华北克拉通东南部太古宙英云闪长岩—奥长花岗岩—花岗闪长岩形成及演化     

刘磊  康诗胜  刘恒  胡天杨  周炜鉴  张云飞 《地质论评》2023,69(1):49-75

华北克拉通是世界范围内少数保存有大量太古宙英云闪长岩—奥长花岗岩—花岗闪长岩(TTG)及多期次岩浆事件记录的克拉通之一,相关研究对揭示全球太古宙时期壳—幔动力学演化过程具有重要的指示意义。笔者等在华北克拉通东南部归纳总结了52个太古宙时期TTG岩石样品的有效地球化学资料。根据地区与岩石成因差异,将样品主要分为3类：霍邱、五河地区低铝、低压型TTG岩石,鲁西(C带)、丰县张河地区中铝、中低压型TTG岩石以及登封地区高铝、高压型TTG岩石。华北克拉通东南部的TTG片麻岩经历了两期明显的地壳生长事件：2.95～2.70 Ga, 2.58～2.48 Ga(峰值为约2.52 Ga)。主、微量数据表明,华北克拉通东南部的TTG片麻岩主体源于低钾镁铁质岩石的部分熔融,并且源区可能受到来自于壳—幔相互作用的影响。其中,霍邱、登封地区的TTG分别受到流体、熔体交代作用;鲁西和张河地区则同时受到熔体和流体交代作用。霍邱地区TTG片麻岩形成于约2.70 Ga,成因可能受鲁西地区地幔柱垂向构造的影响;太古宙末期,鲁西及张河地区与登封地区TTG片麻岩的形成具有一定联系,主要表现为受洋内岛弧地体侧向的洋内俯冲与弧...  相似文献   

英云闪长岩奥长花岗岩花岗闪长岩(TTG)岩石构造组合及其亚类划分     

邓晋福  刘翠  狄永军  冯艳芳  肖庆辉  刘勇  丁孝忠  孟贵祥  黄凡  赵国春  吴宗絮 《地学前缘》2018,25(6):42-50

TTG岩石构造组合(或岩类)表征洋壳俯冲作用。本文提出TTG岩类的4个亚类：(1)镁安山岩系列(MA)低压型TTG亚类,形成于非常年轻和很热的洋壳俯冲,压力≤1 500~1 600 MPa,深度≤50~60 km,例如活动洋中脊俯冲的板片窗的边缘;(2)镁安山岩系列(MA)高压型TTG亚类,形成于比较年轻和较热的洋壳俯冲,压力≥1 500~1 600 MPa,深度≥50~60 km;(3)低镁(或非镁)安山岩系列(LMA)低压型TTG亚类,形成于洋内弧下地壳,压力≤1 500~1 600 MPa,深度≤50~60 km;(4)低镁(或非镁)安山岩系列(LMA)高压型TTG亚类,形成了大陆边缘弧山根带,压力≥1 500~1 600 MPa,深度≥50~60 km。对TTG岩类4个亚类的研究,并结合对无TTG形成的老的冷的俯冲带洋壳和冷的弧地壳以及幔楔有无岩浆产生等方面的研究,可以重建岩浆弧的壳幔结构和热结构,进而可为与洋俯冲有关的成矿作用提供地质背景。  相似文献   

Origin and Geological Significance of TTG Gneisses from the Maevatanana Greenstone Belt in North–Central Madagascar, and A Comparison with India     

LI Peng  LI Jiankang  LIU Shanbao  PEI Rongfu  SHI Guanghai 《《地质学报》英文版》2017,91(3):1003-1024

The Maevatanana greenstone belt in north-central Madagascar contains widespread exposures of tonalite-trondhjemite-granodiorite(TTG) gneisses,and is important for its concentrations of various metal deposits(e.g.,chromium,nickle,iron,gold).In this paper we report on the petrography,and major and trace element compositions of the TTG gneisses within the Berere Complex of the Maevatanana area,as well as LA-ICP-MS U-Pb ages and Lu-Hf isotopic compositions of zircons from the gneisses.The gneisses consist mainly of granitoid gneiss and biotite(±hornblende) plagiogneiss,and analysis of thin sections provides evidence of crushing,recrystallization,and metasomatism related to dynamic metamorphism.Samples have large variations in their major and trace element contents,with SiO_2 = 55.87-68.06 wt%,Al_2O_3 = 13.9-17.8 wt%,and Na_2O/K_2O =0.97-2.13.Geochemically,the granitoid gneisses and biotite plagiogneisses fall on a low-Al trondhjemite to granodiorite trend,while the biotite-hornblende plagiogneisses represent a high-Al tonalite TTG assemblage.Zircon U-Pb dating shows that the Berere Complex TTG gneisses formed at2.5-2.4 Ga.Most ε_(Hf(t)) values of zircons from the biotite(± hornblende) plagiogneisses are positive,while most ε_(Hf(t)) values from the granitoid gneisses are negative,suggesting a degree of crustal contamination.Two-stage Hf model ages suggest that the age of the protolith of the TTG gneisses was ca.3.4-2.6 Ga,representing a period of paleocontinent formation in the Mesoarchean.Geothermometries indicate the temperature of metamorphism of the TTG gneisses was 522-612℃.Based on these data,the protolith of the TTG gneisses is inferred to have formed during the development of a Mesoarchean paleocontinent that is now widely exposed as a TTG gneiss belt(mostly lower amphibolite facies) in the Maevatanana area,and which records a geological evolution related to the subduction of an ancient oceanic crust and the collision of microcontinents during the formation of the Rodinia supercontinent.The lithological similarity of Precambrian basement,the close ages of metamorphism within greenstone belts and the comparable distribution of metamorphic grade all show a pronounced Precambrian geology similarity between Madagascar and India,which can provide significative clues in understanding the possible Precambrian Supercontinent tectonics,and also important constraints on the correlation of the two continental fragments.  相似文献   

内蒙古吉日嘎朗图晚泥盆世侵入岩特征及其构造意义     

白立兵  邓晋福  陶继雄 《地质与资源》2013,22(2):108-113

内蒙古锡林浩特吉日嘎朗图晚泥盆世侵入岩分布于内蒙古自治区二连-贺根山板块对接带北部,其岩石组合为石英闪长岩、英云闪长岩和花岗闪长岩.岩石化学成分SiO₂含量为64.23%~74.47%,Al₂O₃为13.59%~16.26%,TiO₂为0.19%~0.76%,Na₂O+K₂O为6.28%~8.15%,属钙碱性系列,A/CNK=1.06-1.21,属过铝质花岗岩.An-Ab-Or图显示T₂G₁G₂QM组合,属TTG岩类.微量元素显示为火山弧花岗岩.稀土元素以高度分馏的稀土模式和亏损HREE为特征,显示TTG岩类特征.综合反映该套岩石具典型TTG岩类特征,显示为洋壳向陆壳俯冲的产物.在花岗闪长岩中取单颗粒锆石U-Pb年龄为361.1±1.0 Ma,为晚泥盆世侵入岩,因此,西伯利亚板块与华北板块的缝合时间至少应当在晚泥盆世之后.  相似文献