Heating experiments on glass inclusions in Allende (CV3) olivines: Clues to the formation conditions of chondrules?

Several pieces of the Allende CV3 chondrite were heated up to different final temperatures (1100, 1250, 1450 °C) with the aim to study glassy and glass-bearing inclusions in olivines as well as the glass mesostasis of chondrules and aggregates. The experiments were performed in a Pt-Pt90Rh10 heating stage at 1 bar pressure. The oxygen fugacity is estimated to have been between 10-9 and 10-10 atm at 1200 °C. The variation of the chemical composition of the heated glasses gives information concerning the behavior of the incompatible elements (with respect to the host) Al, Ca and Na. The chemical variation in the heated mesostasis glass shows that Ca exchange between the gas and condensed phases at sub-solidus temperatures can occur in a short time. Laboratory heating experiments show that glass inclusions will behave as closed systems and therefore preserved the alkalis they acquired. On the other hand, the mesostasis glass can loose them when heated to temperatures higher than 1100 °C. Evidently, the presence of Na-rich glasses, in chondrules and aggregates available to us, indicate that if there was a thermal process that did affect them, it must have been a low temperature one.Fil: Varela, Maria Eugenia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Complejo Astronómico "El Leoncito". Universidad Nacional de Córdoba. Complejo Astronómico "El Leoncito". Universidad Nacional de la Plata. Complejo Astronómico "El Leoncito". Universidad Nacional de San Juan. Complejo Astronómico "El Leoncito"; Argentin

Glasses in meteorites and the Primary Liquid Condensation Model

Meteoritic glasses are quenched samples of the silicate liquid that was involved in the formation of chondritic constituents and achondritic rocks. Conventional genetic models see them as residual liquids from which the associated minerals crystallized – as demonstrated by terrestrial igneous rocks – or as locally produced impact melts. These models are all closely related to our experiences with terrestrial geology and petrology and, consequently,make planetary processes, such asmixing andmelting of solid precursors and planetary differentiation primarily responsible for the formation of the large variety of meteoritic rocks. However, different types of glasses (e.g., glass inclusions in minerals, mesostasis glasses, glass pockets, glass veins) in a variety of meteorites (chondrites and achondrites) have particular chemical features that cannot be reconciled with these models: 1)Glasses do not showthe chemical signature of crystallization of theminerals they are associated with – a geochemical impossibility; 2) All types of glasses in all types of meteorites reported here show very similar trace element abundance pattern with the refractory lithophile element abundances at ~ 10–20 x CI chondrite abundances. 3) All refractory element abundance patterns in primitive glasses have unfractionated solar relative abundances (they are flat) and medium refractory and volatile elements are depleted relative to the refractory elements. 4) Medium volatile and volatile elements, when present, display chaotic abundance patterns. The ubiquitous pattern for refractory elements signals vapor fractionation rather than geochemical (“igneous”) fractionation or stochasticmixing of precursorminerals (as in shockmelts). It indicates that the same process must have been involved in the origin of all glasses in chondritic constituents aswell as achondritic rocks and, consequently, in the formation of allmeteorite types investigated. The chaotic abundances of volatile elements signal that chaotic processes were involved during condensation. 279 Herewe present a newmodel - the Primary Liquid Condensation (PLC)model – as an alternative to the currently acceptedmodels for the formation ofmeteoritic rocks. The PLCmodel is capable of accommodating all observational and chemical data accumulated so far on meteorites – with the exception of enstatite and SNC meteorites, which record physico-chemical conditions that were different fromthose of themajority ofmeteoritic rocks (the processes, however, could have been the same). The new model identifies a new role for silicate liquids in cosmochemistry as being an essential phase for the formation of early crystalline condensates from the hot solar nebula. Liquids are identified to have been the first major phase to condense from the solar nebula. In order to be capable to produce early liquid condensates, the nebula must have been either enriched in condensable elements over solar abundances (> 500 times) or was at total pressuresmuch higher than the canonically predicted ones (> 500 times, > 0.5 bar ). Our data require that this liquid – we named it “universal liquid” (UL) - had a refractory composition (Ca-Mg-Al-silicate or CMAS) and facilitated condensation of the major minerals for chondritic constituents as well as for achondritic rocks. The process possibly was a variant of the vapor-liquid-solid (VLS) condensation process, which is utilized in industrial crystal growth. Thereby, the liquid condenses first, then nucleates a crystal of the species that is oversaturated in the vapor – in the case of the solar nebula usually olivine. As this olivine grows from the liquid, it depletes the liquid in Mg and Si. The liquid tries to maintain equilibrium with the solar nebula. Thereby, Mg and Si are replenished by condensation from the gas phase and all incompatible elements are kept at an equilibrium concentration by condensation-evaporation equilibrium. Thus, the contents of incompatible refractory elements are kept at an approximately constant level throughout crystallization of the major minerals olivine and pyroxene. This way not only the abundances of incompatible refractory elements are kept at a constant level but also their relative abundances remain unfractionated solar. The UL also represents the long sought for refractory component of chondritic constituents and appears also to be the source of achondritic “igneous” rocks. Variations in the amount of liquid available, the liquid condensation and crystal nucleation rates, as well as different crystal-liquid mixing proportion will allow the formation of objects of highly variable composition. The final composition (chemical and isotopic) of any chondritic object or achondrite, as well as that of the associated glasses, will be determined by different degrees of post-formational metasomatic elemental exchange processes taking place between solids and the cooling nebular gas. These processes add medium volatile and volatile elements to the products of high temperature condensation. As these processes usually don’t run to completion, an infinite number of chaotic compositional variations are produced – and this is exactly what we observe in meteorites.Fil: Varela, Maria Eugenia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Complejo Astronómico "El Leoncito". Universidad Nacional de Córdoba. Complejo Astronómico "El Leoncito". Universidad Nacional de la Plata. Complejo Astronómico "El Leoncito". Universidad Nacional de San Juan. Complejo Astronómico "El Leoncito"; ArgentinaFil: Kurat, G.. Vienna University of Technology; Austri

Glasses in coarse-grained micrometeorites

Micrometeorites (MMs, interplanetary dust particles with 25 - 500 μm diameters) carry the main mass of extraterrestrial matter that is captured by Earth. The coarse-grained MMs mainly consist of olivine aggregates, which - as their counterparts in CC chondrites - also contain pyroxenes and glass. We studied clear glasses in four coarse-grained crystalline MMs (10M12, M92-6b, AM9, and Mc7-10), which were collected from the ice at Cap Prudhomme, Antarctica. Previous studies of glasses (e.g., glass inclusions trapped in olivine and clear mesostasis glass) in carbonaceous and ordinary chondrites showed that these phases could keep memory of the physical-chemical conditions to which extraterrestrial matter was exposed. Here we compare the chemical compositions of MM glasses and glasses from CM chondrites with that in experimentally heated objects from the Allende CV chondrite and with glasses from cometary particles. Our results show that MMs were heated to variable degrees (during entry through the terrestrial atmosphere), which caused a range from very little chemical modification of the glass to total melting of the precursor object. Such modifications include dissolution of minerals in the melted glass precursor and some loss of volatile alkali elements. The chemical composition of all precursor glasses in the MMs investigated is not primitive such as glasses in CM and CR chondrite objects. It shows signs of pre-terrestrial chemical modification, e.g., metasomatic enrichments in Na and Fe2+ presumably in the solar nebula. Glasses of MMs heated to very low degree have a chemical composition indistinguishable from that of glasses in comet Wild 2 particles; giving additional evidence that interplanetary dust (e.g., Antarctic MMs) possibly represents samples from comets. © 2009 Elsevier B.V. All rights reserved.Fil: Varela, Maria Eugenia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Complejo Astronómico "El Leoncito". Universidad Nacional de Córdoba. Complejo Astronómico "El Leoncito". Universidad Nacional de la Plata. Complejo Astronómico "El Leoncito". Universidad Nacional de San Juan. Complejo Astronómico "El Leoncito"; ArgentinaFil: Kurat, G.. Universidad de Viena; Austri

The primary liquid condensation model and the origin of Barred Olivine Chondrules.

Barred olivine (BO) chondrules are some of the most striking objects in chondrites. Their ubiquitous presence and peculiar texture caught the attention of researchers and, as a consequence, considerable effort has been expenced on unraveling their origin(s). Here we report on a detailed study of two types of chondrules: the Classic and the Multiple-Plate Type of BO chondrules from the Essebi (CM2) , Bishunpur (LL3.1), Acfer 214 (CH3) and DAG 055 (C3-UNGR) chondrites, and discuss the petrographic and chemical data of their major mineral phases and glasses. Glasses occur as mesostasis or as glass inclusions, the latter either enclosed inside the olivine bars (plates) or still connected to the mesostasis. The chemical composition of all glasses, characterized by being Si-Al-Ca-rich and free of alkali elements, is similar to those of the constituents , such as chondrules, aggregates, inclusions, mineral fragments, etc.) of CR and CV3 chondrites. They all have high trace element contents (~ 10 x CI) with unfractionated CI-normalized abundances of refractory trace elements and depletions in moderately volatile and volatile elements with respect to the refractory trace elements. The presence of alkali elements (Na+K+Rb) is coupled with a low Ca content and is only observed in those glasses that have behaved as open systems. This result supports the previous finding that Ca was replaced by alkalis (e.g., Na-Ca exchange), presumably through a vapor-solid reaction. The glasses apparently are the quenched liquid from which the olivine plates crystallized. However, they do not show any chemical fractionation that could have resulted from the crystallization of the olivines, but rather have a constant chemical compositions throughout the formation of the chondrule. In a previous contribution we were able to demonstrate the role of these liquids in supporting crystal growth directly from the vapor. Here we extend application of the primary liquid condensation model to formulate a new model for the origin of BO chondrules. based on the ability of dust-enriched solar-nebula gas to directly condense into a liquid, provided the gas/dust ratio is sufficiently low. Thus, propose that chondrules can be formed by condensation of a liquid droplet directly from the solar nebula. The extensive variability in chemical composition of BO chondrules, which ranges from alkali-poor to alkali-rich, can be explained by elemental exchange reactions with the cooling nebula. We calculate the chemical composition of the initial liquid droplet from which BO chondrules could have formed and speculate about the physical and chemical conditions that prevail  in the specific regions of the solar nebula that can promote creation of these objects.Fil: Varela, Maria Eugenia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Complejo Astronómico "El Leoncito". Universidad Nacional de Córdoba. Complejo Astronómico "El Leoncito". Universidad Nacional de la Plata. Complejo Astronómico "El Leoncito". Universidad Nacional de San Juan. Complejo Astronómico "El Leoncito"; ArgentinaFil: Kurat, Gero. Universidad de Viena; AustriaFil: Zinner, Ernst. University of Washington; Estados Unido

DETERMINING THE WINTERING RANGE OF BROAD-WINGED HAWK (BUTEO PLATYPTERUS) IN SOUTH AMERICA USING CITIZEN-SCIENCE DATABASE

Abstract ∙ Several species of raptors that breed in North America migrate to the southern hemisphere during the non-breeding period. The Broad-winged Hawk (Buteo platypterus) is one of them, and its wintering distribution reaches the north and central part of South America, although there are published records for the species in Argentina and southern Brazil. We did an exhaustive search of records of the Broad-winged Hawk for South America, using bibliography, citizen-science initiatives, personal communications, and own records. We obtained 4025 georeferenced records for the 1879–2017 period. Both the numbers of records per year and the geographical range of the species have apparently increased in recent years. We also obtained the first record for Misiones province in Argentina and for Espírito Santo state, in Brazil. The wintering range of this species is estimated to cover 12.5 million km2 of the north central part of South America, including southern Brazil and northern Argentina. While it is possible that the range has expanded 700 km southwards recently, with the data available it is not possible to disentangle this possibility from changes in the distribution of bird observers. Resumen ∙ Determinando el rango invernal del Aguilucho Alas Anchas (Buteo platypterus) en Sudamérica involucrando datos de ciencia ciudadana Varias especies de aves rapaces se reproducen en América del Norte y migran durante los meses de invierno al hemisferio sur. Uno de ellos, el Aguilucho Alas Anchas (Buteo platypterus), alcanza normalmente el norte y centro de Sudamérica, aunque se han publicado registros en Argentina y en el sur de Brasil. Realizamos una búsqueda exhaustiva de registros del Aguilucho Alas Anchas para Sudamérica, en la literatura científica, en proyectos de ciencia ciudadana, comunicaciones personales y registros propios, obteniendo un total de 4025 registros georreferenciados para el período 1879–2017. Tanto el número de registros por año como el rango geográfico de la especie han aumentado en los últimos años. También reportamos el primer registro para la provincia de Misiones en Argentina y para el estado de Espírito Santo en Brasil. La zona de invernada actual de esta especie cubriría aproximadamente 12,5 millones de km2 de la porción central-norte de Sudamérica, incluyendo el sur de Brasil y el norte de Argentina. Si bien es posible que la especie se haya expandido unos 700 km hacia el sur en tiempos recientes, no es posible diferenciar esta posibilidad de cambios en la distribución de observadores de aves

Synthesis, Secondary Structure, and Anion Binding of Acyclic Carbohydrate-Derived Oligo(amide-triazole)s

A family of linear, carbohydrate-derived oligo(amide-triazole)s has been designed and synthesized. These molecules possess a regular distribution of triazole rings (from one to four) linking the carbohydrate units to give dimer to pentamer derivatives. Their binding to halide anions was qualitatively analyzed by means of NMR spectroscopy and mass spectrometry. All the compounds were able to bind chloride anions, with a stoichiometry that depended on the chain length. The dimer and trimer gave 2:1 host/chloride ratio, while the tetramer and pentamer gave 1:1 complexes. The secondary structure of the oligo(amide-triazole)s was studied using NMR spectroscopy and circular dichroism. These studies showed that the larger host molecules (tetramer and pentamer) adopted a stabilized U-turn and were able to bind just one chloride anion. Only the pentamer displayed a helical conformation, which was slightly distorted in the presence of chloride salts. Interestingly, chloride binding involves not only the triazole-CH but also H atoms from the carbohydrate moieties. These compounds could be applied for chloride sensing by ESI-MS.Fil: Fidalgo, Daniela Marina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Centro de Investigaciones en Hidratos de Carbono. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Centro de Investigaciones en Hidratos de Carbono; ArgentinaFil: Monge, Maria Eugenia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Centro de Investigaciones en Bionanociencias "Elizabeth Jares Erijman"; ArgentinaFil: Varela, Oscar Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Centro de Investigaciones en Hidratos de Carbono. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Centro de Investigaciones en Hidratos de Carbono; ArgentinaFil: Kolender, Adriana Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Centro de Investigaciones en Hidratos de Carbono. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Centro de Investigaciones en Hidratos de Carbono; Argentin

New minerals tsangpoite Ca5(PO4)2(SiO4) and matyhite Ca9(Ca0.5□0.5)Fe(PO4)7 from the D'Orbigny angrite

Tsangpoite, ideally Ca5(PO4)2(SiO4), the hexagonal polymorph of silicocarnotite, and matyhite, ideally Ca9(Ca0.5□0.5)Fe(PO4)7, the Fe-analogue of Ca-merrillite, were identified from the D'Orbigny angrite meteorite by electron probe microanalysis, electron microscopy and micro-Raman spectroscopy. On the basis of electron diffraction, the symmetry of tsangpoite was shown to be hexagonal, P63/m or P63, with a = 9.489(4) Å, c = 6.991(6) Å, V = 545.1(6) Å3 and Z = 2 for 12 oxygen atoms per formula unit, and that of matyhite was shown to be trigonal, R3c, with a = 10.456 (7) Å, c = 37.408(34) Å, V = 3541.6 (4.8) Å3 and Z = 6 for 28 oxygen atoms per formula unit. On the basis of their constant association with the grain-boundary assemblage: Fe sulfide + ulvöspinel + Al-Ti-bearing hedenbergite + fayalite-kirschsteinite intergrowth, the formation of tsangpoite and matyhite, along with kuratite (the Fe-analogue of rhönite), can be readily rationalised as crystallisation from residue magmas at the final stage of the D'Orbigny meteorite formation. Alternatively, the close petrographic relations between tsangpoite/matyhite and the resorbed Fe sulfide rimmed by fayalite + kirschsteinite symplectite, such as the nucleation of tsangpoite in association with magnetite ± other phases within Fe sulfide and the common outward growth of needle-like tsangpoite or plate-like matyhite from the fayalite-kirschsteinite symplectic rim of Fe sulfide into hedenbergite, infer that these new minerals and the grain-boundary assemblage might represent metasomatic products resulting from reactions between an intruding metasomatic agent and the porous olivine-plagioclase plate + fayalite-kirschsteinite overgrowth + augite + Fe sulfide aggregates. Still further thermochemical and kinetics evidence is required to clarify the exact formation mechanisms/conditions of the euhedral tsangpoite, matyhite and kuratite at the grain boundary of the D'Orbigny angrite.Fil: Hwang, Shyh Lung. National Dong Hwa University; República de ChinaFil: Shen, Pouyan. National Sun Yat-sen Universit; República de ChinaFil: Chu, Hao-Tsu. Central Geological Survey; República de ChinaFil: Yui, Tzen-Fu. Institute of Earth Sciences; República de ChinaFil: Varela, Maria Eugenia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Instituto de Ciencias Astronómicas, de la Tierra y del Espacio. Universidad Nacional de San Juan. Instituto de Ciencias Astronómicas, de la Tierra y del Espacio; ArgentinaFil: Iizuka, Yoshiyuki. Institute of Earth Sciences; República de Chin

Druse clinopyroxene in D'Orbigny angritic meteorite studied by single-crystal X-ray diffraction, electron microprobe analysis and Mössbauer spectroscopy

The crystal structure of druse clinopyroxene from the D’Orbigny angrite, (Ca0.944 Fe2+ 0.042 Mg0.010Mn0.004) (Mg0.469Fe2+ 0.317Fe3+ 0.035Al0.125Cr0.010Ti0.044) (Si1.742Al0.258) O6, a = 9.7684(2), b = 8.9124(2), c = 5.2859(1) Å, β = 105.903(1)°, V = 442.58 Å3, space group C2/c, Z = 2, has been refined to an R1 index of 1.92% using single-crystal X-ray diffraction data. The unit formula, calculated from electron microprobe analysis, and the refined site scattering values were used to assign site populations. The distribution of Fe2+ and Mg over the M1 and M2 sites suggests a closure temperature of 1000 °C. Mössbauer spectroscopy measurements were done at room temperature on a single crystal and a powdered sample. The spectra are adequately fit by a Voigt-based quadrupole-splitting distribution model having two generalized sites, one for Fe2+ with two Gaussian components and one for Fe3+ with one Gaussian component. The two ferrous components are assigned to Fe2+ at the M1 site, and arise from two different next-nearest-neighbor configurations of Ca and Fe cations at the M2 site: (3Ca,0Fe) and (2Ca,1Fe). The Fe3+/Fetot ratio determined by Mössbauer spectroscopy is in agreement with that calculated from the electron microprobe analysis. The results are discussed in connection with the redox and thermal history of D’Orbigny.Fil: Abdu, Yassir A.. University of Manitoba; CanadáFil: Scorzelli, Rosa B.. Centro Brasileiro de Pesquisas Físicas; BrasilFil: Varela, Maria Eugenia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Complejo Astronómico "El Leoncito". Universidad Nacional de Córdoba. Complejo Astronómico "El Leoncito". Universidad Nacional de la Plata. Complejo Astronómico "El Leoncito". Universidad Nacional de San Juan. Complejo Astronómico "El Leoncito"; ArgentinaFil: Kurat, Gero. Naturhistorisches Museum; AustriaFil: Souza Azevedo, Izabel de. Centro Brasileiro de Pesquisas Físicas; BrasilFil: Stewart, Silvana Jacqueline. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; ArgentinaFil: Hawthorne, Frank C.. University of Manitoba; Canad