王宏, 李友余, 张锦让, 周清. 云南宁蒗水草坝二长花岗斑岩岩石成因:锆石U-Pb年龄及地球化学约束[J]. 地质通报, 2022, 41(8): 1382-1393. DOI: 10.12097/j.issn.1671-2552.2022.08.006
    引用本文: 王宏, 李友余, 张锦让, 周清. 云南宁蒗水草坝二长花岗斑岩岩石成因:锆石U-Pb年龄及地球化学约束[J]. 地质通报, 2022, 41(8): 1382-1393. DOI: 10.12097/j.issn.1671-2552.2022.08.006
    WANG Hong, LI Youyu, ZHANG Jinrang, ZHOU Qing. Petrogenesis of the Shuicaoba monzonitic granite porphyry in Ninglang, Yunnan: constraints from zircon U-Pb geochronology and geochemistry[J]. Geological Bulletin of China, 2022, 41(8): 1382-1393. DOI: 10.12097/j.issn.1671-2552.2022.08.006
    Citation: WANG Hong, LI Youyu, ZHANG Jinrang, ZHOU Qing. Petrogenesis of the Shuicaoba monzonitic granite porphyry in Ninglang, Yunnan: constraints from zircon U-Pb geochronology and geochemistry[J]. Geological Bulletin of China, 2022, 41(8): 1382-1393. DOI: 10.12097/j.issn.1671-2552.2022.08.006

    云南宁蒗水草坝二长花岗斑岩岩石成因:锆石U-Pb年龄及地球化学约束

    Petrogenesis of the Shuicaoba monzonitic granite porphyry in Ninglang, Yunnan: constraints from zircon U-Pb geochronology and geochemistry

    • 摘要: 云南水草坝岩体位于祥云-宁蒗铜金成矿带北段,是金沙江-红河新生代富碱斑岩成矿带的重要组成部分。对水草坝二长斑岩进行了岩相学、锆石U-Pb年龄和岩石地球化学研究,为该区新生代构造岩浆演化提供新的约束。LA-ICP-MS锆石U-Pb分析结果表明,水草坝二长花岗斑岩形成于古近纪渐新世早期(33.1±0.3 Ma)。岩石地球化学特征显示,岩体具有高硅、富碱的特征,且A/CNK大于1,属于过铝质富碱二长花岗斑岩。岩石稀土元素总量较高(ΣREE = 114.68×10-6~384.79×10-6),稀土元素配分模式呈右倾型,轻、重稀土分馏明显((La/Yb)N = 440.37~114.09),Eu无明显异常(0.84~1.14),具有富集轻稀土元素和大离子亲石元素(Rb、Sr、K等)、亏损重稀土元素和高场强元素(Nb、Ta、Ti等),以及高Sr低Y、Yb的特征,属于典型的C型埃达克岩。综合分析认为,水草坝二长花岗斑岩岩浆源区主要为加厚下地壳的部分熔融,可能有少量幔源组分的参与。结合区域构造演化,认为水草坝二长花岗斑岩形成于印度-欧亚板块晚碰撞走滑期构造应力由挤压向伸展转换的动力学背景。

       

      Abstract: The Shuicaoba monzonitic granite porphyry is located north segment of the Xiangyun-ninglang Cu-Au metallogenic belt, and it is also an important part of the Jinshajiang-Red River enozoic alkali-rich porphyry belt.Based on petrography, zircon U-Pb geochronology and petrogeochemical analysis of the Shuicaoba Monzogranite porphyry, new constraints have be provided for the Cenozoic tectonic magmatic evolution in this area.LA-ICP-MS zircon U-Pb dating indicates that Shuicaoba monzonitic granite porphyry is of Early Oligocene (33.1±0.3 Ma).The pluton is rich in SiO2 and alkali, with the ratio of A/CNK > 1, belonging to the peraluminaceous alkali rich monzonite porphyry.The rock has a total high amount of REE elements(ΣREE=114.68×10-6~384.79×10-6), right-leaning REE distribution pattern, and obvious fractionation of LREE((La/Yb)N = 440.37~114.09), showing no significant Eu anomaly(0.84~1.14).The adakite is enriching in LILE(such as Rb, Sr and Ba) and HFSE (such as Th, U, K and La), depleting in HREE, high field strength elements (Nb, Ta, Ti, etc.), with a high amount of Sr and low amount of Y and Yb, which is typical C-type Adakite.Comprehensive analysis shows that the magmatic source area of the Shuicaoba monzogranite porphyry is mainly partial melting of the thickened lower crust, and a small amount of mantle-derived components may be involved.Combined with the regional tectonic evolution, it is considered that the Shuicaoba monzogranite porphyry was formed under the dynamic background of the tectonic stress transition from compression to extension during the late Indian-Eurasian plate collision strike slip period.

       

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