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现代地质 ›› 2012, Vol. 26 ›› Issue (4): 627-634.

• 岩石学 • 上一篇    下一篇

吉林南部三棵榆树组火山岩的成因:锆石U-Pb年龄和Hf同位素证据

 隋振民1, 陈跃军2   

  1. 1吉林农业大学 资源与环境学院,吉林 长春130118;2吉林大学 古生物学与地层学研究中心,吉林 长春130026
  • 收稿日期:2012-03-29 修回日期:2012-05-07 出版日期:2012-08-18 发布日期:2012-08-24
  • 作者简介:隋振民,男,副教授,博士,1963年出生,地质学专业,主要从事岩石学研究。 Email:szm0431@126.com。
  • 基金资助:

    国家自然科学基金项目(30670138);吉林大学平台基地建设项目(450060445364)。

Petrogenesis of Volcanic Rocks from Sankeyushu Formation in Southern Jilin: Evidences from Zircon U-Pb Ages and Hf Isotopes

 DUO  Zhen-Min-1 , CHEN  Ti-Jun-2   

  1. 1College of Resources and Environment, Jilin Agricultural University,Changchun, Jilin130118,China;
    2Research Center of Paleontology and Stratigraphy, Jilin University, Changchun, Jilin130026,China
  • Received:2012-03-29 Revised:2012-05-07 Online:2012-08-18 Published:2012-08-24

摘要:

锆石LA-ICP-MS U-Pb测年结果显示,吉林南部地区三棵榆树组粗面岩形成于118 Ma的早白垩世晚期。岩石地球化学研究表明,三棵榆树组粗面岩的SiO2含量为65.11%~65.61%,富碱(K2O=6.29%~ 7.28%,Na2O=3.71%~4.21%),属于钾玄岩系列,弱过铝质(A/CNK=1.05~1.12),含镁指数Mg#=9~16;稀土元素总量较高(∑REE=317.72×10-6~37130×10-6),轻重稀土分馏明显(LaN/YbN=19.50~22.80),Eu负异常较弱(δEu=0.75~0.81);微量元素富集Rb、Th、Zr、K,明显亏损Nb、Ta和Sr等,显示典型的大陆地壳特征。锆石的176Hf/177Hf比值介于0.282 206~0.282 309之间, εHf(t)值介于-13.32~-16.97之间,Hf模式年龄(TDM2)介于2.0~2.6 Ga之间,平均为2.2 Ga。上述特征表明,吉林南部地区早白垩世粗面岩主要来源于古元古代地壳物质的部分熔融,形成于伸展构造环境。

关键词: 吉林南部, 三棵榆树组, 锆石U-Pb年龄, Hf同位素, 早白垩世, 粗面岩, 伸展构造背景

Abstract:

Zircon U-Pb dating by LA-ICP-MS shows that Sankeyushu Formation trachyte in southern Jilin area formed in 118 Ma of late Early Cretaceous. Study of petrogeochemistry suggests that SiO2 contents from Sankeyushu Formation trachyte are 6511%-6561%,rich in alkali(K2O=6.29%-7.28%,Na2O=3.71%-4.21%).It belongs to shoshonite series with weak peraluminous (A/CNK=1.05-1.12) and low Mg index (Mg#=9-16).The total amount of rare earth elements is relatively high (∑REE=317.72×10-6 -371.30×10-6).Light and weight lanthanon differentiation evidence(LaN/YbN=1950-2280)is noticeable.Eu negative anomaly is weak(δEu=075-081).The trace elements Rb, Th, Zr and K enrichment, Nb,Ta and Sr obvious depletion, show the emblematical character of continent lithosphere.176Hf/177Hf from zircons range from 0.282,206 to 0.282,309, εHf(t) from-13.32 to-16.97, Hf model ages are 2.0-2.6 Ga, average is 2.2 Ga.The above characteristics indicate that the Early Cretaceous trachyte in the study area mainly came from Paleoproterozoic lithosphere partial melting and was formed in an extensional tectonic environment.

Key words: southern Jilin, Sankeyushu Formation, zircon U-Pb age;Hf isotope;Early Cretaceous, trachyte, extensional tectonic environment