Geochemistry of apatite from Zhuxiling tungsten deposit, eastern China: A record of magma evolution and tungsten enrichment

Abstract

The origin and evolution of tungsten ore, a key metal resource, have long been controversial. In order to reveal the origin of tungsten mineralization related to weakly fractionated I-type granites, we have carried out detailed in situ element analysis on apatite from gabbro-diorite enclaves and their host rocks (biotite granodiorites) in Zhuxiling deposit, Jiangnan orogenic belt. The groups of apatite samples were identified, respectively from gabbro-diorite enclaves (Group A) representing deep early magma, and biotite granodiorites with weak tungsten mineralization stage (Group B) and strong tungsten mineralization stage (Group C). The three-group apatite samples with high F (2.15–4.74 wt.%) and low Cl (<0.19 wt.%) contents, belong to fluoroapatite, and have LREE enrichment, negative Eu anomalies (Eu/Eu∗ = 0.27–0.52), and low Sr/Y ratios (mainly <1). The Sr content difference between the apatite studied and host rocks, and the gradual increase of Sr contents from Group A to Group B to Group C, indicate that high tungsten content magma mixing is the dominant cause of mineralization in the Zhuxiling region. The studied apatite samples with different internal zonal textures, suggest that more significant oscillatory growth zone is associated with higher tungsten content, more complex internal compositions, and longer crystallization times. Apatite trace elements (e.g., Sr, Y, Eu/Eu∗, REE) characteristics indicate that the Zhuxiling mineralized intrusions mainly experienced shallow feldspar crystalline differentiation. The F- and Li-rich, high evolution degree, and moderate oxygen fugacity of magma may contribute to tungsten mineralization in the Zhuxiling region.