Geochemical Indicators of the Peraluminous W-Cu-Mo-(±Sn-Li-Ta-Nb) Granites in Dahutang Orefield in Northern Jiangxi and Their Significance for Exploration

The origin of Mesozoic granites associated with the Dahutang W-Cu-Mo orefield in north Jiangxi, which host the world’s second largest tungsten deposit, remains a compelling subject despite extensive geochemical and geochronological studies. In this contribution we present new wolframite mineral and bulk-rock geochemistry and monazite U-Pb ages for the Mesozoic granites in aiming to enhance our understanding the petrogenesis of these granites and its coupling relationship with the mineralization. Two magmatic phases and four types of rocks in study area are identified, i.e., the early stage (152-147 Ma) biotite (G1) granite and the late stage (144-130 Ma) two-mica (G2)＋muscovite (G3)＋albite (G4) granite series. These two magmatic phases are temporally coincident with two mineralization stages (~150 Ma and 139-144 Ma). All the Mesozoic granites share the characteristics of high silica content, peraluminosity (A/CNK > 1.1), and low Zr+Nb+Ce+Y values (< 200 ppm), and they are derived from the partial melting of a Proterozoic crustal source. Specifically, the G1 granite, characterized by relatively high MgO (~0.5%), CaO (~1%), and low P₂O₅(0.13%-0.20%), is classified as an I-type granite. It formed via a relatively higher degree of partial melting at ~766°C (Zr saturation temperatures) driven by biotite breakdown reactions, with minor contributions from mantle-derived materials. In contrast, the G2–G4 granites series exhibits typical peraluminous S-type granite features, such as high Al₂O₃, Na₂O, and P₂O₅ (mostly >0.2%) contents, and low Sr and Ba contents. They are products of low-degree partial melting that occurred under conditions close to muscovite breakdown at ~735°C. Additionally, both granites show clear geochemical evidence of fluid interaction, as reflected by their elevated trace element and volatile contents: Sn>30 ppm, Cs >35 ppm, F >0.4%, Li >250 ppm, W 10–1000 ppm, Rb >500 ppm, K/Rb values < 150, and Nb/Ta< 5. The G1 granite represents a moderately fractionated melt relative to chondrites, as evidenced by its near-chondritic Zr/Hf (22.6-34.1) and Y/Ho (24.5-31.5) ratios, indicating a weaker influence of magmatic fluid-melt interaction. For the G2-G4 granites, however, intense crystal fractionation and late-stage fluid-melt interaction are well-documented by their highly variable and low ratios of Y/Ho (14.8-41.4), Nb/Ta (0.89-5.57), Zr/Hf (8.84-41.67), and K/Rb (13.96-128.29). In the long-lived, reduced, and volatile-rich aqueous environment of the G2–G4 magmas, fractional crystallization and albitization collectively enhanced the solubility and hydrothermal transport capacity of W, Sn, Li, Nb, and Ta by multiple orders of magnitude. In contrast, in the earlier, more oxidized G1 magma (which incorporated mantle materials), the exsolution and hydrothermal transport of Cu and Mo were associated with localized greisenization, but their capacity diminished with fractional crystallization. Historically, mineral exploration in the Dalutang mining area has focused primarily on W, Cu, and Mo. Based on this research, we conclude that there is significant mineral potential for rare metals (particularly Sn, Li, and Ta), and future surveys should prioritize areas adjacent to the evolved G2–G4 peraluminous leucogranites to search for new concealed mineral occurrences.