An experimental investigation into the partition of Mo between aqueous fluids and felsic melts: Implications for the genesis of porphyry Mo ore deposits

Most of the world’s large molybdenum (Mo) deposits are genetically related to magmas that underwent significant fractional crystallization and fluid exsolution, residual silicate melts commonly peralkaline. To understand relationship between melt compositions genesis porphyry Mo mineralization, partition coefficients (DMo) felsic were determined at 850 °C, 900 100 MPa with various values A/NK [molar Al2O3/ (Na2O + K2O) in melt] under an oxygen fugacity around Ni–NiO (NNO) buffer. The results show DMo decreases from 4.23 0.4 increasing 0.75 1.36 carbon dioxide series (fluid composed ofXCO2 = 0.096 CO2/(CO2 H2O)] 17.5 wt% NaCl). A similar trend was observed pure water, varying 0.72 1.23, 0.54 0.15. Significantly, peralkaline is consistently higher than peraluminous melt, even same NBO/T (the ratio non-bridge tetrahedron ion). Our study therefore reveals easily distributed into fluids exsolved magmas. This finding explains why highly fractionated critical for mineralization.