Komplexní petrologický a geochemický výzkum lunárního meteoritu mare-bazaltického složení Northeast Africa 003-A

COMPREHENSIVE PETROLOGICAL AND GEOCHEMICAL STUDY OF LUNAR MARE-BASALT METEORITE NORTHEAST AFRICA 003-A Northeast Africa 003 (NEA 003) is a lunar meteorite found as a two paired stones (6 and 118 g) in Libya in 2000 and 2001. The main portion (~75 vol%) of the 118 g meteorite, used for this study, (NEA 003-A) consists of mare basalt and a smaller adjacent portion (~25 vol%) is a basaltic breccia (NEA 003-B). NEA 003-A has a coarse-grained magmatic texture consisting mainly of olivine, pyroxene and plagioclase. The late-stage mineral association is composed mainly of elongate plagioclase, ilmenite, troilite, fayalite, Si-K-rich glass, apatite and a rare SiO2 phase. Other accessory minerals include ulvöspinel, chromite, and trace Fe-Ni metal. Olivine and pyroxene contain shock-induced fractures, and plagioclase is completely converted into maskelynite. The Fe/Mn values of the whole rock, olivines and pyroxenes, and the bulk-rock oxygen isotopic composition provide evidence for the lunar origin of NEA 003-A meteorite. This is further supported by the presence of Fe-Ni metal and an anhydrous mineral association. NEA 003-A is geochemically and petrographically distinct from previously described mare-basalt meteorites and is not paired with any of them. The petrography and major element composition of NEA...KOMPLEXNÍ PETROLOGICKÝ A GEOCHEMICKÝ VÝZKUM LUNÁRNÍHO METEORITU MARE-BAZALTICKÉHO SLOŽENÍ NORTHEAST AFRICA NEA 003-A Northeast Africa 003 (NEA 003) je lunární meteorit, nalezený ve dvou fragmentech (6 a 118 g) v Libyi v letech 2000 a 2001. Hlavní část 118 g fragmentu meteoritu (~75 obj. %) použitá pro tuto studii (NEA 003-A) byla klasifikována jako lunární mare-bazalt a menší přilehlá část (~25 obj. %) je tvořena bazaltickou brekcií označovanou jako NEA 003-B. Meteorit NEA 003-A je tvořen především olivíny, pyroxeny a plagioklasy s nápadnou hrubozrnnou magmatickou strukturou. Minerální asociace charakteristická pro pozdní stádia krystalizace této horniny se skládá především z lištovitých plagioklasů, ilmenitu, troilitu, fayalitu, Si-K bohatého skla, apatitu a vzácně i SiO2 fází. Dále jsou přítomny akcesorické minerály zahrnující ulvöspinel, chromit a vzácně i ryzí Fe-Ni slitiny. Zrna olivínů a pyroxenů jsou nápadně porušená frakturami, které vznikly v důsledku působení vysokých šokových tlaků, a přítomný plagioklas byl ze stejného důvodu zcela přeměněn na maskelynit. Poměry Fe/Mn celkové horniny, olivínů a pyroxenů a také izotopické složení kyslíku pro celkovou horninu dokládá jednoznačně lunární původ tohoto meteoritu. Dalšími důkazy svědčícími pro lunární původ meteoritu NEA 003-A jsou přítomnost...Institute of Geochemistry, Mineralogy and Mineral ResourcesÚstav geochemie, mineralogie a nerostných zdrojůFaculty of SciencePřírodovědecká fakult

Low temperature magnetic properties of iron bearing sulfides and their contribution to magnetism of cometary bodies

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Shock physics mesoscale modeling of shock stage 5 and 6 in ordinary and enstatite chondrites

Shock-darkening, the melting of metals and iron sulfides into a network of veins within silicate grains, altering reflectance spectra of meteorites, was previously studied using shock physics mesoscale modeling. Melting of iron sulfides embedded in olivine was observed at pressures of 40-50 GPa. This pressure range is at the transition between shock stage 5 (C-S5) and 6 (C-S6) of the shock metamorphism classification in ordinary and enstatite chondrites. To better characterize C-S5 and C-S6 with a mesoscale modeling approach and assess post-shock heating and melting, we used multi-phase (i.e. olivine/enstatite, troilite, iron, pores, and plagioclase) meshes with realistic configurations of grains. We carried out a systematic study of shock compression in ordinary and enstatite chondrites at pressures between 30 and 70 GPa. To setup mesoscale sample meshes with realistic silicate, metal, iron sulfide, and open pore shapes, we converted backscattered electron microscope images of three chondrites. The resolved macroporosity in meshes was 3-6%. Transition from shock C-S5 to C-S6 was observed through (1) the melting of troilite above 40 GPa with melt fractions of similar to 0.7-0.9 at 70 GPa, (2) the melting of olivine and iron above 50 GPa with melt fraction of similar to 0.001 and 0.012, respectively, at 70 GPa, and (3) the melting of plagioclase above 30 GPa (melt fraction of 1, at 55 GPa). Post-shock temperatures varied from similar to 540 K at 30 GPa to similar to 1300 K at 70 GPa. We also constructed models with increased porosity up to 15% porosity, producing higher post-shock temperatures (similar to 800 K increase) and melt fractions (similar to 0.12 increase) in olivine. Additionally we constructed a pre-heated model to observe post-shock heating and melting during thermal metamorphism. This model presented similar results (melting) at pressures 10-15 GPa lower compared to the room temperature models. Finally, we demonstrated dependence of post-shock heating and melting on the orientation of open cracks relative to the shock wave front. In conclusion, the modeled melting and post-shock heating of individual phases were mostly consistent with the current shock classification scheme (Stoffler et al., 1991, 2018).Peer reviewe

Low-temperature magnetism of alabandite : Crucial role of surface oxidation

Manganese(II) monosulphide crystallizes into three different polymorphs (alpha-, beta-, and gamma-MnS). Out of these, alpha-MnS, also known as mineral alabandite, is considered the most stable and is widespread in terrestrial materials as well as in extraterrestrial objects such as meteorites. In this study, a low-temperature antiferromagnetic state of alpha-MnS was investigated using macroscopic magnetic measurements as induced and remanent field-cooled (FC) and zero-field-cooled (ZFC) magnetizations and magnetic hysteresis. Both natural alabandite and synthetic samples show (i) Néel temperatures in a narrow temperature range around 153 K and (ii) a rapid increase of the magnetization around 40 K. An anomalous magnetic behavior taking place at about 40 K was previously ascribed to the magnetic transition from a high-temperature antiferromagnetic to a low-temperature ferromagnetic state documented for non-stoichiometric alpha-MnS slightly enriched in manganese. However, our detailed microscopic observations and, in particular, oxidation experiments indicate that the anomalous magnetic behavior around 40 K is caused by a presence of oxide layer of ferrimagnetic hausmannite (Mn3O4) on the surface of alpha-MnS rather than being an intrinsic property of nearly stoichiometric alpha-MnS.Peer reviewe

Distinguishing between Shock-darkening and Space-weathering Trends in Ordinary Chondrite Reflectance Spectra

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Mineralogy, reflectance spectra, and physical properties of the Chelyabinsk LL5 chondrite, insight into shock induced changes in asteroid regoliths

The mineralogy and physical properties of Chelyabinsk meteorites (fall, February 15, 2013) are presented. Three types of meteorite material are present, described as the light-colored, dark-colored, and impact-melt lithologies. All are of LL5 composition with the impact-melt lithology being close to whole-rock melt and the dark-colored lithology being shock-darkened due to partial melting of iron metal and sulfides. This enables us to study the effect of increasing shock on material with identical composition and origin. Based on the magnetic susceptibility, the Chelyabinsk meteorites are richer in metallic iron as compared to other LL chondrites. The measured bulk and grain densities and the porosity closely resemble other LL chondrites. Shock darkening does not have a significant effect on the material physical properties, but causes a decrease of reflectance and decrease in silicate absorption bands in the reflectance spectra. This is similar to the space weathering effects observed on asteroids. However, compared to space-weathered materials, there is a negligible to minor slope change observed in impact-melt and shock-darkened meteorite spectra. Thus, it is possible that some dark asteroids with invisible silicate absorption bands may be composed of relatively fresh shock-darkened chondritic material.Peer reviewe

Annama H chondrite-Mineralogy, physical properties, cosmic ray exposure, and parent body history

The fall of the Annama meteorite occurred early morning (local time) on April 19, 2014 on the Kola Peninsula (Russia). Based on mineralogy and physical properties, Annama is a typical H chondrite. It has a high Ar-Ar age of 4.4 Ga. Its cosmic ray exposure history is atypical as it is not part of the large group of H chondrites with a prominent 7-8 Ma peak in the exposure age histograms. Instead, its exposure age is within uncertainty of a smaller peak at 30 +/- 4 Ma. The results from short-lived radionuclides are compatible with an atmospheric pre-entry radius of 30-40 cm. However, based on noble gas and cosmogenic radionuclide data, Annama must have been part of a larger body (radius >65 cm) for a large part of its cosmic ray exposure history. The Be-10 concentration indicates a recent (3-5 Ma) breakup which may be responsible for the Annama parent body size reduction to 30-35 cm pre-entry radius.Peer reviewe

The Stubenberg meteorite—An LL6 chondrite fragmental breccia recovered soon after precise prediction of the strewn field

On March 6, 2016 at 21:36:51 UT, extended areas of Upper Austria, Bavaria (Germany) and the southwestern part of the Czech Republic were illuminated by a very bright bolide. This bolide was recorded by instruments in the Czech part of the European Fireball Network and it enabled complex and precise description of this event including prediction of the impact area. So far six meteorites totaling 1473 g have been found in the predicted area. The first pieces were recovered on March 12, 2016 on a field close to the village of Stubenberg (Bavaria). Stubenberg is a weakly shocked (S3) fragmental breccia consisting of abundant highly recrystallized rock fragments embedded in a clastic matrix. The texture, the large grain size of plagioclase, and the homogeneous compositions of olivine (Fa31.4) and pyroxene (Fs25.4) clearly indicate that Stubenberg is an LL6 chondrite breccia. This is consistent with the data on O, Ti, and Cr isotopes. Stubenberg does not contain solar wind-implanted noble gases. Data on the bulk chemistry, IR spectroscopy, cosmogenic nuclides, and organic components also indicate similarities to other metamorphosed LL chondrites. Noble gas studies reveal that the meteorite has a cosmic ray exposure (CRE) age of 36 ± 3 Ma and that most of the cosmogenic gases were produced in a meteoroid with a radius of at least 35 cm. This is larger than the size of the meteoroid which entered the Earth's atmosphere, which is constrained to <20 cm from short-lived radionuclide data. In combination, this might suggest a complex exposure history for Stubenberg.PostprintPeer reviewe

Comprehensive petrological and geochemical study of lunar mare-basalt meteorite Northeast Africa 003 - A

COMPREHENSIVE PETROLOGICAL AND GEOCHEMICAL STUDY OF LUNAR MARE-BASALT METEORITE NORTHEAST AFRICA 003-A Northeast Africa 003 (NEA 003) is a lunar meteorite found as a two paired stones (6 and 118 g) in Libya in 2000 and 2001. The main portion (~75 vol%) of the 118 g meteorite, used for this study, (NEA 003-A) consists of mare basalt and a smaller adjacent portion (~25 vol%) is a basaltic breccia (NEA 003-B). NEA 003-A has a coarse-grained magmatic texture consisting mainly of olivine, pyroxene and plagioclase. The late-stage mineral association is composed mainly of elongate plagioclase, ilmenite, troilite, fayalite, Si-K-rich glass, apatite and a rare SiO2 phase. Other accessory minerals include ulvöspinel, chromite, and trace Fe-Ni metal. Olivine and pyroxene contain shock-induced fractures, and plagioclase is completely converted into maskelynite. The Fe/Mn values of the whole rock, olivines and pyroxenes, and the bulk-rock oxygen isotopic composition provide evidence for the lunar origin of NEA 003-A meteorite. This is further supported by the presence of Fe-Ni metal and an anhydrous mineral association. NEA 003-A is geochemically and petrographically distinct from previously described mare-basalt meteorites and is not paired with any of them. The petrography and major element composition of NEA..

Exegesis, theology and interpretation of 3rd and 4th chapters of the book of Jonah

The introduction of the thesis includes defined main objectives and criteria for selection of studied pericope for exegetic work are justified. Following part of the thesis includes information about literary context and a summary of current knowledge about origin, age and literary genre of studied pericope. Exegetical part of the thesis includes author's translation of the original Hebrew text, the identification and evaluation of significant grammatical and semantic phenomena followed by the interpretation of the verses, based on own observation and study of relevant commentaries. The core of the exegetic part of the thesis is complemented by the literary analysis of the studied pericope. The conclusion includes a chapter where main theological themes and interpretations are identified and evaluated