Chondrules with peculiar REE patterns: implications for solar nebular condensation at high C/O

Area of Science:

• Cosmochemistry
• Planetary Science
• Geochemistry

Background:

• Ordinary chondrites provide insights into early solar system processes.
• Rare earth elements (REEs) are crucial tracers of planetary formation and differentiation.
• Previous models assumed a specific oxygen fugacity for the canonical solar nebula.

Purpose of the Study:

• To investigate the origin of distinct REE anomalies in ordinary chondrite chondrules.
• To test the hypothesis of REE gas/solid fractionation under low oxygen fugacity conditions.
• To infer the chemical environment of the early solar nebula.

Main Methods:

• Analysis of rare earth element concentrations in two ordinary chondrite chondrules.
• Chondrite-normalized REE pattern analysis.
• Modeling of gas/solid fractionation processes.

Main Results:

• Observed distinct negative anomalies for samarium, europium, and ytterbium in chondrule REE data.
• These anomalies are consistent with REE gas/solid fractionation at low oxygen fugacity.
• The findings suggest the incorporation of highly reduced, ultrarefractory condensates.

Conclusions:

• The early solar nebula likely experienced environments with a significant oxygen deficit.
• High-temperature condensation processes occurred under conditions with an enhanced carbon/oxygen ratio.
• This challenges previous assumptions about the oxygen fugacity of the canonical solar nebula.