scholarly journals Fine-grained dust rims in the Tagish Lake carbonaceous chondrite: Evidence for parent body alteration

2005 ◽  
Vol 40 (9-10) ◽  
pp. 1413-1431 ◽  
Author(s):  
Ansgar Greshake ◽  
Alexander N. Krot ◽  
George J. Flynn ◽  
Klaus Keil
Keyword(s):  
Carbonaceous Chondrite ◽  
Parent Body ◽  
Fine Grained

scholarly journals Discovery of fossil asteroidal ice in primitive meteorite Acfer 094

2019 ◽  
Vol 5 (11) ◽  
pp. eaax5078 ◽  
Author(s):  
Megumi Matsumoto ◽  
Akira Tsuchiyama ◽  
Aiko Nakato ◽  
Junya Matsuno ◽  
Akira Miyake ◽  
...  
Keyword(s):  
Solar Nebula ◽  
Carbonaceous Chondrite ◽  
Parent Body ◽  
Carbonaceous Chondrites ◽  
X Ray ◽  
Porous Texture ◽  
Fine Grained ◽  
X Ray Computed ◽  
Source Materials ◽  
Insight Into

Carbonaceous chondrites are meteorites believed to preserve our planet’s source materials, but the precise nature of these materials still remains uncertain. To uncover pristine planetary materials, we performed synchrotron radiation–based x-ray computed nanotomography of a primitive carbonaceous chondrite, Acfer 094, and found ultraporous lithology (UPL) widely distributed in a fine-grained matrix. UPLs are porous aggregates of amorphous and crystalline silicates, Fe─Ni sulfides, and organics. The porous texture must have been formed by removal of ice previously filling pore spaces, suggesting that UPLs represent fossils of primordial ice. The ice-bearing UPLs formed through sintering of fluffy icy dust aggregates around the H2O snow line in the solar nebula and were incorporated into the Acfer 094 parent body, providing new insight into asteroid formation by dust agglomeration.

Machiite, Al2Ti3O9, a new oxide mineral from the Murchison carbonaceous chondrite: A new ultra-refractory phase from the solar nebula

2020 ◽  
Vol 105 (2) ◽  
pp. 239-243 ◽  
Author(s):  
Alexander N. Krot ◽  
Kazuhide Nagashima ◽  
George R. Rossman
Keyword(s):  
Isotopic Composition ◽  
Solar Nebula ◽  
Carbonaceous Chondrite ◽  
Parent Body ◽  
Oxygen Isotopic Composition ◽  
New Mineral ◽  
Calculated Density ◽  
California Institute Of Technology ◽  
Oxygen Isotopic ◽  
Institute Of Technology

Abstract Machiite (IMA 2016-067), Al2Ti3O9, is a new mineral that occurs as a single euhedral crystal, 4.4 μm in size, in contact with an euhedral corundum grain, 12 μm in size, in a matrix of the Murchison CM2 carbonaceous chondrite. The mean chemical composition of holotype machiite by electron probe microanalysis is (wt%) TiO2 59.75, Al2O3 15.97, Sc2O3 10.29, ZrO2 9.18, Y2O3 2.86, FeO 1.09, CaO 0.44, SiO2 0.20, MgO 0.10, total 99.87, giving rise to an empirical formula (based on 9 oxygen atoms pfu) of (Al1.17Sc0.56Y0.10Ti0.084+Fe0.06Ca0.03Mg0.01)(Ti2.714+Zr0.28Si0.01)O9. The general formula is (Al,Sc)2(Ti4+,Zr)3O9. The end-member formula is Al2Ti3O9. Machiite has the C2/c schreyerite-type structure with a = 17.10 Å, b = 5.03 Å, c = 7.06 Å, β = 107°, V = 581 Å3, and Z = 4, as revealed by electron backscatter diffraction. The calculated density using the measured composition is 4.27 g/cm3. The machiite crystal is highly 16O-depleted relative to the coexisting corundum grain (Δ17O = –0.2 ± 2.4‰ and –24.1 ± 2.6‰, respectively; where Δ17O = δ17O – 0.52 × δ18O). Machiite is a new member of the schreyerite (V2Ti3O9) group and a new Sc,Zr-rich ultrarefractory phase formed in the solar nebula, either by gas-solid condensation or as a result of crystallization from a Ca,Al-rich melt having solar-like oxygen isotopic composition (Δ17O~ –25‰) under high-temperature (~1400–1500 °C) and low-pressure (~10-4–10-5 bar) conditions in the CAI-forming region near the protosun. The currently observed disequilibrium oxygen isotopic composition between machiite and corundum may indicate that machiite subsequently experienced oxygen isotopic exchange with a planetary-like 16O-poor gaseous reservoir either in the solar nebula or on the CM chondrite parent body. The name machiite is in honor of Chi Ma, mineralogist at California Institute of Technology, for his contributions to meteorite mineralogy and discovery of many new minerals representing extreme conditions of formation.

scholarly journals Two generations of exsolution lamellae in pyroxene from Asuka 09545: Clues to the thermal evolution of silicates in mesosiderite

2019 ◽  
Vol 104 (11) ◽  
pp. 1663-1672
Author(s):  
Lidia Pittarello ◽  
Seann McKibbin ◽  
Akira Yamaguchi ◽  
Gang Ji ◽  
Dominique Schryvers ◽  
...  
Keyword(s):  
Thermal Evolution ◽  
Parent Body ◽  
Cooling History ◽  
Equilibrium Conditions ◽  
Slow Cooling ◽  
Temperature Range ◽  
Fine Grained ◽  
Two Generations ◽  
Mantle Component ◽  
The Antarctic

Abstract Mesosiderite meteorites consist of a mixture of crustal basaltic or gabbroic material and metal. Their formation process is still debated due to their unexpected combination of crust and core materials, possibly derived from the same planetesimal parent body, and lacking an intervening mantle component. Mesosiderites have experienced an extremely slow cooling rate from ca. 550 °C, as recorded in the metal (0.25–0.5 °C/Ma). Here we present a detailed investigation of exsolution features in pyroxene from the Antarctic mesosiderite Asuka (A) 09545. Geothermobarometry calculations, lattice parameters, lamellae orientation, and the presence of clinoenstatite as the host were used in an attempt to constrain the evolution of pyroxene from 1150 to 570 °C and the formation of two generations of exsolution lamellae. After pigeonite crystallization at ca. 1150 °C, the first exsolution process generated the thick augite lamellae along (100) in the temperature interval 1000–900 °C. By further cooling, a second order of exsolution lamellae formed within augite along (001), consisting of monoclinic low-Ca pyroxene, equilibrated in the temperature range 900–800 °C. The last process, occurring in the 600–500 °C temperature range, was likely the inversion of high to low pigeonite in the host crystal, lacking evidence for nucleation of orthopyroxene. The formation of two generations of exsolution lamellae, as well as of likely metastable pigeonite, suggest non-equilibrium conditions. Cooling was sufficiently slow to allow the formation of the lamellae, their preservation, and the transition from high to low pigeonite. In addition, the preservation of such fine-grained lamellae limits long-lasting, impact reheating to a peak temperature lower than 570 °C. These features, including the presence of monoclinic low-Ca pyroxene as the host, are reported in only a few mesosiderites. This suggests a possibly different origin and thermal history from most mesosiderites and that the crystallography (i.e., space group) of low-Ca pyroxene could be used as parameter to distinguish mesosiderite populations based on their cooling history.

scholarly journals Tungsten isotopic constraints on the age and origin of chondrules

2016 ◽  
Vol 113 (11) ◽  
pp. 2886-2891 ◽  
Author(s):  
Gerrit Budde ◽  
Thorsten Kleine ◽  
Thomas S. Kruijer ◽  
Christoph Burkhardt ◽  
Knut Metzler
Keyword(s):  
Planet Formation ◽  
Solar Nebula ◽  
Carbonaceous Chondrite ◽  
Critical Role ◽  
Parent Body ◽  
Uneven Distribution ◽  
Time Interval ◽  
Ordinary Chondrites ◽  
Chondrule Formation ◽  
Isotopic Constraints

Chondrules may have played a critical role in the earliest stages of planet formation by mediating the accumulation of dust into planetesimals. However, the origin of chondrules and their significance for planetesimal accretion remain enigmatic. Here, we show that chondrules and matrix in the carbonaceous chondrite Allende have complementary 183W anomalies resulting from the uneven distribution of presolar, stellar-derived dust. These data refute an origin of chondrules in protoplanetary collisions and, instead, indicate that chondrules and matrix formed together from a common reservoir of solar nebula dust. Because bulk Allende exhibits no 183W anomaly, chondrules and matrix must have accreted rapidly to their parent body, implying that the majority of chondrules from a given chondrite group formed in a narrow time interval. Based on Hf-W chronometry on Allende chondrules and matrix, this event occurred ∼2 million years after formation of the first solids, about coeval to chondrule formation in ordinary chondrites.

Si-bearing metal and niningerite in Almahata Sitta fine-grained ureilites and insights into the diversity of metal on the ureilite parent body

2014 ◽  
Vol 49 (10) ◽  
pp. 1948-1977 ◽  
Author(s):  
Marian Horstmann ◽  
Munir Humayun ◽  
Mario Fischer-Gödde ◽  
Addi Bischoff ◽  
Mona Weyrauch
Keyword(s):  
Parent Body ◽  
Fine Grained
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