58 
holes (Krinov 1963; Buchwald 1975 - and 
references therein). Many of the masses of Sikhote- 
Alin broke up during impact and some of the 
recovered fragments display the earliest stages of 
shock-metamorphism. Buchwald (1975) noted that 
many of the disrupted fragments showed 
octahedral parting, and that fissures are well 
developed along kamacite grain boundaries that 
are loaded with schreibersite. However, more 
intensely deformed fragments also show shear 
deformation and visibly distorted zones near their 
surfaces. In addition, Buchwald (1975) noted that 
fissures had also developed along the cubic 
cleavage planes of kamacite lamellae in Sikhote- 
Alin, although these appeared to have played a 
minor role during the fragmentation of the 
impacting masses. 
Although of much less intensity, the style of 
thermo-mechanical impact alteration displayed by 
both the Sikhote-Alin and Kaalijarv meteorites is 
very similar to that observed in Veevers fragments. 
SUMMARY AND CONCLUSIONS 
Veevers is the only known crater-forming iron of 
chemical group IIAB. Sub-group IIB irons are rare, 
accounting for only 4% of all iron meteorites, and 
less than 0.5% of all meteorites. The association of 
an unusual meteorite type with an impact crater is 
especially significant. Dry conditions and 
extremely low erosion rates in the arid zone of 
Australia over at least the last 4000 years account 
for the excellent state of preservation of both the 
crater and the surviving fragments of meteorite. 
The metallography of the surviving fragments of 
Veevers shows that the meteorite was subjected to 
a pre-terrestrial history of mild shock-loading of a 
thoroughly annealed structure that resulted in at 
least one generation of Neumann band 
deformation. Subsequently, terrestrial impact 
caused intense shock-loading of the meteorite that 
resulted in shearing and plastic deformation with 
attendant localised heating to >800°C. In 
accommodating the complex pattern of shock 
waves generated by high-velocity impact with the 
Earth, a portion of the meteorite was disrupted 
mainly along kamacite crystal boundaries in the 
original coarsest (> 8.6 mm) octahedral structure. 
Failure may also have occurred as the result of 
fracturing along zones of intense shear- 
deformation that may, in turn, have been 
influenced by the octahedral structure of the 
meteorite. As a result of the disruption of a portion 
of the projectile along brittle-cracking paths some 
of the energy of the impact event may have been 
absorbed, allowing portions of the original 
microstructure of the meteorite to be preserved. 
Most of the remains of the meteorite may be 
mixed widely with the breccia under the crater 
A.W.R. Bevan, E.M. Shoemaker, C.S. Shoemaker- 
floor. A subordinate fraction of the meteorite Was 
broadly sprayed out of the crater and is Aow- 
buried beneath the surrounding sand slwet. 
Subsequently, terrestrial weathering has corroded 
the fragments and may also have contributed to 
further disintegration. However, because oh 
prolonged aridity in the desert region where the 
crater occurs, rusting is not extensive and the 
fragments retain large cores of fresh metal. The 
close approximation of the average thickness of 
fragments (8.6 mm) to the bandwidths (9 - 10 mm) 
of other IIAB irons of similar Ni content suggests 
that corrosional losses due to weathering were 
unlikely to have been greater than 1-2 mih. A 
thorough search of a wide area around the cfater 
may yield larger fragments of Veevers that became 
detached from the projectile during atmospheric 
flight, and that were not involved in the cratering 
event. 
ACKNOWLEDGEMENTS 
The authors thank the late Dr H. J. Axon for 
providing experimentally heat-treated samples of 
Canyon Diablo for study. Assistance in the 
preparation of the Veevers fragments Was 
generously provided by the Electron Microscope 
Centre of the University of Western Australia, 
through Dr B. J. Griffin. Professor J. T. Wasson and 
Dr V. F. Buchwald are thanked for their helpful 
reviews. 
REFERENCES 
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mechanical and thermal alteration of iron meteorite 
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