Sulfur inventory of the young lunar mantle
Ji, Dasgupta, AGU Fall Meeting Abstracts (2024)
Early sulfur solubility experiments with Apollo sample compositions suggested the lunar mantle is sulfide exhausted. However, the existence of S-poor, Fe-rich, high metal/sulfur ratio sulfide, which may be stable under the low oxygen fugacities associated with the lunar mantle, could lower the sulfur concentrations at sulfide saturation (SCSS) dramatically, resulting in the residual mantle to remain S-saturated. To add to the debate on the fate of sulfide in the lunar mantle, we present new SCSS experiments for the putative parental melts of young Chang’e-5 (CE-5) basalt. We further developed a new thermodynamic SCSS model for the saturation of silicate melts with sulfides of variable S contents. Combining our experiments and model calculations, we found that the CE-5 mantle source was likely sulfide-absent. Compared with the mantle of Apollo basalts, the ~2 Gyrs lunar mantle has much lower S abundances, which may suggest sulfur extraction over the magmatic history of the Moon.Trace element partitioning between apatite and silicate melts
Ji, Dygert, Geochimica et Cosmochimica Acta (2024)
This project is aimed at understanding the partitioning behavior between apatite and silicate melts, and developing predictive models through a lens of high temperature and pressure experiments. We determine the effect of equilibrium temperature on the trace elements partitioning in apatite and analyze the partition coefficient between silicate melts and synthetic different end-member apatite (FlAp, OHAp and ClAp) to test the effect of X-site (F, OH, Cl) occupancy. We will build predictive models to calculate the partition coefficients of trace elements between apatite and silicate melts. In addition, a series of experiments with constant initial composition but different metal buffers in piston cylinder apparatus will be conducted to characterize the Eu anomaly of apatite under different oxygen fugacities.Serial processing of the lunar crust
Ji, Dygert, Earth and Planetary Science Letters (2023)
We calculated REE and Eu distributions in lunar anorthosites according to recent fractional crystallization experiments and we find that crystalized plagioclase exhibit lager Eu anomalies than Apollo samples. Accoding to the numerical modeling, we suggest that subsolidus reequilibration after addition of a KREEP component reduces Eu anomalies and elevates Ce/Sm ratios, reproducing variations in the natural samples. We use Monte Carlo simulations to constrain lunar properties and conditions of subsolidus reequilibration, and proposal a serial processing model to reconcile the petrological, geochronological, and isotopic characteristics of lunar anorthosites and contemporaneous magmatism.