Evidence for a Second Generation of Magnesite in Martian Meteorite Allan
نویسندگان
چکیده
Introduction: Single-stage formation mechanisms for carbonate and other secondary minerals in ALH84001 are rapidly being revised to include multiple stages of carbonate growth and later thermal and mechanical events including alteration [1-9]. In an effort to confirm some of these more complex histories we have been studying carbonate-bearing regions within this meteorite. Magnesitic carbonates found in contact with unique " slab " carbonates [9] in two thin sections of ALH84001 show indications of being of a later generation. The results of our observations help clarify the origins of the carbonate and related minerals in ALH84001, and how these minerals can be used to understand the history of interactions between the martian crust and its volatile inventory. Methods: Textural and fracture analyses of car-bonates were performed both petrographically and using backscatter electron images (BSE). These BSE images and additional compositional analyses were obtained using the Cameca SX-50 electron microprobe at the University of Chicago.
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