Tin (Sn) and tungsten (W) behave incompatibly in reduced magmatic systems and may become enriched in late highly-evolved melts. Nonetheless, Sn and W rarely concentrate in the same deposit. In deposits formed by Sn- and W-bearing granites, this separation may be due to the contrasting behavior of Sn and W during exsolution of a magmatic fluid or the scavenging of Sn by silicate minerals. We illustrate the separation of Sn and W for the world-class Zhuxi W skarn deposit (South China). Although tin orebodies have not yet been identified within the Zhuxi deposit, tiny (commonly < 20 μm) cassiterite grains are widespread within the endoskarn and the retrogressed exoskarn. We analyzed the W and Sn contents of the magmatic minerals biotite and ilmenite in ore-forming granites and the prograde anhydrous skarn minerals garnet, pyroxene and vesuvianite. Our data show that (i) magmatic ilmenite (65.5–79.1 ppm Sn; 8.7–14.3 ppm W) and biotite (109–120 ppm Sn; 1.3–6.3 ppm W) from biotite monzogranite strongly enrich Sn relative to W, implying that W partitioned more strongly into the magmatic fluids than Sn, (ii) there is 100 Kt non-recoverable Sn within the Zhuxi deposit in addition to the certified 3.44 Mt WO₃ reserves, and (iii) W is mainly hosted in scheelite, whereas Sn is dominantly sequestered in prograde skarn minerals, most importantly garnet (76–4086 ppm Sn, < 42 ppm W), pyroxene (3–103 ppm Sn, < 1 ppm W), and vesuvianite (43–361 ppm Sn, < 2 ppm W). The formation of secondary cassiterite requires the release of silicate-bound Sn by alteration of primary skarn minerals, which depends on the availability of magmatic or metamorphic fluids. Deep-seated granites such as those associated with the Zhuxi skarn deposit, which crystallized at 5 km to 12.6 km depth, do not release or mobilize copious amounts of fluid. Therefore, the Zhuxi deposit, like other deep-seated reduced skarn systems shows little alteration and most Sn remains in silicate minerals and is economically non-recoverable. Thus, reduced, deep-seated W skarn systems are unlikely to have associated Sn orebodies even if significant amounts of Sn are present.

锡（Sn）和钨（W）在还原岩浆系统中表现不相容，并且可能在晚期高度演化的熔体中富集。尽管如此，Sn和W很少集中在同一矿床中。在由含 Sn 和 W 的花岗岩形成的矿床中，这种分离可能是由于岩浆流体溶出过程中 Sn 和 W 的对比行为或硅酸盐矿物对 Sn 的清除所致。我们举例说明了世界级朱溪钨矽卡岩矿床（华南）的锡和钨的分离情况。尽管朱溪矿床内尚未发现锡矿体，但在内皮卡岩和退积的外皮卡岩中广泛存在微小（通常< 20 μm）的锡石颗粒。分析了成矿花岗岩中岩浆矿物黑云母、钛铁矿和前生无水矽卡岩矿物石榴石、辉石、伏苏云石的W、Sn含量。我们的数据表明，(i) 岩浆钛铁矿 (65.5–79.1 ppm Sn；8.7–14.3 ppm W) 和来自黑云二花岗岩的黑云母 (109–120 ppm Sn；1.3–6.3 ppm W) 相对于 W 而言，强烈富集 Sn，这意味着 W比锡更强烈地分配到岩浆流体中，(ii) 除了已认证的 3.44 Mt WO ₃储量外，朱溪矿床内还有 100 Kt 不可采锡，以及 (iii) W 主要赋存于白钨矿中，而 Sn 则主要存在于白钨矿中。主要存在于顺积夕卡岩矿物中，最重要的是石榴石（76–4086 ppm Sn，< 42 ppm W）、辉石（3–103 ppm Sn，< 1 ppm W）和维苏威石（43–361 ppm Sn，< 2 ppm W） ）。次生锡石的形成需要通过原生夕卡岩矿物的蚀变来释放硅酸盐结合的锡，这取决于岩浆或变质流体的可用性。深部花岗岩，例如与朱溪夕卡岩矿床有关的花岗岩，在 5 公里至 12.6 公里深度结晶，不会释放或移动大量流体。因此，与其他深部还原矽卡岩体系一样，朱溪矿床几乎没有发生蚀变，大部分锡仍保留在硅酸盐矿物中，在经济上是不可回收的。因此，即使存在大量的锡，还原性的深部钨矽卡岩系统也不太可能有相关的锡矿体。