Nanophase iron carbides in fine‐grained rims in CM2 carbonaceous chondrites: Formation of organic material by Fischer–Tropsch catalysis in the solar nebula

Author(s):  
Adrian J. Brearley
Clay Minerals ◽  
1985 ◽  
Vol 20 (4) ◽  
pp. 415-454 ◽  
Author(s):  
D. J. Barber

AbstractCurrent thinking regarding the possible origins and probable evolutionary histories of meteorites is summarized. Selected data concerning the composition, petrology and other characteristics of the CI and CM groups of stony meteorites in which layered minerals principally occur are then presented. Layered compounds, mainly phyllosilicates, are shown to form a major part of the fine-grained matrix of the CI and CM meteorites, which are classified as carbonaceous chondrites. The results of recent investigations of matrix mineralogy are reviewed, with particular emphasis on the findings of electron microscopy. Several forms of Fe-Mg-serpentine have been identified as the principal phyllosilicates. ‘Poorly-characterized phases’ in CM meteorites have proved to be tochilinite and intergrowths of tochilinite with serpentines. The results generally indicate that the phyllosilicates and most other matrix minerals formed by aqueous alteration in the regoliths of the CI and CM parent bodies; but there is isotopic evidence for the incorporation of components and possibly mineral grains which predate the solar nebula. It is concluded that more detailed chemical and mineralogical information about the phyllosilicates and associated minerals will enable useful constraints to be placed on the possible identities of their precursors and the environments in which both they and the matrix minerals formed.


2019 ◽  
Vol 5 (11) ◽  
pp. eaax5078 ◽  
Author(s):  
Megumi Matsumoto ◽  
Akira Tsuchiyama ◽  
Aiko Nakato ◽  
Junya Matsuno ◽  
Akira Miyake ◽  
...  

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.


1993 ◽  
Vol 95 (2) ◽  
pp. L9-L13 ◽  
Author(s):  
A. Trovarelli ◽  
P. Matteazzi ◽  
G. Dolcetti ◽  
A. Lutman ◽  
F. Miani

2020 ◽  
Vol 897 (1) ◽  
pp. 82
Author(s):  
Hauke Vollstaedt ◽  
Klaus Mezger ◽  
Yann Alibert

1982 ◽  
Vol 86 (24) ◽  
pp. 4799-4808 ◽  
Author(s):  
G. Le Caer ◽  
J. M. Dubois ◽  
M. Pijolat ◽  
V. Perrichon ◽  
P. Bussiere

Geosciences ◽  
2019 ◽  
Vol 9 (9) ◽  
pp. 395 ◽  
Author(s):  
Andrey Ivantsov ◽  
Aleksey Nagovitsyn ◽  
Maria Zakrevskaya

We describe traces of macroorganisms in association with the body imprints of trace-producers from Ediacaran (Vendian) deposits of the southeastern White Sea region. They are interpreted as traces of locomotion and are not directly related to a food gathering. The complex remains belong to three species: Kimberella quadrata, Dickinsonia cf. menneri, and Tribrachidium heraldicum. They were found in three different burials. The traces have the form of narrow ridges or wide bands (grooves and linear depressions on natural imprints). In elongated Kimberella and Dickinsonia, the traces are stretched parallel to the longitudinal axis of the body and extend from its posterior end. In the case of the isometric Tribrachidium, the trace is directed away from the margin of the shield. A short length of the traces indicates that they were left by the organisms that were covered with the sediment just before their death. The traces overlaid the microbial mat with no clear signs of deformation under or around the traces. A trace substance, apparently, differed from the material of the bearing layers (i.e., a fine-grained sandstone or siltstone) and was not preserved on the imprints. This suggests that the traces were made with organic material, probably mucus, which was secreted by animals in a stressful situation. The mucus traced the movements of the organism before death. The discovered traces of locomotion are direct evidence of the ability of some Ediacaran macroorganisms to move independently.


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