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EN
The new meteorite was bought as one single stone in 2019 from a dealer in Niger by Tomasz Jakubowski. The meteorite has fusion crust. It contains chondrules of different types with dominance of barred olivine chondrules, with diameter to 1.5 mm. Px and Ol are 78.1 vol%. of the meteorite mass. Pl is up 11.8 vol%. Average fayalite content is 24.93. Metallic phases are 3.0 vol%. Troilite is up to 5.9 vol%. Spinel (Cr-spinel) is up to 0.9 vol%. Average content of the secondary Fe-rich minerals (e.g. hydroxides) is 0.4 vol%. Feldspar composition is: Ab80.2Or5.0An14.8. Mean content of Al2O3, MgO and TiO2 in chromium spinel is 6.70 wt%, 2.05 wt% and 2.02 wt%, respectively. Metal phases are kamacite and tetrataenite. The kamacite has a Ni content in the range 5.83–6.81 wt%, while the Co content is in the range 0.39 to 0.56 wt%. Tetrataenite is has Ni content from 49.68 to 50.46 wt%, and Co up to 0.05 wt%. High-Ca monoclinic pyroxene, similar to diopside, is very rare. Accessory minerals are: chlorapatite and merrylite. Base on chemistry and petrography, the meteorite is classified as ordinary chondrite (L5). The main mass, a 9190 g specimen, is in Krzysztof Socha private collection. Small fragments with the total mass 71 g are stored in Museum of Earth Sciences (catalogue no: WNoZ/Mt/110) at University of Silesia in Katowice, Poland. 39 g was used for thin-section preparation and spectroscopic investigation (Mössbauer spectroscopy).
EN
Mössbauer spectra of equilibrated ordinary chondrites consist of two sextets due to magnetically ordered iron present in metallic phases and troilite and two doublets due to paramagnetic iron present in olivines and pyroxenes. The Mössbauer spectral areas of the different mineralogical phases in meteorites are proportional to the number of iron ions present in olivines, pyroxenes, metallic phase and troilite. This property of Mössbauer spectra was the basis for constructing various methods for the classification of ordinary chondrites. Review of these methods will be presented.
EN
This paper elaborates on gamma rays attenuation in ordinary chondrites. Highly penetrating gamma radiation is emitted as a result of inelastic collisions of ultra-high energy cosmic particles with bulk matter, such as spacecraft hulls. Resources mined from Solar System small bodies may present an alternative construction material for spacecraft cosmic rays shields, which explains research on ionizing radiation attenuation in meteorites. A custom-made, shielded research workstation was constructed to analyse ionizing radiation absorption in pulverized materials. Using the workstation, gamma rays attenuation experiment was performed on pulverized ordinary chondrite – a meteorite originating from S-type asteroid. The experiment resulted in obtaining gamma ray mass attenuation coefficient of S-type chondritic asteroid matter. Obtained results were analysed and final conclusions were formulated. Per unit mass, ordinary chondrites exhibit better gamma rays attenuation properties than any radiation shielding material contemporarily used in astronautics.
PL
W niniejszej pracy poruszono zagadnienie pochłaniania promieniowania gamma w materiale budującym meteoryty należące do grupy chondrytów zwyczajnych, które pochodzą z planetoid typu S. Wysoce przenikliwe promieniowanie gamma powstaje w przestrzeni kosmicznej m.in. jako efekt oddziaływania pierwotnego promieniowania kosmicznego z ośrodkami materialnymi. Materiał pozyskany z małych ciał Układu Słonecznego może stanowić alternatywny budulec ciężkich osłon radiacyjnych statków kosmicznych, co uzasadnia prowadzenie badań nad pochłanianiem promieniowania jonizującego w meteorytach. Opisano tu eksperyment, do celów którego wykonano autorskiej konstrukcji stanowisko badawcze do analizy pochłaniania promieniowania jonizującego w materiałach sypkich. Przy pomocy tego stanowiska, wykorzystując radioaktywny izotop 60Co, określono masowy współczynnik absorbcji promieniowania gamma w sproszkowanym chondrycie zwyczajnym, a otrzymany wynik porównano z wartością obliczoną teoretycznie. W pracy przeprowadzono szczegółową analizę uzyskanych wyników i sformułowano wnioski płynące z przeprowadzonego eksperymentu. Na jednostkę masy, chondryty zwyczajne lepiej osłabiają promieniowanie gamma niż jakiekolwiek materiały osłonowe stosowane obecnie w astronautyce.
EN
In Moessbauer spectrum of Shisr 176 meteorite four main iron-bearing minerals were identified: olivine, pyroxene, kamacite and troilite. Iron distribution among this minerals in Shris meteorite is similar to Sołtmany meteorite and different than in Baszkówka meteorite. As these three meteorites are type L ordinary chondrites this comparison might be used as a basis of a new criterion of the classification of the meteorites.
EN
The 4M method aims to determine the type of equilibrated ordinary chondrite only on the basis of the Mössbauer spectrum of the investigated meteorite. Mössbauer spectrum of non-weathered ordinary chondrite is comprised of four sub-spectra: two doublets and two sextets. One of the doublets consists of a signal from iron present in olivine and the other consists of a signal from iron present in pyroxene. Sextets on the other hand, contain signals from magnetically ordered iron. One sextet is related to the metallic phase (kamacite, taenite), whereas the second is related to troilite. A third of doublets, which emerges in weathered ordinary chondrites, is related to products of the oxidation of iron present in metallic phase. The spectral areas of olivine, pyroxenes, metallic phase and troilite, which were obtained from Mössbauer spectrum are proportional to the number of iron atoms present in relevant mineral phases. Some Mössbauer groups were inspired by this fact to construct different methods to determine the type (H, L, or LL) of investigated meteorites (Gałązka-Friedman et al. 2019, Hyp. Inter. 241(1)). However, these methods, based on subjective criteria, were only qualitative. Our group elaborated a quantitative method, which is based on objective criteria. We called it the "4M method" (where M are derived from meteorites, Mössbauer spectroscopy, multidimensional discriminant analysis (MDA), Mahalanobis distance) (Woźniak et al. 2019). This method was using only the Mössbauer experimental data, to which it applied advanced statistical methods. The base, which was created from Mössbauer data, consisted of three clusters H, L, LL. These clusters were constructed with sets of 4-dimensional vectors. The vectors are comprised of spectral areas of Mössbauer spectrum: ol (value proportional to iron present in olivine), pyr (value proportional to iron present in pyroxene), met (value proportional to iron present in metallic phase), tr (value proportional to iron present in troilite). To determine the type of investigated ordinary chondrite, its ol, pyr, met and tr values with average values of variables obtained for clusters H, L and LL need to be compared. The comparison can be performed with the use of MDA and Mahalanobis distance. Once Mahalanobis distance of the investigated meteoriteis is known, the level of similarity to three types of ordinary chondrites can be calculated. Examples of such calculations were performed for seven ordinary chondrites: Goronyo, Carancas, New Concord, NWA 7733, Leoncin, Sołtmany and Pułtusk. They were made with the use of the new base composed of 62 non-weathered ordinary chondrites. All results obtained with the 4M method yielded results consistent with traditional mineralogical methods.
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vol. 9
126-144
EN
Mean atomic weight Amean of Vicência (LL3.2 S1W0, fall 2013) ordinary chondrite has been calculated using literature data (Keil et al. 2015) on chemical composition of the meteorite and using relationships: between mean atomic weight and Fe/Si atomic ratio, between Amean and grain density, and between Amean and magnetic susceptibility. It was shown that Vicência’s Amean = 22.91 for composition without water. This value is close to the mean atomic weight of LL chondrite falls, is close to Amean value of LL3 chondrite falls, and is close to Amean value of Semarkona LL3.0 chondrite. Vicência’s Fe/Si atomic ratio (0.492±0.050) leads to Amean = 23.06–23.26, which is close to the value determined by bulk composition. Vicência’s Fe/Si atomic ratio is close to the value for Semarkona’s (Fe/Si = 0.511), and is close to LL’s mean Fe/Si ratio (0.520). This confirms that Vicência belongs to LL chondrites, as previously classified. Using dependence between mean atomic weight and grain density leads to Amean = 21.89±0.54 (dgr = 3.28 g/cm3, Keil et al. 2015), and using dependence between Amean and magnetic susceptibility gives Amean = 23.01±0.24 (logc = 4.30, Keil et al. 2015). Arithmetic mean of Amean (dgr), Amean (logc), and Amean(Fe/Si), gives 22.72±0.73, the value close to Amean(bulk composition) determined using compositional data. Mean atomic number Zmean, and Amean/Zmean ratio of the meteorite have been also calculated. Vicência’s Zmean = 11.37, and Amean/Zmean ratio is: 2.015 for composition without water. Vicência’s silicates shown the values: Amean = 21,67, Zmean = 10.76, Amean/Z mean = 2.014, Fe/Si = 0.318, Amean(Fe/Si) = 22.07–22.18, and Fe, Ni metal values: Amean = 56.63, Zmean = 26.53, and Amean/Z mean = 2.135. Two dependences: i) grain density dgr on Amean, and ii) grain density dgr on Fe/Si atomic ratio, were used to determine/verify grain density of Vicência chondrite. It was established that dgr(Amean) leads to the values: 3,42 g/cm3 for Vicência chondrite, 3,25 g/cm3 for silicates, and 7,90 g/cm3 for Fe, Ni metal of Vicência meteorite. Dependence dgr(Fe/Si) predicts density for Vicência chondrite: 3,47–3,49 g/cm3, and for silicates: 3,32–3,35 g/cm3.
EN
Mean atomic weight Amean of Jezersko (H4 S2(3) W2, find in 1992 in Slovenia) ordinary chondrite has been calculated using literature data on chemical composition of the meteorite (Miler et al. 2014) and using relationship between mean atomic weight and Fe/Si atomic ratio (Szurgot 2015c, d, e). It was shown that Jezersko’s Amean = 24.68, for composition without water. This value is close to the mean atomic weight of H chondrite finds (Amean = 24.80), and is somewhat smaller than Amean values for H4 chondrite falls (Amean = 25.09), and for H chondrite falls (Amean = 25.05) (Szurgot 2015e). Jezersko’s Fe/Si atomic ratio (0.742) leads to Amean = 24.66±0.24, which is close to the value determined by bulk composition. Jezersko’s Fe/Si atomic ratio is close to the value for H’s mean Fe/Si ratio: 0.762 for finds, and 0.807 for falls (Szurgot 2016a). This confirms that Jezersko belongs to H chondrites, as previously classified (Miler et al. 2014). Mean atomic number Zmean, and Amean/Zmean ratio of the meteorite have been also calculated. Jezersko’s Zmean = 12.16, and Amean/Zmean ratio is: 2.029 for composition without water. Jezersko’s silicates shown the values: Amean = 21.77, Zmean = 10.78, Amean/Z mean = 2.019, Fe/Si = 0.272, Amean(Fe/Si) = 21.84±0.06, and Jezersko’s Fe,Ni metal values: Amean = 56.12, Zmean = 26.19, and Amean/Z mean = 2.143. Two dependences: i) grain density dgr on Amean (Szurgot 2015a), and ii) grain density dgrain on Fe/Si atomic ratio (Szurgot 2017g), were used to predict grain density of Jezersko chondrite. It was established that dgr(Amean) leads to the values: 3.65±0.07 g/cm3 for Jezersko chondrite, 3.27±0.07 g/cm3 for silicates, and 7.83±0.07 g/cm3 for Fe,Ni metal of Jezersko meteorite. Dependence dgr(Fe/Si) predicts somewhat higher value grain density for Jezersko chondrite: 3.68±0.07 g/cm3, and 3.32±0.07 g/cm3 for silicates. All the predictions lead to the mean value of grain density for its weathering W2 degree: 3.67±0.03 g/cm3 for the whole rock of meteorite, and 3.29±0.03 g/cm3 for the silicates. It was established that due to terrestrial weathering, resulting in W2 weathering stage, Amean value of Jezersko chondrite is about 0.45 lower, Fe/Si atomic ratio is about 0.075 lower, and dgrain is about 0.06 g/cm3 lower than values for unweathered (W0) meteorite. Predicted porosity for Jezersko chondrite is: 10,1±0,7% for W2, and 11,5±0,5% for W0.
EN
The history, how the Mössbauer studies of meteorites began in Poland, was already described in our “Meteorites Odyssey… 20 years have passed”. One late afternoon (it was probably Spring 1995) I [Jolanta Gałązka-Friedman] was sitting in the Nonna Bakun’s office (at Banacha street) and we were talking about planet Mars. Suddenly Mr. Marian Stępniewski jumped to our room saying: We have a new Polish meteorite. It is called Baszkówka. Do you have any suggestion, how could we study this meteorite? Mössbauer spectroscopy – we both answered at the same time. And this is how it started, and it has been continued for the next quarter of a century. The first results of the Mössbauer studies of the Baszkówka meteorite were presented at the ISIAME conference in Johannesburg in 1996. In this paper we present the most important problems related to meteorites, which were investigated by us using Mössbauer spectroscopy. We will, however, show almost no formulas. We will try to explain everything by a method based on plots of Mössbauer spectra. We will try not to boast too much regarding our successes, but to explain also the problems that we were not able to resolve. While investigating the Baszkówka meteorite, we got most fascinated by troilite. We noticed that most of the laboratories determined the Mössbauer parameters of troilite incorrectly. They did not take into account the so-called theta angle, the value of which depends strongly on the number of vacancies and various additives. We thought that the theta angle may show us the parent body of the investigated meteorite. Unfortunately, this hypothesis turned up to be too difficult to defend. Then we studied Morasko meteorite and we discovered, by the comparison with Baszkówka meteorite Mössbauer spectra, and determined – up to now – not identified mineral phases present also in Morasko, such as pyrrhotite, daubréelite, taenite, tetrataenite, antitaenite and cohenite. In 2019 we published in MAPS a paper titled “Application of Mössbauer spectroscopy, multidimensional discriminant analysis and Mahalanobis distance for classification of equilibrated ordinary chondrites” (4M method), in which a new objective method for classification of ordinary chondrites is based on the knowledge of the Mössbauer spectra of the 4 main mineral phases present in the ordinary chondrites of H, L and LL type. Now we are working on the refinement of the 4M method enlarging our collaborative team by various foreign laboratories.
EN
Mössbauer 57Fe measurements of three ordinary chondrites type H and of three ordinary chondrites type LL were performed at room temperature. The spectral areas were fitted using the “Recoil” program (Lagarec i in. 1998). Fitting was repeated three times which allowed us to determinate the differences between the results of fits performed by different persons.
EN
Four stony pieces were delivered to our laboratory for checking if they are fragments of meteorites: first sample (sample No. 1) was a fragment of a rock that fell near Leoncin in Poland, second sample (sample No. 2) was a fragment of a rock found also in Poland in the vicinity of Pultusk, third sample (sample No. 3) was a meteorite specimen bought on the meteorite exchange and fourth sample (sample No. 4) was a stone object whose decline was observed in Europe. We obtained mössbauer spectra of the delivered samples. The mössbauer spectrum of sample No. 1 is very similar to the spectrum of ordinary chondrite of type LL. Comparison of the mössbauer spectrum of sample No. 2 with mössbauer spectrum of Pułtusk meteorite showed very large differences. In the spectrum of sample No. 3, a clear signal from iron-nickel alloy and troilite can be observed. These observations indicate that it is an object of extraterrestrial origin. Mössbauer spectrum of Sample No. 4 is similar to the spectrum of terrestrial magmatic rocks. Based on these spectrum we cannot clearly determine where the examined object comes from. This work demonstrates the usefulness of Mössbauer spectroscopy in recognizing samples that are fragments of meteorites.
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