43 research outputs found
Data for: Petrology and oxygen isotopic composition of large igneous inclusions in ordinary chondrites: Early solar system igneous processes and oxygen reservoirs
No full textElectronic Annex for “Petrology and oxygen isotopic composition of large igneous inclusions in ordinary chondrites: Early solar system igneous processes and oxygen reservoirs”, authors Alex M. Ruzicka, Richard C. Greenwood, Katherine Armstrong, Kristy L. Schepker, Ian A. Franch
Data for: Petrology and oxygen isotopic composition of large igneous inclusions in ordinary chondrites: Early solar system igneous processes and oxygen reservoirs
No full textElectronic Annex for “Petrology and oxygen isotopic composition of large igneous inclusions in ordinary chondrites: Early solar system igneous processes and oxygen reservoirs”, authors Alex M. Ruzicka, Richard C. Greenwood, Katherine Armstrong, Kristy L. Schepker, Ian A. FranchiTHIS DATASET IS ARCHIVED AT DANS/EASY, BUT NOT ACCESSIBLE HERE. TO VIEW A LIST OF FILES AND ACCESS THE FILES IN THIS DATASET CLICK ON THE DOI-LINK ABOV
Electron Backscatter Diffraction (EBSD) Study of Seven Heavily Metamorphosed Chondrites: Deformation Systematics and Variations in Pre-shock Temperature and Post-shock Annealing
No full textWe used electron backscatter diffraction (EBSD) methods to study the crystallography of olivine and other minerals in seven heavily metamorphosed (petrographic type 6 or 6/7) but variably shocked ordinary chondrites from the H (Kernouvé, Portales Valley), L (Leedey, Bruderheim, Morrow County, Park) and LL (Miller Range (MIL) 99301) groups. MIL 99301 contains a large clast that was analyzed separately. Mesoscale (EBSD) data support and extend inferences based on microscale (TEM) observations and provide good evidence that chondrites were shock-deformed at different temperatures and were variably annealed (sintered) after deformation. Various EBSD deformation intensity metrics adequately and quantitatively represent olivine deformation in meteorites on different scales and in different ways. Mean Grain Orientation Spread (GOS, the average misorientation in a grain) is a robust statistic for overall deformation. We developed an EBSD deformation temperature metric based on olivine misorientation rotation axis data, and an EBSD post-shock annealing metric based on the skewness of olivine GOS distributions. The two parameters together define three groups among the meteorites studied, and these are related to shock stages and 40Ar/39Ar ages that record impact times. Group 1 includes cold-deformed and little-annealed but high-shock-stage (S4 and S5) chondrites (Leedey, Bruderheim, Morrow County) that were affected by impacts at a time (4425?Ma, assuming the older of two published ages for MIL 99301 corresponds to host). Group 3 chondrites must have been shocked while warm at the time of impact, at temperatures estimated as \u3e700–800?°C and up to ?1000?°C, i.e., at conditions generally corresponding to thermal metamorphism associated with petrographic type 6 grade, and were subsequently buried and annealed in warm parent bodies. Impact at elevated pre-shock temperature resulted in partly recrystallized troilite in Park and metallic liquids that crystallized as coarse troilite interstitial to silicates in Portales Valley. For Group 3, data are consistent with impact-redistribution on warm parent bodies that were hot at depth, and support a model of early collisional processing of endogenically-heated chondritic planetesimals. In general, EBSD deformation signatures in each of the meteorites studied are dominated by the effects of the prevailing impact, although there is some evidence for multiple impact effects
Iron and Stony-Iron Meteorites: Evidence for the Formation, Crystallization, and Early Impact Histories of Differentiated Planetesimals
No full textBy far most of the melted and differentiated planetesimals that have been sampled as meteorites are metal-rich iron meteorites or stony iron meteorites. The parent asteroids of these meteorites accreted early and differentiated shortly after the solar system formed, producing some of the oldest dated materials. The main heat source responsible for the melting and differentiation of asteroids was 26Al (Chapter 6, This Volume). Unlike the parent bodies of chondrites, the differentiated bodies accreted while 26Al was sufficiently abundant to cause melting. In this review, we summarize properties and interpretations for iron and stony iron meteorites (Plate 13.1). Such meteorites provide important constraints on the nature of metal-silicate separation and mixing in planetesimals undergoing partial to complete differentiation. They include iron meteorites that formed by the solidification of cores (fractionally crystallized irons), irons in which partly molten metal and silicates of diverse types were mixed together (silicate-bearing irons), stony irons in which partly molten metal and olivine from cores and mantles were mixed together (pallasites), and stony irons in which partly molten metal and silicate from cores and crusts were mixed together (mesosiderites
Petrology of silicate inclusions in the Sombrerete ungrouped iron meteorite: Implications for the origins of IIE-type silicate-bearing irons
No full textThe petrography and mineral and bulk chemistries of silicate inclusions in Sombrerete, an ungrouped iron that is one of the most phosphate-rich meteorites known, was studied using optical, scanning electron microscopy (SEM), electron microprobe analysis (EMPA), and secondary ion mass spectrometry (SIMS) techniques. Inclusions contain variable proportions of alkalic siliceous glass (~69 vol% of inclusions on average), aluminous orthopyroxene (~9%, Wo1-4Fs2535, up to ~3 wt% Al), plagioclase (~8%, mainly An7092), Cl-apatite (~7%), chromite (~4%), yagiite (~1%), phosphaterich segregations (~1%), ilmenite, and merrillite. Ytterbium and Sm anomalies are sometimes present in various phases (positive anomalies for phosphates, negative for glass and orthopyroxene), which possibly reflect phosphate-melt-gas partitioning under transient, reducing conditions at high temperatures. Phosphate-rich segregations and different alkalic glasses (K-rich and Na-rich) formed by two types of liquid immiscibility. Yagiite, a K-Mg silicate previously found in the Colomera (IIE) iron, appears to have formed as a late-stage crystallization product, possibly aided by Na-K liquid unmixing. Trace-element phase compositions reflect fractional crystallization of a single liquid composition that originated by low-degree (~48%) equilibrium partial melting of a chondritic precursor. Compositional differences between inclusions appear to have originated as a result of a filter-press differentiation process, in which liquidus crystals of Cl-apatite and orthopyroxene were less able than silicate melt to flow through the metallic host between inclusions. This process enabled a phosphoran basaltic andesite precursor liquid to differentiate within the metallic host, yielding a dacite composition for some inclusions. Solidification was relatively rapid, but not so fast as to prevent flow and immiscibility phenomena. Sombrerete originated near a cooling surface in the parent body during rapid, probably impact-induced, mixing of metallic and silicate liquids. We suggest that Sombrerete formed when a planetesimal undergoing endogenic differentiation was collisionally disrupted, possibly in a breakup and reassembly event. Simultaneous endogenic heating and impact processes may have widely affected silicate-bearing irons and other solar system matter.The Meteoritics & Planetary Science archives are made available by the Meteoritical Society and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform February 202
Accretion of Warm Chondrules in Weakly Metamorphosed Ordinary Chondrites and Their Subsequent Reprocessing
No full textTo better understand chondrite accretion and subsequent processes, the textures, crystallography, deformation, and compositions of some chondrite constituents in ten lithologies of different cluster texture strength were studied in seven weakly metamorphosed (Type 3) and variably shocked ordinary chondrites (Ragland—LL3 S1, Tieschitz—H/L3 S1, NWA 5421—LL3 S2, NWA 5205—LL3 S2, NWA 11905—LL3-5 S3, NWA 5781—LL3 S3, NWA 11351—LL3-6 S4) using optical and electron microscopy and microtomography techniques. Results support a four-stage model for chondrite formation. This includes 1) limited annealing following collisions during chondrule crystallization and rapid cooling in space prior to accretion, as evidenced by olivine microstructures consistent with dislocation recovery and diffusion; 2) initial accretion of still-warm chondrules into aggregates at an effective chondrite accretion temperature of ∼900-950 °C with nearly in situ impingement deformation between adjacent chondrules in strongly clustered lithologies (NWA 5781, Tieschitz, NWA 5421, NWA 5205 Lithology A), as evidenced by intragranular lattice distortions in olivine consistent with high-temperature slip systems, and by evidence that some olivine-rich objects in Tieschitz accreted while partly molten; 3) syn- or post-accretion bleaching of chondrule mesostases, which transferred feldspathic chondrule mesostasis to an interchondrule glass deposit found in strongly clustered lithologies, as evidenced by chemical data and textures; and 4) post-bleaching weak or strong shocks that resulted in destruction of interchondrule glass and some combination of brecciation, foliation of metal and sulfide, and melting and shock-overprinting effects, as evidenced by poor cluster textures and presence of clastic texture, alignment of metal and sulfide grains caused by shock compression, presence of impact-generated glass, and changes in olivine slip systems. The data support the model of Metzler (2012), who suggested that chondrules in ordinary chondrites accreted while still warm to form cluster chondrite textures as a “primary accretionary rock” (our Stage 2), and that subsequent brecciation destroyed this texture to create chondrites with weak cluster texture (our Stage 4)
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Petrology and oxygen isotopic composition of large igneous inclusions in ordinary chondrites: Early solar system igneous processes and oxygen reservoirs
No full textLarge (>3.5 mm and up to 4 cm across) igneous inclusions poor in metal and sulfide are a minor but not uncommon component in ordinary chondrites, and have implications for the nature of physiochemical and melting processes in the early solar system. We obtained petrographic-chemical data for forty-two large igneous inclusions in ordinary chondrites of various groups (H, L, LL) and petrographic types (3-6) and oxygen isotope data for a subset of twelve of these inclusions and their host chondrites. Different inclusions formed both before and after the thermal metamorphism experienced by their host chondrites. The bulk chemical compositions of the inclusions vary broadly around whole-rock chondrite composition, comprise four main chemical types and some other variants, and show little evidence of having formed as igneous differentiates. Oxygen isotope compositions overlap ordinary chondrite compositions and are related to inclusion chemical type. Most prevalent in type 3 and 4 chondrites are inclusions, often droplets, of the vapor-fractionated (Vfr) chemical type, either enriched in refractory lithophile elements, or depleted in volatile lithophile elements, or both. These inclusions have low Δ17O (∼0.1-0.6‰) and high δ18O (∼4-8‰) values and formed in reservoirs with Δ17O lower than their hosts, primarily as evaporative melts and mixtures that probably experienced kinetic isotopic fractionation. Another chemical type (Unfr+K) has unfractionated abundances of lithophile elements except for being strongly enriched in K, a signature also found in some impact melts from melt rocks and melt breccias. These inclusions formed by impact melting of chondritic material and accompanying K enrichment. Inclusions with unfractionated (Unfr) lithophile element abundances are present in type 3-6 chondrites and are prevalent in type 5 and 6. Some are spatially associated with coarse metal-sulfide nodules in the chondrites and likely formed by in situ impact melting. Others were melted prior to thermal metamorphism and were chemically but not isotopically homogenized during metamorphism; they are xenoliths that formed in oxygen reservoirs different than the hosts in which they were metamorphosed. The latter inclusions provide evidence for nebular or collisional mixing of primitive materials prior to thermal metamorphism of asteroid bodies, including transport of H-like source materials to the L body, LL-like source materials to the L body, and low-Δ17O materials to the LL body. Feldspar-rich (FldR) inclusions have compositions similar to melt pockets and could have formed by disequilibrium melting and concentration of feldspar during an impact event to form large droplets or large masses. Overall, the results of this study point to important and varied roles for both “planetary” impact melting and “nebular” evaporative melting processes to form different large igneous inclusions in ordinary chondrites. Chondrules may have formed by processes similar to those inferred for large inclusions, but there are important differences in the populations of these objects
Modelling design of multiphase bubble-bed reactors for advanced food-industry applications
No full textAn EC project (IC15-CT98-0904 / PL979021) under this title commenced November 1998
courtesy of Dr Jindrich Zahradnik, sadly since deceased. In dedication to his memory overviewed
here are contributions from the four partners whose lead investigators appear as authors (plus
coordinator as corresponding author) with principals and researchers recognised in cited
literature. A website (www.copernicus.aston.ac.uk) has been launched to disseminate major
individual components and collaborations facilitated by study exchanges, also envisaged
exploitation by industries. Drawing on this material we outline partners' established expertise and
its unification under EC umbrella funding. To avoid confusion on due credit for contributions,
references are designated by first letters of the above-named authors. At risk of appearing to
favour ones' own wares, we humbly refer readers to our cited papers for contextual
commentaries
Hf-W, Sm-Nd, and Rb-Sr isotopic evidence of late impact fractionation and mixing of silicates on iron meteorite parent bodies
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