| Abstract: | The Haig (IIIA) iron meteorite material (BM 1968,280) in the Collection of the British Museum (Natural History) displays pre-terrestrial shear deformation which transects a small troilite-daubréelite-cohenite nodule. Five globular areas (< 1 mm) with dendritic structures indicating rapid solidification from melts occur within and around the larger part of the transected nodule. All shock deformation structures and shock-heating effects exhibited by Haig. are of pre-terrestrial origin and at least four successive alterations to the original structure are evident. Partial bulk analyses of the melt globules indicate complex mixtures of approximately 55 wt % troilite, 24 wt % metal, 14 wt % daubréelite and 7 wt % cohenite. It is suggested that a compressive environment maintained the melts as discrete pools of liquid. The diameters of the globules (< 0.5 mm) and spacing of the dendrite arms (< 1 μm) indicate solidification at > 106 °C sec?1 which is the fastest cooling rate yet recorded in meteorites. |
