TY - JOUR
T1 - Effect of hot desert weathering on the bulk-rock iron isotope composition of L6 and H5 ordinary chondrites
AU - Saunier, Gaëlle
AU - Poitrasson, Franck
AU - Moine, Bertrand
AU - Gregoire, Michel
AU - Seddiki, Abdelmadjid
PY - 2010/2
Y1 - 2010/2
N2 - Although iron isotopes are increasingly used for meteorites studies, no attempt has been made to evaluate the effect of terrestrial weathering on this isotopic tracer. We have thus conducted a petrographic, chemical, and iron isotopic study of equilibrated ordinary chondrites (OC) recovered from hot Moroccan and Algerian Saharan deserts environment. As previously noticed, we observe that terrestrial desertic weathering is characterized by the oxidation of Fe-Ni metal (Fe0), sulfide and Fe2+ occurring in olivine and pyroxene. It produces Fe-oxides and oxyhydroxides that partially replace metal, sulfide grains and also fill fractures. The bulk chemical compositions of the ordinary chondrites studied show a strong Sr and Ba enrichment and a S depletion during weathering. Bulk meteoritic iron isotope compositions are well correlated with the degree of weathering and S, Sr, and Ba contents. Most weathered chondrites display the heaviest isotopic composition, by up to 0.1‰, which is of similar magnitude to the isotopic variations resulting from meteorite parent bodies' formation and evolution. This is probably due to the release of isotopically light Fe2+ to waters on the Earth's surface. Hence, when subtle Fe isotopic effects have to be studied in chondrites, meteorites with weathering grade above W2 should be avoided.
AB - Although iron isotopes are increasingly used for meteorites studies, no attempt has been made to evaluate the effect of terrestrial weathering on this isotopic tracer. We have thus conducted a petrographic, chemical, and iron isotopic study of equilibrated ordinary chondrites (OC) recovered from hot Moroccan and Algerian Saharan deserts environment. As previously noticed, we observe that terrestrial desertic weathering is characterized by the oxidation of Fe-Ni metal (Fe0), sulfide and Fe2+ occurring in olivine and pyroxene. It produces Fe-oxides and oxyhydroxides that partially replace metal, sulfide grains and also fill fractures. The bulk chemical compositions of the ordinary chondrites studied show a strong Sr and Ba enrichment and a S depletion during weathering. Bulk meteoritic iron isotope compositions are well correlated with the degree of weathering and S, Sr, and Ba contents. Most weathered chondrites display the heaviest isotopic composition, by up to 0.1‰, which is of similar magnitude to the isotopic variations resulting from meteorite parent bodies' formation and evolution. This is probably due to the release of isotopically light Fe2+ to waters on the Earth's surface. Hence, when subtle Fe isotopic effects have to be studied in chondrites, meteorites with weathering grade above W2 should be avoided.
UR - http://www.scopus.com/inward/record.url?scp=77953110960&partnerID=8YFLogxK
U2 - 10.1111/j.1945-5100.2010.01017.x
DO - 10.1111/j.1945-5100.2010.01017.x
M3 - Article
AN - SCOPUS:77953110960
SN - 1086-9379
VL - 45
SP - 195
EP - 209
JO - Meteoritics and Planetary Science
JF - Meteoritics and Planetary Science
IS - 2
ER -