Differentiating W and W–Sb mineralization in the Xuefeng Uplift, South China: An integrated study of scheelite geochemistry

The Xuefeng Uplift Belt in Hunan Province, South China, represents a transitional metallogenic domain between the Nanling Region and Jiangnan Orogen, hosting a series of Au–Sb–W polymetallic deposits formed under contrasting metamorphic and magmatic-hydrothermal regimes. To elucidate the compositional diversity and genetic mechanisms of scheelite in this transitional zone, we conducted an integrated in situ geochemical investigation of scheelites from five representative deposits, covering both metamorphic-related and granite-related systems. In situ laser-ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS) trace-element analyses combined with multivariate statistical approaches reveal that scheelites from these deposits can be clearly discriminated by systematic variations in Mn, Sr, Pb, Ga, Na, Nb, Y, and rare earth elements (REEs). Three major substitution mechanisms, (1) 2Ca2+ ↔ REE3+ + Na+, (2) Ca2+ + W6+ ↔ REE3+ + Nb5+, and (3) 3Ca2+ ↔ 2REE3+ + □Ca, govern REE incorporation into scheelites, with differing dominance between deposit types. The Woxi and Zhazixi scheelites, which are characterized by low Mn contents and weak Eu anomalies, crystallized from oxidizing, low-salinity metamorphic fluids of crustal origin. In contrast, scheelites from Darongxi and Chuankou exhibit strong positive Eu anomalies, high Mn and Nb/Ta ratios, and evidence for reducing, high-salinity, F-rich magmatic-hydrothermal fluids influenced by crust–mantle interaction. The Huxingshan scheelites display transitional geochemical signatures, suggesting fluid mixing between metamorphic and magmatic-hydrothermal components during ore formation. These differences define two dominant endmember metallogenic regimes: (1) a crustal-metamorphic system related to Paleozoic compressional deformation and (2) a magmatic-hydrothermal system linked to Mesozoic crustal extension and granitic magmatism. The results demonstrate that scheelite geochemistry effectively records the difference between metamorphic and magmatic-hydrothermal tungsten systems within the Xuefeng Uplift Belt. The findings highlight the crucial role of fluid evolution, redox conditions, and metal sources in tungsten polymetallic systems, offering a robust framework for understanding large-scale W metallogenesis in South China.