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  • 1
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    New type of primitive meteorite found in Antarcitca (1988)
    In:  CASI
    Details
    Publication Date: 2013-08-29
    Description: A stony meteorite found in Antarctica in 1985, recently identified as a type of chondrite, probably represents material from a previously unsampled region of the solar system. Scientists are currently debating how the object formed. Preliminary results on Allan Hills 85085 (ALH85085) were presented.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst., Nineteenth Lunar and Planetary Science Conference. Press abstracts; p 12-13
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  • 2
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    Implications for the evolution of chondrules from Agglomeratic olivine chondrules (1994)
    In:  Other Sources
    Details
    Publication Date: 2019-01-25
    Description: There is considerable evidence that chondrules formed by the melting of solid materials and, by default, the early solar nebula is the preferred location for chondrule formation. Agglomeratic olivine (AO) chondrules supply perhaps the most intriguing, direct evidence for chondrule formation from agglomeration of solids. We review the characteristics of AO chondrules and discuss their implications for understanding chondrule precursors and chondrule evolution.
    Keywords: ASTROPHYSICS
    Type: Lunar and Planetary Inst., Papers Presented to the Conference on Chondrules and the Protoplanetary Disk; p 44-45
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  • 3
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    Porphyritic versus nonporphyritic chondrules (1994)
    In:  Other Sources
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    Publication Date: 2019-01-25
    Description: Chondrules can be divided into two broad textural types: porphyritic and nonporphyritic. Porphyritic chondrules are the most common in most chondrites and range texturally from olivine-rich (PO) to intermediate (POP) to pyroxene-rich (PP). Barred olivine (BO) chondrules can be considered a special case of porphyritic. Compositionally they can be divided into type I and II. Nonporphyritic are less abundant than porphyritic chondrules in most chondrites -- they make up approximately 125% of the chondrules in ordinary chondrites -- and range texturally from glassy (g) to cryptocrystalline (C) to radial pyroxene (RP). Compositionally nonporphyritic differ from porphyritic chondrules and within this group they are very similar to one another. Here we (1) review and contrast the characteristics of the nonporphyritic and porphyritic chondrules; (2) specify some of the problems associated with the origins of the textural and compositional differences between them; and (3) suggest a possible scenario for their origin, which may have important implications for the evolution of chondrules.
    Keywords: ASTROPHYSICS
    Type: Lunar and Planetary Inst., Papers Presented to the Conference on Chondrules and the Protoplanetary Disk; p 26-27
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  • 4
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    Mineralogy of dark clasts in primitive versus differentiated meteorites (1993)
    In:  Other Sources
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    Publication Date: 2019-01-25
    Description: The presence of dark lithic clasts within meteorites can provide information concerning asteroidal regolith processes, the extent of interactions between asteroids, and the relationship between meteorite types, micrometeorites, and interplanetary dust particles. Accordingly, we have been seeking and characterizing dark clasts found within carbonaceous chondrites, unequilibrated ordinary chondrites, howardites, and eucrites. We find that unequilibrated chondrites in this study contain fine-grained, anhydrous unequilibrated inclusions, while the howardites often contain inclusions from geochemically processed, hydrous asteroids (type 1 and 2 carbonaceous chondrites). Eucrites and howardities contain unusual clasts, not easily classified.
    Keywords: ASTROPHYSICS
    Type: Lunar and Planetary Inst., Twenty-Fourth Lunar and Planetary Science Conference. Part 3: N-Z; p 1583-1584
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  • 5
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    The formation of FeO-rich pyroxene and enstatite in unequilibrated enstatite chondrites: A petrologic-trace element (SIMS) study (1993)
    In:  Other Sources
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    Publication Date: 2019-01-25
    Description: Enstatite (En) chondrites record the most reducing conditions known in the early solar system. Their oxidation state may be the result of condensation in a nebular region having an enhanced C/O ratio, reduction of more oxidized materials in a reducing nebula, reduction during metamorphic reheating in a parent body, or a combination of these events. The presence of more oxidized Fe-rich silicates, two types of En (distinguished by red and blue CL), and the juxtaposition of FeO-rich pyroxenes (Fe-pyx) surrounded by blue En (enstatite) in the UEC's (unequilibrated enstatite chondrites) is intriguing and led to the examination of the question of enstatite chondrite formation. Previously, data was presented on the petrologic-geochemical characteristics of the Fe-pyx and coexisting red and blue En. Here minor and trace element abundances (determined by ion probe-SIMS) on these three types of pyroxenes are reported on in the following meteorites: Kota Kota and LEW87223 (EH3), MAC88136 (EL3), St. Marks (EH4), and Hvittis (EL6). More data are currently being collected.
    Keywords: ASTROPHYSICS
    Type: Lunar and Planetary Inst., Twenty-Fourth Lunar and Planetary Science Conference. Part 3: N-Z; p 1501-1502
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  • 6
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    Carbonates in the Kaidun chondrite (1994)
    In:  Other Sources
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    Publication Date: 2019-04-02
    Description: Kaidun is a remarkable chondrite breccia fall containing lithic clasts that span a wide range of chondrite groups including C and E chondrites, as well as having clasts with characteristics not yet found in existing chondrite samples. The dominant lithology in Kaidun appears to be CR chondritic, consonant with recent O isotope data. The carbonates in Kaidun are presented as one mineralogical basis for comparing it to the other hydrated chondrites and to better understand its relative alteration history. The four polished thin sections of Kaidun studied contained a variety of lithologies that we classified into four groups -- CR, E, CM-like, and dark inclusions (DIs). DIs contain sulfide and magnetite morphologies that superficially resemble CI chondrites, and some of the previously reported CI lithologies in Kaidun may be what we term DIs. Carbonates were found in all lithologies studied. Carbonates in Kaidun are similar in composition to those in CR chondrites. Some of the DIs in Kaidun, previously characterized as CI, have carbonates similar to those in CR chondrites and are unlike those in CI or CM chondrites. Most carbonates in Kaidun and CR chondrites are calcites, some of which formed at temperatures above 250 C. Dolomite is less common and some may be metastable. Alteration temperatures in the Renazzo CR chondrite were estimated to be approximately 300 C, based on O isotope fractionation between phyllosilicates and magnetite. Temperatures of up to 450 C were proposed for the alteration of a CR-like dark inclusion in Kaidun, based on the presence of hydrothermal pentlandite veins. The alteration temperatures for Kaidun and the other CR chondrites are considerably higher than those suggested for CI or CM parent bodies.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Meteoritics (ISSN 0026-1114); 29; 4; p. 549-550
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  • 7
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    Oxygen isotopic relationships between the LEW85332 carbonaceous chondrite and CR chondrites (1993)
    In:  Other Sources
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    Publication Date: 2019-01-25
    Description: LEW85332, originally described as a unique C3 chondrite, was shown to be a C2 chondrite with important linkages to the CR clan. An important petrologic aspect of LEW85332 is that it contains anhydrous chondrules and hydrated matrix, and new oxygen isotopic data on chondrules, matrix and whole rock are consistent with the petrology. Chondrules fall on the equilibrated chondrite line (ECL), with a slope near 1, which goes through ordinary chondrite chondrules. This contrasts with the CR chondrule line which has a lower slope due to hydrated components. LEW85332 chondrules define a new carbonaceous chondrite chondrule line, parallel to the anhydrous CV chondrule line (CCC), consistent with the well-established concept of two oxygen isotopic reservoirs. Matrix and whole rock fall on the CR line. The whole rock composition indicates that the chondrite is dominated by chondrules, and that most of them contain light oxygen similar to that of anhydrous olivine and pyroxene separates in the Renazzo and Al Rais CR chondrites.
    Keywords: ASTROPHYSICS
    Type: Lunar and Planetary Inst., Twenty-Fourth Lunar and Planetary Science Conference. Part 3: N-Z; p 1185-1186
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  • 8
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    Lack of Evidence of In-Situ Decay of Aluminum-26 in a FeO-Poor Ferromagnesian Crystalline Silicate Particle, Pyxie, from Comet Wild 2 (2014)
    In:  CASI
    Details
    Publication Date: 2019-07-19
    Description: One of the important discoveries from the Stardust mission is the observation of crystalline silicate particles that resemble Ca, Al-rich inclusions (CAIs) and chondrules in carbonaceous chondrites], which suggests radial transport of high temperature solids from the inner to the outer solar nebula regions and capture by accreting cometary objects. The Al-Mg isotope analyses of CAI-like and type II chondrule-like particles revealed no excess of Mg-26 derived from in-situ decay of Al-26 (Tau)(sub 1/2) = 0.705Myr; ), suggesting late formation of these particles. However, the number of Wild 2 particles analyzed for Al-Mg isotopes is still limited (n = 3). In order to better understand the timing of the formation of Wild 2 particles and possible radial transport in the protoplanetary disk, we performed SIMS (Secondary Ion Mass Spectrometer) Al-Mg isotope analyses of plagioclase in a FeO-poor ferromagnesian Wild 2 particle, which is the most abundant type among crystalline Wild 2 particles.
    Keywords: Lunar and Planetary Science and Exploration
    Type: JSC-CN-30360 , Lunar and Planetary Science Conference; Mar 17, 2014 - Mar 21, 2014; The Woodlands, TX; United States
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  • 9
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    Highly Reduced Forsterite and Enstatite from Stardust Track 61: Implications for Radial Transport of E Asteroid Material (2013)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The Stardust Mission returned a large fraction of high-temperature, crystalline material that was radially transported from the inner solar system to the Kuiper Belt [1,2]. The mineralogical diversity found in this single cometary collection points to an even greater number of source materials than most primitive chondrites. In particular, the type II olivine found in Wild 2 includes the three distinct Fe/Mn ratios found in the matrix and chondrules of carbonaceous chondrites (CCs) and unequilibrated ordinary chondrites (UOCs) [3]. We also find that low-Ca pyroxene is quite variable (approximately Fs3-29) and is usually indistinguishable from CC, UOC, and EH3 pyroxene as well. However, occasional olivine and pyroxene compositions are found in Wild 2 that are inconsistent with chondrites. The Stardust track 61 terminal particle (TP) is one such example and is the focus of this study. It s highly reduced forsterite and enstatite is consistent only with that in Aubrites, in which FeO is essentially absent from these phases (less than approximately 0.1 wt.% FeO) [4].
    Keywords: Lunar and Planetary Science and Exploration
    Type: JSC-CN-27940 , Lunar and Planetary Science Conference; Mar 18, 2013 - Mar 22, 2013; The Woodlands, TX; United States
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  • 10
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    Northwest Africa (NWA) 8785, an EL3 Chondrite with FeO-Rich Matrix (2019)
    In:  CASI
    Details
    Publication Date: 2019-07-27
    Description: The enstatite (E) chondrites are enigmatic but important for understanding the evolution of the terrestrial planets. They have highly reduced mineral assemblages in which enstatite (near pure in compostion) is the dominant silicate, metal is abundant and contains 〉2.5 wt. % Si in some EH3s, elements which are generally lithophile in most chondrites occur as sulfide and some E3s contain nitrides and carbides. Notably, stable isotope compositions are similar to the Earth-Moon. Aside from E chondrite clasts in the Kaidun breccia, the enstaite chondrites are dry, lacking evidence of ever having hydrous minerals, distinguishing them from most other chondrite groups and suggesting they formed relatively close to the sun, inside of the snow line. Compared to other chondrite groups, the E3s are also matrix-poor, with EH3s having ~4-12 vol. % and EL3s 5 vol % matrix. Here we present a study of NWA 8785, a remarkable new EL3 chondrite with an FeO-rich, fine-grained matrix. Our goals are to understand E chondrite matrix and the evolution and alteration history of the EL3 parent body.
    Keywords: Inorganic, Organic and Physical Chemistry
    Type: JSC-E-DAA-TN68420 , Meteoritical Society Annual Meeting; Jul 07, 2019 - Jul 12, 2019; Sapporo; Japan
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