Abstract-Amoeboid olivine aggregates (AOAs) from the reduced CV chondrites Efremovka, Leoville and Vigarano are irregularly-shaped objects, up to 5 mm in size, composed of forsteritic olivine (F*Io) and a refractory, Ca,Al-rich component. The AOAs are depleted in moderately volatile elements (Mn, Cr, Na, K), Fe,Ni-metal and sulfides and contain no low-Ca pyroxene. The refractory component consists of fine-grained calcium-aluminum-rich inclusions (CAIs) composed of Al-diopside, anorthite (An1 oo), and magnesium-rich spinel (-1 wt% FeO) or fine-grained intergrowths of these minerals; secondary nepheline and sodalite are very minor. This indicates that AOAs from the reduced CV chondrites are more pristine than those from the oxidized CV chondrites Allende and Mokoia. Although AOAs from the reduced CV chondrites show evidence for high-temperature nebular annealing (e.g., forsterite grain boundaries form 120" triple junctions) and possibly a minor degree of melting of Aldiopside-anorthite materials, none of the AOAs studied appear to have experienced extensive (>50%) melting. We infer that AOAs are aggregates of high-temperature nebular condensates, which formed in CAI-forming regions, and that they were absent from chondrule-forming regions at the time of chondrule formation. The absence of low-Ca pyroxene and depletion in moderately volatile elements (Mn, Cr, Na, K) suggest that AOAs were either removed from CAI-forming regions prior to condensation of these elements and low-Ca pyroxene or gas-solid condensation of low-Ca-pyroxene was kinetically inhibited.

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We report major element composition ratios for regions of the asteroid 433 Eros imaged during two solar flares and quiet sun conditions during the period of May to July 2000. Low aluminum abundances for all regions argue against global differentiation of Eros. Magnesium/silicon, aluminum/silicon, calcium/silicon, and iron/silicon ratios are best interpreted as a relatively primitive, chondritic composition. Marked depletions in sulfur and possible aluminum and calcium depletions, relative to ordinary chondrites, may represent signatures of limited partial melting or impact volatilization.

Abstract-Thermodynamic analysis of the compositional profiles across large chemically-zoned Fe,Ni metal grains in the Bencubbin-like chondrite Queen Alexandra Range (QUE) 9441 1 suggests that these grains formed by non-equilibrium gas-solid condensation under variable oxidizing conditions, isolation degree, and Cr depletion factors. The oxidizing conditions must have resulted from the complete vaporization of nebular regions with enhanced dust/gas ratios (-1040 x solar). Because the origin of each of the metal grains studied requires different condensation parameters ( d u d g a s ratio, isolation degree, and Cr depletion factor), a high degree of heterogeneity in the formation region of the Bencubbin-like chondrite metal is required. To preserve compositional zoning of the metal grains and prevent their melting and sulfidization, the grains must have been removed from the hot condensation region into cold regions where the accretion of the Bencubbin-like asteroidal body took place.