International audienceWe have performed a mineralogical and geochemical study of eight metamorphosed basaltic eucrites. These are classified into granulitic eucrites and type 4–7 eucrites on the basis of their textures and pyroxene mineralogy, and display mineralogical evidence for high temperature metamorphism, including partial melting. In particular, rare earth element (REE) patterns of a number of the eucrites studied show varying degrees of light REE depletion due to partial melting, with subsequent melt extraction. A simple correlation between metamorphic grade, as deduced from pyroxene mineralogy, and the degree of light REE depletion was not detected. This can be explained by the fact that homogenization, exsolution and inversion of pigeonite would have required prolonged heating at moderate temperatures (not, vert, similar800–1000 °C), whereas partial melting would have taken place over a short time interval where temperatures exceeded that of the solidus. The eucrites studied therefore record a two stage thermal regime consisting of short, high temperature reheating events superimposed on long duration global crustal metamorphism. The short reheating events may have been caused by impact events and/or intrusions of hot magmas. The results of this study demonstrate that the thermal history of eucritic crust was more complex than can be explained by a simple burial model alone. In particular, the origin of Stannern trend eucrites requires contamination of Main-Group magmas by partial melts extracted from residual eucrites

Abstract-We studied the texture, mineralogy, and bulk chemical composition of Dhofar 007, a basaltic achondrite. Dhofar 007 is a polymict breccia that is mostly composed of coarse-grained granular (CG) clasts with a minor amount of xenolithic components, such as a fragment of Mg-rich pyroxene. The coarse-grained, relict gabbroic texture, mineral chemistry, and bulk chemical data of the coarse-grained clast indicate that the CG clasts were originally a cumulate rock crystallized in a crust of the parent body. However, in contrast to monomict eucrites, the siderophile elements are highly enriched and could have been introduced by impact events. Dhofar 007 appears to have experienced a two-stage postcrystallization thermal history: rapid cooling at high temperatures and slow cooling at lower temperatures. The presence of pigeonite with closely spaced, fine augite lamellae suggests that this rock was cooled rapidly from higher temperatures (>0.5 °C/yr at ∼1000 °C) than typical cumulate eucrites. However, the presence of the cloudy zone in taenite and the Ni profile across the kamacite-taenite boundaries indicates that the cooling rate was very slow at lower temperatures (∼1-10 °C/Myr at <600-700 °C). The slow cooling rate is comparable to those in mesosiderites and pallasites. The two-stage thermal history and the relative abundance of siderophile elements similar to those for metallic portions in mesosiderites suggest that Dhofar 007 is a large inclusion of mesosiderite. However, we cannot rule out a possibility that Dhofar 007 is an anomalous eucrite.