Meteorite 3-D synchrotron microtomography: Methods and applications

Methods of synchrotron X-ray computed microtomograpby (XRCMT) are described, which allow nondestructive, high spatial and contrast resolution imaging of the density structures of meteorites and their components in three dimensions. Images of bulk chondrites (to one cubic centimeter in size) reveal compound chondrules, chondrule/matrix volumetric ratios, metal and sulfide distribution, petrofabrics, and 3-D chondrule and calcium-aluminum inclusion (CAI) sizes and shapes. Images of separated chondrules and CAIs reveal void spaces, mineral intergrowth textures, and the true locations of crystal rims and cores, at resolutions to <8 cubic micron/volume element. Images of achondrites reveal mineral fabrics and crystal zoning. Lunar glass spherules can be searched for phenocrysts bearing deeply sourced melt inclusions. A companion DVD and URL contain images for classroom and research use. Numerical techniques for quantification of X-ray computed microtomography (XRCMT) data and its potential applications are discussed. Three-dimensional X-ray images of meteorites provide a way to discover components of interest and to precisely slice samples to expose these components with minimal damage and loss of material. Three-dimensional studies of petrographic features (size, shape, texture, and modal abundance) of chondrites and their components, as well as other meteorites, have definite advantages over standard 2-D studies using randomly sliced thin sections.