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Tytuł:
Chondryt Sołtmany
Sołtmany chondrite
Autorzy:
Przylibski, Tadeusz A.
Powiązania:
https://bibliotekanauki.pl/articles/1033061.pdf
Data publikacji:
2016
Wydawca:
Polskie Towarzystwo Meteorytowe
Tematy:
Gefion family
L6
asteroid
atomic weight
bulk chemistry
cosmic-ray exposure age
cosmogenic radionuclides
density
fusion crust
magnetic susceptibility
meteorite
meteorite age
meteorite fall
mössbauer spectroscopy
noble gas
ordinary chondrite
organic matter
parent body
porosity
primordial radionuclides
thermophysical properties
troilite thermometer
Opis:
The Sołtmany hammer meteorite is classified as an ordinary chondrite type L6, W0, S2. At present it is the most thoroughly and comprehensively examined Polish meteorite. A comprehensive petrological, mineralogical and geochemical analysis alongside the investigation of its physical and particularly thermophysical properties, and, most of all, analyses of cosmogenic radionuclides and noble gases isotopes content, as well as the use of a troilite thermometer has made it possible to draw interesting conclusions concerning the genesis and evolution of the parent body and the history of the parent meteoroid and, finally, the Sołtmany meteorite. The present report attempts at summing up the results of studies conducted at several European research centres in the last four years. The age of the the Sołtmany chondrite parent rock has been defined at 4.137 billion years. It was formed at a temperature of up to 440–450 K (about 170°C), probably at a depth of up to 3 to 7 km under the surface of the parent body, i.e. at a pressure of the order of 1–2.4 kbar. Such a low temperature during the accretion, diagenesis and metamorphism of the parent body may point to its complicated development, which may be in part due to collisions of partially melted planetesimals. Like with other type L ordinary chondrites, one can infer that the parent body could have been destroyed about 467 million years ago, at the time of a catastrophic collision which led to the formation of Gefion family of planetoids. Perhaps one of the bodies in this family was involved in another collision about 29.2 million years ago, which resulted in ejecting the parent meteoroid of the Sołtmany chondrite onto the Earth collision trajectory. Before entering the Earth’s atmosphere, this meteoroid had the mass of about 36 kg and the diameter of ca 13.5 cm. During its flight through the atmosphere, it rotated and somersaulted, which resulted in the formation of an uniform thin (0.5–0.7 mm) fusion crust, whose temperature reached 1000°C. In the last phase, the Sołtmany meteorite fell almost vertically and its mass was a mere 3% of the mass of the parent meteoroid – 1.066 kg. It hit the roof and then the concrete stairs of a farm building, which caused it to break into two bigger and many small pieces. It was found a few minutes after the fall, which occurred at 6:03 a.m. (CEST, UTC+2:00) on 30 April 2011, by Wydmińskie Lake in northern Poland (54°00,53’N, 22°00,30’E). The Sołtmany chondrite is one of just 14 meteorites in which the activity concentration of the cosmogenic 52Mn has been determined, and one of the few ordinary chondrites where the concentration of organic matter has been defined. As a result, it was found out that unlike in carbonaceous CI chondrites, the composition of organic particles is dominated by less complex compounds (CHO and CHOS) than CHNO and CHNOS compounds. This may indicate the decomposition of more complex organic compounds into particles with simple structures during magmatic and metamorphic processes related to formation of type L ordinary chondrites.
Źródło:
Acta Societatis Metheoriticae Polonorum; 2016, 7; 93-122
2080-5497
Pojawia się w:
Acta Societatis Metheoriticae Polonorum
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Przegląd najważniejszych prac dotyczących próby ustalenia daty spadku meteorytów oraz wieku kraterów Morasko
Review of most important papers regarding attempts to determine the date of Morasko meteorite fall and age of the craters
Autorzy:
Walesiak, Tomasz
Powiązania:
https://bibliotekanauki.pl/articles/1830331.pdf
Data publikacji:
2021
Wydawca:
Polskie Towarzystwo Meteorytowe
Tematy:
age
craters
dating
fall
luminescence
meteorite Morasko
palynological
radiocarbon
Opis:
One of criteria suggesting impact origin may be recognition of extraterrestrial matter inside or around suspected cavities. In case of Morasko some dating results throw doubt on link between craters and meteorites. Conclusion of some past research papers was that cavities were formed about 5 ka BP (e.g. palynological investigation, luminescence dating), while more or less facts testify fall in the Middle Ages (e.g. “young” charcoal pieces in crust of meteorites or shrapnel stuck in the roots of old tree). In this paper we perform comprehensive analysis of each result and check if there exists alternative explanation. During past palynological investigation, there were examined two craters. It was concluded that beginning of accumulation of sediments in smaller cavity started 5500–5000 BP. However, pollen spectrum for largest basin was different suggesting younger age. The problem is that according to bathymetric maps, samples could be collected from inner uplift (similar feature was observed inside Porzadzie and Jaszczulty, unconfirmed impact structures yet). If we compare profiles from craters with recent research (palynological study supported by radiocarbon dating) on sediments in Lake Strzeszynskie (6 km SW from Morasko) pollen spectrum seems to be similar more to results dated to <1000 BP. Especially percentage of non-arboreal pollen for both examined Morasko craters is much higher (5 times greater than it was for layer dated to 5 ka BP in Lake Strzeszynskie). Possibility of short disturbance (related to impact) cannot be excluded, but in such case any time of event should be taken into account. For small lakes (like those filling the craters) also local conditions could play important role. Analysis of luminescence dating may also discuss past conclusions. OSL method applied for samples taken from the thin layer of sand in the bottom of largest structure (under 3,9 m of organic sediments filling the crater) suggested age 5–10 ka BP for 24 aliquots. Same number of samples (24) revealed age 0–5 ka BP (13 samples with age <3 ka BP including several younger than 1 ka BP). Older dates can be explained by partial or even no zeroing, but last contact with light (zeroing signal) of sand grains (excavated from depth of almost 4 meters under organic matter) seems that might occur only during (or shortly after) the impact. It is difficult to find convincing arguments, which can undermine initial radiocarbon dating giving age <1 ka BP for 7 of 9 samples taken from the bottom layer of organic sediments from three Morasko craters. Same issue may exist with small charcoal pieces with age <2 ka BP (and several dated to ~700 BP) discovered deep in sinter-weathering crust of meteorites. Study of charcoal particles excluded their origin during post-sedimentary processes (like forest fire) unless meteorite fragments were laying directly on the surface for period between impact and wildfire (surviving whole time inhospitable climate conditions). There are two other possible explanations of charcoals. Either they were present at location as a result of past forest fire or they were produced during impact. However, similar small charcoal pieces were discovered around many craters (Kaali, Ilumetsa, Campo del Cielo, Whitecourt) and they were successfully used to estimate maximum age of those structures. During second stage of 14C dating the age obtained from three samples (taken few centimeters above the mineral bottom) was estimated ~5 ka BP. Looking for answer why these results are so different from previous once there may be mentioned at least two options. Lake sediments is difficult matter for radiocarbon dating and results may be hundreds or even thousands years older than real age. Second explanation may be that older matter (remnant of trees, paleosoil etc.), distributed around craters during impact, could be displaced by wind, rain, erosion and trapped in the bottom of cavities. The argument, which may be also against hypothesis of impact ~5 ka BP is meteorite shrapnel stuck in the roots of old tree. Result of expertise showed, that there exists mechanical damage in the wood and the only possible explanation is that meteorite has hit living tree. Maximum age, that this type of wood may preserve (inside building) is 1,8 ka while in natural environment not more than 500 years. Anyway some further examinations should be performed. The age obtained during AMS 14C dating of 2 samples from thin layer of paleosoil, discovered under overturned flap around largest Morasko crater, was ~5 ka BP. Observation that preserved layer of paleosoil is approximately 3 times thinner than thickness of modern soil may lead to conclusion that during impact top (younger) layer of organic sediments was removed and only older part “survived” in few locations close to the rim. The conclusion of the research was that dating provides maximum age of the impact (which does not exclude much younger impact <1 ka BP) so could be considered as right explanation of past discrepancies.
Źródło:
Acta Societatis Metheoriticae Polonorum; 2021, 12; 129-148
2080-5497
Pojawia się w:
Acta Societatis Metheoriticae Polonorum
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Pomiary radionuklidów kosmogenicznych w meteorycie z Oslo i interpretacja wyników
The Oslo Meteorite Research for Cosmogenic Radionuclides and The Interpretation of The Results
Autorzy:
Tymiński, Zbigniew
Miśta, Ewelina
Kalbarczyk, Paweł
Powiązania:
https://bibliotekanauki.pl/articles/1032971.pdf
Data publikacji:
2013
Wydawca:
Polskie Towarzystwo Meteorytowe
Tematy:
HPGe gamma spectrometry
Oslo meteorite
cosmogenic radionuclides
meteorites
pre-atmospheric size
terrestrial age
Opis:
Nondestructive high-resolution gamma spectrometry techniques were used to measure cosmogenic radionuclides in 32.5g fragment of Oslo meteorite which the fall was not observed. Five radioisotopes with half-lives ranging from 278.1 days to 7.17´105 years have been detected. The signals observed for 26Al, 22Na, 54Mn, 57Co and 60Co were interpreted in terms of the meteoroid depth profiles and terrestrial age after the fall. The pre-atmospheric radius of the chondrite was estimated to be >100 cm. Concentrations of short-lived nuclides limits the fall date before December 2011.
Źródło:
Acta Societatis Metheoriticae Polonorum; 2013, 4; 115-120
2080-5497
Pojawia się w:
Acta Societatis Metheoriticae Polonorum
Dostawca treści:
Biblioteka Nauki
Artykuł
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