Chemical and isotopic heterogeneity in protosolar matter

It is argued that the inner Solar System is chemically fractionated with re gard to the bulk Solar System. It is enriched in refractory and depleted in volatile elements. Carbonaceous chondrites reflect the major fractionation trends of the present inner Solar System material. Other groups of meteori tes are indicative of processes in more local environments. Although the el ement pattern of material in the inner Solar System bears some resemblance to that in grains of the interstellar medium (ISM), Solar System materials have, with few exceptions, no memory of their ISM origin. After decoupling of the Solar System from ISM, isotopic and elemental remixing occurred foll owed by metal, forsterite and volatile element fractionations.