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.

Eu anomalies in lunar anorthosites

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.

The petrogenesis of early Cretaceous adakitic rocks in Northeast China

Ji, Liu, Li, International Geology Review (2020)

  Large volumes of early Cretaceous adakitic rocks crop out in northeast China. In this paper, we summarize their spatial-temporal distribution and geochemical characteristics, which indicate significant Phanerozoic crust growth in NE China. Based on their geochemistry, these adakitic rocks are mainly derived from partial melting of juvenile lower crust. We interpret the melting to have resulted from extension and associated delamination and we thus propose a new two-stage convergent bidirectional subduction model.