Understanding the mobility of tin (Sn) in magmatic-hydrothermal systems is crucial for unraveling the mechanisms leading to the formation of tin ore deposits. The partitioning of Sn between melt and fluid phases, along with its solubility in either phase, plays a key role in controlling Sn enrichment; yet, these processes remain poorly constrained. Most experimental studies on Sn partitioning and the solubility of Sn in the melt phase rely on quenched samples, where rapid cooling may alter phase equilibria and metal distribution [1], [2], [3]. In contrast, in situ approaches enable direct observation of metal behavior under relevant P-T conditions, minimizing post-experimental modifications. Nevertheless, in situ data on both Sn partitioning and solubility remain scarce [4], [5].  

Here, we address this knowledge gap by utilizing the HDAC in conjunction with Synchrotron X-ray fluorescence (XRF) to directly probe the local distribution of tin between coexisting granitic melts and saline aqueous fluids at magmatic-hydrothermal conditions (< 890 °C and 10 kbar). These experiments reveal a higher affinity of tin for the silicate melt phase under oxidizing conditions, as well as the effects of temperature and salinity on the partition coefficients. Complementary solubility experiments were conducted using an HDAC coupled with a microscope and Raman system to investigate cassiterite dissolution in aqueous fluids (±SiO₂, ±NaCl, ±HCl). The implications of these results for tin extraction from magmatic intrusions and the tin budget of magmatic fluids in ore-forming environments will be discussed.