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.

    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

    • 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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