High resolution X-ray microtomography analysis in non-destructive investigation of internal structure in two chondrites

A comparison of the internal structure of two stony meteorites has been carried out usingcomputer-aided X-ray microtomography (X-ray CT). The meteorites are both chondrites of the petrologicaltype 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 Baszkowkameteorite (5.1 vol.%). The metal grains in the Baszkowka meteorite are generally larger than those in thePultusk meteorite. The Baszkowka meteorite has a much higher void volume (8.7 vol.%) than the Pultuskmeteorite (3.4 vol.%). The voids in the Pultusk meteorite are generally much smaller than the voids in theBaszkowka meteorite. X-ray CT shows that the two meteorites, despite being structurally different, revealin each similar correlations between the structural characteristics of the metal grains and voids. Froman analysis of the structural features of both meteorites it is postulated that more regularly shapedintergranular voids were formed at the same time as the regularly shaped metal and silicate grains. It meansthey had formed when the meteorite parent body had been assembled, i.e. before metamorphism inside themeteorite parent bodies. It is also postulated that the less porous, high aspect ratio void systems seen in thePultusk meteorite (elongated, fissures) formed after pressure metamorphic period and during a shock eventthat fragmented the parent body of this meteorite.