Zircon U-Pb and molybdenite Re-Os dating of the Shangfang tungsten deposit in northern Fujian province: implications for regional mineralization

The newly discovered large-scale Shangfang tungsten deposit represents a new type of tungsten mineralization in Fujian Province offering new pespectives for exploration of tungsten deposits in the province. The ore bodies are mostly hosted in amphibolite and biotite leptynite of the Paleoproterozoic Dajinshan Formation proximal to the Shangfang syenogranite intrusion and less significantly, in the contact zone between the intrusion and the metamorphic rocks. Tungsten mineralization consists of quartz-scheelite veins and disseminated scheelite in alteration assemblages, with scheelite and molybdenite as the main ore minerals coexisting with minor pyrrhotite, pyrite, and chalcopyrite. Field relations and petrographic characterization indicate that the Shangfang deposit is typified by skarn mineralization. Zircons from the Shangfang syenogranite intrusion have LA-ICP-MS U-Pb age of 158.8±1.6 Ma (1σ), whereas five molybdenite separates yield model ages ranging from 159.40±0.86 to 149.92±1.39 Ma with a weighted mean of 156.5 ± 4.0 Ma which is consistent with an isochrone age of 158.1±5.4 Ma (2σ). The geochronological data thus demonstrate that the Shangfang tungsten deposit formed in the Late Jurassic and is genetically related to the syenogranite intrusion in the mine. The data also indicate that the Shangfang deposit resulted from the pervasive Late Mesozoic tunsgten mineralization in South China. It has long been considered that the Late Jurassic tungsten metallogenic belt in South China is restricted in the middle-eastern portion of the Nanling Range covering areas of southern Hunan northern Guangdong, and southern Jiangxi Province. The discovery of the Shangfang deposit, however, allows this metallogenic belt to extend into western and northern Fujian Province which is an integral part of the Wuyishan metallogenic belt. As such, the South China polymetallic belt is distributed along a northeast strike, rather than an east-west extension as previously thought and can be regarded as an important part of the giant Circle-Pacific tectono-magmtic-metallogenic domain.