Metamorphic history of the eucritic crust of 4 Vesta

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Abstract
The petrologic properties of eucrites indicate that most formed as rapidly cooled lava flows that were subsequently metamorphosed at >800°C for periods of about 1 Myr. We have modeled the development of the eucritic crust of the eucrite parent body, assumed to be asteroid 4 Vesta, by the eruption and subsequent burial of lava flows (serial magmatism). The burial of the flows causes them to reheat to metamorphic temperatures (>800°C). Provided that the initial thermal gradient in the upper 5 km was steep, as it would be if 26Al was the heat source, our model shows that most eucrites were metamorphosed for periods over 1 Myr in a crust between 15 and 25 km thick, if volcanism lasted only 1 to a few Myr. Longer periods of volcanism do not result in high enough peak metamorphic temperatures to be consistent with eucrite data. The hot lower crust in Vesta provides an environment in which even small (few meters) dikes could have cooled slowly enough to produce cumulate eucrites and possibly diogenites.