| 华北克拉通中部带云中山石榴斜长角闪岩变质演化及其构造意义 |
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| 引用本文： | 郭敏洁,钱加慧,尹常青,张健,卢成森.华北克拉通中部带云中山石榴斜长角闪岩变质演化及其构造意义[J].地球科学,2021,46(11):3892-3909. |
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| 作者姓名： | 郭敏洁 钱加慧 尹常青 张健 卢成森 |
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| 作者单位： | 广东省地质过程与矿产资源探查重点实验室,中山大学地球科学与工程学院,广东珠海 519082;南方海洋科学与工程广东省实验室,广东珠海 519082 |
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| 基金项目： | 国家自然科学基金项目41972197国家自然科学基金项目41890831广东省基础与应用基础研究基金项目2019A1515012189中央高校基本科研业务费18lgpy17 |
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| 摘 要： | 云中山地体位于华北克拉通中部造山带中部，是衔接吕梁地体和五台-恒山地体的关键位置.确定云中山地体的变质作用演化历史可为深入理解吕梁-云中山-五台-恒山地区的整体地质过程提供重要限定.对云中山石榴斜长角闪岩开展了详细的岩石学、相平衡模拟和锆石年代学研究.两个代表性样品均具有顺时针变质P-T-t轨迹，峰期阶段位于金红石稳定域，温压条件分别为0.96±0.11 GPa/720±8.0℃（L1903）和1.26±0.08 GPa/756±14.0℃（L1906）；峰期后发生降压作用，金红石转变成钛铁矿，石榴石边部生长斜长石（+普通角闪石）冠状边，普通角闪石转变成镁铁闪石；晚期阶段以冷却为主，石榴石的边部出现少量绿泥石交代.对两个样品的岩石组构和化学成分对比表明，石榴斜长角闪岩的部分熔融受全岩成分影响，岩石贫硅钠而富铁镁钛时难熔，反之则易熔.样品变质锆石的U-Pb定年结果为1 928~1 806 Ma.这些锆石相对富集重稀土，利用锆石Ti温度计计算的结晶温度为520~680℃，与岩石的冷却温度相近，因此所获年龄应代表退变冷却时代.吕梁-云中山-五台-恒山地区的整体地质特征对比表明，云中山地体的岩石-地层组成和变质作用演化与五台-恒山地体非常相似，记录了古元古代晚期的碰撞造山事件.
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| 关 键 词： | 华北克拉通 云中山地体 石榴斜长角闪岩 变质P-T-t轨迹 构造意义 岩石学. |
| 收稿时间： | 2021-01-02 |
Metamorphic Evolution and Tectonic Implications of Garnet Amphibolite from Yunzhongshan Terrane in Central North China Craton |
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| Guo Minjie,Qian Jiahui,Yin Changqing,Zhang Jian,Lu Chengsen.Metamorphic Evolution and Tectonic Implications of Garnet Amphibolite from Yunzhongshan Terrane in Central North China Craton[J].Earth Science-Journal of China University of Geosciences,2021,46(11):3892-3909. |
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| Authors: | Guo Minjie Qian Jiahui Yin Changqing Zhang Jian Lu Chengsen |
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| Abstract: | The Yunzhongshan terrane is situated in the middle segment of the Trans-North China Orogen, a key position connecting the Lüliang and Wutai-Hengshan terranes. Addressing its metamorphic evolution is of great importance in understanding the tectonic process of the Lüliang-Yunzhongshan-Wutai-Hengshan areas. Detailed studies of petrology, phase modelling and geochronology were carried out on garnet amphibolite from the Yunzhongshan terrane. Both samples exhibit clockwise P-T-t paths, which are characterized by rutile-bearing peak stages with P-T conditions of 0.96±0.11 GPa/720±8.0℃(L1903) and 1.26±0.08 GPa/756±14.0℃(L1906), respectively. The post-peak stages are dominated by decompression, accompanied by transition of rutile by ilmenite, growth of plagioclase (+hornblende) coronae surrounding garnet and transition of hornblende by cummingtonite. The late stages are dominated by cooling, with local metasomatism of garnet by chlorite. By comparing petrographical features and chemical compositions of the two samples, it can be concluded that the partial melting of garnet amphibolite is affected by the bulk-rock compositions. The rock is refractory when it is rich in Fe, Mg and Ti and poor in Si and Na. Zircon U-Pb dating yields metamorphic ages of 1 928-1 806 Ma, interpreted to represent the cooling stage of metamorphism. This is supported by high concentration of HREE in zircon grains and low crystallization temperatures of 520-680℃ calculated by Ti-in-zircon thermometer. Comparison of the overall geological characteristics of the Lüliang-Yunzhongshan-Wutai-Hengshan areas shows that the lithostratigraphic units and metamorphism evolution in the Yunzhongshan terrane are very similar to those in the Wutai-Hengshan terranes, which record the Late Paleoproterozoic collision orogeny. |
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