FN Archimer Export Format
PT J
TI Crystal-chemistry of interstratified Mg/Fe-clay minerals from seafloor hydrothermal sites
BT 
AF CUADROS, Javier
   MICHALSKI, Joseph R.
   DEKOV, Vesselin
   BISHOP, Janice
   FIORE, Saverio
   DYAR, M. Darby
AS 1:1;2:1;3:2;4:3;5:4;6:5;
FF 1:;2:;3:PDG-REM-GM-LGM;4:;5:;6:;
C1 Nat Hist Museum, Dept Earth Sci, London SW7 5BD, England.
   IFREMER, Lab Geochim & Metallogenie, Dept Geosci Marines, F-29280 Plouzane, France.
   SETI Inst, Mountain View, CA 94043 USA.
   Univ Bari, CNR, Dept Geoenvironm & Earth Sci, Inst Methodol Environm Anal, Bari, Italy.
   Mt Holyoke Coll, S Hadley, MA 01075 USA.
C2 NHM, UK
   IFREMER, FRANCE
   SETI INST, USA
   UNIV BARI, ITALY
   MT HOLYOKE COLL, USA
SI BREST
SE PDG-REM-GM-LGM
IN WOS Ifremer jusqu'en 2018
   copubli-europe
   copubli-int-hors-europe
IF 3.482
TC 37
UR https://archimer.ifremer.fr/doc/00160/27131/25329.pdf
LA English
DT Article
DE ;Interstratified clays;Martian clays;Submarine hydrothermal sites;Thermogravimetry;XRD
AB 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, montmorillonite-like, etc.) 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 μm, 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.
PY 2013
PD DEC
SO Chemical Geology
SN 0009-2541
PU Elsevier Science Bv
VL 360
UT 000327532100014
BP 142
EP 158
DI 10.1016/j.chemgeo.2013.10.016
ID 27131
ER

EF