The world-class Nanling metallogenic belt (Jiangxi, China): W and Sn deposition at 160 Ma followed by 30 m.y. of hydrothermal metal redistribution

Abstract

The W-Sn Maoping deposit and related W-Sn deposits from the world-class Nanling Range in Southeast China formed at ca. 160 Ma and experienced several phases of metal addition and metal redistribution between 160 and 130 Ma. Isotopic dating of ore mineral (wolframite) of Maoping demonstrates that W was deposited first, during a hydrothermal event at ca. 160 Ma. Successive fluid episodes, at ca. 156 Ma (Mo and Sn-rich fluid) and 152 Ma (REE-rich fluid), resulted in the formation of REE- and Fe-Cu-Zn-sulfide minerals. A last fluid event occurring at ca. 130 Ma was responsible for the deposition of Zr-REE-Nb-Ta minerals that are attributed to magmatic fluids derived from unexposed magmatic bodies. The three episodes of fluid circulation post-dating W deposition resulted in partial to complete resetting of the isotopic systems (mica, wolframite, xenotime), which are conventionally used for dating such deposits. We show that W and Sn mineralization in the Nanling Range formed during a unique fluid event at ca. 160 Ma. Later fluid episodes redistributed the previously deposited metals and sequentially introduced additional metals, including Mo-Sn, Fe-Cu-Zn, and Zr-REE-Nb-Ta. Direct dating of paragenetically well-constrained minerals is therefore critical for determining the age and the duration of mineralizing processes and for characterizing the fluid evolution of magmatic-hydrothermal systems, as exemplified in the Nanling Range.