The Baquan uranium deposit is one of the hydrothermal uranium deposits in the Xiangshan volcanic uranium ore field and is hosted in subvolcanic granitic porphyry rocks (GPRs). To constrain sources of the hydrothermal fluids and metals for alteration and mineralisation, respectively, we analysed the chemical compositions of chlorites and pyrites formed during alteration and mineralisation processes, in-situ sulfur isotope compositions of pyrites, whole-rock compositions and sulfur and molybdenum isotopes of the least-altered and altered GPRs, and mineralised GPRs (i.e. uranium ores). The results show distinct differences in mineralogical and geochemical features of the hydrothermally altered GPRs and uranium ores, which are as follows: (1) In the altered GPRs, hydrothermal chlorites (chlorite-I) are mainly daphnite with higher Fe/(Fe + Mg) (0.70–0.75) but lower Fe³⁺/Fe²⁺ (∼0.014), and hydrothermal pyrites (pyrite-I) have low Co and Ni contents (<0.05% and <0.04%, respectively) and a narrow range of δ³⁴S (9.11–9.87‰). In contrast, hydrothermal chlorites (chlorite-II) in the ores are ripidolite and brunsvigite with lower Fe/(Fe + Mg) (0.43–0.62) but higher Fe³⁺/Fe²⁺ (∼0.056), and hydrothermal pyrites (pyrite-II) have high Co and Ni contents (0.02–0.3% and 0.01–0.11%, respectively) and a wide range of δ³⁴S values (2.32–13.8‰). (2) The altered GPRs have Zr and Hf contents (135–187 ppm and 3.39–4.34 ppm, respectively) similar to those of the least-altered GPRs (162–169 ppm, and 3.79–4.01 ppm, respectively), whereas the ores have elevated Zr and Hf contents (184–548 ppm and 4.17–11.6 ppm, respectively). (3) The δ⁹⁸Mo values of the altered GPRs (0.39–0.99‰) and uranium ores (0.52–1.74‰) show contrasting correlations with K₂O or Na₂O contents. These differences suggest that hydrothermal alteration and mineralisation in the Baquan deposit may have been caused by two fluids of different origins. Based on these characteristics and comparisons with possible sources, we suggest that the fluid responsible for the alteration of GPRs most likely originated from the subducting slab, whereas the mineralising fluid forming the Baquan uranium deposit likely originated from the brine of a nearby Cretaceous basin. The uranium in the deposit mainly originated through leaching of the volcanic rocks by the brine-derived hydrothermal fluid.

八泉铀矿床是象山火山铀矿田的热液铀矿床之一，赋存于亚火山花岗斑岩（GPRs）中。为了分别约束蚀变和成矿的热液流体和金属的来源，我们分析了蚀变和成矿过程中形成的绿泥石和黄铁矿的化学成分、黄铁矿的原位硫同位素组成、全岩成分以及硫和钼的同位素最少改变和改变的探地雷达和矿化探地雷达（即铀矿石）。结果表明，热液蚀变探地雷达和铀矿在矿物学和地球化学特征上存在明显差异，具体表现为：(1)蚀变探地雷达中热液绿泥石(绿泥石-I)主要为具有较高Fe/(Fe + Mg ) (0.70–0。³⁺ /Fe ²⁺ (∼0.014) 和热液黄铁矿 (黄铁矿-I) 的 Co 和 Ni 含量低（分别<0.05% 和 <0.04%），δ ³⁴ S 的范围很窄（9.11–9.87‰） . 相比之下，矿石中的热液绿泥石（绿泥石-II）是具有较低 Fe/(Fe + Mg) (0.43–0.62) 但较高 Fe ³⁺ /Fe ²⁺ (~0.056) 和热液黄铁矿（黄铁矿-II) 具有高 Co 和 Ni 含量（分别为 0.02–0.3% 和 0.01–0.11%）和宽范围的 δ ³⁴S 值 (2.32–13.8‰)。(2) 改变的 GPR 的 Zr 和 Hf 含量（分别为 135-187 ppm 和 3.39-4.34 ppm）与那些变化最小的 GPR（分别为 162-169 ppm 和 3.79-4.01 ppm）相似，而矿石的 Zr 和 Hf 含量升高（分别为 184-548 ppm 和 4.17-11.6 ppm）。(3)蚀变的探地雷达(0.39–0.99‰)和铀矿(0.52–1.74‰ )的δ ⁹⁸ Mo值与K ₂ O或Na ₂显示出对比性相关性哦内容。这些差异表明八泉矿床的热液蚀变和成矿可能是由两种不同来源的流体引起的。基于这些特征以及与可能来源的比较，我们认为导致 GPR 蚀变的流体最有可能来自俯冲板片，而形成八泉铀矿床的矿化流体可能来自附近白垩纪盆地的卤水。矿床中的铀主要来源于卤水热液对火山岩的淋溶作用。