乔新星, 周斌, 韩奎, 潘亮, 王峰, 赵焕强. 冈底斯南带东段日多地区米忍岩体地球化学、年代学、锆石Lu-Hf同位素特征及其地质意义[J]. 地质通报, 2019, 38(9): 1417-1430.
    引用本文: 乔新星, 周斌, 韩奎, 潘亮, 王峰, 赵焕强. 冈底斯南带东段日多地区米忍岩体地球化学、年代学、锆石Lu-Hf同位素特征及其地质意义[J]. 地质通报, 2019, 38(9): 1417-1430.
    QIAO Xinxing, ZHOU Bin, HAN Kui, PAN Liang, WANG Feng, ZHAO Huanqiang. Geochemistry, chronology and zircon Lu-Hf isotopic characteristics of the Miren rocks in Riduo area of east part of Southern Gangdise belt and their geological significance[J]. Geological Bulletin of China, 2019, 38(9): 1417-1430.
    Citation: QIAO Xinxing, ZHOU Bin, HAN Kui, PAN Liang, WANG Feng, ZHAO Huanqiang. Geochemistry, chronology and zircon Lu-Hf isotopic characteristics of the Miren rocks in Riduo area of east part of Southern Gangdise belt and their geological significance[J]. Geological Bulletin of China, 2019, 38(9): 1417-1430.

    冈底斯南带东段日多地区米忍岩体地球化学、年代学、锆石Lu-Hf同位素特征及其地质意义

    Geochemistry, chronology and zircon Lu-Hf isotopic characteristics of the Miren rocks in Riduo area of east part of Southern Gangdise belt and their geological significance

    • 摘要: 日多地区米忍岩体位于冈底斯南带东段,2件锆石U-Pb测年样品显示其形成年龄为54.9±1.6Ma和48.6±0.5Ma,岩石SiO2含量为60.18%~71.53%,全碱含量为5.85%~7.49%,K2O/Na2O值为0.58~1.05,里特曼指数在1.79~2.30之间,属钙碱性岩石,A/CNK值为0.85~0.95,投图显示为准铝质岩石,具有I型花岗岩的特征。岩石轻稀土元素及大离子亲石元素(Rb、K、Ba、Th、U)相对富集,重稀土及高场强元素(Nb、P、Hf、Ti)相对亏损,弱负Eu异常,具火山弧岩浆岩地球化学特征。176Hf/177Hf平均值为0.282945,Hf同位素二阶段模式年龄较年轻(613~719Ma),εHf(t)值为2.74~10.47,表明其岩浆源区以新生地壳的部分熔融为主或有地幔物质参与了成岩过程,据C/MF-A/MF投图分析,可能为基性或铁镁质岩浆底侵,导致中下地壳的物质发生熔融,这些特征均表明,日多地区始新世花岗闪长岩的形成可能与新特提斯洋板片的回转、断离有关。

       

      Abstract: The Miren rock in the Riduo Area is located in the eastern part of southern Gangdise belt. Zircon U-Pb dating of two samples reveals that the formation ages are 54.9±1.6Ma and 48.6±0.5Ma, and SiO2 content of the rock is 60.18%~71.53%, total alkali content is 5.85%~7.49%, K2O/Na2O ratio is 0.58~1.05, and Liteman index (σ) is 1.79~2.30, suggesting calc-alkaline rocks, with A/CNK value being 0.85~0.95. The diagram shows a quasi-aluminous rock with characteristics of type I granite. The light rare earth and large lithosphere ionic elements (Rb, K, Ba, Th, and U) are relatively enriched, and the characteristics of heavy rare earth and high-field strength elements (Nb, P, Hf, Ti) are relatively depleted with weak negative Eu anomalies, showing features of volcanic arc magma. The ratio of 176Hf/177Hf is 0.282819~0.283036, 0.282945 on average. The Hf isotope two-stage model is younger (613~719Ma) and the εHf(t) value is between 2.74 and 10.47, indicating that the magma source area was part of the new genetic crust. Melting or mantle material was involved in the rock-forming process. According to C/MF-A/MF mapping analysis, it may be basic or iron-magnesian magmatic intrusion, resulting in melting of material in the middle and lower crust. The formation of the Riduo granodiorite may have been related to the rotation and separation of the Neo-Tethys plate.

       

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