Highly fractionated rare-earth elements in ferromagnesian chondrules from the Felix (CO3) meteorite

Abstract

Chondrules and Ca, Al-rich inclusions (CAIs) are important constituents of chondritic meteorites which preserve a record of chemical fractionation at high temperature in the early solar nebula¹. Cosmochemical research on these components of meteorites shows that chondrules were formed by melting of preexisting solid precursor materials^2–4. Although highly fractionated rare-earth element (REE) patterns have been known for CAIs^5,6 and are considered as evidence for high-temperature fractionation in the nebula^7,8, little is known about refractory precursor components of chondrules. In addition, chondrules so far studied rarely exhibit fractionated REE patterns, except in a few cases^9,10, so that no single variety of refractory precursor component can be invoked as the fractionated REE carrier in chondrules. Here we describe two ferromagnesian chondrules from the Felix (Ornans-subtype) carbonaceous chondrite which carry a marker signature of REE fractionation in the nebula. Both show positive Ce and Yb anomalies and one exhibits a light/heavy REE fractionation similar to those of Group II CAI⁶. On the basis of the REE characteristics of these chondrules, as well as those of Allende (CV) (ref. 11), we suggest that one of the precursor materials of chondrules in CO–CV carbonaceous chondrites is a high-temperature condensate from the nebular gas.