Las mineralizaciones de Caolín de Puebla de Montalbán (Toledo)

Abstract

Three thick kaolin ore deposits are located near Puebla de Montalban (Toledo, Central Spain) in relationship with the saprolite developed over the Hercynian basement which is fossilized by the Paleogene detritial facies (essentially kaolinitic sands) of the Southwestern border of the Tajo Basin. Quality of the different ore deposits is very irregular as the saprolitic mineralization was weathering-controlled being associated to pockets in relationship with zones where the granitic basement was more altered. Generally the kaolin obtained from these ore deposits is quite pure. Mean composition consists of: 12-18% of quartz, 60-80% of phyllosilicates, 2-5% of opal, and sometimes traces of feldspars. Phyllosilicates consist of: 60-80% of kaolinite, 30-35% of smectite and 0-10% of illite. Characteristics of this kaolinite are high titanium and low iron contents, and a high degree of crystallinity and a very ordered arrengement. Genetic processes of these kaolinite ore deposits are related to an intense and long episode of weathering affecting to granitic basement during Early ’Paleogene, and even Late Cretaceus time.