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[en] For Moessbauer studies of the Morasko meteorite three different samples were isolated: troilite, kamacite and taenite. Investigated spectra revealed new mineralogical phases: taenite, tetrataenite and antitaenite. That is first such identification in meteorite found in Poland.
[en] Antimony concentrations determined by radiochemical neutron activation analysis in 60 iron meteorites range from 0.2 ng/g to 36 μg/g. The meteorites with the highest Sb concentrations are those of the non-magmatic groups IAB and IIICD, while the lowest Sb concentrations are found in groups IVA and IVB, the groups with the lowest concentrations of the other most volatile siderophiles Ge and Ga. In all groups Sb is positively correlated with Ni. In each of the magmatic groups slopes on log Sb vs.log Ni plots decrease with increasing Ni. This decrease may reflect an increasing tendency to avoid schreibersite during the analysis of high-Ni meteorites because Sb partitions strongly into schreibersite. (orig./ME)
[en] Silicate inclusions from two IIE iron meteorites were dated by the I-Xe and 40Ar-39Ar techniques. Weekeroo Station, a 'normal' IIE iron, shows no loss of radiogenic 40Ar at low temperature, and the well defined 40Ar-39Ar plateau yields an age of 4.54 +- 0.03 Byr. The xenon data define a good I-Xe correlation with an age of + 10.9 +- 0.5 Myr relative to Bjurbole. Despite its relatively young age, Weekeroo Station's (129Xe/132Xe)sub(trapped) ratio (= 0.84 +- 0.05) lies significantly below the solar value. Netschaevo silicate has a chondritic composition, unlike 'normal' IIE silicate which is more differentiated. Nevertheless Netschaevo gives a 40Ar-39Ar plateau-age of only 3.79 +- 0.03 Byr, with the xenon data failing to define an I-Xe isochron. Only irons from the IAB and IIE groups contain silicate inclusions, but these two groups differ in many other respects, mostly suggesting that IAB meteorites are more primitive. The I-Xe chronology supports this suggestion inasmuch as Weekeroo Station formed well after IAB silicates. The four silicate-bearing IIE irons which have now been dated can be subdivided into distinct pairs: Weekeroo Station and Colomera formed near the beginning of the solar system, while Netschaevo and Kodaikanal both formed only 3.8 Byr ago. A review of other properties of these meteorites generally supports this subdivision. This work underscores the complexity of the history of IIE meteorites; in particular, an adequate model must account for the formation of two IIE irons at 3.8 Byr without disturbing rare gases in Weekeroo Station. All formation models are quite speculative, but the one which seems best to fit the available evidence postulates two parent bodies: the 3.8 Byr old silicate formed on one parent body, all other IIE material resided in a separate body, and subsequent collision(s) mixed the young silicate with IIE metal. (author)
[en] Retuerta del Bullaque is a new Spanish iron meteorite. Found in 1980, has been recovered from the Province of Ciudad Real, near the northern limit of the Cabaneros National Park (39 degree centigrade 27 min 32 s N, 4 degree centigrade 22 min 39 s W). The specimen is a coarse octahedrite of about 100 kg in weight, with many concave regmaglyphes in one surface and moderate terrestrial weathering. The atmospheric heat-affected rim (≤1.5 mm) is partially preserved. Analysis by ICP-AES (Ni: 7.527 and Co: 0.475 in wt%) and by ICP-MS (Ga: 68.9, Ge: 365, As: 13.7, W: 0.95, Ir: 1.95 and Au: 1.70 in ppm) we used to classify the specimen as an IAB complex (Main Group). Chemically, Retuerta del Bullaque iron is similar to Kaalijarv iron but its mineralogy and texture are more like other low Ni-Au irons of main group (e.g. Diablo Canyon). The bulk of the specimen is a Wid-manstatten kamacite (band-width estimated at 2.0 ± 0.3 mm) with large and tabular crystals of cohenite and polygonal kamacite without cohenite that exhibits abundant Neumann lines. Schreibersite (irregular crystals + rhabdite) is rare in the two sectors. Taenite is present in thick lamellae between kamacite bands and pearlitic plessite. Lamellar cohenite is very abundant (9.5% of the total area into two sections 77.7 and 41.1 cm2), is partially covered of schreibersite and contains kamacite-taenite spherules. The larger sections display irregularly shaped troilite-graphite nodules (max. size, 5-12 mm), located in the central areas of the kamacite polygonal sectors. Each nodule has a rim of schreibersite + cohenite. The original morphology of the specimen was preserved making replicas as molds and casts (using elastomers, resins and modified plasters) and a 3D-laser scan. (Author)