Microstructural and Magnetic Characterization of the NWA 6259 Iron Meteorite (original) (raw)
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Pure iron and other magnetic minerals in meteorites
Solar System Research, 2015
The results of thermomagnetic and microprobe analyses of 37 samples from 25 different types of meteorite are analyzed with the focus on the presence of pure (nickel free) iron in them. It is established that the metallic particles in the studied meteorites cluster in three isolated groups: (1) pure iron, (2) kamacite with mode 3-6% Ni, and (3) taenite with mode ~50% Ni. The hiatuses in the Fe-Ni alloy compositions between these groups of magnetic grains contradict the Fe-Ni phase diagram, which predicts a continuous series of solid solutions in this system. This isolated distribution of the compositions of the metallic particles in the meteorites is reasonably accounted for by the specific properties of the melt (melts) and the processes of their crystallization and decomposition in space. It is suggested that pure iron in the meteorites could have been formed by either of two scenarios. According to the "primary," pure iron crystallizes from the melt, and according to the "secondary" scenario, it is produced by the decomposition of the solid solution.
Investigations on five iron meteorites
Hyperfine Interactions, 1994
In the present paper, we report an analysis of five iron meteorites belonging to the private collection of the mineralogy museum of the University of Parma (Italy). The collection is made up of eighteen samples, collected over two centuries. Up to now, they have never been studied by spectroscopical techniques and their classification was estimated on the basis of morphological inspection. Electron microscopy (SEM), X-ray diffraction (XRD), X-ray fluorescence (XRF), and M~issbauer spectroscopy (MS) have been used to analyse the samples.
Crystalline Structure, Stoichiometry and Magnetic Properties of the Morasko Meteorite
Acta Physica Polonica A, 2010
The composition and structure of iron-nickel alloys smithereens extracted from the Morasko (Poland) Meteorite (fell ∼ 5 ka BP) were investigated by optical metallographic techniques, scanning electron microscopy and electron microprobe analysis, thermal analyses, magnetic measurements and X-ray diffraction. Microstructural analysis by scanning electron microscopy and optical microscopy has shown that the sample is composed from large grains of Fe-Ni alloy in which secondary phase crystals with well developed crystal habits and the size about 10 micrometers are distributed. Thermal analyses confirmed that the transformation from alpha to gamma Fe-Ni solid solution appearing as a function of temperature corresponds to about 5 wt% Ni in the Fe-Ni alloy. Possible scenario of the extraterrestrial sample solidification is related to the microstructural and magnetic behavior.
Low-temperature magnetic properties of the Neuschwanstein EL6 meteorite
Earth and Planetary Science Letters, 2007
The low-temperature magnetic properties of the Neuschwanstein EL6 meteorite as well as of the daubreelite (FeCr 2 S 4 ), troilite (FeS), and FeNi mineral phases were investigated. Low-temperature magnetic behavior of the Neuschwanstein meteorite appears to be controlled mostly by FeNi. However, two magnetic features at ∼ 70 K (T m ) and 150 K (T c ), are due to a magnetic transition in and Curie temperature of ferrimagnetic daubreelite. The ∼10 K variations in T m and T c among daubreelite in the Neuschwanstein meteorite, daubreelite from the Coahuila meteorite and synthetic daubreelite [Tsurkan, V., Baran, M., Szymczak, R., Szymczak, H., Tidecks, R., 2001a. Spin-glass like states in the ferrimagnet FeCr 2 S 4 . Physica B, 296, 301−305.] might be due to slightly different Fe/Cr stoichiometric ratios, the presence of impurities, or crystalline lattice defects.
Magnetic, in situ, mineral characterization of Chelyabinsk meteorite thin section
2016
Magnetic images of Chelyabinsk meteorite's (fragment F1 removed from Chebarkul lake) thin section have been unraveled by a magnetic scanning system from Youngwood Science and Engineering (YSE) capable of resolving magnetic anomalies down to 10 À3 mT range from about 0.3 mm distance between the probe and meteorite surface (resolution about 0.15 mm). Anomalies were produced repeatedly, each time after application of magnetic field pulse of varying amplitude and constant, normal or reversed, direction. This process resulted in both magnetizing and demagnetizing of the meteorite thin section, while keeping the magnetization vector in the plane of the thin section. Analysis of the magnetic data allows determination of coercivity of remanence (B cr) for the magnetic sources in situ. Value of B cr is critical for calculating magnetic forces applicable during missions to asteroids where gravity is compromised. B cr was estimated by two methods. First method measured varying dipole magnetic field strength produced by each anomaly in the direction of magnetic pulses. Second method measured deflections of the dipole direction from the direction of magnetic pulses. B cr of magnetic sources in Chelyabinsk meteorite ranges between 4 and 7 mT. These magnetic sources enter their saturation states when applying 40 mT external magnetic field pulse.
53 Mn and 60 Fe in iron meteorites—New data, model calculations
Meteoritics & Planetary Science
We measured specific activities of the long-lived cosmogenic radionuclides 60 Fe in 28 iron meteorites and 53 Mn in 41 iron meteorites. Accelerator mass spectrometry was applied at the 14 MV Heavy Ion Accelerator Facility at ANU Canberra for all samples except for two which were measured at the Maier-Leibnitz Laboratory, Munich. For the large iron meteorite Twannberg (IIG), we measured six samples for 53 Mn. This work doubles the number of existing individual 60 Fe data and quadruples the number of iron meteorites studied for 60 Fe. We also significantly extended the entire 53 Mn database for iron meteorites. The 53 Mn data for the iron meteorite Twannberg vary by more than a factor of 30, indicating a significant shielding dependency. In addition, we performed new model calculations for the production of 60 Fe and 53 Mn in iron meteorites. While the new model is based on the same particle spectra as the earlier model, we no longer use experimental cross sections but instead use cross sections that were calculated using the latest version of the nuclear model code INCL. The new model predictions differ substantially from results obtained with the previous model. Predictions for the 60 Fe activity concentrations are about a factor of two higher; for 53 Mn, they are~30% lower, compared to the earlier model, which gives now a better agreement with the experimental data.
2017
The initial intent of this paper was dedicated to the task of presenting very simple methods to determine meteorites as well as tektites that could be easily performed by anyone. As this paper developed, it now also describes a new method in the form of a very simple device that has been developed and can be performed for the measurement of magnetic susceptibilities of minerals and rocks. Simple, straightforward and versatile, the main features of the apparatus are economical utilising equipment at everyone's disposal. The paper also introduces a proposed new approach to a Magnetic susceptibility Logχ ordinal scale that distinctly shows ordered qualitative characteristics such as, mineral diversity, groupings of visible optical properties attributed to their magnetic nature and is possibly the easiest method for determining the differentiation between the tektite-strewn fields, other impactite glasses and obsidian. These results have led to interesting conclusions that not only complement the current body of knowledge with new theories but also lead to new potential directions of research that could be investigated. Such as how magnetism could play a role in accretion, the final clumping and unification of small matter, as it is believed that all matter attracts other matter to it through gravity as all atoms are magnetic i.e. they have charges moving around within them and that a relation between gravity and electromagnetism exists. This is based on a formula that show that it is the cross-sectional surface area between two magnetic rocks that lead to an interaction of two masses dipped into a surrounding space, where it is clearly seen that a lower pressure " shading force " exists between them based on their masses and cross-sectional areas, which has two main known physical properties currently attributed to it, permeability and Permittivity and could be a description of the property of gravity as defined by Maxwell's equations.
The influence of terrestrial processes on meteorite magnetic records
In early solar system history there are several electromagnetic processes (electric discharges, pressure shock waves, electric discharges and currents) capable of magnetizing the primitive solid particles condensating from the solar nebula. The record of these magnetic events is the main objective of rock magnetic laboratory studies of meteorites found on the Earth. However, terrestrial environment can affect the magneto-mineralogy, can cause changes in magnetic parameters and can overprint the primary magnetic record. The entry of a meteorite into the terrestrial atmosphere causes surface heating and pressure effects due to large initial velocity. The effect of surface heating was the subject of the study with the CM2 Murchison meteorite. Results show the remagnetised zone to be at least 6 mm thick. On CM3, Allende meteorite we studied an effect of pressure during the atmospheric entry. According to our results the pressure does not seem to be a source responsible for meteorite remagnetization. Some meteorites are found several days after the fall, some are deposited in a desert or on the Antarctic ice for thousands of years. Most of them contain visible traces of terrestrial oxidation and weathering. We used the sample of an L6 chondrite DaG 979 found in the Libya desert, sample of the iron meteorite Campo del Cielo (found in Argentina 5000 years after the fall), and sample of the H5 Zebrak meteorite (found several days after the fall) for weathering simulations. Weathering plays an important role in the meteorite terrestrial history and is capable of complete remagnetization of the meteoritic material. To document the terrestrial processes that influence meteorite magnetism we monitored changes in magnetic remanence and magnetic hysteresis parameters. Our results indicate that the terrestrial processes are capable of changing magnetic properties and can overprint the primary magnetic record. Therefore, an extreme care is required when selecting the meteorite samples for primary magnetic component study.