Three late-Mesozoic fluorite deposit belts in southeast China and links to subduction of the (paleo-) Pacific plate

Rocks and ore deposits in subduction zones can provide clues to material cycling and related subduction processes. Here we demonstrate, based upon a new data compilation from more than 240 late-Mesozoic fluorite deposits in southeast China that most of them can be divided into three fluorite deposit belts (FDB) with distinct ages and orientations. The two older inland FDB with a NE-SW orientation were formed at 165-150 Ma and 150-130 Ma, respectively, whereas the younger coastal FDB, roughly perpendicular to the others, was generated at 110-70 Ma. The temporal-spatial distributions of the FDB are compatible with the subduction of the (paleo-) Pacific plate. We propose that the genesis of the earlier two inland FDB was due to northeastward slab rollback during low-angle subduction, while formation of the coastal FDB resulted mainly from high-angle northwestward hot/warm subduction. Large amounts of F, mainly derived from the decomposition of phengite (+/- apatite) in the subducted slabs, could be transported into the overlying crust via F-rich fluids and alkalic magmas. Subsequently, extensive crustal magmatism and fluid activities associated with subduction further concentrate F from the magmas and/or wall-rocks and facilitate fluorite mineralization. This study provides new insights into the interaction between the subducting (paleo-) Pacific plate and overlying eastern Eurasian continent in the late Mesozoic. It also highlights the potential genetic association of F transport/deposition with plate subduction that could be a common phenomenon in ancient and modern subduction zones.

Automated summary

A study on late Mesozoic fluorite deposits in southeast China reveals that they can be divided into three fluorite deposit belts with distinct ages and orientations, formed in relation to the subduction of the (paleo-) Pacific plate. The genesis of these deposits is attributed to different subduction processes, providing new insights into the interaction between the subducting plate and the overlying continent.