Publication: Palaeoenvironmental implications of aluminium phosphate-sulphate minerals in
Early–Middle Triassic continental sediments, SE Iberian Range (Spain)
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Publication Date
2013
Authors
Galán Abellán, Ana Belén
Barrenechea, José F.
Horra del Barco, Raúl de la
Luque del Villar, Francisco Javier
Alonso Azcárate, Jacinto
Arche, Alfredo
López Gómez, José
Lago San José, Marceliano
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Elsevier
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Abstract
The presence of Sr-rich aluminium-phosphate sulphate (APS) minerals in continental sedimentary rocks from the Cañizar and Eslida Formations along the eastern part of the Iberian Range (Spain) is considered as evidence of acidic and oxidising conditions during Early–Middle Triassic times. The formation of APS minerals occurred shortly after sedimentation, in early diagenetic stages, prior to the compaction of the sediments and most probably was related to the circulation of acidic meteoric waters. Such conditions might result from a sustained, damaged environment or from multiple environmental crises, but would have delayed the recovery of life after the end-Palaeozoic mass extinction. APSminerals occur as small disseminated and idiomorphic pseudo-cubic crystals (0.5 to 6 μmlong) or as massive and polycrystalline aggregates replacing fragments of fine- rainedmetamorphic rocks (mainlymetapelites). Textural data indicate that the formation of the APS minerals predated the quartz and illite cements, and that they resulted from the destabilisation of pre-existing minerals, as evidenced by the replacement of slate fragments by APSminerals and hematite and by the close association of the disseminated APS crystals and kaolinitewith altered detrital mica plates. Electronmicroprobe analyses and X-ray diffraction study of the APSminerals indicate a rather homogeneous composition in different parts of the basin, corresponding to solid solutions among woodhouseite, svanbergite, crandallite and goyazite. The sources of strontium in the APS minerals remain unclear. Phosphorous was primarily supplied by dissolution of detrital phosphates under acidic conditions, and sulphur derives from the weathering of pyrite.