METALLOGRAPHY AND THERMO-MECHANICAL TREATMENT OF THE VEEVERS (IIAB) CRATER-FORMING IRON METEORITE

WA Museum Records and Supplements | Updated 1 decade ago

Abstract - Thirty six fragments of iron meteorite (group HAB Wasson et al. 1989) totalling 298.1 g found at Veevers crater in Western Australia (22°58'06"S, 125°22'07"E) represent the disrupted remnants of the craterforming projectile, and confirm an origin for the ca. 75 m crater by meteorite impact. The morphology and metallography of the residual material show that the impacting meteorite was a coarsest octahedrite with a kamacite bandwidth of > 8.6 mm. Disruption of the meteorite during impact probably occurred along the grain boundaries of a-kamacite crystals in the original octahedral structure, but may also have resulted from failure related to intense shear deformation. Further disintegration of the surviving fragments may have occurred as the result of prolonged terrestrial weathering. Thermomechanical alteration of the micro-structure of the meteorite as a result of impact includes transient, localised re-heating to >800°C, shearing and plastic deformation. Failure of parts of the meteorite along brittle-cracking paths, such as crystal boundaries, may have absorbed some of the energy of terrestrial impact and allowed portions of the original micro-structure of the meteorite to be preserved. Veevers is the only known group HAB iron associated with an impact crater.