Title:Carbonates in meteorites: Tracers of fluid and ice in asteroids – Speaker:Myriam Telus Assistant Professor, Earth & Planetary Sciences, UCSC– Abstract: Carbonaceous chondrites show evidence for fluid alteration in planetesimals within a few million years of the Solar System’s formation. To constrain the aqueous alteration history of CM chondrites, we measured the C and O isotopic composition of carbonates and the O isotopic composition of magnetite. These minerals form through direct precipitation from the fluid or water-rock interactions in the parent asteroid.
We observe a wide range in the C and O isotope composition of carbonates. d13C vs d18O fall into two groups, one consisting of primary calcite and the other consisting of dolomite and secondary calcite. Our results are consistent with a CO2-CH4 gas mixture as the source of C for carbonate formation. These gases were likely released during melting of ice in the parent body. Carbonate and magnetite oxygen isotope fractionation are consistent with formation temperatures between 30°C and 100°C.
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