Zaccagnaite-3R, a new Zn-Al hydrotalcite polytype from El Soplao cave (Cantabria, Spain)

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dc.contributor.author Lozano Fernández, Rafael Pablo
dc.contributor.author Rossi, Carlos
dc.contributor.author La Iglesia, Ángel
dc.contributor.author Matesanz, Emilio
dc.date.accessioned 2020-12-18T05:03:13Z
dc.date.available 2020-12-18T05:03:13Z
dc.date.issued 2012
dc.identifier.citation American Mineralogist, vol.97, n.4, 513-523 es_ES
dc.identifier.issn 1945-3027
dc.identifier.uri http://hdl.handle.net/20.500.12468/729
dc.description.abstract We have recently discovered significant amounts of zaccagnaite, a natural Zn-Al-CO3 hydrotalcite in the El Soplao cave (north Spain). The El Soplao zaccagnaite is speleothemic, i.e., formed in the cave, and therefore it represents a new cave mineral. The origin of El Soplao zaccagnaite is related to the diagenesis of Zn- and Al-rich ferromanganese speleo-stromatolites, where it occurs as a porefilling cement that likely precipitated at low temperature (≤ ~11 °C). In some stromatolite layers, the abundance of zaccagnaite crystals is large enough to enable their physical separation. This has allowed us to obtain its X-ray powder-diffraction pattern, infrared spectrum, and differential thermal/thermogravimetric profiles. The cell parameters of the El Soplao zaccagnaite, refined from X-ray powder diffraction data are: a = 3.06616(1) and c = 22.6164(1) Å [α = β = 90°, γ = 120°; V = 184.139(1) Å3 ; Z = 3], consistent with a new trigonal polytype of zaccagnaite: zaccagnaite-3R. Besides, the El Soplao zaccagnaite shows some features previously unknown in natural hydrotalcites, such as octahedral-like morphologies and fluorescence zoning. Electron microprobe analyses revealed that the El Soplao zaccagnaite-3R has an unusual chemistry for natural hydrotalcites, as it is significantly more rich in Al (Zn2+/Al3+ = 1.6) than the hexagonal (2H) polytype (Zn2+/Al3+ = 2.0). The simplified chemical formula deduced from electron microprobe analysis is (Zn0.6Al0.4)(OH)2(CO3)0.2⋅0.5H2O, where C and water were calculated by stoichiometry. The carbon content calculated by stoichiometry (2.2 wt%) is in good agreement with that measured with the electron microprobe on gold-coated samples (2.5 wt%). The presence of interlayer water and CO3 groups was confirmed by thermogravimetric analysis coupled to mass spectroscopy, and by the analysis of the infrared spectrum es_ES
dc.description.sponsorship Museo Geominero, Instituto Geológico y Minero de España, España es_ES
dc.description.sponsorship Departamento de Petrología y Geoquímica, Universidad Complutense de Madrid, España es_ES
dc.description.sponsorship Instituto de Geología Económica, Consejo Superior de Investigaciones Científicas, España es_ES
dc.description.sponsorship Instituto de Geología Económica, Universidad Complutense de Madrid, España es_ES
dc.description.sponsorship Centro de Asistencia a la Investigación de Difracción de Rayos X, Universidad Complutense de Madrid, España es_ES
dc.language.iso en es_ES
dc.publisher Mineralogical Society of America es_ES
dc.rights Otro es_ES
dc.subject zaccagnaite es_ES
dc.subject hydrotalcite es_ES
dc.subject speleothem es_ES
dc.subject Cueva El Soplao es_ES
dc.subject España es_ES
dc.title Zaccagnaite-3R, a new Zn-Al hydrotalcite polytype from El Soplao cave (Cantabria, Spain) es_ES
dc.type Postprint es_ES
dc.relation.publisherversion http://www.minsocam.org/MSA/AmMin/TOC/Abstracts/2012_Abstracts/Apr12_Abstracts/Lozano_p513_12.pdf es_ES
dc.description.funder Instituto Geológico y Minero de España, España es_ES
dc.description.funder Gobierno de Cantabria, España es_ES
dc.description.funder Turismo del Nansa S.L., España es_ES
dc.identifier.doi http://dx.doi.org/10.2138/am.2012.3908 es_ES
dc.coverage.spatialStudy Cueva El Soplao, Cantabria, España es_ES


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