辽东半岛大金山花岗岩体SHRIMP U-Pb年龄、元素地球化学和Hf同位素特征及地质意义  

SHRIMP U-Pb Ages,Elements Geochemistry and Hf Isotopic Characteristics of the Dajinshan Granite in Liaodong Peninsula and Geological Significance

作　　者：杨佳林[1] 顾玉超[1,2] 杨凤超[1] 李东涛 鞠楠[1] 贾宏翔 YANG Jialin1, GU Yuchao1,2 , YANG Fengchao1, LI Dongtao1, JU Nan1, JIA Hongxiang1(1. Shenyang Institute of Geology and Mineral Resources, China Geological Survey, Shenyang, 110034; 2. School of Earth Sciences and Resources, China University of Geosciences （Beijing） , Beijing, 100083)

机构地区：[1]中国地质调查局沈阳地质调查中心,沈阳110034 [2]中国地质大学(北京)地球科学与资源学院,北京100083

出　　处：《地质论评》2018年第6期1541-1556,共16页Geological Review

基　　金：中国地质调查项目(编号:DD20160049);国家重点研发计划"深地资源勘查开采"重点专项(编号:2016YFC0600108)的成果~~

摘　　要：辽东半岛早白垩世时期受到强烈的构造—岩浆作用使岩石圈构造环境由挤压造山向伸展减薄转变,前人对其成因有所争议。本文通过锆石SHRIMP U-Pb测年、原位Lu-Hf同位素和主量、微量、稀土元素测试对辽东半岛大金山花岗岩体进行了系统研究,结果显示:大金山花岗岩体结晶年龄为~124 Ma,侵位于早白垩世岩浆活动的高峰期。岩石地球化学特征显示大金山花岗岩属弱过铝质~过铝质岩石,经历了高程度的结晶分异过程,富集Rb、Th、U、K等大离子亲石元素(LILE),亏损P、Ti等高场强元素(HFSE),中等Eu负异常,为I型花岗岩。TW003样品εHf(t)值为-25. 8^-14. 2,TDM2为2093~2805 Ma,岩浆物质来源于新太古代—古元古代下地壳火成岩的部分熔融。根据年代学和岩石地球化学研究认为大金山花岗岩是古太平洋板块向欧亚大陆板块俯冲所形成的活动大陆边缘弧花岗岩,辽东半岛早白垩世的伸展环境是受板块俯冲造山后伸展作用和下地壳拆沉作用的联合制约。Objectives： Liaodong Peninsula is known to have been subjected to strong tectonism and magmatism which transitions from a compressional orogeny to extension and lithosphere thinning in the early Cretaceous. Previous researchers still have a disagreement on such a formation process.Methods： We performed the zircon SHRIMP U-Pb isotopic dating,in situ micro-area Lu-Hf isotope test,major elements and trace elements compositions of the monzonitic granite from Dajinshan Pluton of Liaodong Peninsula.Results： The crystallization age of the Dajinshan granite is 124 Ma,which belongs to peak period of the Early Cretaceous magmatic activity. The geochemical characteristics of the rocks show that Dajinshan granite is a kind of rock which experienced a high degree of crystallization process,belongs to weak peraluminous ～ peraluminous rock series. The Dajinshan granite is I-type granite which enriched with LILE such as Rb,Th,U and K; yet deficient on HFSE like P,Ti,etc,and Eu is medium negative anomalous. The zircon εHf（ t） values of TW003 are between-25.8 ～-14.2,TDM2 are between 2093 Ma and 2805 Ma.Conclusions： Dajinshan granite is the active continental margin arc granite formed by the Paleo-Pacific plate subduction to the Eurasia plate. The lithogenous materials are the product of partial melting of mafic—ultramafic source rock in late Archean—Palaeoproterozoic lower crust,and mixed with felsic materials from upper crust during magma invasion. The Cretaceous extensional environment is influenced by the effect of the postorogenic extension and delamination of lower crust in the Liaodong Peninsula.

关 键 词：伸展环境 下地壳 锆石SHRIMP U-PB测年 LU-HF同位素 大金山花岗岩 辽东半岛 

分 类 号：P588.121[天文地球—岩石学]