Search

Due to their numerous isotopic similarities to terrestrial rocks, enstatite chondrites (ECs) are commonly proposed as Earth's main building blocks. Although ECs contain sufficient H concentrations to account for the mass of Earth's oceans, the physicochemical process(es) behind their H incorporation remain under constrained. Here, we combined secondary ion mass spectrometry analyses of volatile contents (H, C, F, Cl, S) and H isotopic compositions with Raman spectroscopy analyses of H speciation in the glassy mesostases of EC chondrules. EC chondrule mesostases (68–830 wt. ppm H) contain much more H than chondrule silicates (5–25 wt. ppm) and are characterized by H isotopic compositions of δ D = −109 ± 27‰. Hydrogen and sulfur contents are positively correlated in EC chondrule mesostases, and we commonly observed well-resolved Raman peaks at 2580 cm−1, corresponding to HS− or H 2 S bonding. These results illustrate that the high H abundances in EC chondrule mesostases do not result from terrestrial contamination or secondary asteroidal processes, nor were their high volatile contents inherited from chondrule precursors. Instead, they were established at high temperature during chondrule formation via interactions between Fe-poor melts and S-rich gas under extremely reducing conditions. Our data confirm that ECs contain sufficient primordial hydrogen to explain the terrestrial water budget, and likely contributed important amounts of other volatile elements such as carbon, which was fundamental to the formation of life. • High H, C, S, F and Cl abundances measured by SIMS in EC mesostasis. • H and S positive correlation and H-S speciation were identified. • H in EC chondrules is unlikely to result from terrestrial or asteroidal contamination. • H likely dissolved in the FeO-poor and S-rich EC chondrule melts at high-temperature. • EC-like materials carried hydrogen in the inner solar system when Earth formed. [ABSTRACT FROM AUTHOR]