Volcanic eruptions and intrusions on the asteroid 4 Vesta

Authors:
  • LWLionel Wilson
    Lionel Wilson
  • KKKlaus Keil
    Klaus Keil
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Abstract
We use basic principles of fluid mechanics to explore the intrusive and eruptive consequences of early, large‐scale silicate melting within the asteroid 4 Vesta and relate our findings to the properties of the howardite‐eucrite‐diogenite meteorites. Surface lava flows on Vesta would commonly have had widths ranging from a few hundred meters to a few kilometers, and lengths lying between a few kilometers and at least several tens of kilometers. Flow thicknesses would have occupied a much narrower range, lying between about 5 and 20 m. These thicknesses imply cooling rates and plagioclase crystal growth rates which are extremely similar to those measured in the eucrite meteorites. Intrusions may have formed at very shallow depths, as cooling dikes failed to erupt their contents completely to the surface, or at the base of the crust, where rising magmas would have been neutrally buoyant as the density structure of Vesta's crust evolved. Deep intrusions would have had lateral extents up to 30 km and thicknesses up to 3 m; shallow intrusions would have had vertical extents less than 10 km and widths of ∼1 m. None of these intrusions and surface flows would have been thick enough or have formed frequently enough at a given location to have caused extensive thermal alteration of earlier eruptives, lending support to the idea that burial and subsequent long‐term exposure to the rising geothermal gradient was the main mechanism of thermal metamorphism.

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