Bulk trace elements of Mg-rich cryptocrystalline and ferrous radiating pyroxene chondrules from Acfer 182: Their evolution paths

Abstract

A trace element study of Mg-rich cryptocrystalline (CC)and ferrous radiating pyroxene (RP)chondrules, covering from the ultra-refractory Zr to the volatile K, was performed to better understand the processes involved in chondrule formation and their subsequent evolution. The shape, textures and bulk chemical compositions (CC and RP)of the studied chondrules indicate that they once must have been hypersthene-olivine normative liquids that were quenched. Their chondritic Ca/Al ratio and the positive Yb vs. La correlation around primordial values point to a cosmochemical process as responsible of chondrules formation. Based on their REE patterns, and regardless of their mineralogy, chondrules are divided in two populations: Fractioned-REE (F-REE)and Unfractionated-REE (U-REE). Both populations show different evolution paths, while cooling of the nebula gas and give new hints about chondrule-forming reservoirs.