辽东半岛丹东地区中生代花岗岩锆石U-Pb年龄、Hf同位素特征及其地质意义  

Zircon U-Pb Ages, Hf Isotopes and Geological Significance of Mesozoic Granites in Dandong Area, Liaodong Peninsula

作　　者：张朋[1] 赵岩[1] 寇林林[1] 沙德铭[1] 毕中伟[1] 杨凤超[1] Zhang Peng;Zhao Yan;Kou Linlin;Sha Deming;Bi Zhongwei;Yang Fengchao(Shenyang Geological Survey Center,China Geological Survey,Shenyang 110034,China)

机构地区：[1]中国地质调查局沈阳地质调查中心

出　　处：《地球科学》2019年第10期3297-3313,共17页Earth Science

基　　金：国家重点研发计划(Nos.2016YFC0600108,2018YFC0603804);国家自然科学基金项目(No.41502093);中国地质调查局地质调查项目(Nos.DD20190165,DD20190042-3,DD20160049)

摘　　要：为了确定辽东半岛丹东地区中生代花岗岩岩石类型、成岩时代及其形成构造背景.选取三股流岩体、五龙背岩体和丁岐山岩体开展岩相学、锆石LA-ICP-MS U-Pb年代学、岩石地球化学和锆石Hf同位素地球化学研究.结果表明:三股流岩体由花岗闪长岩、似斑状黑云母二长花岗岩和中粗粒黑云母二长花岗岩组成,后两者成岩年龄分别为137.2±1.2 Ma和123.2±1.3 Ma;丁岐山岩体由中细粒碱长花岗岩、石英正长岩和石英二长岩组成,获得中细粒碱长花岗岩成岩年龄为121.1±1.5 Ma;五龙背岩体由中粗粒二长花岗岩组成,成岩年龄为146.8±0.8 Ma.元素和同位素地球化学特征表明,三股流岩体的花岗闪长岩为钾玄岩系列,似斑状黑云母二长花岗岩和中粗粒黑云母二长花岗岩以及五龙背岩体和丁岐山岩体均为高钾钙碱性,3个岩体不同岩石类型的A/CNK均小于1.1,为I型花岗岩;岩体均富集轻稀土元素和大离子亲石元素,亏损重稀土元素和高场强元素,具Eu负异常;εHf(t)值为-22.40^-9.77,两阶段Hf模式年龄TDM2为2999~1915 Ma,揭示三股流岩体、五龙背岩体和丁岐山岩体可能是古元古代古老地壳部分熔融形成.结合区域构造演化认为三股流岩体、五龙背岩体和丁岐山岩体均形成于活动大陆边缘,五龙背岩体形成于古太平洋板块向欧亚板块的俯冲挤压的构造背景,三股流岩体和丁岐山岩体形成于古太平洋板块向欧亚板块的俯冲后的伸展环境.In order to determine the rock types,petrogenic age and tectonic setting of the Mesozoic granites from the Dandong area in Liaodong peninsula,the lithology identification,zircon LA-ICP-MS U-Pb dating,major and trace elements,and Hf isotope data for the Sanguliu,Wulongbei and Dingqishan granites are presented in this paper.The LA-ICP-MS U-Pb ages of the Sanguliu pluton of the porphyritic biotite monzogranite and the medium-coarse grained biotite monzogranite are 137.2±1.2 Ma and 123.2±1.3 Ma.The LA-ICP-MS U-Pb geochronology of the Wulongbei medium-fine grained biotite monzogranite and Dinqishan alkali feldspar granite are 146.8±0.8 Ma and 121.1±1.5 Ma.The results of elemental and isotope geochemistry show that the Sanguliu granodiorite belong to shoshonite series,while the porphyritic biotite monzogranite and the medium-coarse grained biotite monzogranite,the Wulongbei medium-fine grained biotite monzogranite and Dinqishan alkali feldspar granite belong to high potassium Ca-alkaline series.Their aluminum indexes(A/CNK ratios)are all less than 1.1,showing the special feature of I-type granite.The samples of the Sanguliu,Wulongbei and Dingqishan granites are enriched in LREE and LILE,but depleted in HREE and HFSE with minor negative Eu anomalies.The zirconεHf(t)values of the three pluton are from-22.40 to-9.77,TDM2 are between 2999 and 1915 Ma,suggesting that the Sanguliu,Wulongbei and Dingqishan granites were mainly derived from the partial melting of the Paleoproterozoic crustal material.Combined with regional tectonic evolution,it is proposed that the Sanguliu,Wulongbei and Dinqishan rock plutonic diagenetic tectonic environment is the active continental margin,the Wulongbei rock may be formed in the compression tectonic environment and the Sanguliu rock and Dinqishan rock may be formed in the extension tectonic environment,which is closely associated with the subduction of the Paleo-Pacific plate.

关 键 词：三股流岩体 五龙背岩体 丁岐山岩体 锆石U‐Pb 地球化学 辽东半岛丹东 岩石学 

分 类 号：P581[天文地球—岩石学]