Type 1 aqueous alteration in CM carbonaceous chondrites: Implications for the evolution of water-rich asteroids

1A. J. King, 1P. F. Schofield, 1S. S. Russell
Meteoritics & Planetary Science (in Press) Link to Article [DOI: 10.1111/maps.12872]
1Department of Earth Sciences, Natural History Museum, London, UK
Published by arrangement with John Wiley & Sons

The CM carbonaceous chondrite meteorites experienced aqueous alteration in the early solar system. They range from mildly altered type 2 to almost completely hydrated type 1 chondrites, and offer a record of geochemical conditions on water-rich asteroids. We show that CM1 chondrites contain abundant (84–91 vol%) phyllosilicate, plus olivine (4–8 vol%), magnetite (2–3 vol%), Fe-sulfide (120 °C), although higher water/rock ratios may also have played a role. The modal data provide constraints for interpreting the composition of asteroids and the mineralogy of samples returned from these bodies. We predict that “CM1-like” asteroids, as has been proposed for Bennu—target for the OSIRIS-REx mission—will have a high abundance of Mg-rich phyllosilicates and Fe-oxides, but be depleted in calcite.

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