地学前缘 ›› 2011, Vol. 18 ›› Issue (2): 62-78.

• 论文 • 上一篇    下一篇

赞皇杂岩中太古宙末期菅等钾质花岗岩的成因及动力学背景

杨崇辉，杜利林，任留东，宋会侠，万渝生，颉颃强，刘增校   

  1. 1. 中国地质科学院 地质研究所，  北京  100037
    2. 北京离子探针中心，  北京  100037
    3. 河北省地质矿产调查研究所，  河北 廊坊 065000
  • 收稿日期:2011-01-30 修回日期:2011-02-21 出版日期:2011-03-15 发布日期:2011-04-15
  • 作者简介:杨崇辉(1965—),男,研究员,岩石学专业,主要从事前寒武纪地质研究。E-mail:chhyang@cags.ac.cn
  • 基金资助:

    中国地质调查局地质调查项目(1212010611802, 1212010711815); 中国地质科学院地质研究所基本科研业务费项目(J0907)

Petrogenesis and geodynamic setting of Jiandeng potassic granite at the end of the Neoarchean in Zanhuang Complex, North China Craton.

杨崇辉，杜利林，任留东，宋会侠，万渝生，颉颃强，刘增校   

  1. 1. Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China
    2. Beijing SHRIMP Center, Beijing 100037, China
    3. Hebei Institute of Geology and Mineral Resources, Langfang 065000, China
  • Received:2011-01-30 Revised:2011-02-21 Online:2011-03-15 Published:2011-04-15

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摘要：

赞皇杂岩中的菅等花岗岩体位于临城县西北，主要由钾长花岗岩和二长花岗岩组成，偶见暗色包体。菅等花岗岩SHRIMP锆石UPb年龄为（2 490±13） Ma。岩石具有高硅（SiO2 743%～754%）、高钾（K2O 576%～937%）、富碱（ALK 616%～951%）、贫钙（CaO 014%～081%）、低镁、铁（MgO 002%～049%，TFeO 026%～105%）和钛（TiO2 004%～015%）的特征，A/CNK=097～107，为弱过铝质的钾玄岩系列。岩石的稀土总量较低（ΣREE=（1207～16038）×10-6），轻稀土相对富集，Eu异常变化较大（Eu/Eu*=046～197）。岩石富Rb、Ba和Th等元素，贫Sr、Zr、Nb、Y、Yb等元素，具有较高Rb/Sr和Rb/Ba值以及较低的Y/Nb值。菅等花岗岩具有正的εNd(t)值（285～366），两阶段Nd模式年龄TDM2集中于255～264 Ga。石英闪长岩包体SHRIMP锆石UPb年龄为（2 506±13） Ma，高铝（Al2O3  1716%）、富钙（CaO 434%）、高钠（Na2O 447%）、富铁（TFeO 526%），高Rb、高Sr、高Zr，稀土总量较高（ΣREE=21282×10-6），有弱的负Eu异常（Eu /Eu*=083），具TTG岩类的特征；该包体岩石具有正的εNd(t)值（305），两阶段Nd模式年龄TDM2为263 Ga。这些特征显示菅等花岗岩具有同碰撞和后碰撞的S型花岗岩的特征，为新生地壳在由挤压向伸展转换的构造背景下部分熔融所形成，石英闪长质包体为源区残留的岩石。这期钾质花岗岩的形成，标志着华北克拉通太古宙末期岩浆事件的结束以及稳定陆壳的形成。

关键词: 菅等花岗岩, 赞皇杂岩, 新太古代, 构造背景, 华北克拉通

Abstract:

Jiandeng granite in the Zanhuang Complex is located in the northwestern Lincheng County, Hebei Province. The pluton consists mainly of Kfeldspar granite and monzogranite with few quartz diorite enclaves. SHRIMP dating of zircon from the granite yielded an age of (2490±13)Ma. The rocks have high contents of SiO2 (743%—754%), K2O (576%—937%) and alkali with K2O+Na2O=616%—951%, and low contents of CaO (014%—081%), TiO2(004%—015%), MgO (002%—049%) and total FeO(026%—105%), belonging to shoshonitic series with slightly peraluminous feature. They have lower REE contents((1207—16038)×10-6), with relative enrichment of the LREE and variational Eu anomaly (Eu/Eu*=046—197). The rocks are rich in largeion lithophile elements (LILE) Rb, Ba and Th, and poor in Sr, Zr, Nb, Y and Yb, with high Rb/Sr and Rb/Ba ratios. They have positive εNd (t) value ranging from 285 to 366, with TDM2 ages between 255 and 264 Ga. SHRIMP dating of zircon from the quartz diorite enclave yielded an age of （2506±13）Ma. The quartz diorite is high in Al2O3(1716%), Na2O(447%), CaO(434%) and TFeO (526%), and shows higher total REE content of 21282×10-6, with a small Eu anomaly (Eu/Eu*=083). This rock is rich in Rb, Sr and Zr, and has an εNd (t) value of 305 and a TDM2 age of 263 Ga. The geochemical data show that the Jiandeng granite is similar to the Stype granite formed by anatexis of the juvenile crust in a tectonic transition setting from compression to extension, and the quartz diorite may represent a residue of the source rock. The formation of Jiandeng granite marks a tectonomagmatic event resulting in stabilization of the North China Craton at the end of the Neoarchean.

Key words:  Jiandeng granite, Zanhuang Complex, Neoarchean, tectonic setting, North China Craton

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