Alkali recondensation into chondrulesOPEN ACCESS
Emmanuel Jacquet, Yves Marrocchi, Sébastien Charnoz
Icarus, In Press, Journal Pre-proof, Available online 23 January 2026
“Highlights
- Alkalis recondensed into chondrules after olivine crystallization.
- Solid density in chondrule-forming regions constrained to 10-6±1 kg/m.
- Chondrules formed in settled dust disk near pressure bumps.”
“While sub-mm melt droplets should rapidly lose alkali elements in a vacuum at liquidus temperatures, chondrules are only modestly depleted in them (by less than one order of magnitude). The detection of sodium in olivine cores has previously suggested very high saturating partial pressures of gaseous
sodium, but we show that alkalis were lost during heating and recondensed at lower temperatures, essentially in the present-day chondrule mesostases. This recondensation was accompanied by mass-dependent enrichment in light isotopes (for multi-isotope alkalis such as K and Rb), but its limited extent
indicates a cooling acceleration (or “quenching”). The isotopic fractionation also constrains the ratio of the chondrule density and the cooling rate prior to the quench around 10−6 kg.m−3.K−1.h suggesting ensities above ∼ 10−6 kg/m3. In a nebular context, this is achievable by radial and vertical concentrations near pressure bumps.”
