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    张超，李志丹，张锋，段明，俞礽安，陈军强，谢瑜. 2024. 内蒙古阿拉善左旗亚干铜镍钴矿辉长岩LA–ICP–MS锆石U–Pb定年、Hf同位素特征及其地壳伸展作用[J]. 中国地质, 51(4): 1368−1386. DOI: 10.12029/gc20210401001
    引用本文: 张超，李志丹，张锋，段明，俞礽安，陈军强，谢瑜. 2024. 内蒙古阿拉善左旗亚干铜镍钴矿辉长岩LA–ICP–MS锆石U–Pb定年、Hf同位素特征及其地壳伸展作用[J]. 中国地质, 51(4): 1368−1386. DOI: 10.12029/gc20210401001
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    Zhang Chao, Li Zhidan, Zhang Feng, Duan Ming, Yu Reng'an, Chen Junqiang, Xie Yu. 2024. Zircon U–Pb age, Hf isotopic characteristics and crustal extension of the gabbro in the Yagan Cu–Ni–Co deposit, Alxa Left Banner, Inner Mongolia[J]. Geology in China, 51(4): 1368−1386. DOI: 10.12029/gc20210401001
    Citation: Zhang Chao, Li Zhidan, Zhang Feng, Duan Ming, Yu Reng'an, Chen Junqiang, Xie Yu. 2024. Zircon U–Pb age, Hf isotopic characteristics and crustal extension of the gabbro in the Yagan Cu–Ni–Co deposit, Alxa Left Banner, Inner Mongolia[J]. Geology in China, 51(4): 1368−1386. DOI: 10.12029/gc20210401001
    shu

    内蒙古阿拉善左旗亚干铜镍钴矿辉长岩LA–ICP–MS锆石U–Pb定年、Hf同位素特征及其地壳伸展作用

    Zircon U–Pb age, Hf isotopic characteristics and crustal extension of the gabbro in the Yagan Cu–Ni–Co deposit, Alxa Left Banner, Inner Mongolia

      摘要
    • 摘要:
      研究目的 阿拉善左旗亚干铜镍钴矿床是内蒙古西部典型硫化物矿床，发育于超基性—中基性岩浆岩带，辉长岩为成矿母岩，正确认识该岩体的岩浆活动与成矿规律及构造背景成为亟待解决的地质问题。
      研究方法 本文采集相关样品，对亚干地区出露的辉长岩开展了岩相学、岩石地球化学及锆石U–Pb年代学和Hf同位素分析研究。
      研究结果 亚干辉长岩具有高Al2O3（15.99%~17.47%）、亚碱性（K2O+Na2O=4.94%~5.86%）、低TiO2（0.81%~1.12%）、低P2O5（0.14%~0.21%）、富MgO（3.18%~5.64%）、低K2O（1.14%~2.05%）特征，属钙碱性系列。稀土总量（ΣREE）为71.43×10−6~94.22×10−6，呈轻稀土相对富集、重稀土亏损的右倾配分模式，明显亏损高场强元素Nb、P、Ta，富集不相容元素U、Sr，表明亚干辉长岩来源于岩石圈地幔，岩浆后期经历了结晶分异作用。亚干辉长岩锆石U–Pb加权平均年龄为（268.8±3.1）Ma，限定其成岩时代属中二叠世。锆石εHf(t)值介于–7.1~2.9，二阶段模式年龄介于1272~2177 Ma。
      结论 区域地质资料及地球化学特征表明，亚干辉长岩原始岩浆在运移过程中可能受到部分地壳物质的交代混染作用，形成构造背景可能为晚古生代后碰撞伸展环境。亚干地区位于珠斯楞—杭乌拉构造带，自石炭纪开始向南俯冲，从被动大陆边缘转为主动大陆边缘。此外，亚干辉长岩的侵位时代限定了该区域碰撞闭合时间，为该区铜镍钴矿研究提供了新的制约。

       

      Abstract:
      This paper is the result of mineral exploration engineering.
      Objective The copper–nickel–cobalt deposit in the Alxa Left Banner is a typical sulfide deposit in western Inner Mongolia, developed in the ultrabasic−medium basic magmatic rock zone. The gabbro is an ore–forming rock, and recognizing the magmatic activity, metallogenic regularity and tectonic background have become an urgent geological problem.
      Methods Related samples were collected to study petrography, petrogeochemistry, zircon U–Pb chronology and Hf isotope.
      Results Geochemical characteristics shows that the Yagan gabbro has the characteristics of high Al2O3 (15.99%–17.47%), sub−alkaline (K2O+Na2O=4.94%–5.86%), low TiO2 (0.81%–1.12%), low P2O5 (0.14%–0.21%), high MgO (3.18%–5.64%), low K2O (1.14%–2.05%), indicating of the calcium alkaline series. The total amount of rare earth (ΣREE) is 71.43×10−6–94.22×10−6, presents right–inclined distribution model, the light rare earth is relatively enriched and the heavy rare earth is depleted. The high field strength elements (Nb, P, Ta) are obviously depleted, incompatible elements (U, Sr) are enriched, suggested that the Yagan gabbro originated from the lithospheric mantle and experienced crystallization differentiation in the late magmatic stage. The zircon U–Pb weighted average age of the Yagan gabbro is (268.8±3.1) Ma, indicating the age of diagenesis belongs to Middle Permian. The εHf(t) values is −7.1–2.9 and two staged Hf model age is 1272–2177 Ma.
      Conclusions Regional geological data and geochemical characteristics indicate that the Yagan gabbro original magma may be confused by some crustal materials during the migration process. The formation tectonic background may be the post–collision and extension environment in the Late Paleozoic. In addition, the emplacement age of Yagan gabbro limited the collision closing time, which provides new constraints for the study of Cu–Ni–Co deposits in this region.

       

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