CARBONACEOUS CHONDRITE CLASTS IN THE HOWARDITES BHOLGHATI AND EET87513

Twenty-two carbonaceous chondrite clasts from the two howardites Bholg hati and EET87513 were analyzed. Clast N from EET7513 is a fragment cl assified as CM2 material on the basis of texture, bulk composition, mi neralogy, and bulk O isotopic composition. Carbonaceous chondrite clas ts from Bholghati, for which less data are available because of their small size, can be divided into two petrologic types: C1 and C2. C1 cl asts are composed of opaque matrix with rare coarse-grained silicates as individual mineral fragments; textures resemble CI meteorites and s ome dark inclusions from CR meteorites. Opaque matrix is predominantly composed of flaky saponite; unlike typical CI and CR meteorites, serp entine is absent in the samples we analyzed. C2 clasts contain chondru les, aggregates, and individual fragments of coarse-grained silicates in an opaque matrix principally composed of saponite and anhydrous fer romagnesian silicates with flaky textures similar to phyllosilicates. These anhydrous ferromagnesian silicates are interpreted as the produc t of heating of pre-existing serpentine. The carbonaceous chondrite cl asts we have studied from these two howardites are, with one notable e xception (clast N from EET7513), mineralogically distinct from typical carbonaceous chondrites. However, these clasts have very close affini ties to carbonaceous chondrites and have also experienced thermal meta morphism and aqueous alteration, but to different degrees.