Microstructural study of micron‐sized craters simulating Stardust impacts in aluminum 1100 targets     

Hugues Leroux  Janet Borg  David Troadec  Zahia Djouadi  Friedrich Hrz 《Meteoritics & planetary science》2006,41(2):181-196

Abstract— Various microscopic techniques were used to characterize experimental microcraters in aluminum foils to prepare for the comprehensive analysis of the cometary and interstellar particle impacts in aluminum foils to be returned by the Stardust mission. First, scanning electron microscopy (SEM) and energy dispersive X‐ray spectroscopy (EDS) were used to study the morphology of the impact craters and the bulk composition of the residues left by soda‐lime glass impactors. A more detailed structural and compositional study of impactor remnants was then performed using transmission electron microscopy (TEM), EDS, and electron diffraction methods. The TEM samples were prepared by focused ion beam (FIB) methods. This technique proved to be especially valuable in studying impact crater residues and impact crater morphology. Finally, we also showed that infrared microscopy (IR) can be a quick and reliable tool for such investigations. The combination of all of these tools enables a complete microscopic characterization of the craters.  相似文献   

A micro-Raman survey of 10 IDPs and 6 carbonaceous chondrites     

Eric Quirico  Janet Borg  Pierre-Ivan Raynal  Gilles Montagnac  Louis d&#x;Hendecourt 《Planetary and Space Science》2005,53(14-15):1443-1448

This paper presents a micro-Raman survey of a set of 10 IDPs and 6 pristine carbonaceous chondrites. The higher sensitivity of the present micro-spectrometers allowed to record a dozen of spectra for each objects, whereas only one was available in previous studies. First, as in previous studies, the first-order carbon bands G and D were the only detected features, superimposed onto a fluorescence background of variable intensity, and the spectral characteristics of these bands point to a very disordered polyaromatic organic matter (OM). Nevertheless, these new data reveal that in IDPs, unlike chondrites, the presence of the Raman bands is not systematic, evidencing a much higher heterogeneity in the spatial distribution or the chemical composition of OM. Second, as a consequence, a single spectrum is not representative of a whole IDP, and the classification previously proposed by Wopenka [ 1988. Raman observations on individual interplanetary dust particules. Earth and Planet. Sci. Lett. 88, 221—231.] is no longer tenable. At last, this study shows that the fluorescence signal induced by the laser irradiation mostly originates from OM.  相似文献   

Paleomagnetism of the Cu�CZn�CPb-bearing Kupferschiefer black shale (Upper Permian) at Sangerhausen, Germany     

David T. A. Symons  Kazuo Kawasaki  Sabine Walther  Gregor Borg 《Mineralium Deposita》2011,46(2):137-152

Syngenetic, diagenetic and epigenetic models have been proposed for the Cu?CZn?CPb Kupferschiefer mineralization at Sangerhausen, Germany. Paleomagnetic and rock magnetic measurements have been made on 205 specimens from mine workings on the margin of the Sangerhausen Syncline. The mineralization is richest in the ??0.5-m-thick Upper Permian (258?±?2?Ma) Kupferschiefer black marly shale (nine sites) and dies out over ??0.2?m in the underlying Weisliegend sandstones (three sites) and overlying Zechstein carbonates (two sites). Except for one site of fault zone gypsum, characteristic remanent magnetization directions were isolated for all 14 sites using alternating field and thermal step demagnetization. These directions provide a negative fold test, indicating that the remanence postdates Jurassic fault block tilting. Rock magnetic measurements show that the Kupferschiefer shale marks a redox front between the oxidized Weissliegend sandstones and non-oxidized Zechstein carbonates. The 14 site directions give a Late Jurassic paleopole at 149?±?3?Ma. It is significantly different from the paleopole reported by E.C. Jowett and others for primary or early diagenetic Rote F?ule alteration that gives an age of 254?±?6?Ma on the current apparent polar wander path and is associated with Kupferschiefer mineralization. We suggest that the Late Jurassic extensional tectonic event that formed the nearby North German Basin also reactivated Variscan basement faults and extended them up through the overlying strata, thereby allowing hydrothermal basement fluids to ascend and epigenetically mineralize the Kupferschiefer shale. The possibility of a 53?±?3?Ma mineralization age is also considered.  相似文献   

Speciation and thermodynamic properties for cobalt chloride complexes in hydrothermal fluids at 35-440 °C and 600 bar: An in-situ XAS study     

Weihua Liu  Stacey J. Borg  Denis Testemale  Barbara Etschmann  Jean-Louis Hazemann  Joël Brugger 《Geochimica et cosmochimica acta》2011,75(5):1227-1248

Aqueous Co(II) chloride complexes play a crucial role in cobalt transport and deposition in ore-forming hydrothermal systems, ore processing plants, and in the corrosion of special Co-bearing alloys. Reactive transport modelling of cobalt in hydrothermal fluids relies on the availability of thermodynamic properties for Co complexes over a wide range of temperature, pressure and salinity. Synchrotron X-ray absorption spectroscopy was used to determine the speciation of cobalt(II) in 0-6 m chloride solutions at temperatures between 35 and 440 °C at a constant pressure of 600 bar. Qualitative analysis of XANES spectra shows that octahedral species predominate in solution at 35 °C, while tetrahedral species become increasingly important with increasing temperature. Ab initio XANES calculations and EXAFS analyses suggest that in high temperature solutions the main species at high salinity (Cl:Co >> 2) is CoCl₄²⁻, while a lower order tetrahedral complex, most likely CoCl₂(H₂O)_2(aq), predominates at low salinity (Cl:Co ratios ∼2). EXAFS analyses further revealed the bonding distances for the octahedral Co(H₂O)₆²⁺ (^octCo-O = 2.075(19) Å), tetrahedral CoCl₄²⁻ (^tetCo-Cl = 2.252(19) Å) and tetrahedral CoCl₂(H₂O)_2(aq) (^tetCo-O = 2.038(54) Å and ^tetCo-Cl = 2.210(56) Å). An analysis of the Co(II) speciation in sodium bromide solutions shows a similar trend, with tetrahedral bromide complexes becoming predominant at higher temperature/salinity than in the chloride system. EXAFS analysis confirms that the limiting complex at high bromide concentration at high temperature is CoBr₄²⁻. Finally, XANES spectra were used to derive the thermodynamic properties for the CoCl₄²⁻ and CoCl₂(H₂O)_2(aq) complexes, enabling thermodynamic modelling of cobalt transport in hydrothermal fluids. Solubility calculations show that tetrahedral CoCl₄²⁻ is responsible for transport of cobalt in hydrothermal solutions with moderate chloride concentration (∼2 m NaCl) at temperatures of 250 °C and higher, and both cooling and dilution processes can cause deposition of cobalt from hydrothermal fluids.  相似文献   

Zn speciation in acetate-rich hydrothermal solutions,an X-ray absorption spectroscopy study     

Stacey J. Borg  Weihua Liu 《Journal of Geochemical Exploration》2009

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Mössbauer study of behavior of oriented single crystals of riebeckite at low temperatures and their magnetic properties     

R. J. Borg  I. Y. Borg 《Physics and Chemistry of Minerals》1980,5(3):219-234

A series of powdered and oriented single crystals of riebeckite-arfvedsonite have been examined with the Mössbauer technique above and below the magnetic ordering temperatures. Using fitted spectra that result in essentially similar quadrupole pairs, site occupancies were determined for 5 samples. Fitted spectra of oriented single crystals are associated with inequal pairs. The quadrupole splitting and isomer shifts are indistinguishable from those of the powdered samples. For the purpose of determining site occupancy paramagnetic spectra at L.N. temperatures appear to have little advantage over those obtained at room temperatures. The use of cryogenics to obtain magnetic hyperfine splitting increases experimental times several fold; however we conclude that in most cases the additional information and greater accuracy of Fe⁺²/Fe⁺³ warrants the additional effort. Magnetic order detected at cryogenic temperatures has an overall antiferromagnetic character. The orientation of the magnetic moment for Fe⁺³ is not parallel to a principal crystallographic axis, and its orientation near 〈316〉 suggests that there is magnetic coupling between the cation ribbons containing the octahedrally coordinated iron. The magnetic behavior can be interpreted satisfactorily using the Ising model developed for two dimensional lattices and extended to loosely coupled chains.  相似文献   

The Uppsala seismograph array station     

Harry Borg  Markus Båth 《Pure and Applied Geophysics》1971,89(1):19-31

Summary The Seismological Institute at Uppsala, Sweden, has operated a triangular array station for one year, August 1969 to August 1970. The triangle is almost equilateral with around 100 km side, with one corner at Uppsala and the other two at Hedemora and Kungsör. Short-period vertical-component seismographs of type Grenet-Coulomb are used. The signals are transmitted over commercial telephone lines to the central recording unit at Uppsala. This paper describes all technical details of the system, with particular emphasis on the signal transmission. Experiences from the operation are given. In spite of only three points in the array, it serves its purposes very well, primarily because of its location on very homogeneous ground, the Baltic shield. Moreover, the installation and operation of such an array is generally possible within the limited budgets of a university Institute.  相似文献   

Constraints on the petrogenesis of Martian meteorites from the Rb-Sr and Sm-Nd isotopic systematics of the lherzolitic shergottites ALH77005 and LEW88516     

Lars E. Borg  Larry E. NyquistHenry Wiesmann  Young Reese 《Geochimica et cosmochimica acta》2002,66(11):2037-2053

Detailed Rb-Sr and Sm-Nd isotopic analyses have been completed on the lherzolitic shergottites ALH77005 and LEW88516. ALH77005 yields a Rb-Sr age of 185 ± 11 Ma and a Sm-Nd age of 173 ± 6 Ma, whereas the Rb-Sr and Sm-Nd ages of LEW88516 are 183 ± 10 and 166 ± 16 Ma, respectively. The initial Sr isotopic composition of ALH77005 is 0.71026 ± 4, and the initial ε_Nd value is +11.1 ± 0.2. These values are distinct from those of LEW88516, which has an initial Sr isotopic composition of 0.71052 ± 4 and an initial ε_Nd value of +8.2 ± 0.6. Several of the mineral and whole rock leachates lie off the Rb-Sr and Sm-Nd isochrons, indicating that the isotopic systematics of the meteorites have been disturbed. The Sm-Nd isotopic compositions of the leachates appear to be mixtures of primary igneous phosphates and an alteration component with a low ¹⁴³Nd/¹⁴⁴Nd ratio that was probably added to the meteorites on Mars. Tie lines between leachate-residue pairs from LEW88516 mineral fractions and whole rocks have nearly identical slopes that correspond to Rb-Sr ages of 90 ± 1 Ma. This age may record a major shock event that fractionated Rb/Sr from lattice sites located on mineral grain boundaries. On the other hand, the leachates could contain secondary alteration products, and the parallel slopes of the tie lines could be coincidental.Nearly identical mineral modes, compositions, and ages suggest that these meteorites are very closely related. Nevertheless, their initial Sr and Nd isotopic compositions differ outside analytical uncertainty, requiring derivation from unique sources. Assimilation-fractional-crystallization models indicate that these two lherzolitic meteorites can only be related to a common parental magma, if the assimilant has a Sr/Nd ratio near 1 and a radiogenic Sr isotopic composition. Further constraints placed on the evolved component by the geochemical and isotopic systematics of the shergottite meteorite suite suggest that it (a) formed at ∼4.5 Ga, (b) has a high La/Yb ratio, (c) is an oxidant, and (d) is basaltic in composition or is strongly enriched in incompatible elements. The composition and isotopic systematics of the evolved component are unlike any evolved lunar or terrestrial igneous rocks. Its unusual geochemical and isotopic characteristics could reflect hydrous alteration of an evolved Martian crustal component or hydrous metasomatism within the Martian mantle.  相似文献   

First results from the plasma composition spectrometer PROMICS-3 in the Interball project     

I. Sandahl  S. Barabash  H. Borg  E. Yu. Budnik  E. M. Dubinin  U. Eklund  H. Johansson  H. Koskinen  K. Lundin  R. Lundin  A. Mostrom  R. Pellinen  N. F. Pissarenko  T. Pulkkinen  P. Toivanen  A. V. Zakharov 《Annales Geophysicae》1997,15(5):542-552

PROMICS-3 is a plasma experiment flown in the Russian project Interball. It performs three-dimensional (3D) measurements of ions in the energy range 4 eV–70 keV with mass separation and of electrons in the energy range 12 eV–35 keV. The Interball project consists of two main satellites, the Tail Probe and the Auroral Probe, each with one subsatellite. The Interball Tail Probe was launched on 3 August 1995, into a 65° inclination orbit with apogee at about 30 R_E. Both main satellites carry identical PROMICS-3 instruments and thus direct comparisons of the particle distributions will be possible once the Auroral Probe is launched. Furthermore, PROMICS-3-Tail is the first instrument measuring the 3D ion distribution function in the magnetospheric boundary layers at high latitudes. In this paper we describe the PROMICS-3 instrument and show initial results from the Tail probe, measurements of the mag-netosheath, plasma sheet, and ring current plasmas.  相似文献   

Big returns on small samples: Lessons learned from the analysis of small lunar samples and implications for the future scientific exploration of the Moon     

C.K. Shearer  L.E. Borg 《Chemie der Erde / Geochemistry》2006,66(3):163-185

Samples returned from the surface of planetary bodies are both complementary to orbital and in situ observations and provide a unique perspective for understanding the nature and evolution of that body. This unique perspective is based on the scale the sample is viewed (mm-Å), the ability to manipulate the sample, the capability to analyze the sample at high precision and accuracy, and the ability to significantly modify experiments as logic and technology dictates over an extended period of time (decades). Unlike the Apollo missions, robotic sample return missions in the next decade will result in the return of relatively small sample mass. Such robotically returned samples are scientifically more valuable if they can be placed within a planetary context through orbital observations and if information concerning planetary-scale processes and conditions can be extracted from them. Conversely, samples give remotely sensed data ground truth. That is, they act as a “calibration standard” for these data allowing a much enhanced global view to be constructed.The Moon is an example that illustrates how information can be extracted from small samples and then extended to planetary and solar system scales. Three examples from the Moon illustrate this point. First, multi-analytical and experimental studies of minute (10-500 μm) glass beads representing near-primary magmas provide constraints on the composition and condition of the lunar mantle, the style of early planetary differentiation, the history and character of early mantle dynamics and melting, and the isolation of the lunar mantle from late-stages of lunar accretion. Second, trace element analysis of individual mineral grains via ion microprobe and isotopic analysis of small rock fragments representing some of the oldest and youngest periods of lunar magmatism illustrate their usefulness for both fingerprinting distinct episodes of lunar magmatism and reconstructing the evolution of lunar magmatism. Third, mechanisms for primitive planetary mantles degassing and volatile transport on airless bodies can be understood by the analysis of volatile coatings on glass and mineral fragments in the lunar regolith.As many of our insights about the Moon are based on samples that primarily were collected within a limited lunar terrain, our understanding of the Moon is somewhat biased. Future scientifically strategic sampling targets are young mare basalts (Roris basalt in Oceanus Procellarum), far-side mare basalts (Mare Moscoviense), large pyroclastic deposits and potential mantle xenoliths (Aristarchus plateau, Rima Bode) major unsampled crustal lithologies outside the Procellarum KREEP terrane (central peak in Tsiolkovsky crater, South-pole Aitken basin), basin and crater melt sheets (South-pole Aitken basin, Giordano Bruno) and H deposits in permanently shaded areas (South-pole Aitken basin). Sampling these locations would further our understanding of processes at work during the early evolution of the terrestrial planets, provide a comprehensive history of endogenous (e.g., primary volcanic degassing) and exogenous (e.g., solar wind, galactic cosmic rays, volatiles from comets) volatile reservoirs and volatile transport and would provide unique historical information about events and processes that affected the entire inner solar system, a record obscured on the Earth and Mars.  相似文献