Petrogenetic and metallogenic implications of the Late Mesozoic intrusive rocks in the Xuancheng ore district, eastern China: insight from in situ analysis of apatite

Abstract

The Xuancheng ore district is a newly discovered ore district within the Middle-Lower Yangtze River Metallogenic Belt (MYRMB) of Eastern China. Here we investigated the major and trace element concentrations of apatite crystallizes in ore-related intrusions from three skarn deposits with distinctive metal endowments in this region to further reveal their implications for petrogenesis, metallogenesis, and potential for polymetallic mineralization. The studied apatite samples identified as fluorapatite, display identical contents of F (2.04-3.25 wt%), whereas distinctive variations of Cl (0.04-1.42 wt%). The different correlations between Sr contents and (La/ Yb) N , (La/Sm) N , and (Sm/Yb) N reflect the differentiation process of the magma evolution in the Xuancheng area. Furthermore, the negative Eu/Eu* and Ce/Ce* correlation, and high log fO 2 values (-10.02 to -17.40) of apatite studied, further indicate more oxidized and moderate oxidized environments. Apatite chemistry is characterized by LREE enriched patterns and has high (La/Yb) N ratios with a moderate negative Eu anomaly, suggesting that these plutons originated from enriched mantle mixing with various degrees of crustal components. Meanwhile, the visible differences in apatites among skarn Cu fertile, Cu-Mo fertile, and Cu-W fertile plutons were attributed to distinctive source affinities that ultimately control their metal endowments. Also, our study demonstrates that the Cl, F/Cl, and Eu/Eu* ratios in apatite can act as powerful pointers for ore varieties and mineral exploration.