Transformation of meteoritic material in experiments with shock compression at pressures of 500 and 1000 kbar produced by explosions

Abstract

1. Experiments were conducted on shock compression (with conservation of material) of the carboniferous chondrite Migei at p=500 kbar and of the graphite from the Yardymlinskii iron meteorite at p=1000 kbar with the goal of explaining the transformations of meteoritic material due to strong shock waves. 2. Diamonds were synthesized from the carbonaceous matter in the carboniferous chondrite Migei (p=500 kbar) and from the graphite in the Yardymlinskii iron meteorite (p-1000 kbar) as microcrystals (<1μ) which were found in concretions with graphite and in concretions identified with lonsdaleite and chaoite. The synthetic diamond-graphite concretions were similar in morphology and phase composition to the diamondgraphite concretions in meteorites. 3. Material from the meteorite Migei experimentally subjected in an explosion to p=500 kbar acquired a structure similar to that of the ureilites. Its mineral composition differs from that of the original carboniferous chondrite and is similar to the material in ureilites. It is shown experimentally that there are transformations of the principal mineral phases: hydrous silicates, olivine, and magnetite, characteristic of carboniferous chondrites, into olivine, pigeonite, and camasite, which are characteristic of ureilitites. 4. The amounts of Mn, Ti, Al. Ni, and S (which have various volatilities) contained in the experimental sample of Migei subjected to an explosion at p=500 kbar differ from those in the original carboniferous chondrite Migei and are close to the amounts in the ureilites. 5. These experiments confirm that the ureilites are meteorites of secondary origin, formed from the material in carboniferous chondrites as a result of strong shock waves in outer space.