Parameterizations of calcic clinopyroxene—Melt trace element partition coefficients

Semiempirical parameterizations of the values and trends of variation of Nernst trace element partition coefficient data for Ca‐rich clinopyroxene ( cpx/liquid D) are provided, applicable mainly to common terrestrial magmatic suites. cpx/liquid D data for most trace elements show significant variability which cannot be neglected when modeling melting and crystallization. The influence of pressure on cpx/liquid D is strong for many elements, particularly Na and Sr, which increase as pressure rises, and most high‐field strength elements, which decrease with increasing pressure. Most cpx/liquid D values increase as temperature decreases, as wt % melt MgO, MgO# (MgO/MgO+FeO total ), CaO, and FeO contents drop, as cpx molar Mg# (Mg/Mg+Fe total ) decreases, and as wt % melt SiO 2 and Na 2 O+K 2 O increase. No clear trends are seen for variations of cpx/liquid D against melt H 2 O. For mafic melts, many elements show well‐defined trends of cpx/liquid D increase as the clinopyroxene tetrahedral Al content (cpx Al iv ) increases. Many cpx/liquid D are well correlated against cpx/liquid D Ti , and many “near‐neighbor” elements show good cpx/liquid D intercorrelations (e.g., Zr‐Hf, U‐Th, Nb‐Ta, La‐Ce, Yb‐Lu). Cpx/liquid D profiles calculated from these parameterizations can constrain changes of D values during melting or crystallization. Cpx/liquid D for the rare earth elements were fit to the lattice strain model to derive fits that can reproduce the cpx/liquid D REE profile shapes (REE = rare earth elements). These fits indicate that cpx/liquid D REE for melts more evolved than picritic basalts cannot be modeled assuming that all REE are in octahedral coordination in a single M2 site, but also require sixfold partitioning into an M1 site for Lu‐Yb‐Tm‐Er.