Titre du document / Document title

Trace element geochemistry of Martian iddingsite in the Lafayette meteorite : Mars volatile evolution, Part 2

Auteur(s) / Author(s)

TREIMAN A. H. ⁽¹⁾ ; LINDSTROM D. J. ⁽²⁾ ;

Affiliation(s) du ou des auteurs / Author(s) Affiliation(s)

⁽¹⁾ Lunar and Planetary Institute, Houston, Texas, ETATS-UNIS
⁽²⁾ NASA Johnson Space Center, Houston, Texas, ETATS-UNIS

Résumé / Abstract

The Lafayette meteorite contains abundant iddingsite, a fine-grained intergrowth of smectite clay, ferrihydrite, and ionic salt minerals. Both the meteorite and iddingsite formed on Mars. Samples of iddingsite, olivine, and augite pyroxene were extracted from Lafayette and analyzed for trace elements by instrumental neutron activation. Our results are comparable to independent analyses by electron and ion microbeam methods. Abundances of most elements in the iddingsite do not covary significantly. The iddingsite is extremely rich in Hg, which is probably terrestrial contamination. For the elements Si, Al, Fe, Mn, Ni, Co, and Zn, the composition of the iddingsite is close to a mixture of ∼50% Lafayette olivine +∼40% Lafayette siliceous glass + ∼10% water. Concordant behavior among these elements is not compatible with element fractionations between smectite and water, but the hydrous nature and petrographic setting of the iddingsite clearly suggest an aqueous origin. These inferences are both consistent, however, with deposition of the iddingsite originally as a silicate gel, which then crystallized (neoformed) nearly isochemically. The iddingsite contains significantly more magnesium than implied by the model, which may suggest that the altering solutions were rich in Mg²⁺.

Revue / Journal Title

Journal of geophysical research   ISSN 0148-0227 

Source / Source

1997, vol. 102, n^oE4, pp. 9153-9163 (35 ref.)

Langue / Language

Anglais

Editeur / Publisher

American Geophysical Union, Washington, DC, ETATS-UNIS  (1949) (Revue)

Mots-clés anglais / English Keywords

meteorites ; chemical analysis ; trace-element analyses ; iddingsite ; intergrowths ; smectite ; ferrihydrite ; Mars ; olivine ; augite ; neutron activation analysis ; petrography ; alteration ; hydration ; models ; rare earths ; electron probe data ; silicates ; clay minerals ; sheet silicates ; hydroxides ; oxides ; nesosilicates ; clinopyroxene ; pyroxene ; chain silicates ;

Mots-clés français / French Keywords

Météorite ; Analyse chimique ; Analyse élément trace ; Iddingsite ; Intercroissance ; Smectite ; Ferrihydrite ; Planète Mars ; Olivine ; Augite ; Analyse activation neutronique ; Pétrographie ; Altération ; Hydratation ; Modèle ; Terre rare ; Donnée microsonde électronique ; Météorite Lafayette ; Silicate ; Argile minéral ; Phyllosilicate ; Hydroxyde ; Oxyde ; Nésosilicate ; Pyroxène clino ; Pyroxène ; Inosilicate ;

Mots-clés espagnols / Spanish Keywords

Meteorito ; Análisis químico ; Análisis elementos traza ; Iddingsita ; Esmectita ; Ferrihidrita ; Planeta Marte ; Olivino ; Augita ; Petrografía ; Alteración ; Hidratación ; Modelo ; Tierras raras ; Dato sonda electrónica ; Silicato ; Arcilla mineral ; Filosilicato ; Hidróxido ; Óxido ; Piroxeno clino ; Piroxeno ;

Localisation / Location

INIST-CNRS, Cote INIST : 3144, 35400006534441.0100