Andrei V. Ivanov

The Kaidun Microbreccia Meteorite: A Harvest from the Inner and Outer Asteroid Belt

Abstract We summarize the results of two decades of research into the complex Kaidun microbrecccia meteorite. This meteorite contains an unprecedented accumulation of materials from many different asteroids, principally carbonaceous and enstatite chondrites, but also many other frequently strange materials. The following well-known meteorite types are definitely present in Kaidun: EH3–5, EL3, CV3, CM1-2, and R chondrites. Also present in Kaidun are new C1 and C2 type lithologies, unique alkaline-enriched clasts, impact melt products, phosphide-bearing clasts, vein- and cavity-filling materials, new enstatite-bearing clasts, and Ca-rich achondrite materials. Many further materials have yet to be characterized. Obviously, the Kaidun parent object accumulated materials from across the entire main asteroid belt. Many of these materials were subjected to varying levels of physical processing, heating, shock, melting, and aqueous alteration. Kaidun is important because it contains many asteroidal materials we have not seen before, providing a more complete view of the diversity of materials in the asteroid belt than has been provided by other meteorites. This is possible because of the small, generally sub-millimeter-size of the component clasts in Kaidun – it is far easier for these smaller objects to scatter throughout the solar system than it is for larger, conventionally-sized meteorites. We suggest that the final parent object where Kaidun was assembled was a large body with a C-type asteroid signature – possible asteroid 1-Ceres or the martian moon Phobos.

Florenskyite, FeTiP, a new phosphide from the Kaidun meteorite

Abstract Florenskyite is a new phosphide species from the Kaidun chondritic meteorite, which fell in South Yemen in 1980. Kaidun is a unique chondritic breccia containing a huge variety of fragments of different chondritic types. Florenskyite was found as four dispersed grains with a maximum dimension of 14 μm within a single mass of Fe-rich serpentine within one Kaidun clast. Florenskyite is associated with submicrometer-sized grains of pentlandite and small (up to 1.5 μm in width) laths of a still uncharacterized Fe-Cr phosphide. Florenskyite is creamy white in reflected light, and its luster is metallic. The average of three electron microprobe analyses gave (wt%) Fe 40.52, Ti 30.08, Ni 5.47, Cr 0.93, V 0.91, Co 0.60, P 21.69, Si 0.59, sum 100.79, corresponding to Fe1.01(Ti0.87Ni0.13Cr0.03V0.02Co0.01)1.06(P0.97Si0.03). Single-crystal structure analysis was performed on florenskyite using a Laue pattern collected from a multiple crystal by in-situ synchrotron X-ray diffraction. Florenskyite crystallizes in the space group Pnma, and has the anti-PbCl2 structure. Previously determined cell constants of synthetic material [a = 6.007(1), b = 3.602(1), c = 6.897(1) Å] were used in the single-crystal data reduction. We used the POWD12 program to calculate a powder XRD pattern; the 5 most intense reflections are d = 2.301 (I = 100), 2.188 (88), 2.307 (47), 1.938 (45), and 1.801 Å (45). Florenskyite is only the fourth phosphide to be described from nature. Its paragenesis may be unique, and may be due to melting of a mineral assemblage including Fe-Ni metal, schreibersite, daubreelite, osbornite, or heideite and subsequent crystallization of phosphides from the melt.

Study of conformations and hydrogen bonds in the configurational isomers of pyrrole‐2‐carbaldehyde oxime by 1H, 13C and 15N NMR spectroscopy combined with MP2 and DFT calculations and NBO analysis

The 1H, 13C and 15N NMR studies have shown that the E and Z isomers of pyrrole‐2‐carbaldehyde oxime adopt preferable conformation with the syn orientation of the oxime group with respect to the pyrrole ring. The syn conformation of E and Z isomers of pyrrole‐2‐carbaldehyde oxime is stabilized by the Nuf8ffH···N and Nuf8ffH···O intramolecular hydrogen bonds, respectively. The Nuf8ffH···N hydrogen bond in the E isomer causes the high‐frequency shift of the bridge proton signal by about 1 ppm and increase the 1J(N, H) coupling by ∼3 Hz. The bridge proton shows further deshielding and higher increase of the 1J(N, H) coupling constant due to the strengthening of the Nuf8ffH···O hydrogen bond in the Z isomer. The MP2 calculations indicate that the syn conformation of E and Z isomers is by ∼3.5 kcal/mol energetically less favorable than the anti conformation. The calculations of 1H shielding and 1J(N, H) coupling in the syn and anti conformations allow the contribution to these constants from the Nuf8ffH···N and Nuf8ffH···O hydrogen bondings to be estimated. The NBO analysis suggests that the Nuf8ffH···N hydrogen bond in the E isomer is a pure electrostatic interaction while the charge transfer from the oxygen lone pair to the antibonding orbital of the Nuf8ffH bond through the Nuf8ffH···O hydrogen bond occurs in the Z isomer. Copyright

CH···N and CH···O intramolecular hydrogen bonding effects in the 1H, 13C and 15 N NMR spectra of the configurational isomers of 1‐vinylpyrrole‐2‐carbaldehyde oxime substantiated by DFT calculations

According to the 1H, 13C and 15N NMR spectroscopic data and DFT calculations, the E‐isomer of 1‐vinylpyrrole‐2‐carbaldehyde adopts preferable conformation with the anti‐orientation of the vinyl group relative to the carbaldehyde oxime group and with the syn‐arrangement of the carbaldehyde oxime group with reference to the pyrrole ring. This conformation is stabilized by the Cuf8ffH···N intramolecular hydrogen bond between the α‐hydrogen of the vinyl group and the oxime group nitrogen, which causes a pronounced high‐frequency shift of the α‐hydrogen signal in 1H NMR (∼0.5 ppm) and an increase in the corresponding one‐bond 13C–1H coupling constant (ca 4 Hz). In the Z‐isomer, the carbaldehyde oxime group turns to the anti‐position with respect to the pyrrole ring. The Cuf8ffH···O intramolecular hydrogen bond between the H‐3 hydrogen of the pyrrole ring and the oxime group oxygen is realized in this case. Due to such hydrogen bonding, the H‐3 hydrogen resonance is shifted to a higher frequency by about 1 ppm and the one‐bond 13C–1H coupling constant for this proton increases by ∼5 Hz. Copyright

Concentrically zonal textures in a sample of the Kaidun meteorite

The paper reports the results of the textural and mineralogical studying of clast Kaidun #d6A. The principal minerals of the clast are phyllosilicates, carbonates, and sulfides, but the clast contains no anhydrous silicates. The clast is characterized by extremely high concentration of inclusions, which broadly vary in size, composition, and texture, from completely remelted to practically unchanged when brought to the parent body. The latter group includes two inclusions having a concentrically zonal texture, which have never before been found in meteorites. One of the inclusions consists of serpentine replaced by talc in the margins. The inclusion was formed in relation to silification under the effect of silicon-bearing aqueous fluid at a temperature of more than 300°C. The other inclusion consists of alternating Ca carbonate and phyllosilicate zones. The texture and composition of the inclusion suggest that its genesis was related to the metasomatic alteration of carbonates under the effect of silicon- and alumina-bearing aqueous fluids at temperatures of about 400–500°C. These processes are typical of large differentiated planets, and there are no reasons to expect them in the parent bodies of carbonaceous chondrites, such as Kaidun. Our results obtained on clast #d6A are in good agreement with the hypothesis that the parent body of the Kaidun meteorite was Phobos [1]. Correspondingly, inclusions #d6Aa and #d6Ab likely originated from Mars, as previously examined alkali-rich clasts did. The clast described in this publication seems to originate from the surface regolith of Phobos, which was compacted in the process of the aqueous alteration of the material and subsequently buried at a greater depth.

Kaidun meteorite: A fragment of crystalline rock from a new parent body

Two sections subsequently sawed from meteorite fragment Kaidun #d(4–5)C were examined under an optical and scanning electron microscope. The major minerals of the fragment are pigeonite and anorthite; the accessory minerals are spinels and occasional grains of ilmenite, Ca phosphate, and Fe sulfide. The compositions of the minerals broadly vary. The texture of the fragment, its mineralogy, and mineral chemistries definitely indicate that the fragment originated from a crystalline rock affected by partial melting during an impact event. The chemical compositions of both minerals (the concentration of the anorthite end member of plagioclase An99 and the Fe/Mn atomic ratio of 44 in the pyroxenes) differ from those in other known meteorite samples and suggest that fragment d(4–5)C of the Kaidun meteorite represents a new differentiated parent body that has never been sampled before.

Pegmatoid objects in a sample of the Kaidun meteorite

We report the results of textural and mineralogical investigations of fragment #d(3–8)B of the Kaidun meteorite. The fragment is represented by six polished thin sections obtained by sequential sawing of a meteorite sample. Its main mineral is magnesian olivine; pyroxenes, augite and enstatite, are less abundant. The minor minerals are Fe-Ni sulfides, and the accessory minerals are chromian magnetite and apatite. The minerals show highly variable compositions. Several lithological types of material were distinguished on the basis of texture and composition. A characteristic feature is the presence of fractures, whose walls are enriched in olivine and, occasionally, sulfides. Some fractures contain relatively large euhedral crystals of zoned olivine. Olivines occurring on the walls of fractures and within fractures show a negative correlation between Mg# values and nickel content. The fragment has been subjected to multiple impact events. The material of the fragment bears evidence for intense multistage metasomatic alteration with the influx of olivine material and formation of pegmatoid-type segregations. This process has never previously been observed in meteorites, but is quite common in terrestrial massifs. The results of this study are in good agreement with our hypothesis that Phobos is the parent body of the Kaidun meteorite and indicate a possible Martian origin for Kaidun fragment #d(3–8)B.

Kaidun meteorite: Crystals of oxides in cavities

Cavities in two texturally and genetically distinct clasts of the Kaidun meteorite were found out to contain crystals of distinct morphology, but of a similar composition. Cavities in chondrite breccia #d3A contain thin (<4 μm) elongated (up to 25 μm long) crystals that grew perpendicular to the walls of the cavity. The walls of the cavities in partly fused clast #d(3–5)D are covered with clusters of acicular crystals. In both clasts, the crystals are covered by films of phyllosilicates and always have a composition approximated by the formula (Mg,Fe,Mn)5Al2O8·nH2O. No mineral phase of this composition has ever been found in nature. The genesis of the mineral phases in the cavities is thought to be related to the crystallization from a fluid of similar composition. The fluid was produced during the cooling of the melt that produced clast #d(3–5)D. The unusual composition of the crystals testifies that this fluid had an unusual composition. This can be explained by the unique nature of clast #d(3–5)D, for which there are good reasons to propose a Martian origin.

Oil spills on ALMAZ-1 and ERS-1 SAR images: results from the DOSE-91 experiment

This paper presents the results of the oil spill observations using Almaz-1 and ERS-1 SAR images collected in the Norwegian Sea during the Dedicated Oil Spill Experiment (DOSE-91) in 1991. Three artificial spills were released from a vessel in August 1991 and data on sea and weather conditions near the test area were determined. The analysis of the acquired SAR images shows that the reduction of the backscatter from oil-covered sea surface attained values of up to 10–15 dB. For the first time an effect of an intensification of wind waves both within the area of the spill and at the windward edge of the oil spill, expressed as a magnification of the SAR image brightness, was detected. The increase in relative backscatter power was up to 2.0 dB. It is concluded that both Almaz-1 and ERS-1 SARs are valuable tools for oil spill detection and localisation, but that the detectability essentially depended on wind speed, sea state and age of spills.