ISSN 1009-6248CN 61-1149/P 双月刊

主管单位：中国地质调查局

主办单位：中国地质调查局西安地质调查中心
中国地质学会

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    马玉见，刘亚剑，梁涛，等. 华北克拉通南缘角子山花岗岩的锆石U−Pb定年、岩石地球化学特征及构造背景[J]. 西北地质，2024，57（1）：95−109. doi: 10.12401/j.nwg.2023160
    引用本文: 马玉见，刘亚剑，梁涛，等. 华北克拉通南缘角子山花岗岩的锆石U−Pb定年、岩石地球化学特征及构造背景[J]. 西北地质，2024，57（1）：95−109. doi: 10.12401/j.nwg.2023160
    shu
    MA Yujian，LIU Yajian，LIANG Tao，et al. Zircon U–Pb Dating and Geochemical Features of the Jiaozishan Granite in the South Margin of the North China Craton and Its Tectonic Implications[J]. Northwestern Geology，2024，57（1）：95−109. doi: 10.12401/j.nwg.2023160
    Citation: MA Yujian，LIU Yajian，LIANG Tao，et al. Zircon U–Pb Dating and Geochemical Features of the Jiaozishan Granite in the South Margin of the North China Craton and Its Tectonic Implications[J]. Northwestern Geology，2024，57（1）：95−109. doi: 10.12401/j.nwg.2023160
    shu

    华北克拉通南缘角子山花岗岩的锆石U−Pb定年、岩石地球化学特征及构造背景

    Zircon U–Pb Dating and Geochemical Features of the Jiaozishan Granite in the South Margin of the North China Craton and Its Tectonic Implications

      摘要
    • 摘要: 角子山岩基是秦岭造山带东端伏牛山余脉规模居第二位的燕山期侵入岩，其岩石成因模型有助于深入认识华北克拉通南缘伏牛山余脉早白垩世酸性岩浆的形成规律和深部构造演化。角子山花岗岩体LA−ICP−MS锆石U−Pb定年样品的30个测点中，18个有效锆石测点的U−Pb年龄集中于（129.5±1.4）Ma（1个）和（116.1±1.4）～（122.2±1.3）Ma（17个）两组，形成了锆石年龄谱，后者的加权平均年龄为（119.3±0.9）Ma。结合前人10个有效锆石测点的U−Pb年龄数据，27颗锆石的加权平均年龄为（118.2±1.2）Ma，代表了角子山花岗岩的形成时代。角子山花岗岩样品具有富Si和碱、贫Ca和Mg的特征，为高钾钙碱性系列岩石，属于准铝质–弱过铝质花岗岩。在微量元素蛛网图中，角子山花岗岩样品显示了Rb、Th及Zr、Hf的正异常和Sr、P、Ti的负异常。角子山花岗岩稀土总量为20.9×10−6～204×10−6，（La/Yb）N值为4.24～21.0，δEu值为0.53～0.78，稀土配分模式呈轻稀土富集（右倾平滑）和中、重稀土亏损（近水平）的特征。角子山花岗岩样品的LaN–（La/Yb）N投点显示了正相关关系，表明其成分变异受控于部分熔融作用。角子山花岗岩的部分熔融源残余相包括角闪石、斜长石和金红石，无石榴子石残余，表明它形成于正常厚度地壳，存在深度大致为40～50 km和小于30 km的两个部分熔融岩石源区。角子山花岗岩形成于秦岭早白垩世陆（板）内造山阶段，经历了岩浆/流体混合再活化作用，是~120 Ma区域岩石圈拆沉作用的产物。

       

      Abstract: The Jiaozishan batholith was a Yanshanian intrusive rock with the second largest area in the stretching branch of the Funiu Mountains, eastern of the Qinling orogenic belts. Its petrogenetic model was significant to understand the regular pattern of the early Cretaceous acid magma and deep tectonic evolution in the stretching branch of the Funiu Mountains. Among the total 30 zircon spots from dating sample JZS07 by LA–ICP–MS dating method, the U–Pb isotopic results of 18 zircon spots were available, and they were divided into two groups with (129.5±1.4) Ma (1 spot) and (116.1±1.4)～(122.2±1.3) Ma (17 spots), which had formed the zircon age spectrum. The weighted mean age of the second group was (119.3±0.9) Ma. Combined with the previous zircon U–Pb age data of 10 available zircon spots, the weighted average age of 27 zircons was (118.2±1.2) Ma, which represented the formation age of the Jiaozishan granite. The samples of the Jiaozishan granite were characterized by higher SiO2 and alkali, and lower MgO and CaO, and compositional spots fell into high–K calc-alkaline series in the SiO2–K2O diagram. The positive anomalies of Rb, Th, Zr and Hf, and negative anomalies of Sr, P and Ti were shown in spider diagram. Their total REEs contents were from 20.9×10−6 to 204×10−6 with (La/Yb)N ratios of 4.24～21.0. They had shown the characteristics of LREE–enrichment, MREE and HREE depletion with Eu negative anomalies (δEu values were 0.53～0.78). In the LaN– (La/Yb)N diagram, the sample points of the Jiaozishan granite had shown a positive correlation, indicating that the compositional variation was controlled by partial melting of source rock. The residual phases of its partial melting source included mainly hornblende, plagioclase and rutile, and no garnet. The Jiaozishan granite was formed in the crust with normal thickness, and there are two partial melting sources with depths of roughly 40～50 km and less than 30 km, respectively. The Jiaozishan granite experienced magma/fluid mixing and reactivation, and its formation tectonic setting was intraplate orogenic environment. The Jiaozishan granite was one of the products of the lithosphere delamination in～120 Ma.

       

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