Magnetic particles found by raking the deep sea bottom

Abstract

A collection of strongly magnetic material on the ocean floor was one of the many subjects undertaken by the Danish Deep Sea Expedition - The Galathea Expedition 1950–1952. In the following a description of the instrument, the magnetic rake, is given by its constructor, A. Fr. Bruun, and the way it was handled on the Galathea is mentioned. The description of the material is given by Hans Pauly. His conclusions are further supported by experiments carried out and described by E. Langer. The magnetic rake, an oak-board 100 × 15 × 5 cm, carrying 63 magnets in three rows, was drawn along the ocean bottom and is considered to have covered about 45,000 m 2. Apart from insignificant amoutns of artificial material and varying amounts of magnetite-sand more than 300 particles of a very remarkable character were obtained. Most particles were spheres with a diameter of less than half a millimetre. A lot of them consist wholly of magnetite, but many have a silicate groundmass loaded with magnetite crystallites. In nearly all spherical cavities occur. Seven metallic particles were found in the material. Those examined were seen to contain: NiFe, carbides, phosphides, etc. The structure and composition of these metallic particles seem to require high temperatures and rapid cooling in the formation-process. Discussions of similar material from bottom cores taken by the Swedish Deep Sea Expedition, certain features in crusts of two Danish stony meteorites, the whole picture of the material from the Galathea Expedition 1950–1952 and the Challenger Expedition 1872–1976 seem to favour the ideas of Murray and Renard. The particles are supposed to represent material torn off from meteors due to air-resistance on their passage through the atmosphere; it only seems necessary to add stony meteorites as an important source. It is considered convenient to give these particles a special name in order to distinguish them from meteorites and cosmic dust, and it is therefore suggested to call them caudaites.