Most of the global Sn resources are from granite-related ore deposits, which form in response to cassiterite precipitation from hydrothermal fluids. However, the physical and chemical controls on the efficiency of Sn extraction from upper crustal plutons by exsolving magmatic fluids are still unclear. In this study, we determine the partition coefficient of Sn between aqueous fluids and granitic melts (${\mathrm{D}}_{\mathrm{S}\mathrm{n}}^{\mathrm{f}\mathrm{l}\mathrm{u}\mathrm{i}\mathrm{d}/\mathrm{m}\mathrm{e}\mathrm{l}\mathrm{t}}$) at 800 °C, 150 MPa and the fO₂ of the Ni-NiO buffer. To obtain equilibrium partition coefficients, a new experimental method has been used relying on local equilibrium between silicate melt and microscopic-sized fluid bubbles. The latter formed synthetic fluid inclusions in the quenched glasses, which in turn were analyzed by laser ablation inductively coupled plasma mass spectrometry along with the enclosing glass. The results show that at constant aluminum saturation index (ASI = 1.05-1.08) of the silicate melt, ${\mathrm{D}}_{\mathrm{S}\mathrm{n}}^{\mathrm{f}\mathrm{l}\mathrm{u}\mathrm{i}\mathrm{d}/\mathrm{m}\mathrm{e}\mathrm{l}\mathrm{t}}$ increases from 1.9 to 35.0 as the total Cl concentration (m_Cl^total) in fluid increases from 1.0 to 16.6 mol/kg H₂O. At a fixed m_Cl^total = 2 mol/kg H₂O, $D_{\mathit{Sn}}^{\mathit{fluid}/melt}$ increases from 4.3 to 10.6 as the HCl concentration in the solution increases from 0.15 to 0.79 mol/kg H₂O, which in turn is a function of the ASI of the melt (ASI = 1.06-1.29). Numerical modeling suggests that Sn is extracted by magmatic fluids from upper crustal plutons most efficiently at the late stage of crystallization and degassing. At a similar degree of crystallization, granitic magma with lower initial water concentration and higher ASI will separate a fluid phase with higher Sn concentration and thus has higher Sn mineralization potential. Due to the relatively high ${\mathrm{D}}_{\mathrm{S}\mathrm{n}}^{\mathrm{f}\mathrm{l}\mathrm{u}\mathrm{i}\mathrm{d}/\mathrm{m}\mathrm{e}\mathrm{l}\mathrm{t}}$ value, fluids exsolved from highly evolved magmas can sequester enough Sn to form Sn deposits and the sub-solidus remobilization of Sn from granite bodies is not a pre-requisite for ore genesis.

大多数全球锡资源来自与花岗岩相关的矿床，这些矿床是响应热液中锡石沉淀形成的。然而，岩浆流体溶出对上地壳岩体提取锡效率的物理和化学控制尚不清楚。在这项研究中，我们确定了 Sn 在水性流体和花岗岩熔体之间的分配系数（${\mathrm{D}}_{\mathrm{秒}\mathrm{n}}^{\mathrm{F}\mathrm{升}\mathrm{你}\mathrm{一世}\mathrm{d}/\mathrm{米}\mathrm{电子}\mathrm{升}\mathrm{吨}}$) 在 800 °C、150 MPa 和Ni-NiO 缓冲液的f O ₂下。为了获得平衡分配系数，一种新的实验方法依赖于硅酸盐熔体和微观流体气泡之间的局部平衡。后者在淬火玻璃中形成合成流体夹杂物，然后通过激光烧蚀电感耦合等离子体质谱法与封闭玻璃一起分析。结果表明，在恒定铝饱和指数（ASI = 1.05-1.08）的硅酸盐熔体下，${\mathrm{D}}_{\mathrm{秒}\mathrm{n}}^{\mathrm{F}\mathrm{升}\mathrm{你}\mathrm{一世}\mathrm{d}/\mathrm{米}\mathrm{电子}\mathrm{升}\mathrm{吨}}$随着流体中总 Cl 浓度（m _Cl^总量）从 1.0 增加到 16.6 mol/kg H ₂ O，从 1.9 增加到 35.0 。在固定的 m _Cl^总量= 2 mol/kg H ₂ O 下，$D_{\mathit{锡}}^{\mathit{体液}/米\mathrm{电子}升吨}$随着溶液中 HCl 浓度从 0.15 增加到 0.79 mol/kg H ₂ O，它从 4.3 增加到 10.6 ，而这又是熔体 ASI 的函数（ASI = 1.06-1.29）。数值模拟表明，在结晶和脱气后期，岩浆流体从上地壳岩体中提取 Sn 的效率最高。在相似的结晶度下，具有较低初始水浓度和较高 ASI 的花岗岩岩浆将分离出具有较高 Sn 浓度的流体相，因此具有较高的 Sn 矿化潜力。由于相对较高${\mathrm{D}}_{\mathrm{秒}\mathrm{n}}^{\mathrm{F}\mathrm{升}\mathrm{你}\mathrm{一世}\mathrm{d}/\mathrm{米}\mathrm{电子}\mathrm{升}\mathrm{吨}}$ 价值，从高度演化的岩浆中溶出的流体可以螯合足够的 Sn 以形成 Sn 沉积物，并且 Sn 从花岗岩体中的亚固相线再动员并不是矿石成因的先决条件。