The abundance and distribution of chlorine in iron meteorites

The abundance and distribution of chlorine in thirteen iron meteorites has been studied by neutron activation analysis and metallographic examination. It is found that terrestrial processes have affected the Cl in some finds and that weathering can lead to severe contamination effects, raising the Cl content over certain localized regions by many orders of magnitude. The contamination process appears to act in conjunction with the penetration of ground water into the interior. The pathways utilized are cleavages, grain boundaries, Neumann lines, and even direct passage through the matrix. Measurements of primordial (non-terrestrial) Cl in the meteorites show that it is inhomogeneously distributed in the metal phase, being strongly depleted in kamacite and accumulating near grain boundaries, around inclusions, and in chloride minerals. It is difficult to calculate an average value for the primordial Cl content of irons on the basis of the data obtained, but indications are that a representative value is much lower than previous data which were not sufficiently cognizant of contamination effects.