Publication
Names
  • L. Bonal
  • C.M.O'D. Alexander
  • G.R. Huss
  • K. Nagashima
  • E. Quirico
  • P. Beck
Title
Hydrogen isotopic composition of the water in CR chondrites
Abstract
The thermal and aqueous alteration experienced by QUE 99177, MET 00426, EET 92042, GRA 95229, Renazzo and Al Rais CR chondrites was assessed through multi-technique characterization of their the carbonaceous matter and hydrated mineral phases. Each of the chondrites escaped long duration thermal metamorphism as reflected by the low structural order of the polyaromatic carbonaceous matter assessed by Raman spectroscopy. The infrared spectra of the matrix grains clearly reveal the presence of hydrated minerals in each of the CR chondrites. In particular, the extent of aqueous alteration experienced by QUE 99177 and MET 00426 may have been previously underestimated. The H isotopic compositions of the altering fluids were measured in situ in fine-grained phyllosilicates and individual coarse-grained hydrated silicates. In the analyzed CR chondrites, the main observations are that (i) the water is systematically enriched in D, and the enrichments (δDwater up to 1600‰) can be even higher than the highest D-enrichments reported for cometary water; (ii) the isotopic composition of the water is highly variable at the micrometer scale; (iii) there is no clear trend observed in the isotopic composition of the water (maximum D-enrichment, range of variation) along the aqueous alteration sequence. The D-enrichments and spatial variability are easier to explain as secondary signatures acquired through parent body processes, rather than as being due to the accretion of at least two ices with distinct isotopic compositions and sources that did not fully mix when they melted at the start of the aqueous alteration process.
Keywords
spectroscopy, Raman micro-spectrometer, FTIR micro-spectrometer, carbonaceous chondrites, CR chondrites, meteorite QUE 99177, meteorite MET 00426, meteorite EET 92042, meteorite Renazzo, meteorite Al Rais, meteorite GRA 95229
Content
material-matter, spectral data
Year
2013
Journal
Geochimica et Cosmochimica Acta
Volume
106
Pages
111 - 133
Pages number
23
Document type
article
Publication state
published
Experiment/Spectra