Trace element partitioning between immiscible silicate melts with H2O, P, S, F, and Cl

- Trace-element partition values (D) in immiscible volatile-rich melts are determined.
- Experimental conditions are T = 1200 °C, P = 200 MPa, and fO2 = QFM, NNO and MH.
- H2O alone or with P or S produces nearly parallel partitioning trends for HFSE and REE.
- D values for transition elements are strongly dependent on anionic composition.

The partitioning of the trace elements Rb, Cs, Zr, Nb, Hf, Th, U, La, Ce, Nd, Sm, Eu, Dy, Er, Yb, Mn, Co, Mo, Ni, Cu, Zn, Cr, Cr, V, Ti and Ag between immiscible silicate melts in the systems Fe2SiO4-Fe3O4-KAlSi2O6-SiO2, Fe3O4-KAlSi2O6-SiO2, Fe3O4-Fe2O3-KAlSi2O6-SiO2, and Fe3O4-Fe2O3-KAlSi2O6-SiO2-Ca0.5Na.5Al1.5Si2.5O8 (An50) with or without H2O, P, S, F and Cl at 1200 °C, P = 200 MPa has been determined at fO2 = QFM, NNO and MH oxygen buffers. H2O is shown to increase the partitioning of HFSE, REE and transition elements into the Fe-rich melt. H2O alone or with 6.67 × 10− 4 mol/g of P or S produces nearly similar partitioning trends for HFSE and REE, at experimental fO2 = QFM, NNO and MH. H2O + F causes Rb and Cs to partition into the Fe-rich melt and significantly increases U partitioning into the Fe-rich melt. Absolute partitioning values of Mn, Co, Mo, Ni, Cu, Zn, Cr, Cr, V, Ti and Ag are strongly dependent on the H2O, P, S, F, and Cl compositions of the melt.