大兴安岭新林镇岩体的同位素特征及其地质意义  

Isotopic Characteristics and Its Significance of the Xinlin Town Pluton,Great Hinggan Mountains

作　　者：张彦龙[1] 葛文春[1] 柳小明[2] 张吉衡[1] 

机构地区：[1]吉林大学地球科学学院,长春130061 [2]西北大学地质系／大陆动力学国家重点实验室,西安710069

出　　处：《吉林大学学报（地球科学版）》2008年第2期177-186,共10页Journal of Jilin University：Earth Science Edition

基　　金：国家自然科学基金项目(40372038)

摘　　要：新林镇岩体位于大兴安岭北部,主要由花岗闪长岩、石英二长岩、二长花岗岩、碱长花岗岩组成,局部见到细粒辉长岩和闪长岩包体。岩石地球化学和岩石学特征表明,该杂岩体属于高钾钙碱性I型花岗岩。两个花岗闪长岩的锆石LA-ICP-MS U-Pb定年结果分别为（132±3）Ma和（131±3）Ma,属于早白垩世岩浆活动的产物。样品的Sr-Nd同位素组成比较均一,而Hf同位素特征变化较大,其εHf（t）变化介于1.328.32之间,Hf模式年龄与Nd模式年龄一致,表明花岗质岩浆主要起源于元古代增生的地壳物质,在岩石形成过程中有地幔组分的贡献。岩体的同位素特征将额尔古纳地块地壳增生时间限定在新元古代,而兴安地块地壳增生发生在新元古代—显生宙,暗示它们具有不同的地壳演化过程。The Xinlin Town pluton locates in the northern Great Hinggan Mountains. Lithologically, it comprises granodiorite, adamellite, quart fine-grained gabbroic and dioritic enclaves. Pet pluton is high-K calc-alkaline I-type granite. Z z-monzodiorite and alkaline-feldspar granite, with locally rological and geochemical characteristics indicate that the ircon LA - ICP - MS U - Pb dating of two granodiorites yielded emplacement ages of （132 ±3）Ma and （131 ±3）Ma. The ages indicate that the pluton was the product of the Early Cretaceous magmatic event. Though Sr - Nd isotopic compositions of the samples are relatively uniform, their εHf（t） values are relatively varied, ranging between 1.32 and 8.32; the yiel- ded Nd and Hf model ages are Neoproterozoic. The isotopic data indicate that the granitic magma mainly originated from the juvenile Neoproterozoic accreted crustal materials with the involvements mantle components. The isotopic characteristics indicate that the Erguna terrain accreted in Neoproterozoic at least, but the Xing＇an terrain accreted in Neoproterozoic- Phanerozoic. It suggests that they have the different tectonic natures and evolvement history.

关 键 词：新林镇 花岗闪长岩 U-PB年龄 SR-ND-HF同位素 地壳增生 

分 类 号：P597[天文地球—地球化学]