Bentonites from Cabo de Gata, Almería, Spain: a mineralogical and geochemical overview

Abstract

The Neogene volcanic region of Cabo de Gata, Almería, SE Spain, is dotted with many outcrops of bentonite, some of them of significant economic interest. The bentonites have their origin in the hydrothermal alteration of pyroclastic rocks (15-7 Ma). The deposits are usually associated with fractures. The major mineral is a dioctahedral Fe- and Mg-smectite (89-75%) and this is accompanied by minor amounts of feldspars, quartz, amphiboles, pyroxenes, biotite, zeolites, disordered tridymite, calcite, etc. This paper describes the geological background, the general characteristics of the bentonites and major aspects of their formation, e.g. type of low-temperature hydrothermal solutions, mass balance, chemical evolutions of the smectites and geochemistry of trace elements. Finally, the characteristics of three of the most important deposits are described.

Vanadium oxide supported on porous clay heterostructure for the partial oxidation of hydrogen sulphide to sulfur

“…As was indicated in previous works [18,20,21], the main mineralogical component is 8 montmorillonite. Moreover it is noticeable the presence of minor amounts of plagioclase, cristobalite, calcite and almost undetectable amount of quartz [20,21].…”

“…Moreover it is noticeable the presence of minor amounts of plagioclase, cristobalite, calcite and almost undetectable amount of quartz [20,21].…”

“…This material was previously characterized in several researches revealing that the bentonite is formed in a large proportion for montmorillonite (> 90%) [20,21]. 5 In order to purify the montmorillonite fraction, the bentonite was collected by sedimentation.…”

CuO-CeO2 supported on montmorillonite-derived porous clay heterostructures (PCH) for preferential CO oxidation in H2-rich stream

“…The raw bentonite, used for the synthesis of PCH, was previously characterized [45,46]. The largest (> 90 wt%) mineralogical component of this bentonite is montmorillonite.…”

Barreras de ingeniería para el aislamiento de residuos radiactivos

“…En España, se ha seleccionado la bentonita FEBEX, o bentonita de "la Serrata" (Almería), como bentonita de referencia en el concepto de AGP. Esta bentonita posee un contenido de montmorillonita de 92 ± 3% en peso (8). Barreras de ingeniería para el aislamiento de residuos radiactivos Engineered barriers for radioactive waste confinement necesario estudiar el comportamiento químico, físico y mineralógico a largo plazo en las sucesivas interfases entre materiales, destacando la interacción que tendrá lugar entre el hormigón y la bentonita.…”