| 华北南缘信阳古元古代花岗岩的年代学和地球化学特征及其对地壳演化的启示 |
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| 引用本文： | 艾磊,平先权,郑建平,苏玉平.华北南缘信阳古元古代花岗岩的年代学和地球化学特征及其对地壳演化的启示[J].地球科学,2020,45(6):2044-2058. |
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| 作者姓名： | 艾磊 平先权 郑建平 苏玉平 |
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| 作者单位： | 中国地质大学地球科学学院, 湖北武汉 430074 |
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| 基金项目： | 国家自然科学基金项目41503018国家自然科学基金项目41873038国家重点研发计划“深地资源勘查开采”重点专项资助项目2016YFC0600403中央高校基本科研业务费专项资金资助项目CUGCJ1814江苏省地质矿产勘查局科研项目2018KY05 |
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| 摘 要： | 华北克拉通南缘古元古代发育有多期次的岩浆活动和变质事件，记录了南缘基底和构造演化过程，但古元古代中-晚期的岩浆记录却相对较少.对华北南缘信阳地区古元古代中-晚期花岗岩进行了详细的岩石学、地球化学、锆石U-Pb年代学及Lu-Hf同位素研究.信阳地区花岗岩主要包括潘庄钾长花岗岩和陈庄黑云钾长花岗岩，其岩浆锆石结晶年龄分别为1 868 Ma和1 955 Ma，即形成于古元古代中-晚期.所有的岩石样品具有高SiO2、富碱、低CaO、P2O5、MgO等特征，且A/CNK介于1.12~1.28，属过铝质岩石.同时它们富集LILEs（如Rb、Th和K），贫HFSEs（如Nb、Ta和Ti）、亏损Sr、P等元素，并具有中等-弱的负Eu异常.此外，潘庄岩体和陈庄岩体整体具有相似的锆石εHf（t）值（-0.6~+2.6），两阶段Hf模式年龄（Tcrust）范围为2.40~2.64 Ga.表明信阳地区太古代末-古元古代早期地壳在古元古代中-晚期经历了强烈的改造.结合华北克拉通南缘的岩浆活动和变质事件记录，认为信阳地区花岗岩的形成可能与华北东、西陆块的碰撞有关，且该区频繁的古元古代岩浆活动（2.24~1.85 Ga）可能是东、西陆块间古大洋及西部陆块东向俯冲的结果.
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| 关 键 词： | 花岗岩 古元古代 地壳演化 碰撞 华北克拉通南缘 岩石学 |
| 收稿时间： | 2019-09-28 |
Geochronology and Geochemistry of Paleoproterozoic Granites in Xinyang Area: Implications for Crustal Evolution of Southern North China Craton |
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| Abstract: | The multistage magmatism and metamorphism in the Paleoproterozoic of the southern North China craton (NCC) have recorded the basement and tectonic evolution of the southern NCC. However, the magmatism in Middle-Late Paleoproterozoic were rarely reported. In this paper, it presents a detailed study of petrology, geochemistry, zircon U-Pb geochronology and Lu-Hf isotope for the Middle-Late Paleoproterozoic granites in the Xinyang area of southern NCC. They include the Panzhuang K-feldspar granite and Chenzhuang biotite K-feldspar granite. The magmatic zircons from them yield the crystallization ages of 1 868 Ma and 1 955 Ma, respectively, indicating that they formed in the Middle-Late Paleoproterozoic. All the studied granites have high SiO2, and total alkaline, but low CaO, P2O5 and MgO contents. Their A/CNK values range from 1.12 to 1.28, suggesting that they are peraluminous rocks. Meanwhile, they show enrichment of LILEs (e.g. Rb, Th and K) but depletion of HFSEs (e.g. Nb, Ta and Ti), Sr and P with moderate to weak negative Eu anomalies. Moreover, the Panzhuang and Chenzhuang plutons have similar zircon εHf(t) values (-0.6-+2.6), with the two-stage Hf model ages (Tcrust) ranging in 2.40-2.64 Ga. All of these evidences indicate that the Late Archean to Early Paleoproterozoic crust in the Xinyang area were strongly modified in Middle-Late Paleoproterozoic. Combined with the records of magmatism and metamorphic events in the southern margin of the NCC, it is suggested that the formation of the granites in the Xinyang area may be related to the collision between the eastern and western blocks of NCC. Furthermore, the frequent Paleoproterozoic magmatic activities (2.24-1.85 Ga) in this area probably resulted from an eastward-directed subduction of an ancient ocean between the eastern and western blocks, and the western block. |
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