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Geochemistry and Biomarker Analysis of the Bentonites from Esquivias (Toledo, Spain)

Department of Geology, University of Salamanca, 37008 Salamanca, Spain
Instituto de Geociencias (IGEO) (Complutense University of Madrid—Consejo Superior de Investigaciones Científicas), 28040 Madrid, Spain
Laboratory of Biomolecular Stratigraphy, Polytechnic University of Madrid, 28003 Madrid, Spain
Department of Mineralogy and Petrology, Complutense University of Madrid, 28040 Madrid, Spain
Author to whom correspondence should be addressed.
Minerals 2018, 8(7), 291;
Received: 16 May 2018 / Revised: 3 July 2018 / Accepted: 6 July 2018 / Published: 9 July 2018
(This article belongs to the Special Issue Authigenic Clay Minerals: Mineralogy, Geochemistry and Applications)
The Tajo Basin is one of the richest in Mg-clays known around the world. Mg-bentonites, kwon as pink clays and green clays, alter in the Intermediate Unit of the Miocene sediments. In this work, a new approach to the genesis of these bentonites is performed by studying for the first time the biomarkers present in these clays in relation to the mineralogy and geochemistry, as well as using discriminatory criteria between green and pink clays. Samples were collected at a quarry of Mg-bentonites, in the proximities of Esquivias (Toledo, Spain). Mineralogical characterization and semi-quantification (X-ray diffraction (XRD)) allowed a well-defined classification according to the mineralogical content of the samples to be established, differentiating four associations. Geochemical analyses are clearly linked to the mineralogy and provide criteria to differentiate the genesis of the materials studied. In this regard, green clays are interpreted as having a more detrital character than pink clays, which present a more authigenic character. Biomarkers (n-alkanes and n-alkanoic acids) were studied, not showing a clear link with the mineralogy as in the case of the geochemistry, but providing interesting information about the origin and degradation of the organic matter. Pink clays have higher contents in biomarkers than green clays, providing a discriminative criterion. View Full-Text
Keywords: bentonite; saponite; authigenic clays; geochemistry; biomarker analysis bentonite; saponite; authigenic clays; geochemistry; biomarker analysis
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García-Rivas, J.; Suárez, M.; Torres, T.; Sánchez-Palencia, Y.; García-Romero, E.; Ortiz, J.E. Geochemistry and Biomarker Analysis of the Bentonites from Esquivias (Toledo, Spain). Minerals 2018, 8, 291.

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