Results of I-Xe analyses have been obtained from meteorite samples that experienced different extents of thermal processing in the early Solar System in order to help characterise the movements of iodine and xenon in the early Solar System and constrain the timing of these movements using the I-Xe chronometer. Samples were irradiated to convert 127I to 128Xe* and allow simultaneous measurements of iodine and xenon isotopes. Xe isotopes were measuring using the RELAX mass spectrometer.I-Xe ages of material of different metamorphic grade from R-chondrites NWA 6492, NWA 830 and NWA 3364 suggest a link between the time of closure to Xe-loss and extent of metamorphism on the R-chondrite parent body. However, further I-Xe analyses of R5 material from NWA 6492 and R4 and R6 material from other R-chondrites are needed to confirm this. The most primitive material analysed give I– Xe ages between 4559 – 4554 Myr, slightly later than reported Mn-Cr ages. This may support the ideal of radial heterogeneity of 53Mn in the early Solar System. However differences could also be due to variations in the samples analysed. Future analyses of I-Xe and Mn-Cr ages in mineral separates from the same R-chondrite are recommended in order to investigate this hypothesis. Closure to Xe-loss in chondrules on the R-chondrite parent body appears to have occurred ~5 – 10 Myr later than on the ordinary and enstatite parent bodies. This implies either later accumulation of material or slower cooling in a larger body.Comparisons of I-Xe systematics in anomalous eucrites Bunburra Rockhole and Ibitira and “nomalous” eucrites Juvinas and Béréba show lower 129I/244Pu ratios in the “nomalous” eucrites. This is not due to formation on a less volatile-rich body but instead reflects extended loss of Xe on 4 Vesta. 129I/244Pu ratios indicate igneous processing continued on 4 Vesta for ~50-100 Myr after geological activity had ceased on the anomalous eucrites parent bodies. The extended processing seen in Juvinas and Béréba is attributed to formation on a larger body that retained heat for longer. If, as the data suggest, the anomalous eucrites formed on a separate parent body it must have been catastrophically disrupted as Vesta is thought to be the only remaining differentiated asteroid. The larger size of Vesta may explain why it has uniquely survived the impacts that destroyed its siblings. Analyses of the unique achondrite GRA 06129 show that the I-Xe system in this meteorite has no chronological significance. The data instead suggest that iodine-bearing plagioclase formed early but thermal metamorphism resulted in loss of 129Xe* from iodine bearing sites. Uranium-bearing apatite appears to be a secondary mineral that incorporated parentless 129Xe* and 129Xe*that had been redistributed during earlier metamorphism. A trapped-Xe component released at high-temperatures may be a primitive component such as Q-Xe, though terrestrial–Xe acquired during weathering cannot be ruled out by this study. If Q-Xe is present, it is most likely hosted in a primary phase other than plagioclase. During its terrestrial residence time GRA 06129 acquired iodine via Antarctic weathering. I-Xe analyses on Antarctic meteorites should therefore be carried out with caution. Further Xe analyses of mineral separates from GRA 06129 would help constrain the host phase of the trapped Xe. That the I-Xe system of the plagioclase has been completely reset make it a good candidate mineral for I-Xe dating of primary processes whereas I-Xe dating of apatite appears more problematic.

abstract: This study explores how bulk composition and oxygen fugacity (fO2) affect the partitioning of sulfur between the molten mantle and core of an early planetesimal. The model can be used to determine the range of potential sulfur concentrations in the asteroid (16) Psyche, which is the target of the National Aeronautics and Space Administration/Arizona State University Psyche Mission. This mission will be our visit to an M-type asteroid, thought to be dominantly metallic. The model looks at how oxygen fugacity (fO2), bulk composition, temperature, and pressure affect sulfur partitioning in planetesimals using experimentally derived equations from previous studies. In this model, the bulk chemistry and oxygen fugacity of the parent body is controlled by changing the starting material, using ordinary chondrites (H, L, LL) and carbonaceous chondrites (CM, CI, CO, CK, CV). The temperature of the planetesimal is changed from 1523 K to 1873 K, the silicate mobilization and total melting temperatures, respectively; and pressure from 0.1 to 20 GPa, the core mantle boundary pressures of Vesta and Mars, respectively. The final sulfur content of a differentiated planetesimal core is strongly dependent on the bulk composition of the original parent body. In all modeled cores, the sulfur content is above 5 weight percent sulfur; this is the point at which the least amount of other light elements is needed to form an immiscible sulfide liquid in a molten core. Early planetesimal cores likely formed an immiscible sulfide liquid, a eutectic sulfide liquid, or potentially were composed of mostly troilite, FeS. / Dissertation/Thesis / Masters Thesis Geological Sciences 2020

The origin of the earliest solids in the solar system, preserved for 4.56 Ga in primitive chondritic meteorites, is poorly understood, in particular because of the lack of detailed chemical data on individual phases within these solids. Because chondrite constituents record the environmental conditions and local chemistry of the protoplanetary disk in which they were formed, examining their chemical composition across chondrite groups enhances our understanding of and provides quantitative constraints on the origin of the earliest solar system bodies, the precursors to our planets. This dissertation examines chondritic meteorites using (1) geochemical analysis of the major and trace element distributions within and among carbonaceous chondrite constituents to address chemical source reservoirs and formation mechanisms, and (2) visible near-infrared (VNIR) spectroscopy of ordinary chondrites under a variety of conditions to improve compositional interpretations of remotely sensed asteroids. Chapter 1 presents a brief introduction to the field of meteoritics via an overview of meteorite types and the various contexts they preserve. Primitive chondritic meteorites and their components fossilize the chemical and physical conditions that existed at the time of their formation in the early solar system, whereas achondritic meteorites provide insight into the structure of planetary interiors. This chapter also reviews fundamentals of mineral condensation in the early solar system environment, and the implications of the presence (or lack) of these minerals in the components that comprise chondrites. In Chapter 2 of this dissertation, I investigate the distribution of trace elements in the components of the carbonaceous Vigarano-type (CV) chondrite group to better reveal the solar system processes that led to the fundamental cosmochemical mechanisms of chondrule formation and chondrite accretion. While the major element and bulk chemical compositions of chondritic meteorites are well established, the distribution of trace elements amongst chondrite components and in the individual minerals within them is not well constrained. The geochemical behavior of trace elements enables them to reveal precursor characteristics, formation conditions, and processing histories of chondrite constituents. In determining the large-scale distribution of trace elements, in particular the rare earth elements (REE), across multiple meteorites in the CV chondrite group, I produced a statistically significant trace element dataset that complements existing major element and isotopic datasets. I observe variable REE patterns in individual mineral phases in chondrite components which combine to produce overall flat bulk REE patterns for each meteorite. This chemical evidence, which is necessary to constrain dynamical accretion mechanisms in astrophysical models of the early solar system, supports the idea of a single reservoir origin for these chondrites, and suggests that some chondrules are in chemical disequilibrium and have inherited CAI-like precursor material. In Chapter 3, I evaluate common standardization techniques used for analysis of laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) data and assess the implications for high-precision elemental analyses. LA-ICP-MS has become popular in part due to its ability to measure low trace element abundances in small sample volumes while preserving petrographic context. The capacity for in-situ mineral-scale and sub-mineral scale analyses is particularly useful for diffusion studies or for assessing element partitioning between co-existing solids. Standardization techniques have been developed in order to obtain high-precision concentration data from LA-ICP-MS analyses. Common practice dictates the use of reference material spot sizes similar or equal to the chosen spot sizes of the unknown samples under investigation. However, the effects of using reference material spot sizes for calibration that differ from sample spot sizes are not quantitatively constrained. In this chapter I evaluate the coupled effects of differences in ablation yield and of matching compositions between samples and reference materials (matrix matching), as well as the differences in calculated element abundance resulting from internal standard element choice. I show that element abundances derived from LA-ICP-MS analyses are heavily dependent on the chosen combination of measured element, internal standard element, unknown spot size, and reference spot size. Even varying just one of these parameters does not necessarily yield predictable effects on resulting data. In Chapter 4, I explore the effects of both chemical and physical variables on laboratory infrared spectral analysis of well-characterized meteorite samples with the goal of better quantitatively analyzing asteroid remote sensing data in conjunction with returned extraterrestrial samples. Temperature and grain size are known to each have individual effects on the VNIR spectra of silicate and meteorite powders. Here, I examine the combined effects of physical variables (temperature, particle size) and chemical variables (petrologic type, metal fraction) on VNIR spectra of ordinary chondrite meteorite powders. I prepared six equilibrated (petrologic types 4-6) ordinary chondrite meteorite falls, spanning groups H, L, and LL, at a variety of particle sizes to capture the spectral diversity associated with asteroid regoliths dominated by various grain sizes. VNIR spectra of the ordinary chondrite materials were measured under simulated asteroid surface conditions (~10-6 millibar, -100°C chamber temperature, and low intensity illumination) at a series of temperatures chosen to mimic near-Earth asteroid surfaces. Iused X-ray element maps of meteorite thick sections to calculate the exact mineral abundances for each meteorite, in order to characterize changes in spectral features due to variations in mineralogy. The VNIR spectra show minimal variation in both major orthosilicate absorption bands across the simulated near-Earth asteroid temperature regime. Spectral changes due to particle size are consistent across samples, with the smallest and largest grain sizes having the highest reflectance. Unlike previous spectral investigations of ordinary chondrites, I retained the metal fraction in the meteorite powders instead of analyzing the silicate fraction only. In the measurements, I observe distinct offsets in spectral features when compared to analyses of purely silicate fractions. XRD analysis shows that the largest size fraction of nearly every sample contains relatively more metal, likely due to the retention of metal nuggets in the largest size fraction during sieving. The more petrologically pristine samples (e.g., LL4) from each ordinary chondrite group display relatively shallower band depths than their more petrologically altered counterparts (e.g., LL6). The band depths shift to higher wavelengths as temperature, grain size, and petrologic type increase. Spectral studies of meteorites combined with detailed petrologic analysis of the samples should greatly enhance interpretation of current and future planetary remote sensing data sets. Importantly, understanding the spectral contribution of the metal fraction will aid in upcoming investigations of metal-rich mission targets such as asteroid 16 Psyche.

<p>This thesis reports on the results of investigating Fe-containing minerals in meteorites, with focus on Fe-Ni minerals and their magnetic properties, along with some synthetic Fe-Ni analogues. The New Halfa meteorite, which fell in Sudan 1994, has been studied using Mössbauer spectroscopy, X-ray diffraction, and electron microprobe analysis techniques, and classified as an ordinary L-type chondrite of petrologic type 4. Mössbauer spectra of taenite-enriched samples from the metal particles of the New Halfa (L4) and Al Kidirate (H6) meteorites identify the following γ (fcc) Fe-Ni phases: the ferromagnetic atomically ordered taenite (<i>tetrataenite</i>) with ~ 50 at % Ni, the ferromagnetic disordered taenite with ~ 50 at % Ni, the low-Ni (~ 25 at %) paramagnetic taenite (<i>antitaenite</i>). The presence of the superstructure of tetrataenite is confirmed by synchrotron X-ray diffraction.</p><p>Fe-rich γ (fcc) Fe-Ni alloys with compositions Fe₇₉Ni₂₁, Fe₇₆Ni₂₄, and Fe₇₃Ni₂₇, which serve as synthetic analogues of antitaenite, are prepared by mechanical alloying and subsequent annealing at 650 °C. The Mössbauer results indicate that these alloys are inhomogeneous and contain a high moment (HM) ferromagnetic Ni-rich phase (> 30 at % Ni) and a low moment (LM) paramagnetic Fe-rich phase, which orders antiferromagnetically at low temperature. The coexistence of these phases is attributed to phase segregation occurring on short range, probably nanometer scale, consistent with the Fe-Ni phase diagram below 400 °C where there is a miscibility gap associated with a spinodal decomposition in alloys with < 50 at % Ni.</p><p>The combined high field Mössbauer spectroscopy and SQUID magnetometry results on these alloys at room temperature indicate large induced local magnetic moments in the paramagnetic part of the sample, which increases with increasing the Ni content. The results, when compared with the high field Mössbauer results on antitaenite from the metal particle of Al Kidirate and New Halfa meteorites may be used to estimate the Ni content of antitaenite in meteorites.</p><p>High pressure ⁵⁷Fe Mössbauer spectroscopy measurements up to ~ 41 GPa have been carried out at room temperature using the diamond anvil cell (DAC) technique in order to investigate the magnetic properties of γ (fcc) ⁵⁷Fe₅₃Ni₄₇ alloy. The results indicate a pressure induced Invar effect at ~ 7 GPa and a non-magnetic or paramagnetic state above 20 GPa, demonstrating the volume dependence of the magnetic moment of γ (fcc) Fe-Ni alloys.</p>

This thesis reports on the results of investigating Fe-containing minerals in meteorites, with focus on Fe-Ni minerals and their magnetic properties, along with some synthetic Fe-Ni analogues. The New Halfa meteorite, which fell in Sudan 1994, has been studied using Mössbauer spectroscopy, X-ray diffraction, and electron microprobe analysis techniques, and classified as an ordinary L-type chondrite of petrologic type 4. Mössbauer spectra of taenite-enriched samples from the metal particles of the New Halfa (L4) and Al Kidirate (H6) meteorites identify the following γ (fcc) Fe-Ni phases: the ferromagnetic atomically ordered taenite (tetrataenite) with ~ 50 at % Ni, the ferromagnetic disordered taenite with ~ 50 at % Ni, the low-Ni (~ 25 at %) paramagnetic taenite (antitaenite). The presence of the superstructure of tetrataenite is confirmed by synchrotron X-ray diffraction. Fe-rich γ (fcc) Fe-Ni alloys with compositions Fe79Ni21, Fe76Ni24, and Fe73Ni27, which serve as synthetic analogues of antitaenite, are prepared by mechanical alloying and subsequent annealing at 650 °C. The Mössbauer results indicate that these alloys are inhomogeneous and contain a high moment (HM) ferromagnetic Ni-rich phase (&gt; 30 at % Ni) and a low moment (LM) paramagnetic Fe-rich phase, which orders antiferromagnetically at low temperature. The coexistence of these phases is attributed to phase segregation occurring on short range, probably nanometer scale, consistent with the Fe-Ni phase diagram below 400 °C where there is a miscibility gap associated with a spinodal decomposition in alloys with &lt; 50 at % Ni. The combined high field Mössbauer spectroscopy and SQUID magnetometry results on these alloys at room temperature indicate large induced local magnetic moments in the paramagnetic part of the sample, which increases with increasing the Ni content. The results, when compared with the high field Mössbauer results on antitaenite from the metal particle of Al Kidirate and New Halfa meteorites may be used to estimate the Ni content of antitaenite in meteorites. High pressure 57Fe Mössbauer spectroscopy measurements up to ~ 41 GPa have been carried out at room temperature using the diamond anvil cell (DAC) technique in order to investigate the magnetic properties of γ (fcc) 57Fe53Ni47 alloy. The results indicate a pressure induced Invar effect at ~ 7 GPa and a non-magnetic or paramagnetic state above 20 GPa, demonstrating the volume dependence of the magnetic moment of γ (fcc) Fe-Ni alloys.

The aim of this work is to assess the feasibility of asteroid exploitation as a potential source of valuable elements for a future green energy society and achieving a long-term sustainable development of our society. This research is based on the compilation of chemical data of elements concentration of 13 groups of iron meteorites from literature. These data were used to feed mathematical models to fit the historical world production data of each element and predicts the peak year and the future trend of their world production until 2100. Eventually, this work aims to calculate the required mass of asteroids for reaching different productions, and identify the most suitable groups of iron meteorites for exploitation.

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.

Thesis: Ph. D., Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2018. / Cataloged from PDF version of thesis. / Includes bibliographical references. / This thesis investigates the timing and source(s) of water and volatile elements to the inner solar system by studying the basaltic meteorites angrites and eucrites. In chapters 2 and 3, I present the results from angrite meteorites. Chapter 2 examines the water and volatile element content of the angrite parent body and I suggest that some water and other volatile elements accreted to inner solar system bodies by ~2 Myr after the start of the solar system. Chapter 3 examines the D/H of this water and I suggest it is derived from carbonaceous chondrites. Chapter 4, 5, 6, and 7 addresses eucrite meteorites. Chapter 4 expands on existing models to explain geochemical trends observed in eucrites. In Chapter 5, I examine the water and F content of the eucrite parent body, 4 Vesta. In chapter 6, I determine the source of water for 4 Vesta and determine that carbonaceous chondrites delivered water to this body. Chapter 7 discusses degassing on 4 Vesta while it was forming. / by Adam Robert Sarafian. / Ph. D.

Determining mafic mineral composition of asteroid bodies is a topic reviewed by M.J. Gaffey et al. (2002). The iterative procedure discussed can be implemented as an algorithm, and such efforts revealed weaknesses that are examined in this work. We seek to illustrate the limits of this method and graphically determine its predictions. There are boundaries in the formulae given where the equations break down. In ranges where mafic mixtures are predicted, a method is illustrated that allows a decoupling of these mixtures into the constituents.

Calcium (Ca) is the fifth most abundant element in the rocky planets. As a lithophile, refractory element, Ca does not partition into planetary cores nor is it volatilized during planetary accretion. These characteristics make Ca ideal for investigating the earliest stages of planetary formation and the subsequent chemical evolution of planetary mantles and crusts. This thesis presents observations of and explores the mechanisms involved in high-temperature mass-dependent Ca isotope fractionation in terrestrial, lunar, and meteoritic material. Chapter 1 reports Ca isotope fractionation among a co-genetic suite of samples from the Guelb el Azib ultramafic-mafic-anorthosite complex, which represents the fractional crystallization sequence of a terrestrial igneous magma chamber. The measurements imply that Ca isotope fractionation in an evolving crystallizing magma is mineralogically controlled and that the degree of fractionation can vary according to the Ca composition of the residual magma. Chapter 2 investigates ureilites, a distinctive group of achondritic meteorites, widely regarded to be mantle remnants of a disrupted asteroidal parent body. To date, it is not clear which of their features were inherited from the original chondritic body and which were created during post-accretionary igneous processes such as partial melting. This chapter presents evidence that partial melting on the ureilite parent body is responsible for two such ambiguous characteristics, Ca isotopic and magnesium number (Mg / Doctorat en Sciences / info:eu-repo/semantics/nonPublished