HIGH RESOLUTION X-RAY MICROTOMOGRAPHY ANALYSIS IN NON-DESTRUCTIVE INVESTIGATION OF INTERNAL STRUCTURE IN TWO CHONDRITES

Ab s t r a c t. A comparison of the internal structure of two stony meteorites has been carried out using computer-aided X-ray microtomography (X-ray CT). The meteorites are both chondrites of the petrological type 5 with one (Baszkowka) being a group L chondrite and the other (Pultusk) being a group H chondrite. The volume of metal grains in the Pultusk meteorite (7.7 vol.%) is larger than that in the Baszkowka meteorite (5.1 vol.%). The metal grains in the Baszkowka meteorite are generally larger than those in the Pultusk meteorite. The Baszkowka meteorite has a much higher void volume (8.7 vol.%) than the Pultusk meteorite (3.4 vol.%). The voids in the Pultusk meteorite are generally much smaller than the voids in the Baszkowka meteorite. X-ray CT shows that the two meteorites, despite being structurally different, reveal in each similar correlations between the structural characteristics of the metal grains and voids. From an analysis of the structural features of both meteorites it is postulated that more regularly shaped intergranular voids were formed at the same time as the regularly shapedmetal and silicate grains. It means they had formed when the meteorite parent body had been assembled, i.e. before metamorphism inside the meteorite parent bodies. It is also postulated that the less porous, high aspect ratio void systems seen in the Pultusk meteorite (elongated, fissures) formed after pressure metamorphic period and during a shock event that fragmented the parent body of this meteorite. Key-words: Pultusk meteorite, Baszkowka meteorite, chondrite, X-ray microtomograph