江西婺源东坑口酸性岩体年代学及成因研究  

Geochronology and genesis of Dongkengkou acid pluton in Wuyuan,Jiangxi Province

作　　者：武彬[1] 张雪辉[1] 余峰 孙建东[1] 张勇[1] 吕劲松[1] 徐敏成 高天山[1] 叶现韬[3] WU Bin;ZHANG Xuehui;YU feng;SUN Jiandong;ZHANG Yong;LÜ Jinsong;XU Mincheng;GAO Tianshan;YE Xiantao(Nanjing center,China Geological Survey,Nanjing 210016,Jiangsu,China;Jiangshan Natural Resources and Planning Bureau,Jiangshan 324100,Zhejiang,China;College of Oceanography,Hohai University,Nanjing 210098,Jiangsu,China)

机构地区：[1]中国地质调查局南京地质调查中心,江苏南京210016 [2]江山市自然资源和规划局,浙江江山324100 [3]河海大学海洋学院,江苏南京210098

出　　处：《中国地质》2021年第5期1580-1595,共16页Geology in China

基　　金：中国地质调查局项目(DD20160038)资助。

摘　　要：文章选取赣东北地区东坑口酸性岩体作为研究对象,对酸性岩体的岩相学、年代学及锆石原位Hf同位素、岩石地球化学进行研究。通过LA-ICP-MS锆石U-Pb定年得出东坑口酸性岩体中花岗斑岩的年龄为(134.25±0.99)Ma,花岗闪长斑岩加权平均年龄为(132.6±1.3)Ma,可以判断其形成时代属燕山晚期。东坑口酸性岩体主量元素地球化学特征基本一致,均为高钾钙碱性花岗岩,SiO_(2)含量较高,铝饱和指数A/CNK值均小于1.1,属于典型的I型花岗岩;微量元素地球化学表现为富集大离子亲石元素Rb、Th、U,明显亏损高场强元素Ti、P,轻微亏损Ba、Sr的特征;酸性岩体稀土元素特征具有一致性,Eu亏损不明显。结合Hf同位素表明酸性岩体的岩浆由下地壳变质砂岩部分熔融组合形成,且东坑口岩体具有典型的埃达克岩特征,为低Mg^(#)埃达克岩系。该酸性岩体是在陆陆碰撞过程中,碰撞挤压致使下地壳加厚以后,向伸展减薄转换的体制中形成的。产出环境为陆内造山环境,太平洋板块向华南大陆俯冲引起的弧后多阶段岩石圈伸展作用。Dongkengkou acid pluton in northeast Jiangxi Province was selected as a study case to expound its petrography,chronology,zircon Hf isotopes and petrogeochemistry.The LA-ICP-MS zircon U-Pb dating of granite porphyry and granodiorite porphyry yields ages of(134.25±0.99)Ma and(132.6±1.3)Ma respectively,indicating that the Dongkengkou pluton was emplaced during the late Yanshanian.The main element geochemical characteristics of Donggangkou acidic pluton are basically the same.They are all high-k calc-alkaline granites with high SiO_(2) content and aluminum saturation index A/CNK values less than 1.1,which belong to typical I-type granite.The pluton is enriched in large ion lithophile elements such as Rb,Th and U,depleted in high field strength elements such as Ti and P,and slightly depleted in Ba and Sr.The characteristics of rare earth elements in acidic rocks are consistent,but Eu deficit is not obvious.Combined with Hf isotopes,it is indicated that the magma of the pluton was formed by the partial melting of metamorphic sandstone from the lower crust.It has typical characteristics of adakite rocks with low Mg.It is inferred that the pluton was formed during the transformation from crust thickening due to collision and compression to crust thinning due to extension in the process of continent-continent collision.The tectonic environment is intracontinental orogen.The subduction of the Pacific plate to the South China Continent results in the back-arc multi-stage lithospheric extension.

关 键 词：酸性岩体 年代学 成因 地质调查工程 东坑口 婺源 江西 

分 类 号：P588.121[天文地球—岩石学] P597[天文地球—地质学]