Southeastern (SE) Yunnan is a major Sn polymetallic province of China, with the Dulong large Sn-Zn polymetallic deposit (in the Laojunshan orefield) being one of the most representative deposits. Our recent work had first identified helvine-group minerals in this deposit. These minerals mainly occur in massive sphalerite ores, and coexist with sphalerite, pyrrhotite, biotite, talc, cassiterite, and fluorite. Raman spectroscopic, X-ray diffraction (XRD), scanning electron microscopic (SEM), and electron probe microanalysis (EPMA) analyses indicate that these helvine-group minerals are oscillatory-zoned helvine-danalite. Both the helvine and danalite zones are mixed with varying proportion of the other helvine-group end-member, and our studies indicate that the oscillatory zoning was formed mainly by periodic fluctuations of the fluid physicochemical conditions (notably fS2 and fO2), but less related to the variation of the fluid Mn, Fe, and Zn contents. The helvine zone was likely formed in a higher fS2 but lower fO2 environment than the danalite zone. In this study, we present the first LA-ICP-MS in situ trace element data for the helvine-danalite minerals from Dulong, and the results indicate that the helvine has considerably high contents and a wide range of trace elements. The helvine is rich in Ca, Al, Sc, and Y, while the danalite is rich in Sn and P (reaching thousands of parts per million). Such trace element enrichments are likely controlled by their respective ionic size and chalcophile behavior.Meanwhile, the fO2 and fS2 conditions during the zoning formation may have also influenced the trace element distributions: trace elements may have mainly entered the helvine-group minerals by substituting into the M-sites in M4[BeSiO4]3S, for instance Al, Sc, and Y substitute for Mn, and Sn and Mg for Fe and Zn. It is noteworthy that the helvine and danalite zones are all HREE-enriched and have distinct negative Eu anomalies. This may be related to the high fluid F-Y-P contents during the mineral formation. High-F-Y fluids can readily incorporate HREEs into helvine-group minerals, and phosphates incorporate HREEs more readily in alkali fluids. Europium occurs as Eu2+ in the fluid, causing the negative Eu anomalies observed. We have also identified grains of cassiterite in the helvine-group minerals and its coexisting sphalerite. U-Pb dating on these cassiterite grains yielded 86.5 ± 1.6 Ma, coeval with the reported sulfide mineralization age. This indicates that both the Be and Sn-Zn polymetallic mineralization occurred in the Cretaceous, and may have been products of the Late Yanshanian Laojunshan magmatic-hydrothermal activity. Considering the close relations with many W(-Be) deposits nearby (e.g., Nanyangtian, Saxi, and Maka), the Laojunshan orefield may also have substantial Be mineralization potential.

中文翻译：

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滇东南独龙锡锌多金属矿床长方石矿物学

云南东南部是我国重要的锡多金属大省，独龙大型锡锌多金属矿床（老君山矿区）是最具代表性的矿床之一。我们最近的工作首先确定了该矿床中的海尔文族矿物。这些矿物主要产于块状闪锌矿中，与闪锌矿、磁黄铁矿、黑云母、滑石、锡石、萤石共存。拉曼光谱、X 射线衍射 (XRD)、扫描电子显微镜 (SEM) 和电子探针显微分析 (EPMA) 分析表明，这些海尔文族矿物是振荡带状海尔文-丹那石。helvine 和 danalite 区都与不同比例的其他 helvine 组末端成员混合，我们的研究表明，振荡区带主要是由流体物理化学条件（特别是 fS2 和 fO2）的周期性波动形成的，但与流体 Mn、Fe 和 Zn 含量的变化相关性较小。与丹拿岩区相比，赫尔文区可能是在 fS2 较高但 fO2 较低的环境中形成的。在本研究中，我们首次展示了独龙山海藻石矿物的 LA-ICP-MS 原位微量元素数据，结果表明海海石矿具有相当高的含量和广泛的微量元素。Helvine 富含 Ca、Al、Sc 和 Y，而 danalite 富含 Sn 和 P（达到百万分之千）。这种微量元素富集可能受它们各自的离子大小和嗜热行为控制。同时，分带形成过程中的 fO2 和 fS2 条件也可能影响微量元素的分布：微量元素可能主要通过置换到 M4[BeSiO4]3S 中的 M 位点进入赫尔文族矿物，例如 Al、Sc 和Y 代替 Mn，Sn 和 Mg 代替 Fe 和 Zn。值得注意的是，海尔文和丹拿岩带均富含高稀土元素，并具有明显的负Eu异常。这可能与矿物形成过程中流体 FYP 含量高有关。高 FY 流体可以很容易地将高稀土元素结合到海尔文族矿物中，而磷酸盐更容易将高稀土元素结合到碱性流体中。铕在流体中以 Eu2+ 的形式出现，导致观察到的 Eu 负异常。我们还在赫尔文族矿物及其共存闪锌矿中发现了锡石晶粒。这些锡石晶粒的 U-Pb 测年产生了 86.5 ± 1.6 Ma，与报道的硫化物成矿年龄同时发生。这表明Be和Sn-Zn多金属矿化均发生在白垩纪，可能是燕山晚期老君山岩浆热液活动的产物。考虑到与附近许多 W(-Be) 矿床（如南洋田、萨西和马卡）的密切关系，老君山矿田也可能具有相当大的 Be 成矿潜力。