| 南岭威溪矿区花岗岩的岩石成因——来自地球化学、锆石U-Pb年代学及Hf同位素制约 |
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| 引用本文：马慧英,陈剑锋,杜云,文春华,向轲,黄建中,田磊,曾广乾,梁恩云,黄乐清,李湘玉,王灵珏.2026.南岭威溪矿区花岗岩的岩石成因——来自地球化学、锆石U-Pb年代学及Hf同位素制约[J].地球学报,47(3):565-579. |
| DOI：10.3975/cagsb.2025.122521 |
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| 基金项目:本文由湖南省自然科学基金(编号: 2024JJ8318; 2025JJ80404; 2025JJ80405; 2025JJ80045)、有色金属成矿预测与地质环境监测教育部重点实验室(中南大学)开放基金(编号: 2023YSJS16)、国家科技重大专项项目子课题(编号: 2025ZD1007803)、国地球深部探测与矿产资源勘查国家科技重大专项(编号: 2023YFC2906405)和湖南省自然资源重大科研项目(编号: 20240102DZ)联合资助。 |
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| 中文摘要:威溪矿区出露花岗质糜棱岩和斑状黑云母二长花岗岩, 岩石地球化学分析表明, 前者属弱过铝质-强过铝质(A/CNK为1.10~1.83); 后者属准铝质-弱过铝质(A/CNK为1.00~1.08); 花岗质糜棱岩表现出强负Eu异常(δEu=0.37~0.53)和呈不对称“海鸥型”分布的稀土元素配分模式, 与壳源花岗岩特征一致; 微量元素特征显示富集Rb、Th、U、Zr、Hf等元素, 亏损Ba、Sr、P、Ti等元素。LA-ICP-MS锆石U-Pb定年获得花岗质糜棱岩和黑云母二长花岗岩的形成年龄分别为(825±3) Ma(MSWD=0.04)和(431±2) Ma(MSWD=0.06), 分别代表新元古代和加里东期岩浆活动。锆石Hf同位素分析显示, 花岗质糜棱岩的εHf(t)值为–4.05 ~ +11.27(均值–1.38), 指示其岩浆源区存在幔源物质加入; 而黑云母二长花岗岩的εHf(t)值为–9.13 ~ –3.31(均值–6.91), 指示其源于古老地壳物质重熔。两期花岗岩的锆石Hf同位素二阶段模式年龄(TDM2)分别为980~ 1 824 Ma和1 473~1 794 Ma, 共同揭示岩浆源区均有中元古代古老地壳物质的显著贡献。综合研究表明, 花岗质糜棱岩形成于Rodinia超大陆裂解的伸展构造环境, 而黑云母二长花岗岩则形成于加里东造山运动的后碰撞伸展环境。区内钨多金属成矿作用主要与加里东期花岗岩相关, 其为矽卡岩型钨多金属矿床的形成提供了关键的热液和成矿物质来源, 新元古代岩体可能为成矿元素(W)的早期预富集提供了物源基础。 |
| 中文关键词:钨多金属矿床 S型花岗岩 锆石U-Pb定年 Hf同位素 岩浆源区 |
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| Genesis of Granites in the Nanling Weixi Mining Area: Constraints from Geochemistry, Zircon U-Pb Geochronology, and Hf Isotopes |
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| Abstract:Granitic mylonite and biotite monzogranite are exposed in the Weixi mining area. Geochemical analyses indicate that the former is weakly to strongly peraluminous (A/CNK=1.10–1.83), whereas the latter is metaluminous to weakly peraluminous (A/CNK=1.00–1.08). The granitic mylonite exhibited a pronounced negative Eu anomaly (δEu=0.37–0.53) and a “seagull-shaped” rare earth element pattern, consistent with the characteristics of crust-derived granites. Trace-element data showed enrichment in Rb, Th, U, Zr, and Hf, and depletion in Ba, Sr, P, and Ti. Laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS) zircon U-Pb dating yielded ages of (825±3) Ma (MSWD=0.04) for the granitic mylonite and (431±2) Ma (MSWD=0.06) for the biotite monzogranite, corresponding to Neoproterozoic and Caledonian magmatic activities, respectively. Zircon Hf isotope analyses showed εHf(t) values ranging from –4.05 to 11.27 (mean: –1.38) for the granitic mylonite, suggesting involvement of mantle-derived material in the magma source, whereas εHf(t) values for the biotite monzogranite ranged from –9.13 to –3.31 (mean: –6.91), indicating derivation from the partial remelting of ancient crustal components. Two-stage zircon Hf model ages (TDM2) of 1 472–1 824 Ma and 1 473– 1 794 Ma, respectively, point to significant contributions from Mesoproterozoic crustal material. Integrated geochemical and isotopic evidence suggests that the granitic mylonite formed in an extensional tectonic setting during the rifting of the Rodinia supercontinent, whereas the biotite monzogranite crystallized in a post-collisional extensional regime related to the Caledonian orogeny. Tungsten polymetallic mineralization in this region is primarily associated with Caledonian granite, which provided essential hydrothermal fluids and metallogenic material for skarn-type W polymetallic deposits. The Neoproterozoic pluton likely contributed to early enrichment of ore-forming elements (W). |
| keywords:tungsten polymetallic deposit S-type granite zircon U-Pb dating Hf isotopes magma source |
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