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Paper: Chemical, Mineralogical and Isotopic Properties of Chondrules: Clues to Their Origin
Volume: 341, Chondrites and the Protoplanetary Disk
Page: 251
Authors: Jones, R.H.; Grossman, J.N.; Rubin, A.E.
Abstract: We review chemical, mineralogical and isotopic properties of chondrules that can be used to investigate chondrule origins. Although many interpretations of chondrule properties are hampered by the lack of sufficient data for the least-equilibrated chondrites, we can make general inferences about formation conditions. Chondrules exhibit considerable diversity in their bulk chemistries, oxygen isotope ratios, and oxidation states that are present both within and among individual chondrite groups. Chondrules formed by melting of solid precursors composed of aggregates that included a mixture of fine-grained or amorphous material (silicates, oxides, Fe,Ni-metal, sulfides, carbon) and larger silicate grains that were likely derived from previous generations of chondrules. Bulk compositions generally show varying abundances of (unfractionated) refractory lithophile elements (Ca, Al, Ti, rare earth elements), and varying degrees of fractionation of moderately volatile lithophile (Mn, Na, K) and siderophile (Fe, Ni, Co) elements. Bulk compositions were probably modified during chondrule-forming events by open system behavior. Most material in the chondrule forming region was heated at least twice. Diversity in chondrule precursors can be attributed to random aggregation of diverse mineral grains, as well as progressive changes in solid compositions with time and/or space in the solar nebula.

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