大兴安岭东北部早古生代花岗岩锆石U-Pb年龄、Hf同位素特征及地质意义  

Zircon U-Pb ages,Hf isotopic characteristics and their implications of the Early Paleozoic granites in the northeastern Da Hinggan Mts.,northeastern China

作　　者：葛文春[1] 隋振民[1] 吴福元[2] 张吉衡[1] 徐学纯[1] 程瑞玉[1] 

机构地区：[1]吉林大学地球科学学院,长春130061 [2]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

出　　处：《岩石学报》2007年第2期423-440,共18页Acta Petrologica Sinica

基　　金：国家自然科学基金(40372038;40325006);高等学校博士学科点专项科研基金(20060184021)项目资助成果

摘　　要：大兴安岭东北部早古生代花岗岩属于Ⅰ型花岗岩。锆石的LA-ICPMS U-Pb年代学研究表明,十八站岩体、内河岩体、白银纳岩体的形成年龄分别为499±1、500±1和460±1Ma,而查拉班河岩体为一多次侵入的杂岩体,其形成年龄在465～481Ma。结合本区和邻区其它早古生代花岗岩体的锆石U-Pb年龄,限定了大兴安岭东北部地区早古生代花岗岩浆活动的时限为460～500Ma。锆石的LA-MC-ICPMS Hf同位素研究显示,本区早古生代花岗岩的锆石ε_(Hf)(t)多数介于+1.5～+3.8之间,二阶段模式年龄介于1.1～1.4Ga,表明其主要起源于中-新元古代增生的地壳物质。结合兴安地块其它花岗岩的锆石Hf同位素资料,认为额尔古纳地块在中-新元古代时期曾发生一次重要的地壳增生事件,与兴安地块主要为显生宙地壳的特点明显不同。Abstract The Paleozoic granites in the Ergun block, exposed in the northeastern Da Hinggan Mts. , northeastern China, are of I-type. Zircon U-Pb dating by LA-ICPMS technique indicates that the Shibazhan, Neihe and Baiyinna plutons were emplaced with ages of 499 ± 1, 500 ± 1 and 460 ± 1Ma; whereas the Chalabanhe pluton was formed by several pulses with age between 465 ~ 481Ma. Considering other previously reported age data, it is proposed that the granitic magmatism in the northeastern Da Hinggan Mts. during the Early Paleozoic took place at 460~500Ma. Zircon Hf analyses conducted by LA-MC-ICPMS show that these granites have БHf （t） values of ＋ 1.5 ~ ＋ 3.8 with Hf modal ages of 1.1 ~ 1.4Ga, indicating that the crust in the Ergun block was extracted from mantle during Meso-Neoproterozoic, which is much different from the Xing＇an block to the south, in that it shows a characterized Phanerozoic crustal age.

关 键 词：锆石U-PB年龄 HF同位素 花岗岩 早古生代 大兴安岭东北部 

分 类 号：P588.121[天文地球—岩石学] P597.3[天文地球—地质学]