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Beda A. HOFMANN Silvio LORENZETTI Otto EUGSTER Urs KRÄHENBÜHL Gregory HERZOG Feride SEREFIDDIN Edwin GNOS Manuel EGGIMANN John T. WASSON 《Meteoritics & planetary science》2009,44(2):187-199
Abstract— The original mass (15915 g) of the Twannberg IIG (low Ni‐, high P) iron was found in 1984. Five additional masses (12 to 2488 g) were recovered between 2000 and 2007 in the area. The different masses show identical mineralogy consisting of kamacite single crystals with inclusions of three types of schreibersite crystals: cm‐sized skeletal (10.5% Ni), lamellar (17.2% Ni), and 1–3 × 10 μm‐sized microprismatic (23.9% Ni). Masses I and II were compared in detail and have virtually identical microstructure, hardness, chemical composition, cosmic‐ray exposure (CRE) ages, and 10Be and 26Al activities. Bulk concentrations of 5.2% Ni and 2.0% P were calculated. The preatmospheric mass is estimated to have been at least 11,000 kg. The average CRE age for the different Twannberg samples is 230 ± 50 Ma. Detrital terrestrial mineral grains in the oxide rinds of the three larger masses indicate that they oxidized while they were incorporated in a glacial till deposited by the Rhône glacier during the last glaciation (Würm). The find location of mass I is located at the limit of glaciation where the meteorite may have deposited after transport by the glacier over considerable distance. All evidence indicates pairing of the six masses, which may be part of a larger shower as is indicated by the large inferred pre‐atmospheric mass. 相似文献
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Feride Serefiddin Gregory F. Herzog Christian Koeberl 《Geochimica et cosmochimica acta》2007,71(6):1574-1582
By using accelerator mass spectrometry, we measured 10Be (T1/2 = 1.5 Ma) concentrations in nine Ivory Coast (IVC) tektites, in six soil samples collected near the Bosumtwi impact crater, the likely source region, and in a depth profile taken through a 23 g moldavite. In the core of the moldavite sample we also measured an upper limit on the 36Cl (T1/2 = 0.3 My) concentration. The average 10Be concentration in IVC tektites of (22 ± 11) × 106 atom/g exceeds reasonable limits for a meteoritic component or cosmic-ray production in situ after tektite formation. The 10Be must be meteoric, which implies that IVC tektites formed from soils or sediments. Corrected to the time of formation (ToF) 1.07 Ma ago and for a small in situ component, the average 10Be concentration of (35 ± 7) × 106 atom/g (1 − σ mean) is considerably lower than those of contemporary Bosumtwi soils, ∼250 × 106 atom/g, or of Australasian tektites at their ToF, 0.8 Ma B.P. near Lake Bosumtwi today the soil column is only ∼1 m thick. If the landscape was similar 1.07 Ma ago, then the total thickness of the tektite formation zone probably did not exceed 10 m. With increasing depth below the surface of the moldavite, the 10Be concentrations decrease rapidly owing to the presence of a surface component, probably of recent origin. The main interior mass of the sample contains ∼0.8 × 106 atom 10Be/g and fewer than 0.1 × 106 atom 36Cl/g, little of which can be meteoritic. Although not definitive, consideration of several possible cosmic-ray exposure histories suggests that about half the interior 10Be has a meteoric origin, which if corrected to the time of formation yields a concentration compatible with those measured in typical contemporary soils. The observations are consistent with the formation of three of the four main tektite groups from surface soils or sediments. 相似文献
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Sara B. Akkas Ayse O. Kepenek Meryem Beklioglu Feride Severcan 《Aquatic Sciences - Research Across Boundaries》2010,72(1):71-83
Diel vertical migration (DVM) bioassay-guided Fourier transform infrared spectroscopy can be a prominent non-destructive and
innovative approach for ecological studies. During the characterization of the nature of the fish-exuded kairomone, the peak
area results from the spectroscopic analysis of the control, fish-conditioned (F) and temperature incubated fish-conditioned
(IF) treatments of the DVM bioassays demonstrated that there was a strong correlation between the alterations of the amine
N–H, amide II, amide IV and CH3 asymmetric vibrations, suggesting that both N–H and CH3 molecules may be main components of the fish-exuded kairomone cocktail. The IF treatment, which showed similar results with
the control treatment, supported that the kairomone is inactivated by bacterial biodegradation. The seasonal variations in
the peak areas of the N–H and CH3 bands suggested that DVM response varied seasonally, where migration response developed quickly in warmer seasons. The peak
area of the amine N–H band of the F and IF treatments relative to control conditions can be used as an ideal indicator of
the absence or presence and the promptness of migration, at all seasons. 相似文献
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