Extreme hydrothermal pressure transitions and fluid evolution in a felsic magmatic-hydrothermal system: a case study of Wondong Fe-W deposit, Korea

• Two distinct brine fluids evolved during the transition from lithostatic to hydrostatic pressure conditions. • The Wondong magmatic–hydrothermal system is associated with a small and isolated magma chamber. • Limited skarn development and rapid magma fractionation at Wondong constrained extensive W mineralization. We investigated magmatic-hydrothermal evolution associated with Paleogene quartz–feldspar porphyry intruded into Cambrian carbonates in the Wondong area, Korea. These “Wondong porphyry” intrusions are spatially associated with skarn mineralization containing magnetite, subeconomic scheelite, and Zn–Pb carbonate-replacement ores. 40 Ar/ 39 Ar dating of phlogopite from magnetite-bearing skarn yielded an age of 50.0 ± 0.03 Ma. The porphyries were subsequently crosscut by numerous thin, subparallel quartz veins. Microthermometry of pseudosecondary fluid inclusions hosted in quart…