Negative δ18O values in Allan Hills 84001 carbonate: Possible evidence for water precipitation on mars

Details Negative δ18O values in Allan Hills 84001 carbonate: Possible evidence for water precipitation on mars Negative δ18O values in Allan Hills 84001 carbonate: Possible evidence for water precipitation on mars

Mar 2005

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2005gecoa..69.1359h&link_type=abstract

Geochimica et Cosmochimica Acta, Volume 69, Issue 5, p. 1359-1370.

Computer Science

6

Scientific paper

The Martian meteorite ALH84001 contains ˜1% by weight of carbonate formed by secondary processes on the Martian surface or in the shallow subsurface. The major form of this carbonate is chemically and isotopically zoned rosettes which have been well documented elsewhere. This study concentrates upon carbonate regions ˜200 μm across which possess previously unobserved magnesium rich inner cores, interpreted here as rosette fragments, surrounded by a later stage cement containing rare Ca-rich carbonates (up to Ca81Mg07Fe04Mn07) intimately associated with feldspar. High spatial resolution ion probe analyses of Ca-rich carbonate surrounding rosette fragments have δ18OV-SMOW values as low as -10‰. These values are not compatible with deposition from a global Martian atmosphere invoked to explain ALH84001 rosettes. The range of δ18O values are also incompatible with a fluid that has equilibrated with the Martian crust at high temperature or from remobilisation of carbonate of rosette isotopic composition. At Martian atmospheric temperatures, the small CO2(gas)-CO2(ice) fractionation makes meteoric CO2 an unlikely source for -10‰ carbonates. In contrast, closed system Rayleigh fractionation of H2O can generate δ18OH2O -30‰, as observed at high latitudes on Earth. We suggest that atmospheric transport and precipitation of H2O in a similar fashion to that on Earth provides a source of suitably 18O depleted water for generation of carbonate with δ18OV-SMOW = -10‰.

Affiliated with

Also associated with

No associations

Rating

Negative δ18O values in Allan Hills 84001 carbonate: Possible evidence for water precipitation on mars does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Negative δ18O values in Allan Hills 84001 carbonate: Possible evidence for water precipitation on mars, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Negative δ18O values in Allan Hills 84001 carbonate: Possible evidence for water precipitation on mars will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-1216051