华北克拉通南缘四十里长山地区中生代脉岩的锆石 U-Pb 定年及成因初探  

Preliminary study on zircon U-Pb dating and petrogenesis of Mesozoic dike rocks in Sishilichang Mountain area of southern margin of North China Carton

作　　者：李振生[1] 牛浩[1] 张妍[1] 李全忠[1] 王创[1] 刘德良[2] 

机构地区：[1]合肥工业大学资源与环境工程学院,合肥230009 [2]中国科学技术大学地球与空间科学学院,合肥230026

出　　处：《地质科学》2016年第4期1137-1162,共26页Chinese Journal of Geology(Scientia Geologica Sinica)

基　　金：国家自然科学基金项目（编号：41172117,41372194）和中国地质调查局地质调查项目（编号：1211302108023-1）资助.

摘　　要：华北克拉通南缘四十里长山地区岩浆活动弱，仅发育中生代脉岩，因此缺乏对形成时代和岩浆作用的研究。本文依据四十里长山地区脉岩的锆石LA-ICPMS U-Pb定年结果和全岩元素地球化学分析确定其形成时代及成因。四十里长山地区脉岩由基性、酸性两个端元组成，按岩性可分为煌斑岩脉岩、花岗斑岩脉岩及正长岩类脉岩，其侵位年龄分别为：80.9±1.8 Ma、86.1±1.0 Ma和85.6±1.0 Ma，构成一套晚白垩世双峰式侵入岩组合。四十里长山地区基性煌斑岩起源于富集大陆岩石圈地幔的部分熔融岩浆，内含416 Ma左右的继承性锆石和偏钠质的煌斑岩，暗示了地幔源区含俯冲扬子陆壳的混入岩和软流圈地幔的改造；酸性脉岩属于A型花岗质岩石，起源于底侵的幔源基性岩浆诱发地壳物质部分熔融形成的壳源酸性岩浆以及它们的混合岩浆。中国东部乃至东北亚地区晚白垩世火成岩的空间展布特征证实，四十里长山地区双峰式脉岩的形成与太平洋板块向欧亚大陆下俯冲作用相联系，其形成于类似弧后盆地的板内伸展环境。A little Mesozoic dike rocks develop in Sishilichang Mountain area of southern margin of North China Carton,where magmatic activity were rare. Because of lack of age and petrogenetic investigation of the Mesozoic dike rocks, its formation age and origin would be investigated by LA-ICPMS zircon U-Pb dating and element geochemistry. The dike rocks in Sishilichang Mountain area consist of lamprophyre,granite porphyry and syenite rocks,whose emplacement ages were 80.9±1.8 Ma,86.1±1.0 Ma and 85.5±1.4 Ma respectively. The dike rocks constitute Late Cretaceous bimodal intrusive rock for similar age and components of basic and acid endmembers, and the acid endmembers belong to A-type granites. The lamprophyres of basic dike rocks were derived by partial melting of enrichment lithospheric mantle source,which were contaminated by materials of subducted ancient crust of Yangtze Craton and asthenosphere mantle since its contained ～416 Ma inherited zircons and was close to sodic type. While the acid dike rocks were derived mostly from crust-derived magma, which were formed from melting crustal materials heated by underplating of mantle-derived basic magma, as well as their mixed magma. Combined spatial distribution characteristics of Late Cretaceous igneous rocks in eastern China and Northeast Asia,it was suggested that the bimodal dike rocks in Sishilichang Mountain area formed under back-arc intraplate extensional setting related to the subduction of the paleo-Pacific plate.

关 键 词：A型花岗质岩石 晚白垩世 双峰式侵入岩 锆石U-PB年龄 四十里长山 

分 类 号：P588[天文地球—岩石学] P597[天文地球—地质学]