佳木斯地块北部晚寒武世花岗闪长岩U-Pb年代学、地球化学及其构造意义  

Geochronology,Geochemistry and Tectonic Implication of Late Cambrian Granodiorite in the Northern Jiamusi Block

作　　者：王冠 王键 许成瀚 范兴竹 WANG Guan;WANG Jian;XU Chenghan;AN Xingzhu(School of Mining Engineering,Heilongjiang University of Science&Technology,Harbin,150022,China;Ang'angxi Physical Geological Data Field Observation and Research Station of Heilongjiang Province,Qiqihar,161031,China)

机构地区：[1]黑龙江科技大学矿业工程学院,哈尔滨150022 [2]黑龙江省昂昂溪实物地质资料野外科学观测研究站,齐齐哈尔161031

出　　处：《黑龙江国土资源》2024年第1期38-46,共9页Heilongjiang land and Resources

基　　金：黑龙江省普通本科高等学校青年创新人才培养计划(UNPYSCT-2020030)资助。

摘　　要：研究目的:厘定岩石形成时代,探讨岩浆源区和岩石形成的构造环境。研究方法:锆石U-Pb年代学和岩石地球化学分析。研究结果:卫国村似斑状花岗闪长岩呈岩株状产出。年代学研究表明似斑状花岗闪长岩中锆石LA-ICP-MSU-Pb加权平均年龄为500.9±1.5Ma,MSWD=0.42,属晚寒武世。岩石地球化学研究显示其主量元素SiO_(2)、Al_(2)O_(3)和Mg0含量分别为61.28%~67.28%、14.06%~16.42%和2.40%~3.60%,全碱含量为6.09%~6.95%,属准铝质高钾钙碱性系列花岗岩。似斑状花岗闪长岩样品富集大离子亲石元素(Rb、K、Th),相对亏损高场强元素(Nb、Ta、PSr、Ti)和重稀土元素,(La/Yb)为4.12~9.59,具有弱的Eu负异常(8Eu=0.56~0.91)。综合分析认为,研究区似斑状花岗闪长岩样品岩浆源区为下地壳的镁铁质岩石,可能有不同程度的新生地壳物质的加入。结合区域构造演化和构造判别,本文认为岩石形成于碰撞后伸展的构造环境,为加厚的镁铁质下地壳部分熔融的产物。The purposes of this paper are to determine the zircon U-Pb age,explore the magmatic origin and the tectonic setting.The research methods include geochronology analysis as well as geochemistry analysis.Zircon U-Pb dating demon-strates that the weighted mean 206Pb/238U age for the zircons from the porphyric granodiorite is 500.9±1.5 Ma(MSWD=0.42),i.e.,the Late Cambrian.The geochemical data indicate that the contents of SiO_(2)(61.28%~67.28%),Al_(2)O_(3)(2.40%~3.60%),Mg0(2.40%~3.60%),K,0+Na,0(6.09%~6.95%).The rocks belong to the metaluminous high-K calc-alkaline series.The porphyric granodiorites are enriched in large ion lithophile elements(Rb,K,Th),and relatively depleted in Nb,Ta,P,Sr,Ti and HREEs with high(La/Yb)n rations(4.12~9.59)and negative Eu anomaly(SEu 0.56~0.91).Element data demonstrate that the intrusion was produced by the partial melting of thickened mafic lower crust with possible different degrees of addition of juvenile materials.Combined with regional tectonic evolution and discrimina-tion of tectonic setting,we suggest that the porphyric granodiorite was formed in the post-collision setting,which was probably related to the partial melting of a thickened mafic lower crust.

关 键 词：花岗闪长岩 晚寒武世 锆石U-Pb年龄 地球化学 构造环境 佳木斯地块 

分 类 号：P597[天文地球—地球化学]