The quartz-vein type scheelite deposits distributed in the Hunchun SN-trending gold-copper-tungsten belt in eastern Yanbian, Jilin Province, are a group of recent discovery for the past decade. To determine properties of the ore-forming fluids and the mineralization mechanism, in situ laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) rare earth elements (REE) analysis of the ore mineral scheelite was carried out for the selected Yangjingou and Sidaogou scheelite deposits in this metallogenic belt. The results showed that the substitution of REE³⁺ for Ca²⁺ in scheelite from the Yangjingou scheelite deposit can be accounted for the substitution mechanism: 3Ca²⁺ = 2REE³⁺ + □Ca (where □ is a site vacancy). It shows a slightly right-dipped flat REE pattern with distinct positive Eu anomalies. The Sidaogou scheelite deposit, completes the substitution via the 2Ca²⁺ = REE³⁺ + Na⁺ and Ca²⁺ + W⁶⁺ = REE³⁺ + Nb⁵⁺ mechanisms. It shows left-dipped REE pattern with relative enrichment of MREEs (mainly Dy) with negative Eu anomalies in the scheelite core and no or insignificant positive Eu anomalies in the scheelite rim. By comparing with the REE of granites which are close related to mineralization in the area, the ore-forming fluids of these two scheelite deposits are determined to be mainly derived from magmatism. The inapparent correlation between Eu_N and Eu*_N of the Yangjingou scheelite deposit and the high Eu_N/Eu*_N values indicate that its ore-forming fluids are reducing fluids. Its strong positive Eu anomalies are not entirely inherited from the mineralized tonalite, but is due to the release of Eu from the water-rock reaction. The good correlation between Eu_N and Eu*_N and the low Eu_N/Eu*_N values in the Sidaogou scheelite deposit indicate that the ore-forming fluids are oxidizing fluids. This may be caused by the mixing of the original magmatic fluid with a large amount of meteoric water. This study suggests that the water-rock reaction is an important mineralization mechanism for the quartz vein-type scheelite deposits in eastern Yanbian. In addition, fluid mixing is also important for the Sidaogou scheelite deposit. All these mechanisms influence the REE compositional characteristics of scheelite. The initial ore-bearing fluids metasomatized the metamorphic rocks of Wudaogou Group, resulting in water-rock reaction, and enriched ore-forming materials such as Ca and W. As the ore-forming fluids migrated upward along the NW-trending structures, the escape of CO₂ and CH₄ caused by the tectonic decompression disrupted the physiochemical balance of the ore-forming fluid system, catalyzed the combination of Ca²⁺ and WO₄²⁻, resulting in the precipitation and enrichment of the scheelite.

中文翻译：

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延边东部石英脉型白钨矿成矿流体特征——来自洋井沟和四道沟矿床原位LA-ICP-MS稀土元素的证据

分布在吉林省延边东部珲春SN向金铜钨带的石英脉型白钨矿是近十年新发现的一组矿床。为了确定成矿流体的性质和成矿机制，对选定的矿石矿物白钨矿进行了原位激光烧蚀-电感耦合等离子体质谱（LA-ICP-MS）稀土元素（REE）分析。该成矿带中的洋井沟和四道沟白钨矿床。结果表明，洋金沟白钨矿床中的稀土元素³⁺取代了Ca ²⁺可以解释其取代机制：3Ca ²⁺  = 2REE ³⁺+ □Ca（其中□是场地空缺）。它显示了一个略微向右倾斜的平坦 REE 模式，具有明显的正 Eu 异常。四道沟白钨矿通过2Ca ²⁺  = REE ³⁺ + Na ⁺和Ca ²⁺ + W ⁶⁺  = REE ³⁺ + Nb ^{5+完成置换}机制。它显示了左倾 REE 模式，MREEs（主要是 Dy）相对富集，在白钨矿芯中具有负 Eu 异常，而在白钨矿边缘没有或不显着的 Eu 正异常。通过与该地区与成矿作用密切相关的花岗岩的稀土元素含量比较，确定这两个白钨矿床的成矿流体主要来源于岩浆作用。_{阳金沟白钨矿床Eu N}和Eu* _N与高Eu _N /Eu* _N相关性不明显值表明其成矿流体为还原流体。其强烈的正Eu异常并不完全来自矿化的云母岩，而是由于Eu从水-岩反应中释放出来的。_{Eu N}和 Eu* _N之间的良好相关性和低 Eu _N /Eu* _N四道沟白钨矿床的数值表明成矿流体为氧化流体。这可能是原始岩浆流体与大量大气水混合造成的。研究表明，水岩反应是延边东部石英脉型白钨矿床的重要成矿机制。此外，流体混合对四道沟白钨矿也很重要。所有这些机制都会影响白钨矿的 REE 组成特征。初始含矿流体交代五道沟群变质岩，发生水岩反应，富集Ca、W等成矿物质。随着成矿流体沿NW向构造向上运移，逃逸CO ₂和 CH ₄构造减压破坏了成矿流体体系的理化平衡，催化Ca ²⁺与WO ₄ ^2-结合，导致白钨矿沉淀富集。