Micrometer- to submicrometer-scale indium-rich domains are preserved within sphalerite included in hornfels-hosted pyrrhotite from the Dulong polymetallic skarn, Yunnan, China. The nano-mineralogy of the ZnS-bearing blebs was investigated using scanning transmission electron microscopy on thinned foils extracted in situ from pyrrhotite. Indium incorporation in sphalerite occurs via the coupled substitution 2Zn2+ ↔ Cu+ + In3+; the results thus allow insights into phase relationships in the system ZnS-CuInS2 in which solubility limits are debated with respect to a cubic to tetragonal phase transition. The highest concentrations of In are measured in basket-weave domains from the smallest ZnS blebs or from un-patterned areas in coarser, irregular ZnS inclusions in pyrrhotite. Indium-rich domains contain 17–49 mol% CuInS2, whereas In-poor sphalerite contains <5 mol% CuInS2. Atomic-scale metal ordering observed in In-(Cu)-rich ZnS domains was modeled as mixed sites in a cubic structure with P43m symmetry and empirical formula [(Cu,In,Zn)3(Zn0.5Fe0.5)]4S4. This sphalerite modification is distinct from the cubic-tetragonal phase transition reported elsewhere for analogous, synthetic phases with abundant planar defects. The Zn1.5Fe0.5CuInS4 nanophase described here potentially represents a Fe-bearing polymorph of Zn2CuInS4, considered as an end-member in the sakuraiite solid-solution series. At ≤50 mol% CuInS2 in the ZnS-CuInS2 system, incorporation of In via coupled In+Cu substitution is promoted within a cubic ZnS phase with lower symmetry than sphalerite rather than into the spatially coexisting chalcopyrite of tetragonal symmetry. Solid-state diffusion accounts for phase re-equilibration resulting in the basket-weave textures typical of In-(Cu)-rich domains in the smallest blebs, whereas fluid percolation assists grain coarsening in the irregular inclusions. The results show evidence for the existence of a more complex phase transition than previously recognized from experimental studies, and, intriguingly, also to a potential eutectic in the system ZnS-CuInS2. Pyrrhotite-bearing hornfels in skarns may concentrate In and other critical metals hosted in sphalerite and related sulfides due to the efficient scavenging from fluid by these minerals and the subsequent preservation of those included phases by sealing within the pyrrhotite matrix.

中文翻译：

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ZnS-CuInS2系统中的相关系：含铟闪锌矿的纳米研究的启示

微米级至亚微米级的富铟域被保存在云南独龙族多金属矽卡岩的角铁型黄铁矿中的闪锌矿中。使用扫描透射电子显微镜对从黄铁矿现场提取的薄箔进行扫描，研究了含ZnS的气泡的纳米矿物学。闪锌矿中的铟掺入通过耦合取代2Zn2 +↔Cu + + In3 +发生；因此，结果可以洞悉ZnS-CuInS2系统中的相关系，其中关于立方到四方相变的溶解度极限受到争议。In的最高浓度是从最小的ZnS气泡或在黄铁矿中较粗，不规则的ZnS夹杂物的无图案区域中的篮状结构域中测得的。富铟域包含17–49 mol％CuInS2，而贫贫闪锌矿含有<5 mol％CuInS2。在富In-（Cu）的ZnS域中观察到的原子尺度金属有序建模为具有P43m对称性和经验公式[（Cu，In，Zn）3（Zn0.5Fe0.5）] 4S4的立方结构中的混合位点。这种闪锌矿变体不同于其他地方报道的类似的具有大量平面缺陷的合成相的立方四方相变。此处描述的Zn1.5Fe0.5CuInS4纳米相可能表示Zn2CuInS4的含铁多晶型物，被认为是樱红色固溶体系列的末端成员。在ZnS-CuInS2系统中，CuInS2≤50 mol％时，在立方ZnS相中以比闪锌矿低的对称性促进了通过耦合的In + Cu置换引入In，而不是在空间上共存的四方对称黄铜矿中。固态扩散说明了相的重新平衡，从而在最小的气泡中形成了In-（Cu）-富集区域中典型的篮状织构，而流体渗滤有助于不规则夹杂物中的晶粒粗化。结果表明存在比以前的实验研究更复杂的相变的证据，并且有趣的是，还存在于系统ZnS-CuInS2中的潜在共晶。由于这些矿物有效地清除了流体，并随后通过密封在黄铁矿基质中，对其中包括的相进行了保存，因此矽卡岩中的含滑铁矿的角铁可能会富集In和其他重要金属，这些金属将包含在闪锌矿和相关硫化物中。渗流有助于不规则夹杂物的晶粒粗化。结果表明存在比以前的实验研究更复杂的相变的证据，并且有趣的是，ZnS-CuInS2体系中还存在潜在的共晶。由于这些矿物有效地清除了流体，并随后通过密封在黄铁矿基质中，对其中包括的相进行了保存，因此矽卡岩中的含滑铁矿的角铁可能会富集In和其他重要金属，这些金属将包含在闪锌矿和相关硫化物中。渗流有助于不规则夹杂物的晶粒粗化。结果表明存在比以前的实验研究更复杂的相变的证据，并且有趣的是，还存在于系统ZnS-CuInS2中的潜在共晶。由于这些矿物有效地清除了流体，并随后通过密封在黄铁矿基质中，对其中包括的相进行了保存，因此矽卡岩中的含滑铁矿的角铁可能会富集In和其他重要金属，这些金属将包含在闪锌矿和相关硫化物中。