Neoformación de minerales de la arcilla en la España Peninsulartendencias termodinánicas basadas en la composición de las aguas de los ríos españoles

Resumo

Stable or metastable minerals are established for 381 sampling points from river water compositians for every spanish watershed along the years 1974-75, 1975-76, 1981-82, 1982-83 and 1983-84, as published by the spanish Department of Public Works. Phase diagrams for the systems SiO2-Al2O3-H2O, K2O-SiO2-Al2O3-H2O, Na2O-SiO2-Al2O3-H2O, MgO-SiO2-Al2O3-H2O y CaO-SiO2-Al2O3-H2O, for 298 K and 1 atm. conditions, are used in order to determine the mineralogical stability, and therefore neoformation trends. Stable and metastable phases were taken into accaunt to draw the diagrams (Fernandez Marcos and Macias, 1987). The prevailing trend in the Peninsula, according to this method, is towards kaolinite neoformation. Nevertheless differences are observed between watersheds. So kaolinite is the only stable mineral neoformed in the North watersheds while there exist several stable minerals (kaolinite, mica, chlorite, pyraphillite) or metastable ones (smectite) in the Tajo, Guadiana, Guadalquivir, South, Jucar, Segura and East Pyrenees watersheds, depending on sampling point and date. Geographic distribution of different minerals is satisfactorily explained by taking into account: rainfall distribution, sileceous or calcareous nature of ground, and upper, medium or lower position in the river course.