The metal phase in unequilibrated ordinary chondrites and its implications for calculated accretion temperatures

The abundance, composition and grain size of the metal available to volatile siderophile elements strongly affect the condensation of these elements. These parameters are redefined on the basis of published chemical analyses and new mechanical analyses of the unequilibrated ordinary chondrites. The results suggest that previous workers have seriously overestimated the amount of metal present and available during condensation, and seriously underestimated the heat of solution of Bi in chondritic metal. Correction of these parameters results in nominal accretion temperatures for Bi which are substantially (95–110°K) lower than those calculated earlier, and which are discordant with the temperatures inferred for chalcophile trace elements.