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现代地质 ›› 2025, Vol. 39 ›› Issue (01): 194-208.DOI: 10.19657/j.geoscience.1000-8527.2025.007

• 宝石地质学 • 上一篇    下一篇

中国黔桂地区基性岩交代型软玉地球化学特征及成因

田冉婷(), 白峰(), 许玲玲, 李净净, 车延东, 杜季明   

  1. 中国地质大学(北京)珠宝学院,北京 100083
  • 出版日期:2025-02-10 发布日期:2025-02-20
  • 通信作者: 白 峰,男,博士,教授,1971年出生,主要从事宝石教学与科研工作。Email: baifeng@cugb.edu.cn
  • 作者简介:田冉婷,女,硕士研究生,2000年出生,材料与化工专业,主要从事宝石矿物学方向的研究。Email:2109220001@email.cugb.edu.cn
  • 基金资助:
    中国地质大学(北京)基科研费科研启动基金项目“国内新发现软玉矿床的成因及玉石矿物学特征研究”(35932011270)

Geochemical Characteristics and Genesis of Basaltic Metasomatic Nephrite in the Qiangui Region, China

TIAN Ranting(), BAI Feng(), XU Lingling, LI Jingjing, CHE Yandong, DU Jiming   

  1. School of Gemmology, China University of Geosciences (Beijing), Beijing 100083, China
  • Published:2025-02-10 Online:2025-02-20

摘要:

软玉作为重要的矿物资源,其地球化学特征对于理解矿床成因与评估资源潜力具有关键作用。本文选择贵州罗甸、广西大化和广西巴马地区的基性岩交代型软玉为研究对象,通过电子探针技术和激光剥蚀-电感耦合等离子体质谱法(LA-ICP-MS),对代表性软玉样品进行了系统的主微量及稀土元素含量分析。研究结果显示,黔桂地区基性岩交代型软玉的主要成分以SiO2、CaO和MgO为主,其平均含量低于透闪石矿物的理论值,而SiO2的整体含量高于超基性岩矿床,呈现出与围岩及后期热液硅供给密切相关的成矿特征。微量元素分析中,U、La、Sm表现出显著的正异常,而Nb则为负异常,缺乏Ba负异常的特征进一步强化了其与其他成因软玉的区别。稀土元素的配分模式具有较高一致性,轻重稀土元素分异明显,轻稀土元素的富集以及Ce和Eu的负异常使其在成因上可与其他软玉类型有效区分。此外,贵州和广西的辉绿岩与峨眉山玄武岩在稀土元素配分特征上呈现出较高的相似性。综上所述,通过分析不同产地软玉的δCe、δEu及∑REE值,构建的树状图有效实现了对其的分类与区分。本研究为深入理解华南地区软玉的成矿机制及资源开发提供了基础性地球化学依据。

关键词: 软玉, 基性岩交代型矿床, 主微量元素, 稀土元素

Abstract:

Nephrite is an important mineral resource, and its geochemical characteristics are crucial for understanding the genesis of mineral deposits and assessing resource potential. This study investigates the basaltic rock-hosted nephrite from the Guizhou Luodian, Guangxi Dahua, and Guangxi Bama regions. Utilizing electron microprobe analysis and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), we systematically analyzed the major, trace, and rare earth element compositions of representative nephrite samples. The findings indicate that the primary chemical constituents of basaltic rock-hosted nephrite in the Qiangui region are SiO2, CaO, and MgO, with average concentrations lower than the theoretical values for tremolite minerals. The SiO2 content is found to be higher than that of ultramafic deposits, yet shows no significant difference when compared to neutral acidic nephrite, suggesting a relationship with silica supplied by surrounding rocks and late-stage hydrothermal fluids. Trace element analysis reveals pronounced positive anomalies for U, La, and Sm and a notable negative anomaly for Nb, while Ba exhibits no negative anomalies, providing a means to differentiate this nephrite from other genetic varieties. The rare earth element distribution patterns of Guizhou and Guangxi basaltic rock-hosted nephrite demonstrate significant similarity, with clear distinctions between light and heavy rare earth elements. Light rare earth elements are particularly enriched, and there are recognizable negative anomalies for Ce and Eu. Furthermore, the diabase associated with Guizhou and Guangxi nephrite shows strong affinity to Emeishan basalt, as reflected in their similar rare earth element distribution patterns. Finally, based on the variations in δCe, δEu, and ∑REE values among nephrite from different sources, effective differentiation can be achieved through dendrogram analysis.

Key words: nephrite, basaltic rock-hosted metasomatic deposit, major and trace element, rare earth element

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