F igure 19. Crustal isotherms between 4.56 Ga and 4.55 Ga based on the Ghosh and McSween (1998) thermal model of Vesta. The locations of Pasamonte and Haraiya in the crust are based on the calculated cooling rates. Pasamonte cooled rapidly at the surface and was reburied in a shallow ejecta

F igure 14. Haraiya: BSE image of augite lamellae in pigeonite showing a constant lamellar thickness to grain boundary.

F igure 15. Haraiya: BSE image of a mosaic assemblage of recrystallized pyroxenes. Note the triple junctions, multiple orientations of exsolution, and epitaxial intergrowths of augite (dark) and pigeonite (light).

F igure 12. Haraiya: Fine-grained subophitic clast type A (upper left) and coarse ophitic clast type B (lower right). A thin selvage of glass separates the clasts. Note the relatively constant width of exsolution lamellae in pyroxenes in both clast types, the mild deformation of the lamellae

F igure 13. Haraiya: BSE image of coarse-grained clast. Compact aggregate of fragmented and subsequently annealed pyroxene grains adjacent to plagioclase showing preservation of original “magmatic” grain boundaries. Note variable thicknesses of augite lamellae in pigeonite, preserved Ca zoning

F igure 16. Haraiya: Measured and deconvolved profile of (001) augite lamellae (crosses) with superimposed simulated profiles calculated using variable cooling rates and the diffusion data of Stimpfl et al. (2003) . TEM-EDS analyses of 1.5 μm augite lamellae and partially inverted pigeonite

F igure 18. Evolution of lamellar wavelengths as a function of time. Cooling rates constrained by lamellar coarsening. Event 1: primary cooling of basalt ( Walker et al. 1978 ). Events 2–4: cooling of Pasamonte as a function of peak metamorphic temperature. Events 5–7: cooling of Haraiya

intersection temperature for Haraiya bulk pigeonite is also plotted (open square). Pigeonite compositions were not used to calculate closure temperatures due to the steepness of the pigeonite limb.

composition of pyroxene used in Nord and McCallister (1979) experiments, P5 = Pasamonte5 bulk (modally recombined = TEM-EDS analyses). ( b ) Pyroxene compositions in Haraiya used to calculate peak metamorphic temperature and closure temperature. Bulk augite and pigeonite = black squares; host lamellae pairs