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扬子地块西南缘乌斯河富锗闪锌矿矿物标型特征与锗的替代机制

Typomorphic Characteristics of Germanium-Enriched Sphalerite Minerals and the Substitution Mechanism of Germanium from Wusihe in Southwestern Margin of the Yangtze Block

  • 摘要: 锗(Ge)是中国优势战略性关键金属之一,扬子地块西南缘乌斯河铅锌矿床是川—滇—黔成矿带的一个重要富锗铅锌矿床,其矿床成因仍存在争议,矿床中闪锌矿的标型特征是否影响Ge的富集程度与替代方式亟待进行解析。为探讨富Ge闪锌矿的标型特征及Ge的替代机制,本文通过显微镜下观察、显微分光光度计、激光剥蚀电感耦合等离子体质谱(LA-ICP-MS)等分析测试方法对其进行定量研究。结果表明该矿床热液期存在Ⅰ阶段颜色较深闪锌矿和Ⅱ阶段颜色较浅闪锌矿,视觉反射率均值分别为16.126%、16.187%,反射色主波段均值分别为474.179nm、474.164nm,反射色饱和度均值分别为0.048、0.043,Ge含量均值分别为244.33×10−6、43.22×10−6。通过对实验结果的总结认为,Ge以类质同象的形式存在于闪锌矿中,且更易在反射色饱和度高的闪锌矿中富集。Ge的替代方式与Cu、Ag有关,两阶段分别为Ge4++2Cu+↔3Zn2+、Ge4++2(Cu, Ag)+↔3Zn2+。富Ge闪锌矿的反射色颜色指数特征指示成矿温度上限为203.0~293.0℃,微量元素特征指示成矿温度下限为83.3~199.0℃,矿床成因类型为密西西比河谷型(MVT)铅锌矿床。

     

    Abstract: The Wusihe lead-zinc deposit, situated at the southwestern margin of the Yangtze Block and a prominent Ge-enriched deposit within the Sichuan—Yunnan—Guizhou lead-zinc metallogenic province, faces ongoing debates regarding its genesis. The influence of sphalerite typomorphic characteristics on Ge enrichment and substitution mechanisms within the deposit remains a crucial puzzle to unravel. To address this, our study employs quantitative analyses using microspectrophotometry and laser ablation inductively coupled plasma-mass spectrometry (LA-ICP-MS). Results reveal the presence of two sphalerite stages during the hydrothermal period: a darker Stage I and a lighter Stage II. Despite similar mean values for visual reflectance and the dominant wavelength of reflectance color, the mean reflectance color saturation differs (0.048 and 0.043, respectively), with corresponding average Ge contents of 244×10−6 and 43.2×10−6. The experimental outcomes conclude that Ge exists in sphalerite as isomorphism and is more concentrated in sphalerite with higher reflectance color saturation. The substitution of Ge is related to Cu and Ag, with two stages of Ge4++2Cu+ ↔ 3Zn2+, Ge4++2 (Cu, Ag)+↔ 3Zn2+. The ore-forming temperature is medium to low, classifying the deposit as a Mississippi Valley-type lead-zinc deposit. The BRIEF REPORT is available for this paper at http://www.ykcs.ac.cn/en/article/doi/10.15898/j.ykcs.202406210138.

     

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