The melting of planetesimals was a widespread geologic phenomenon taking place in the early inner solar system. Petrologic and geochemical evidence shows that this melting frequently resulted in full differentiation of planetary bodies into a core, mantle, and crust. The extent of this early planetary melting is evidenced in the breadth of achondrite meteorites. In the achondrite meteorite group, there exist meteorites that experienced low degrees of melting, such that the parent body underwent partial melting and did not fully differentiate. These meteorites, called the primitive achondrites, are a window to the first stage of melting in the early solar system. The primitive achondrites with FeO-poor silicate compositions have been well-studied, but little is known about the formation conditions and history of the FeO-rich primitive achondrites, which includes the brachinites and several ungrouped meteorites.The brachinites are olivine-dominated meteorites with a recrystallized texture that show evidence of partial melting and melt removal on their parent body. The ungrouped primitive achondrites are also olivine-dominated meteorites with a recrystallized texture, but they exhibit a larger range in mineralogy with most being essentially chondritic and containing relict chondrules. In this dissertation, I present a study of the petrology, geochemistry and formation conditions of the FeO-rich primitive achondrites. I analyze the petrology and bulk composition of the meteorites, and I conduct thermodynamic modelling of the mineral assemblages to determine oxidation conditions during their formation. Finally, I attempt to simulate the formation of the brachinite meteorites through 1-atmosphere, gas-mixing partial melting experiments of an FeO-rich chondritic meteorite.These meteorites represent a continuum of partial melting, akin to that seen in the acapulcoite-lodranite clan of primitive achondrites. Mineral compositions and oxygen fugacity formation conditions indicate that the brachinites could have formed from a parent body much like the R chondrites. Gas-mixing, partial melting experiments of a R4 chondrite LaPaz Ice Field 03639 at 1250 °C and an oxygen fugacity of IW-1 create the mineralogy and mineral compositions of the brachinites. The experiments also confirm that the brachinites formed by the partial melting of an FeO-rich chondritic source and not as igneous cumulates.

Vor 200 Jahren fiel ein Meteorit in der Nähe von Erxleben, der von den drei deutschen Chemikern Stromeyer, Klaproth und Bucholz analysiert wurde. Aus diesem Anlass wird eine Übersicht der chemischen Analyse von Meteoriten beginnend mit den ersten Untersuchungen gegeben. In jenen Jahren wurden die Hauptkomponenten bestimmt. In den meisten Steinmeteoriten fand man sehr ähnliche Gehalte der Hauptbestandteile, charakteristische Körner aus Eisen und Eisensulfid in einer mineralischen Grundmasse aus Bittererde und Kieselerde genannten Oxiden von Magnesium und Silicium. Man fand in den Eisenmeteoriten und den metallischen Körnern der Steinmeteoriten hohe Gehalte an Nickel, wie sie nicht in natürlichen irdischen Materialien vorkommen. Der britische Chemiker Howard und Klaproth waren die ersten, die Chladnis Theorie akzeptierten, dass die Meteoriten aus dem Kosmos stammen / 200 years ago a meteorite was fallen near Erxleben between Magdeburg und Helmstedt, which was analyzed by the three German Chemist Stromeyer, Klaproth and Bucholz. For this reason a survey of chemical analysis of meteorites from the first investigation in 1769 until 1820 is given. In this period the contents of main components were determined and were found to be similar for most of the stony meteorites, which contains characteristic grains of iron and iron sulfide in a mineral matrix of oxides of magnesium and silicon in German named “Bittererde” and “Kieselerde”. The metal in iron meteorites and in the metallic grains of stony meteorites contain a high content of nickel, which was not found in natural iron on the earth. The British Chemist Howard and Klaproth were the first, who accepted the Theory of Chladni, that the meteorites have been fallen from the sky.

Im frühen Sonnensystem fanden während der Kondensation der chemischen Elemente volatilitätskontrollierte Fraktionierungsprozesse statt. Gegenstand dieser Doktorarbeit sind Fraktionierungen refraktär-lithophiler Elemente in einzelnen Chondritkomponenten sowie zwischen Bulk-Chondriten, Achondriten und Planeten. Mittels laser ablation inductively coupled plasma mass spectrometry wurden die Gehalte der Seltenen Erden (REE) sowie von Nb, Ta, Zr und Hf analysiert. Einzelne Chondritkomponenten wurden in-situ an dem CV-Chondrit Leoville untersucht. Von den Bulk-Chondriten, Achondriten und terrestrischen Proben wurden Gesamtgesteinsproben durch Laserschmelzen unter aerodynamischer Levitation angefertigt. Die Untersuchung der verschiedenen Bestandteile des Leoville-Chondrits ergab, dass die refraktären Einschlüsse volatilitätskontrollierte fraktionierte REE group-II-Muster und subchondritische Nb/Ta-Verhältnisse aufweisen. Sie sind demzufolge aus einem residualen Gas entstanden, von dem zuvor eine ultrarefraktäre Komponente isoliert worden war. Chondren haben zumeist relativ unfraktionierte REE-Muster sowie unfraktionierte Zr/Hf- und Nb/Ta-Verhältnisse. Einige Typ-1-Chondren, die Al-reichen Chondren und die Chondritmatrix weisen jedoch fraktionierte REE-Muster auf. Dies ist ein Hinweis auf Beimengungen refraktären Materials mit REE group-II-Muster. Die Analysen an Bulk-Chondriten zeigen, dass kohlige Chondrite im Vergleich zu dem CI-Chondrit Orgueil charakteristische volatilitätskontrollierte REE-Muster (ultrarefraktär oder group-II) besitzen, was auf den Einbau refraktärer Komponenten mit fraktionierten Seltenen Erden zurückgeführt wurde. Die Mehrheit der gewöhnlichen, Rumuruti- und Enstatit-Chondrite hat dagegen relativ unfraktionierte REE-Muster. Es konnte gezeigt werden, dass sowohl gewöhnliche, Enstatit- und Rumuruti-Chondrite als auch Proben von Achondriten, Mars, Mond und Erde geringe negative Tm-Anomalien gegenüber dem CI-Chondrit Orgueil aufweisen. Die Objekte des inneren Sonnensystems wurden daher anhand ihrer relativen Gehalte an schweren Seltenen Erden (HREE) in zwei Gruppen eingeteilt: Ein kohliges und ein nichtkohliges Chondrit-Reservoir, dem auch die Achondrite, Mars, Erde und Mond angehören. Es wurde angenommen, dass die Objekte des nichtkohligen Chondrit-Reservoirs die HREE-Verhältnisse des Sonnensystems widerspiegeln; kohlige Chondrite haben dagegen variable Tm-Anomalien, welche durch den Eintrag fraktionierter refraktärer Komponenten in ihre Entstehungsregion zu erklären sind. CI-Chondrite, welche allgemein als die chemisch primitivste Chondritgruppe angesehen werden, hätten in diesem Fall eine positive Tm-Anomalie von 4,8 ± 0,9 % und stimmten somit chemisch nicht mit dem Sonnensystem überein. Durch eine Beimengung von nur 0,2 Gewichtsprozent einer refraktären Komponente mit REE group-II-Muster zu den CI-Chondriten konnte diese Tm-Anomalie erklärt werden.

Thèse (D.R.Min.) -- Université du Québec à Chicoutimi, programme en association avec l'Université du Québec à Montréal, 2006. / Bibliogr.: f. 95-101. Document électronique également accessible en format PDF. CaQCU

abstract: Carbonaceous chondrites (CCs) present a unique opportunity for learning about the earliest organic chemistry that took place in our Solar System. The complex and diverse suite of meteoritic organic material is the result of multiple settings and physicochemical processes, including aqueous and thermal alteration. Though meteorites often inform origin-of-life discussions because they could have seeded early Earth with significant amounts of water and pre-biotic, organic material, their record of abiotic, aqueous, and organic geochemistry is of interest as well. CC materials previously resided on asteroidal parent bodies, relic planetesimals of Solar System formation which never accreted enough material to develop long-lived, large-scale geological processes. These bodies were large enough, however, to experience some degree of heating due to the decay of radiogenic isotopes, and the meteorite record suggests the existence of 100-150 parent bodies which experienced varying degrees of thermal and aqueous alteration for the first several 10 Myr of Solar System history. The first chapter of this dissertation reviews literature addressing aqueous alteration as an essential participant in parent body geochemistry, organic synthesis, or both (though papers which address both are rare). The second chapter is a published organic analysis of the soluble organic material of Bells, an unclassified type 2 chondrite. Analytical approaches to assess terrestrial contamination of meteorite samples are also reviewed in the first chapter to allow introduction in chapter 3 of kinetic modeling which rules out certain cases of contamination and constrains the timing of thermal and aqueous alteration. This is the first known application of isoleucine epimerization for either of these purposes. Chapter 4 is a kinetic study of D-allo-isoleucine epimerization to establish its behavior in systems with large, relative abundances of alloisoleucine to isoleucine. Previous epimerization studies for paleontological or geological purposes began with L-isoleucine, the only protein amino acid of the four isoleucine stereoisomers. Kinetic model calculations using isoleucine stereoisomer abundances from 7 CR chondrites constrain the total duration of the amino acids' residence in the aqueous phase. The comparatively short timescales produced by the presented modeling elicit hypotheses for protection or transport of the amino acids within the CR parent body. / Dissertation/Thesis / Doctoral Dissertation Chemistry 2014

Orientadores: Carlos Roberto de Souza Filho, Cristiano de Carvalho Lana / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Geociências / Made available in DSpace on 2018-08-23T13:22:26Z (GMT). No. of bitstreams: 1 Silva_Dailto_D.pdf: 6673922 bytes, checksum: ad586d69e4694b3e81cab5a383dfef3f (MD5) Previous issue date: 2013 / Resumo: A pesquisa foi realizada na cratera de impacto de meteorito de Araguainha (Goiás / Mato Grosso, Brasil) e compreendeu três desenvolvimentos científicos principais. O primeiro engloba a petrografia e geoquímica de rochas graníticas parcialmente fundidas do núcleo da cratera de impacto. Foi possível separar, por petrografia e posicionamento geográfico, os litotipos do granito preservado (GP) dos litotipos de fusão (granito parcialmente fundido (GPF), veios de fusão (VF) e capa de fusão (CF)). Contudo, estes litotipos apresentam características geoquímicas muito semelhantes para elementos maiores, menores, traços e terras raras. O diagrama que se mostrou o melhor discriminante entre os litotipos de fusão e os granitos preservados foi o Th/U x TiO2, que indica enriquecimento relativo na razão Th/U nos granitos. O granito preservado é também rico em quartzo e apresenta empobrecimento em elementos como Ti, Zr, Ce, Y, Eu, Nb e elementos terras raras. Essas características permitem postular uma possível influência hidrotermal na geração dos litotipos de fusão. O segundo desenvolvimento aborda a mobilidade dos elementos traço e geração de fusões félsicas na crosta terrestre durante o impacto de meteoritos e implicações para a evolução da crosta Hadeana. Nesse caso, o processo de acresção crustal por impacto pode ser um mecanismo complementar, capaz de explicar uma importante modificação da crosta terrestre Hadeana ocorrida entre 3.9-4.5 Ga. O terceiro desenvolvimento trata dos efeitos do impacto na indução de fusão incongruente da crosta da Terra, tendo como base a fusão da biotita. O estudo mostrou que a biotita pré-impacto é distinta daquela pós-impacto, com texturas, estrutura e quimismo contrastantes. Demonstrou-se que até 9% do granito de Araguainha é produto de cristalização a partir da quebra da biotita. A biotita funde incongruentemente durante o processo de impacto, produzindo uma fusão aluminosa, que preenche bolsões e rede de fraturas nas rochas. Impactos do tamanho de Araguainha ou maiores são capazes de gerar volumes substanciais de fundidos aluminosos na crosta / Abstract: The focus of this PhD thesis is on granitic targets impacted by meteorites and felsic melting generation in the crust during impacts. Key features of the Araguainha impact crater (Goiás / Mato Grosso, Brazil) were employed as a control. Field, petrographic and analytical data collected in the study area were grouped into three, central scientific developments. The first comprises the petrography and geochemistry of partially melted granitic rocks observed in the core of the Araguainha crater. The work shows that it is possible to separate, by petrography and geographical positioning, preserved granite rocks from melt rock types, such as the partially melted granite (GPF), the melted veins (VF), and the melted caps (CF). These rock types have very similar geochemical characteristics regarding major, minor, trace and rare earth elements. However, melt rock types are readily discriminated from preserved granites in Th/U x TiO2 scatergrams; granites show relative enrichment in the ratio Th/U. Another noteworthy feature is that the preserved granite rich in quartz is depleted in Ti, Zr, Ce, Y, I, Nb and REE, indicating a possible influence of hydrothermal systems in the formation of melt products. The second development provides clues on the mobility of trace elements and generation of felsic melts in the crust during the meteorite impact, and implications for the evolution of the Hadean crust. It is argued that process of crustal accretion by impacts may have been one of the mechanisms that can explain important modification of the Earth's crust during the Hadean (3.9-4.5 Ga). The third development deals with the effects of shock-induced incongruent melting within Earth's crust, using the case of biotite melting. It was demonstrated that pre-impact and pos-impact biotites found in Araguainha show distinct textures, structures and chemistry. Results show that up to 9% of Araguainha granite is a product of magma crystallization from breakdown of biotite. The biotite melts incongruently during the impact process, producing an aluminous fusion, which fulfills pockets and fracture networks of the rocks. Impacts of the size of Araguainha or larger seem to be capable of generating substantial amounts of aluminous melt in the crust / Doutorado / Geologia e Recursos Naturais / Doutor em Ciências

Des anomalies nucléosynthétiques ont été observées dans des météorites pour plusieurs éléments. L’ampleur de ces anomalies ainsi que leur répartition entre les objets du système solaire renseigne sur le degré d’hétérogénéité de la nébuleuse solaire. L’étude des phases porteuses de ces anomalies procure des informations sur les processus à l’origine de cette hétérogénéité. Les datations par radiochronomètres de courte période reposent sur la répartition hétérogène des éléments père et fils. L’utilisation de ces outils nécessite donc l’étude parallèle des variations nucléosynthétiques de ces éléments. / Nucleosynthetic anomalies have been observed in meteorites for many elements. The magnitude and repartition of these anomalies provide information about the degree of heterogeneity of the solar nebula. The study of the nucleosynthetic anomalies carriers could also give insight into the processes responsible for this heterogeneity. The presence or absence of small variations in nucleosynthetic processes is a key for the use of the short-lived radiochronometers. Small variations in the repartition of the parent or daughter isotope can lead to misinterpretations of relative ages.

Many topics in planetary studies demand an estimate of the collision probability of two objects moving on nearly Keplerian orbits. In the classic works of Opik and Wetherill, the collision probability was derived by linearizing the motion near the collision points, and there is now a vast amount of literature using their method. We present here a simpler and more physically motivated derivation for non-tangential collisions in Keplerian orbits, as well as for tangential collisions that were not previously considered. Our formulas have the added advantage of being manifestly symmetric in the parameters of the two colliding bodies. In common with the Opik-Wetherill treatments, we linearize the motion of the bodies in the vicinity of the point of orbit intersection (or near the points of minimum distance between the two orbits) and assume a uniform distribution of impact parameter within the collision radius. We point out that the linear approximation leads to singular results for the case of tangential encounters. We regularize this singularity by use of a parabolic approximation of the motion in the vicinity of a tangential encounter.

Les météorites carbonées sont les objets les plus primitifs du système solaire. Ils contiennent jusqu'à 4 % de carbone, principalement présent sous forme de matière organique insoluble (MOI). Celle-ci contient des informations essentielles sur les processus d’organo-synthèse qui se déroulent dans le système solaire, qui sont jusqu'ici mal compris. Un modèle statistique a été récemment proposé pour la structure moléculaire de la MOI ainsi qu'une voie de synthèse possible pour le squelette hydrocarboné de cette macromolécule (Derenne et Robert, 2010). Le premier objectif de ce travail était de tester expérimentalement cette voie avec un plasma organique comme source de radicaux CHx. Ce dispositif a permis la formation de matière organique soluble et insoluble. La MOI a été analysée par les mêmes techniques que celles utilisées précédemment pour la MOI chondritique, révélant de nombreuses similitudes entre les deux matériaux et validant le mécanisme proposé. En outre, des analyses NanoSIMS ont révélé, à une résolution spatiale sub-micrométrique, de grandes variations isotopiques qui sont du même ordre de grandeur que celles observées dans la MOI chondritique. Ensuite, la source des hétéroatomes (N et O) dans la MOI a été expérimentalement étudiée en ajoutant des précurseurs contenant des heteroelements aux radicaux hydrocarbonés. En ce qui concerne l'azote, deux types de précurseurs ont été considérés : l’hexylamine comme source d'hydrures et l'azote moléculaire N2. Bien que les deux précurseurs conduisent à l'incorporation d'azote dans la MOI, les hydrures d'azote semblent être plus pertinents, d’après la nature des fonctions azotées formées. Deux types d'expériences ont été effectuées afin d'étudier la source potentielle d'oxygène dans la MOI chondritique. Elles ont été conçues pour tester les deux principaux scénarios proposés pour rendre compte de la présence d’oxygène dans la MOI chondritique : soit l’altération aqueuse sur le corps parent ou l’incorporation d’oxygène pendant l’organo- synthèse dans la nébuleuse solaire primitive. Lors de l’expérience simulant l'altération aqueuse, la composition chimique de la matière organique soluble et insoluble est en accord avec ce qui est observé dans la matière organique des météorites. En revanche, aucun élément en faveur de l'incorporation directe d’oxygène par des radicaux OH n’a pu être apporté. / Carbonaceous meteorites are the most primitive objects of the solar system. They contain up to 4% of carbon, mainly occurring as insoluble organic matter (IOM). This IOM contains key information about the organo-synthesis processes taking place in the Solar System, which are so far poorly understood. A statistical model was recently proposed for the IOM molecular structure along with a possible synthesis pathway for its hydrocarbon backbone (Derenne and Robert, 2010).The first aim of this work was to test experimentally this pathway using an organic plasma as a source of CHx radicals. This device allowed the formation of both soluble and insoluble OM. The IOM was analyzed through the same techniques as those previously used for the chondritic IOM, revealing numerous similarities between both materials and thus supporting the proposed pathway. Moreover, NanoSIMS analyses revealed large isotopic variations at a sub-micrometric spatial resolution that are commensurable with those observed in chondritic IOM.Then, the source of heteroatoms (N and O) into the IOM was experimentally investigated through the addition of heteroelement-containing precursors to the hydrocarbonaceous radicals. As for nitrogen, two types of precursors were considered: hexylamine as a source of nitrogen hydrides and N2. Although both precursors led to nitrogen incorporation in the IOM, nitrogen hydrides seem to be more relevant based on the nitrogen speciation. Two types of experiments were performed to investigate the potential source of oxygen in the chondritic IOM. They were designed to address the two main scenarios proposed in the literature to account for the origin of the oxygen in the chondritic IOM: either aqueous alteration on the asteroidal parent body or O incorporation during the organo-synthesis in the primitive solar nebula. When the aqueous alteration is mimicked, the chemical composition of the SOM and IOM makes this pathway a reasonable source of the chondrite oxygen moieties. In contrast, no evidence for direct incorporation of O from OH radicals could be brought.

Le flux de météorites vers la Terre peut être déterminé en observant des bolides, ou en étudiant des collections de météorites. Pour estimer l’intensité et la composition du flux, nous avons collecté et classifié une collection de 213 météorites issues du désert de l’Atacama (Chili). Nous avons développé un protocole chimique afin d’extraire des nucléides cosmogéniques de chondrites ordinaires. La fraction métallique est d’abord séparée de la météorite. Les échantillons sont ensuite dissouts dans l’acide, et les éléments utiles sont extraits et purifiés grâce à des résines échangeuses d’ions et des précipitations contrôlées. Après la mesure par SMA, les concentrations de nucléides cosmogéniques nous permettent de calculer l’âge terrestre, le rayon pré-atmosphérique et la profondeur dans le météoroide, en utilisant l'approche développée par Leya & Masarik (2009). En combinant le nombre de météorites par unité de surface et les spectres d’âge terrestre, nous pouvons déterminer un flux de 218 météorites>10g/Ma/km2 sur une période de 700 ka avec la méthode 41Ca.Dans le cadre d’une collaboration avec l’Université de Bern (Suisse), nous avons aussi mesuré les concentrations en gaz rares dans certaines de ces météorites. Les concentrations en gaz rares et en nucléides radiogéniques ont ensuite été étudiées avec le modèle développé par Ammon et al. (2009), afin de déterminer le temps d’exposition dans l’espace, l’âge terrestre, le rayon pré-atmosphérique et la profondeur dans le météoroide. / Meteorite flux to the Earth can be determined using observations of fireballs or studying meteorites collections. To estimate the intensity and the composition of the flux, we collected and classified a 213 samples collection from the Atacama desert (Chile). We developed a mathematical model to help pairing of meteorites, and hence get a reliable number of falls per unit of surface. A chemical procedure to extract the cosmogenic nuclides 10Be, 26Al, 36Cl and 41Ca from ordinary chondrites was developed. The metallic fraction was extracted from the bulk meteorite. Samples were dissolved into acid and the elements of interest were extracted and purified using ion-exchange resins and pH controlled precipitation. After measurements using the Accelerator Mass Spectrometry (AMS) technique, the cosmogenic nuclides concentrations enable us to calculate terrestrial age, pre-atmospheric radius and shielding depth, using the Leya & Masarik (2009) model. Combining the number of meteorites per km2 and the terrestrial ages spectrum, we determine a flux of 218 meteorites > 10g/Ma/km2 over 700 ka with the 41Ca calculation method. Applying the same procedure as described above, we studied a selection of iron meteorites in which noble gases (He, Ne and Ar isotopes) concentrations were measured in collaboration with the University of Bern (Switzerland). Stable and radiogenic nuclides concentration results were then used according to the Ammon et al. (2009) model to determine Cosmic Ray Exposure (CRE) ages, terrestrial ages, pre-atmospheric radii and shielding depths.