皖南伏岭A型花岗岩的成因:地球化学、锆石U-Pb年龄及Lu-Hf同位素特征制约?
DOI:
作者:
作者单位:

1.合肥工业大学资源与环境工程学院,安徽省地质调查院(安徽省地质科学研究所);2.合肥工业大学资源与环境工程学院;3.安徽省地质调查院(安徽省地质科学研究所)

作者简介:

通讯作者:

中图分类号:

基金项目:


Petrogenesis of Fuling A- type granite in the southern Anhui Province:Constraints from petrogeochemistry , Zircon U-Pb age and Lu-Hf isotope characters
Author:
Affiliation:

1.School of Resources and Environmental Engineering, Hefei University of Technology;2.Geological Survey of Anhui Provice(Anhui Institute of Geological Sciences)

Fund Project:

单位:
  • 摘要
  • |
  • 图/表
  • |
  • 访问统计
  • |
  • 参考文献
  • |
  • 相似文献
  • |
  • 引证文献
  • |
  • 资源附件
  • |
  • 文章评论
    摘要:

    伏岭岩体为一花岗岩体,位于江南造山带东段的皖浙相邻区,岩浆岩沿着近北东向的宁国—绩溪深大断裂断分布。笔者等对伏岭岩体鱼龙川(γ53(2))单元花岗岩开展了系统的全岩岩石地球化学、LA-ICPMS锆石U-Pb同位素年龄和锆石原位Lu-Hf同位素地球化学研究。LA-ICP-MS锆石 U-Pb定年获得花岗岩的侵位年龄为131.8±0.9Ma,属于江南造山带中生代晚阶段岩浆活动的产物。主量元素地球化学特征表明岩体富硅、富碱、贫钙、贫铁。微量元素特征显示具有较高的Rb、Th、U、Ga、Zr和Y含量,较低的Sr、Ba和Nb含量。稀土配分曲线呈现典型的“海鸥式”分布特征,显示强烈的负Eu异常;微量元素原始地幔标准化蛛网图显示明显的Ba、Sr、Nb的负异常,其高SiO2含量和Rb/Sr值、低Ba、Sr含量具备江南造山带东段皖南地区A型花岗岩的典型特征。岩体具有同源岩浆演化特征,源区可能存在磷灰石、钛铁矿矿物的分离结晶作用,而辉石类矿物的分离较少。伏岭岩体源岩主要来源于地壳中镁铁质岩石的部分熔融,其地球化学特征继承于源岩。锆石εHf(t)变化范围较小,均在-7.0~-4.6之间,二阶段模式年龄(TDM2)为1478~1630Ma,伏岭花岗岩可能由中元古代古老下地壳部分熔融形成,其源区物质以古老的下地壳壳源物质为主。伏岭岩体δEu正异常和部分样品的高Sr含量表明岩浆源区较深,其Th/U值、Th/Nb值、Th/La值均高于大陆地壳平均值,La/Nb值略低于大陆地壳平均值,这些地球化学特征均表明伏岭花岗岩的形成可能有地幔物质混入。伏岭岩体的形成可能受到碰撞作用的影响,岩体形成于后碰撞期,软流圈上涌导致了陆下岩石圈地幔的熔融,从而产生了大量新生的玄武质岩浆,随着这些新生幔源物质的底侵,中元古代的基底岩石被大范围的熔融,从而产生了伏岭A型花岗岩。

    Abstract:

    Objectives: The Fuling pluton is a granitic body located in the adjacent area of Anhui and Zhejiang provinces in the eastern section of the Jiangnan orogenic belt. The magmatic rocks are distributed along the Ningguo-Jixi deep fault extending near the NE direction. The research work on the Yulongchuan (γ53 (2) )unit granite in Fuling Pluton has been carried out in this paper. Methods: Based on the field work, we finished microscope observation, whole-rock geochemical analysis, LA-ICP-MS zircon U-Pb dating and in situ Lu-Hf isotope geochemistryfor the Yulongchuan (γ53 (2) ) unit granite. Results: The LA-ICP-MS zircon U-Pb dating shows that the emplaced age of the granite is 131.75±0.91Ma, which is the product of magmatic activity in the late stage of the Jiangnan orogenic belt. The pluton is rich in silica and alkali, and poor in calcium and iron. The characteristics of trace elements show that there are higher Rb, Th, U, Ga, Zr and Y contents, and there are lower Sr , Ba and Nb. The rare earth partition curve presents a typical "seagull" distribution, showing strong negative Eu anomalies. Negative anomalies of Ba, Sr and Nb are found in the primitive normalized mantle spider map of trace elements. The zircon εHf (t) of Fuling granite varies from -7.0 to -4.6, and the two-stage model age (TDM2) ranges from 1478 to 1630Ma. The Th/U values, Th/Nb values and Th/La values are all higher than the average continental crust value, and the La/Nb values is slightly lower than the average continental crust value. Conclusions: The high SiO2 content, Rb/Sr value and low Ba and Sr content show that the Fuling granite has the typical characteristics of the A-type granite in the eastern part of Jiangnan orogenic belt, southern Anhui Province. The Fuling pluton has the characteristics of homologous magmatic evolution, and the separation and crystallization of apatite and ilmenite minerals may exist in the source area, while the separation of pyroxene minerals is less. The source rocks of Fuling pluton are mainly derived from partial melting of mafic rocks in the crust, and their geochemical characteristics are inherited from the source rocks. The Fuling granite may have been formed by partial melting of the ancient lower crust in Mesoproterozoic, and its source material is mainly the ancient lower crust. The positive δEu anomaly of Fuling pluton and the high Sr content of some samples indicate that the magma source is deep. These geochemical characteristics all indicate that the formation of Fuling granite may have been mixed with mantle materials.The formation of Fuling pluton may be influenced by collision. The rock mass was formed in post-collision. Asthenosphere upwelling led to the melting of the subcontinental lithosphere mantle, which produced a large number of new basaltic magma. Thus, Fuling A-type granite is produced.

    参考文献
    相似文献
    引证文献
引用本文
分享
文章指标
  • 点击次数:
  • 下载次数:
  • HTML阅读次数:
  • 引用次数:
历史
  • 收稿日期:2023-05-05
  • 最后修改日期:2023-08-22
  • 录用日期:2023-10-23
  • 在线发布日期:
  • 出版日期: