Temperatures of aqueous alteration on carbonaceous chondrite parent bodies

Abstract

Aqueous alteration of primitive meteorites is among the earliest and the most widespread geological processes in the solar system. A better understanding of these processes would help us constrain the early evolution condition of the solar system and test models of thermal and chemical evolution of planetesimals. In this study, we extended our previous work on CM chondrites by further applying carbonate clumped isotope thermometry to other types of carbonaceous chondrites (GRO 95577, CR1; Orgueil, CI; and Tagish Lake, ungrouped type 2) to determine the conditions of their aqueous alteration. Carbonate in GRO 95577 is almost exclusively calcite; both Orgueil and Tagish Lake contain complex mixtures of several carbonates, which necessitated stepped phosphoric acid digestion to separately analyze calcite, dolomite/ankerite and breunnerite. CO_2 gases derived from these acid digestions are exceptionally rich in sulfur and organic contaminants. While so far no consistent evidence suggests their influences on Δ_(47) after extensive purification, we are continuing working on this issue.

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