Iron-Nickel Microparticles in the Sedimentary Rocks as Indicators of Cosmic Processes

The microstructure, chemical and mineral composition of iron-nickel microparticles from the sedimentary deposits of the Peri-Caspian Depression were studied. It was found that the microspheres developed as a result of the fractional condensation of a Fe-Ni melt and its crystallization at the early stage of the evolution of the substance of the protosolar nebula. Upon reaching the atmosphere of the Earth, these microspheres undergo changes in terms of partial oxidation of magnetite to hematite and native nickel to nickel oxides, melting of fusible metals in the core part, and atmospheric entry under the influence of the “pulverization effect” resulting in the development of awaruite microparticles of various shapes. The obtained data are most likely to prove the extraterrestrial origin of Fe–Ni microparticles and their relation to the fallings of cosmic bodies on the Earth in the geological past

Dependence of the composition of the Zarnitsa pipe picroilmenites (Yakutia) on their formation conditions (from data of thermomagnetic studies)

A thermomagnetic analysis has been performed for 737 picroilmenite samples from the cores of eight boreholes in the N-S-striking drilling profile of the Zarnitsa kimberlite pipe in the Daldyn kimberlite field, Yakutia. Based on the shapes of thermomagnetic curves and the Curie points, 29 samples were chosen for detailed microprobe studies of chemical composition and elucidation of the dependence of their thermomagnetic parameters on the content of the hematite end-member in the picroilmenites. The thermomagnetic curves of most of the studied picroilmenite samples are approximated by a two-component model for the hematite end-member distribution: the main and supplementary distribution. The average hematite end-member content in the main distribution coincides with the probe microanalysis data and is always lower than the average content in the supplementary distribution. The relative hematite end-member contents in the main and supplementary distributions within the picroilmenite grains are indicators of the dynamics of mineral formation in different parts of the Zarnitsa pipe. The data obtained testify to the multistage formation of the pipe under unstable thermodynamic conditions, which explains the intricate distribution pattern of picroilmenite. © 2014