Oxygen isotope relationships in iron meteorites

Abstract The separation factor, aM-0= (18O/16O) magnetite/' (18O/16O) atmospheric oxygen, between the magnetite crust of iron meteorites and atmospheric oxygen has been determined to be 0.9946 ± 0.0005. It is concluded that this fractionation of the oxygen isotopes is the consequence of an equilibrium isotope effect at high temperatures. It can be assumed that this is also valid for cosmic spherules, which are mainly ablation products of iron meteorites. As these spherules are found in sediments of different geological ages, their oxygen isotope ratio can give information on the development of atmospheric oxygen. The difference of the oxygen isotope ratios between magnetite from the lithosphere and airborne magnetite can be used to distinguish between terrestrial and extraterrestrial material.

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Oxygen Isotope Variation in Stony-Iron Meteorites

Science ◽

10.1126/science.1128865 ◽

2006 ◽

Vol 313 (5794) ◽

pp. 1763-1765 ◽

Cited By ~ 74

Author(s):

R. C. Greenwood

Keyword(s):

Oxygen Isotope ◽

Iron Meteorites ◽

Isotope Variation

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Oxygen isotope and petrological study of silicate inclusions in IIE iron meteorites and their relationship with H chondrites

Geochimica et Cosmochimica Acta ◽

10.1016/j.gca.2015.10.014 ◽

2016 ◽

Vol 173 ◽

pp. 97-113 ◽

Cited By ~ 17

Author(s):

Kathryn H. McDermott ◽

Richard C. Greenwood ◽

Edward R.D. Scott ◽

Ian A. Franchi ◽

Mahesh Anand

Keyword(s):

Oxygen Isotope ◽

Iron Meteorites ◽

Silicate Inclusions ◽

H Chondrites

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Electron Microscope Observations of Mechanical Metamorphism in Iron Meteorites

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100069430 ◽

1970 ◽

Vol 28 ◽

pp. 488-489

Author(s):

D. Faulkner ◽

G.W. Lorimer ◽

H.J. Axon

Keyword(s):

Electron Microscope ◽

Defect Structure ◽

Shock Loading ◽

List Type ◽

Iron Meteorites

It is now generally accepted that meteorites are fragments produced by the collision of parent bodies of asteroidal dimensions. Optical metallographic evidence suggests that there exists a group of iron meteorites which exhibit structures similar to those observed in explosively shock loaded iron. It seems likely that shock loading of meteorites could be produced by preterrestrial impact of their parent bodies as mentioned above.We have therefore looked at the defect structure of one of these meteorites (Trenton) and compared the results with those made on a) an unshocked ‘standard’ meteorite (Canyon Diablo)b) an artificially shocked ‘standard’ meteorite (Canyon Diablo) andc) an artificially shocked specimen of pure α-iron.

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Evidence for ordered Fe3Ni

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100125981 ◽

1987 ◽

Vol 45 ◽

pp. 216-217

Author(s):

K.B. Reuter ◽

D.B. Williams ◽

J.I. Goldstein

Keyword(s):

Experimental Data ◽

Martensitic Transformation ◽

Electron Diffraction ◽

Room Temperature ◽

Direct Evidence ◽

Transformation Product ◽

Iron Meteorites ◽

X Ray ◽

Ni Content ◽

Temperature Transformation

In the Fe-Ni system, although ordered FeNi and ordered Ni3Fe are experimentally well established, direct evidence for ordered Fe3Ni is unconvincing. Little experimental data for Fe3Ni exists because diffusion is sluggish at temperatures below 400°C and because alloys containing less than 29 wt% Ni undergo a martensitic transformation at room temperature. Fe-Ni phases in iron meteorites were examined in this study because iron meteorites have cooled at slow rates of about 10°C/106 years, allowing phase transformations below 400°C to occur. One low temperature transformation product, called clear taenite 2 (CT2), was of particular interest because it contains less than 30 wtZ Ni and is not martensitic. Because CT2 is only a few microns in size, the structure and Ni content were determined through electron diffraction and x-ray microanalysis. A Philips EM400T operated at 120 kV, equipped with a Tracor Northern 2000 multichannel analyzer, was used.

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