U-Pb and Hf-W dating of young zircon in mesosiderite Asuka 882023

Mesosiderites are unique stony-iron meteorites, composed of eucrite-like silicates and Fe-Ni metals. Their formation, including silicate-metal mixing and metamorphisms, provides important insights into early planetary processes in the inner solar system. This report describes the first in situ U-Pb and Hf-W dating of zircon in a mesosiderite Asuka 882023. The U-Pb (4502 ± 75 Ma) and Hf-W (4532.8 + 5.7/−10.5 Ma) ages may represent timing of the zircon formation, which is considerably younger than crustal differentiation of the parent body. This evidence, combined with earlier studies of chronology, implies that mesosiderites were reheated at 4530–4520 Ma, clearly after the silicate-metal mixing.