| 华北克拉通崤山太华群TTG质片麻岩年代学与地球化学特征:岩石成因机制探讨 |
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| 引用本文： | 罗铮娴,黄小龙,王雪,杨帆,韩丽.华北克拉通崤山太华群TTG质片麻岩年代学与地球化学特征:岩石成因机制探讨[J].大地构造与成矿学,2018(2):332-347. |
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| 作者姓名： | 罗铮娴 黄小龙 王雪 杨帆 韩丽 |
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| 作者单位： | 中国科学院 广州地球化学研究所;同位素地球化学国家重点实验室,广东 广州 510640;中国科学院大学, 北京 100049
中国科学院 广州地球化学研究所;同位素地球化学国家重点实验室,广东 广州 510640 |
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| 基金项目： | 国家自然科学基金项目(41373032 |
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| 摘 要： | 华北克拉通中部造山带南段崤山地区太华群变质杂岩中的TTG质片麻岩具较宽范围的Si O2(63.00%~73.13%)、Al2O3(14.22%~19.38%)和较低的Mg O(0.42%~1.62%)、Cr(4.7~19.2μg/g)和Ni(2.28~16.3μg/g),显示低Yb(0.54~1.16μg/g)、Y(5.49~11.6μg/g)以及高(La/Yb)N(22.4~47.7)和Sr/Y(12.4~84.3)的特征。其稀土元素配分曲线具明显Eu负异常,在微量元素蛛网图上显示显著的Nb-Ta、Ti负异常。崤山TTG片麻岩的原岩形成于新太古代晚期(~2.52 Ga)的加厚下地壳部分熔融,源区残留石榴子石及角闪石,斜长石结晶分异作用降低了岩浆体系的Sr含量和Sr/Y值。绝大部分继承锆石的形成时代(2544±8 Ma)接近于TTG岩浆结晶年龄,表明加厚下地壳源区物质组成相对较年轻。另外,崤山TTG质片麻岩具有正的岩浆锆石εHf(t)值(0.39~4.76)以及略低的继承锆石εHf(t)值(-1.88~3.05),与登封群新太古代TTG相似,均明显高于鲁山太华群新太古代早期TTG。因此,崤山TTG片麻岩具有明显的新生地壳组分,暗示了显著的地壳生长,可能与华北克拉通中部造山带南段新太古代活动大陆边缘增生造山过程相关。
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| 关 键 词： | TTG 年代学 加厚下地壳 太华群 华北克拉通 tonalite-trondhjemite-granodiorite geochronology thickened lower crust Taihua Group North China Craton |
Geochronology and Geochemistry of the TTG Gneisses from the Taihua Group in the Xiaoshan Area,North China Craton: Constraints on Petrogenesis |
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| LUO Zhengxian,HUANG Xiaolong,WANG Xue,YANG Fan,HAN Li.Geochronology and Geochemistry of the TTG Gneisses from the Taihua Group in the Xiaoshan Area,North China Craton: Constraints on Petrogenesis[J].Geotectonica et Metallogenia,2018(2):332-347. |
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| Authors: | LUO Zhengxian HUANG Xiaolong WANG Xue YANG Fan HAN Li |
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| Abstract: | The tonalite-trondhjemite-granodiorite (TTG) gneisses from the Taihua Group in the Xiaoshan area, the southern segment of the Trans-North China Orogen, have highly varied SiO2(63.00% 73.13%) and Al? 2O3(14.22%?19.38%), and relatively low MgO (0.42% ?1.62%), Cr (4.7?19.2 μg/g) and Ni (2.28?16.3 μg/g). They are characterized by very low contents of Yb (0.54?1.16 μg/g) and Y (5.49?11.6 μg/g), with moderate (La/Yb)N(22.4 47.7) and? Sr/Y (12.4 84.3) ratios, showing significant negative Eu anomalies on the chondrite? -normalized REE patterns and pronounced negative Nb-Ta and Ti anomalies on the primitive mantle normalized trace element spider diagrams. The protolith of the Xiaoshan TTG gneisses was derived from partial melting of thickened lower crust at the end of Late Neoarchean (~2.52 Ga), with garnet and amphibole in residuals, while the low Sr contents and Sr/Y ratios might have resulted from plagioclase fractionation. Most relict zircons are only slightly older (2544±8 Ma) than the crystallization age of the TTG gneisses, suggesting overall juvenile materials of the thickened lower crust. In addition, magmatic zircons in the Xiaoshan TTG gneisses have positive εHf(t) values (0.39 4.76) whereas the ? relict zircons have slightly low εHf(t) values (from -1.88 to 3.05), which are similar to these of the Later Neoarchean TTG in the Dengfeng Complex, but higher than those of the Early Neoarchean TTG from the Taihua Complex in the Lushan area. Thus, the Xiaoshan TTG gneisses derived mainly from juvenile crustal material, suggesting noteworthy crustal accretion, which probably due to the Late Neoarchean accretionary orogeny of an active continental margin in the southern segment of the Trans-North China Orogen. |
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