Low-temperature carbonate concretions in the martian meteorite ALH84001: Evidence from stable isotopes and mineralogy
- Univ. of Wisconsin, Madison, WI (United States)
- California Institute of Technology, Pasadena, CA (United States); and others
The martian meteorite ALH84001 contains small, disk-shaped concentrations of carbonate with concentric chemical and mineralogical zonation. Oxygen isotope compositions of these concretions, measured by ion microprobe, range from {delta}{sup 18}O = +9.5 to +20.5{per_thousand}. Most of the core of one concretion is homogeneous (16.7 {+-} 1.2{per_thousand}) and over 5{per_thousand} higher in ({delta}{sup 18}O = 4.6 {+-} 1.2{per_thousand}). Secondary SiO{sub 2} has {delta}{sup 18}O = 20.4{per_thousand}. Carbon isotope ratios measured from the core of one concretion average {delta}{sup 13}C = 46 {+-} 8{per_thousand}, consistent with formation on Mars. The isotopic variations and mineral compositions offer no evidence for high temperature (>650{degrees}C) carbonate precipitation and suggest non-equilibrium processes at low temperatures (<{approximately} 300{degrees}C). 44 refs., 3 figs., 1 tab.
- OSTI ID:
- 468974
- Journal Information:
- Science, Vol. 275, Issue 5306; Other Information: PBD: 14 Mar 1997
- Country of Publication:
- United States
- Language:
- English
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