30 likes | 198 Views
The Complicated Geologic History of Asteroid 4 Vesta. Spectral studies of the HED meteorites show that they likely come from asteroid 4 Vesta. HED stands for: Howardites, which are mixtures of: Eucrites (basaltic lava flows) Diogenites (orthopyroxenites)
E N D
The Complicated Geologic History of Asteroid 4 Vesta • Spectral studies of the HED meteorites show that they likely come from asteroid 4 Vesta. • HED stands for: • Howardites, which are mixtures of: • Eucrites (basaltic lava flows) • Diogenites (orthopyroxenites) • The howardites contain rock and mineral fragments, and impact-produced glasses • The glass fragments and spherules record the compositions of a wide range of lithologies on Vesta
The Complicated Geologic History of Asteroid 4 Vesta • Rock samples of eucrites plot in the basalt field on this widely-used diagram to classify igneous rocks. • Most glasses are similar to the rocks, but are enriched in alkalis • A few glasses are enriched in SiO2 and alkalis, falling into the dacite field (≈ granite) • This indicates that extensive fractional crystallization of magmas occurred on Vesta
The Complicated Geologic History of Asteroid 4 Vesta An interesting picture of Vesta: • Metamorphism • Intrusions into the crust: magmatic differentiation, contact metamorphism • Partial melting of the crust in some places • Magma mixing between crustal partial melts and eucrite basalt magma • Eucrite basalt magma migration through crust • Granites could form in intrusions or in the residual magma ocean