The Geyer tin skarn in the Erzgebirge, Germany, comprises an early skarnoid stage (stage I, ~ 320 Ma) and a younger metasomatic stage (stage II, ~ 305 Ma), but yet, the source and distribution of Sn and the physicochemical conditions of skarn alteration were not constrained. Our results illustrate that contact metamorphic skarnoids of stage I contain only little Sn. REE patterns and elevated concentrations of HFSE indicate that garnet, titanite and vesuvianite of stage I formed under rock-buffered conditions (low fluid/rock ratios). Prograde assemblages of stage II, in contrast, contain two generations of stanniferous garnet, titanite-malayaite and vesuvianite. Oscillation between rock-buffered and fluid-buffered conditions are marked by variable concentrations of HFSE, W, In, and Sn in metasomatic garnet. Trace and REE element signatures of minerals formed under high fluid/rock ratios appear to mimic the signature of the magmatic-hydrothermal fluid which gave rise to metasomatic skarn alteration. Concomitantly with lower fluid-rock ratio, tin was remobilized from Sn-rich silicates and re-precipitated as malayaite. Ingress of meteoric water and decreasing temperatures towards the end of stage II led to the formation of cassiterite, low-Sn amphibole, chlorite, and sulfide minerals. Minor and trace element compositions of cassiterite do not show much variation, even if host rock and gangue minerals vary significantly, suggesting a predominance of a magmatic-hydrothermal fluid and high fluid/rock ratios. The mineral chemistry of major skarn-forming minerals, hence, records the change in the fluid/rock ratio, and the arrival, distribution, and remobilization of tin by magmatic fluids in polyphase tin skarn systems.

德国厄尔士山脉的盖尔锡矽卡岩包括早期的矽卡岩阶段（第一阶段，约320 Ma）和较年轻的交代阶段（第二阶段，约305 Ma），但目前对锡的来源和分布以及理化条件尚不了解。矽卡岩蚀变没有受到限制。我们的结果表明，第一阶段的接触变质矽卡岩只含有很少的锡。稀土元素模式和 HFSE 浓度升高表明，第一阶段的石榴石、钛矿和维苏威矿是在岩石缓冲条件（低流体/岩石比）下形成的。相比之下，第二阶段的顺积组合包含两代含锡石榴石、钛铁矿-马拉雅石和维苏威石。岩石缓冲和流体缓冲条件之间的振荡以交代石榴石中 HFSE、W、In 和 Sn 浓度的变化为标志。在高流体/岩石比率下形成的矿物的痕量和稀土元素特征似乎模仿了引起交代夕卡岩蚀变的岩浆-热液流体的特征。伴随着较低的流体-岩石比，锡从富锡硅酸盐中被重新活化并以马来亚石的形式重新沉淀。第二阶段末期大气水的进入和温度下降导致锡石、低锡角闪石、绿泥石和硫化物矿物的形成。即使母岩和脉石矿物变化很大，锡石的微量和微量元素成分也没有表现出太大的变化，这表明岩浆热液占主导地位并且流体/岩石比率较高。因此，主要形成夕卡岩矿物的矿物化学记录了流体/岩石比率的变化，以及多相锡夕卡岩系统中岩浆流体对锡的到达、分布和再活化。