大兴安岭北部察哈彦岩体的Hf同位素特征及其地质意义

J4 ›› 2009, Vol. 39 ›› Issue (5): 849-856.

大兴安岭北部察哈彦岩体的Hf同位素特征及其地质意义

隋振民¹,葛文春², 吴福元³, 徐学纯²,张吉衡²

1．吉林农业大学资源与环境学院,长春 130118;2.吉林大学地球科学学院| 长春 130061;3．中国科学院地质与地球物理研究所/岩石圈演化国家重点实验室|北京 100029

收稿日期:2009-02-26 出版日期:2009-09-26 发布日期:2009-09-26
通讯作者: 葛文春（1963-），男，黑龙江富锦人，教授，博士生导师，主要从事岩石学研究 E-mail:gewenchun@jlu.edu.cn
作者简介:隋振民(1963-)|男|黑龙江穆棱人|副教授|博士|主要从事岩石学研究|E-mail:szm0431@126.com
基金资助:
国家自然科学基金项目（40372038，40325006 , 40739905）

Hf isotopic Characteristics and Geological Significance of the Chahayan Pluton in Northern Daxing’anling Mountains

SUI Zhen-min¹|GE Wen-chun²|WU Fu-yuan³|XU Xue-chun²|ZHANG Ji-heng²

1.College of Resource and Environmental Science, Jilin Agricultural University|Changchun 130118|China;2.College of Earth Sciences,Jilin University,Changchun 130061,China;3.Institute of Geology and Geophysics/State Key Laboratory of Lithospheric Evolution, |Chinese Academy of Sciences,Beijing 100029,China

Received:2009-02-26 Online:2009-09-26 Published:2009-09-26

摘要/Abstract

摘要：

察哈彦岩体位于大兴安岭东北部额尔古纳地块之上，主要岩性为斑状黑云母正长花岗岩。岩体中锆石呈自形晶，发育细微振荡生长环带，显示高的Th/U值(0.32~1.12)，表明锆石的岩浆成因。锆石LA-ICP-MS U-Pb 定年结果为(236±1)Ma，属中三叠世岩浆活动的产物。察哈彦岩体未见变形，具有块状构造，地球化学显示为弱过铝质、高钾钙碱性系列，富集LREE和Rb、K等元素，亏损Nb、Ta、P、Ti等元素，与后造山I型花岗岩特征相似，应形成于引张的构造环境。结合区域构造研究成果，其成因应与华北板块和西伯利亚板块碰撞造山后岩石圈伸展环境有关。察哈彦岩体的 Hf(t)值为－3.94~2.19，其模式年龄为1.1~1.5 Ga，与额尔古纳地块早古生代花岗岩和中生代花岗岩基本相同，表明额尔古纳地块地壳增生的时间主要发生在中-新元古代。

关键词: 额尔古纳；察哈彦岩体；花岗岩；U-Pb年龄；Hf同位素；地壳增生

Abstract:

The Chahayan pluton is located in the Eerguna block in the eastern Daxing’anling Mountains, and mainly consists of porphyritic biotitic syenogranite. The zircon grains separated from the syenogranite sample in the Chahayan pluton show generally euhedral form with fine oscillatory zoning on their CL images, and high Th/U ratios (0.32-1.12), which exhibit the features of magmatic zircons. LA-ICP-MS zircon U-Pb dating reveals that the Chahayan pluton emplaced at (236±1) Ma, belonging to the products of middle Triassic magmatism. Chahayan pluton displays massive structure without obvious deformation, and is characterized by enriched LILEs such as LREEs, Rb and K with negative Nb, Ta, P and Ti anomalies in geochemistry, which is similar to that of post-orogenic I-type granotoids, indicating the pluton probably formed in an extensional tectonic environment. Combined with previous studies in regional tectonics, the petrogenesis of Chahayan pluton is related to the lithosphere extension after the collision orogenic processes between the North China craton (NCC) and the Siberia plate. The Chahayan pluton has ε_Hf(t) values ranging from -3.94 to 2.19 with model ages from 1.1 to 1.5 Ga close to those of Early Paleozoic and Mesozoic granotoids in this region, indicating that the crustal accretion event of Eerguna block occurred mainly in Middle-and Neo-Proterozoic period.

Key words: Eerguna, Chahayan pluton, granite, U-Pb dating, Hf isotope, crustal growth

中图分类号:

P597

隋振民, 葛文春, 吴福元, 徐学纯, 张吉衡. 大兴安岭北部察哈彦岩体的Hf同位素特征及其地质意义[J]. J4, 2009, 39(5): 849-856.

SUI Zhen-min, GE Wen-chun, WU Fu-yuan, XU Xue-chun, ZHANG Ji-heng. Hf isotopic Characteristics and Geological Significance of the Chahayan Pluton in Northern Daxing’anling Mountains[J]. J4, 2009, 39(5): 849-856.

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