Veevers crater-forming iron meteorite 
57 
account for the isolated areas of incipiently melted 
schreibersite, attenuation of shock waves at grain 
boundaries and shearing could have generated 
localised 'hot spots' where temperatures may have 
approached 1000°C. Incipient melting of schrei¬ 
bersite at grain boundaries as the result of intense 
shear deformation observed in Veevers is identical 
to that described by Axon et al. (1977) from 
similarly deformed phosphide inclusions in the 
crater-forming iron Canyon Diablo. Evidence from 
fragment WAM 13735 indicates that extensive 
shock-melting in Veevers may have occurred along 
those grain boundaries containing abundant 
troilite. Troilite has a low shock impedence relative 
to Fe and is known to induce high shock- 
temperatures even under conditions of moderate 
shock-loading. 
The shock pressures required to produce the 
structural changes in Veevers fragments can be 
inferred from the estimated residual temperatures 
indicated by the thermal alteration of minerals in 
the meteorite. The relationship between shock 
pressure and residual temperature for pure iron 
has been determined experimentally by McQueen 
et al. (1962) and for iron meteorite material by 
Heymann et al. (1966). In shocked iron meteorites, 
extensive or complete transformation to a 2 - 
kamacite occurs at applied pressures in the range 
0.8 — 1Mb (Heymann et al. 1966). In specimens of 
the Odessa meteorite shocked to pressures in this 
range, Heymann et al. (1966) also noted that small 
patches of shock-hardened e-kamacite may occur 
once in sectional areas up to 20 cm 2 . The apparent 
absence of e-kamacite in Veevers may simply be a 
function of the small sectional area of the meteorite 
examined. 
As suggested by Wasson et al. (1989), the plate¬ 
like morphology of the surviving fragments of 
Veevers indicates that the meteorite broke up 
during impact predominantly along a-a crystal 
boundaries in the original octahedral structure. 
Large crystals of schreibersite, such as that 
observed in Veevers fragment WAM 13761, also 
provide brittle-cracking paths that could have 
facilitated break-up. From a study of shrapnel-like 
fragments of the Henbury crater-forming iron, 
Axon and Steele-Perkins (1975) have suggested that 
fracturing of that meteorite took place along 
surfaces of shear-faulting generated during impact. 
Parting along zones of shear displacement may 
have provided an additional mechanism of failure 
in the Veevers meteorite, and this is supported by 
the occurrence of shear-zones that parallel the 
outer surfaces of the fragments. The angles of 
intersection ( ca. 60°) of some of the shear-zones in 
Veevers coincides with the angles between the 
(111) directions of kamacite in the octahedral 
structure of iron meteorites. It is possible that the 
habit planes of the octahedral structure and other 
cubic planes in Veevers influenced the shearing 
forces generated by impact. Subsequently, the 
penetration of terrestrial oxidation along grain 
boundaries and shear-zones may have led to 
further disintegration of the surviving fragments, 
as suggested by Wasson et al. (1989). 
Much of the pre-terrestrial micro-structure of 
Veevers has been destroyed or modified as the 
result of thermo-mechanical alteration during 
crater-forming impact. Nevertheless, portions of 
the original micro-structure of the meteorite have 
been preserved. The observed Neumann bands 
that have been plastically deformed and partially 
degenerated by re-heating appear to pre-date 
terrestrial impact. The sinuous lines of stained 
metal observed in fragment WAM 13761 are 
interpreted as the resorped lamellae of an as yet 
unidentified mineral, probably roaldite. 
Comparison with other crater-forming irons 
Out of the twelve other crater-forming irons 
known (Grieve 1991), the most extensively studied 
are Canyon Diablo (IAB), Odessa (IAB) and 
Henbury (IIIAB) (Buchwald 1975). Canyon Diablo 
and Odessa are both coarse octahedrites, whereas 
Henbury is a medium octahedrite. All three 
meteorites are associated with craters that are very 
much larger than Veevers. In the case of Henbury, 
the impact resulted in some thirteen craters 
including several that are of similar size to 
Veevers. Structural variations between the crater¬ 
forming irons and differences in the magnitude of 
their impacting events have resulted in an 
enormous range of shock-induced features in the 
surviving fragments. Notwithstanding, there are 
strong similarities in the overall nature of thermo¬ 
mechanical alteration and mechanism of disruption 
suffered by many crater-forming irons. 
In terms of crater size, the closest analogue to 
Veevers is the largest of a group of nine craters at 
Kaalijarv, located on Saaremaa Island, Estonia 
(Buchwald 1975). The largest crater measures 110 
m in diameter and eight smaller craters vary from 
12 - 40 m in diameter (Tiirmaa 1992). Kaalijarv is a 
coarse octahedrite (IAB) and the material recovered 
from the craters comprises small slugs of metal 
generally less than 20 g in weight (Buchwald 1975). 
Metallographically, the Kaalijarv meteorite shows 
shock hardening, shear deformation and localised 
recrystallization of metal. Overall, the thermal 
alteration of Kaalijarv fragments is less than those 
observed in Veevers fragments and is generally 
confined to zones of shear deformation. 
The IIAB iron Sikhote-Alin, that fell in eastern 
Siberia in 1947, is the largest known shower in 
historical times and is structurally and chemically 
similar to Veevers. Some 23.2 tons of fragmental 
material were recovered from a large strewnfield 
covering 1.6 sq. km and including 122 impact 
