Evidence Against Chondrule-Matrix Complementarity as Seen in CO, CM, and CR Chondrites

Introduction: We have undertaken a comprehensive study of carbonaceous chondrites (CCs) to determine the abundances and average compositions of their main components, and to examine the possible genetic relationship between the two major components, chondrules and matrix [1]. Two scenarios for the origins of chondrules and matrix have been much debated: (a) chondrule-matrix complementarity, which is based on the observation that absolute element ratios like Si/Mg, Fe/Mg, Ti/Al and Ca/Al exhibit opposite trends in CC chondrules and matrices, proposes a common origin and co-genetic evolution of both components [2 and ref. therein]; (b) chondrules and matrix are not genetically related [e.g., 3-7], with matrix having a ~CI-like composition and chondrules being largely responsible for the moderately volatile element fractionations in bulk CCs.