Résumé
Different from most other W-skarns in the world, the Late Jurassic Weijia scheelite skarn in the Nanling Range of South China is magnesian, and is characterized by the occurrence of serpentine and phlogopite, and the lack of forsterite and spinel. Because of the high abundance of fluorite, an investigation of the relationship between fluorine and the unusual magnesian skarn and tungsten mineralization was undertaken. A high fluorine activity for the granite-related mineralization is indicated by the abundances of fluorine-rich minerals and the estimated HF concentrations. A fall of fluorine activity with decreasing temperature is reflected by the compositions of different micas. The decrease of fluorine activity should be directly induced by the progressive formation of fluorite and other fluorine-rich minerals. The obvious positive correlation between the grade of WO3 and the content of fluorite indicates a strong coupling relationship of tungsten and fluorine. The scheelite mineralization is most probably triggered by the decrease of fluorine activity. The low temperature condition of ore-forming fluids which exsolve from the fluorine-rich melts and experience a further evolution in sedimentary strata is not favourable for the development of high-temperature prograde forsterite and spinel in the magnesian skarn.