Composition of the Metallic Phases in some Stone and Stony-Iron Meteorites

Abstract

TEN chondrites and two siderolites have been investigated, using electron-probe microanalysis to measure the concentration of nickel in the metallic phases. Information about the composition of the metal particles in chondrites is of value in deciding whether they were formed in situ or by the accumulation of fragments of large metallic bodies. Conventional chemical analysis is limited to determining the average composition of the metal, owing to the smallness of the particles. Ringwood¹ measured the lattice parameters of the kamacite (α-nickel–iron) and tænite (γ-nickel–iron) in a number of chondrites, and deduced compositions from these measurements. It is preferable to use a more direct method of obtaining compositional information: electron-probe microanalysis has the advantage for this purpose of combining reasonable precision (± 1 per cent of the concentration measured) with high spatial resolution (about 1µ).