín Pozas et al, 1981); Lebrija (Galán and Ferrero, 1982); and also in central and central-southern Tilllisia (Zaaboub et al" 2005), in the Serinhisar-Acipayam Basin (Turkey) (Akbulut and Kadir, 2003), and in the deep-sea mid-Atlantic ridge, of hydrothennal origin (Bowles et al" 1971). In the Allou Kagne deposit, sepiolite and palygorskite appear together.…”

Geology, Occurrence, and Genesis of Eskişehir Sepiolites, Turkey

“…Sepiolite occurs in both medium-to thick-bedded, black or white sedimentary-type layers and in snow-white nodular concretions. Sepiolite beds have also been reported from playa lake deposits in Nevada and California (Post, 1978;Hewett, 1956), Saudi Arabia (Shadfan et aL, 1985), and Spain (Galan and Ferrero, 1982). Sepiolite and palygorskite beds are common in lacustrine Spanish Tertiary basins, and some deposits have great economic importance.…”

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“…En el contacto con el Plioceno marino se reconoce la presencia de un paleosuelo. La potencia total estimada es de 45 m (Galán y Ferrero, 1982).…”

“…La asociación de fauna de los materiales del Plioceno continental, indican claramente una sedimentación lacustre con oogonios de Characeas, Ostracodos y gasterópodos continentales (Galán y Ferrero, 1982).…”