Seminar

South China is characterized by extensive Mesozoic magmatism, associated with large-scale mineralization that formed many world-class tungsten skarn deposits. These deposits are mainly clustered in the Nanling and Yangtze River regions. The tungsten skarn deposits in the Nanling region are primarily of the oxidized type, which are characterized by the occurrence of abundant andraditic garnet and Mo-rich scheelite. The tungsten mineralization primarily took place in the Middle to Late Jurassic. On the other hand, the tungsten skarn deposits in the Yangtze River region are chiefly of the reduced type, which are featured by the occurrence of abundant diopsidic pyroxene and Mo-poor scheelite. Majority of these tungsten deposits formed in the Early Cretaceous. These periods of tungsten mineralization are closely related to the subduction of the paleo-Pacific plate. In the Middle Jurassic, break-off of the subducting oceanic plate resulted in emplacement of highly fractionated granites in the Nanling region. Later anticlockwise rotation of the paleo-Pacific plate created widespread S-type granitoids and associated Middle to Late Jurassic oxidized skarn tungsten mineralization in the interior of South China. Since the Early Cretaceous, rollback of the subducting Pacific plate resulted in the reduced tungsten skarn mineralization in the Yangtze River region.

The main source of tungsten mineralization during skarnization is the metasomatic fluid of magmatic origin. The later input of the meteoric fluids and the variations in temperature and oxygen fugacity lead to ore deposition. The model ages of the tungsten-mineralized granites imply that the ultimate sources of tungsten are the Paleo- to Mesoproterzoic juvenile crust, perhaps related to the evolution of Columbia supercontinent.