http://www.cnr.it/ontology/cnr/individuo/prodotto/ID275492

Crystal-chemistry of interstratified Mg/Fe-clay minerals from seafloor hydrothermal sites (Articolo in rivista)

Type

Articolo in rivista (Classe)
Prodotto della ricerca (Classe)

Label

Crystal-chemistry of interstratified Mg/Fe-clay minerals from seafloor hydrothermal sites (Articolo in rivista) (literal)

Anno

2013-01-01T00:00:00+01:00 (literal)

Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#doi

10.1016/j.chemgeo.2013.10.016 (literal)

Alternative label

Cuadros, J.a , Michalski, J.R.a, Dekov, V.b, Bishop, J.c, Fiore, S.d, Dyar, M.D.e (2013)
Crystal-chemistry of interstratified Mg/Fe-clay minerals from seafloor hydrothermal sites
in Chemical geology; Elsevier, Amsterdam (Paesi Bassi)
(literal)

Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#autori

Cuadros, J.a , Michalski, J.R.a, Dekov, V.b, Bishop, J.c, Fiore, S.d, Dyar, M.D.e (literal)

Pagina inizio

142 (literal)

Pagina fine

158 (literal)

Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#url

http://www.sciencedirect.com/science/article/pii/S000925411300452X# (literal)

Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#numeroVolume

360 (literal)

Rivista

Chemical geology (Rivista)

Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#pagineTotali

17 (literal)

Note

ISI Web of Science (WOS) (literal)
Scopu (literal)

Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#affiliazioni

a Department of Earth Sciences, Natural History Museum, Cromwell Road, London SW7 5BD, United Kingdom b Laboratoire de Géochimie et Métallogénie, Département Géosciences Marines, IFREMER, Z.I. Pointe du diable, BP 70 - 29280 Plouzané, France c SETI Institute, Mountain View, CA 94043, United States d Institute of Methodologies for Environmental Analysis,IMAA, CNR, Department of Geoenvironmental and Earth Sciences, University of Bari, Via Orabona 4, Bari, Italy e Mount Holyoke College, 50 College St., South Hadley, MA 01075, United States (literal)

Titolo

Crystal-chemistry of interstratified Mg/Fe-clay minerals from seafloor hydrothermal sites (literal)

Abstract

Seafloor hydrothermal sites generate abundant Mg- and Fe-rich clays. These clays are structurally and compositionally interesting because these environments are characterized by large, dynamic temperature and chemical gradients in their deposition environment, which promote the formation of chemically and structurally complex clays, including interstratified phases. The system is also interesting as a proxy for the study of the large Mg- and Fe-rich phyllosilicate deposits on Mars, which are broadly characterized as smectitic clay of hydrothermal, volcanic or sedimentary origin. Thirty submarine samples and four terrestrial ones, for comparison, were studied by means of X-ray diffraction (XRD), thermogravimetry (TG), mid-IR and Mössbauer spectroscopies and chemical analysis. The samples include nontronite and the mixed-layer phases glauconite-nontronite, talc-nontronite and talc-saponite. Some of the talc-saponite samples have Fe contents well above those typical for these Mg-rich, trioctahedral phases (up to 1.69 Fe per O10[OH]2, in the tetrahedral and octahedral sheets). Tetrahedral Fe ranges from 0 to 0.66 atoms per O10[OH]2 across the samples. As found in previous studies of similar specimens, Fe promotes the retention of molecular water that is released upon heating above 200 C, and is mainly emplaced in non-expandable layers (talc and glauconite layers). In talc-nontronite and talc-saponite octahedral Fe (both di- and trivalent) appears to be bound to this trapped molecular water, whereas in glauconite-nontronite the bond appears to be with tetrahedral Fe. Samples typically show more than one dehydroxylation event in the TG analysis. The weight loss at each dehydroxylation event is broadly consistent with the proportion of individual layers as determined by means of XRD, but there is no good correlation between both. By contrast, the weight loss at each dehydroxylation event correlates with the chemistry of the layers, where certain cations promote chemical domains in the octahedral sheet (e.g., trioctahedral, nontronite-like, and montmorillonite-like) that dehydroxylate at the several temperatures. The correlations found for talc-nontronite and glauconite-nontronite samples suggest that the distribution of cations in the octahedral sheets of most, but not all, samples is intermediate between total dispersion and total segregation, perhaps random. The talc-nontronite samples have talc layers with cation-deficient octahedral sheets. The above results are best explained by layers of polar character, where the octahedral sheets are composed of domains with different chemical characteristics corresponding to the two types of layers in the interstratified clay. The existence of molecular water (bands at 1635 and 3300-3500 cm- 1, or ~ 6.1 and 2.9-3.1 ?m, respectively) bound in non-expanding layers is relevant to the mineral characterization of Martian Fe-rich clays with spectroscopic methods, where molecular water is so far assumed to be linked to smectite. The variety of mixed-layer clays in which Fe is found in the submarine samples suggests that mixed-layering may be important in Martian clays, which are spectroscopically variable but generally Fe-rich. (literal)

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