辽东半岛隆昌地区～2113 Ma变辉长岩地球化学与Hf同位素研究：对胶辽吉造山带构造演化的制约  

Characteristics of Geochemistry and Hf Isotope from Meta-Gabbro in Longchang Area, Liaodong Peninsula:Implications on Evolution of the Jiao-Liao-Ji Paleoproterozoic Orogenic Belt

作　　者：赵岩[1,2] 寇林林 张朋[1,2] 毕中伟 李东涛[1,2] 陈聪 Zhao Yan;Kou Linlin;Zhang Peng;Bi Zhongwei;Li Dongtao;Chen Cong(Shenyang Center of Geological Survey,China Geological Survey,Shenyang 110034,China;Northeast China Center for Geoscience and Innovation,Shenyang 110034,China)

机构地区：[1]中国地质调查局沈阳地质调查中心,辽宁沈阳110034 [2]东北地质科技创新中心,辽宁沈阳110034

出　　处：《地球科学》2019年第10期3333-3345,共13页Earth Science

基　　金：国家重点研发计划项目(Nos.2018YFC0603804,2016YFC0600108);中国地质调查局项目(Nos.DD20190156,DD20190042-03)

摘　　要：辉长岩的成岩时代、成因等研究对限定胶辽吉造山带构造背景等关键问题具有重要意义.对其开展详细的岩石地球化学分析、全岩Nd同位素和锆石U-Pb测年及原位Hf同位素分析,结果显示样品受蚀变影响不大,TiO2含量较低(<1.31%),FeOT(11.91%~14.25%)、MgO(6.88%~7.62%)含量不高,K2O含量中等偏高(0.85%~1.23%),属钙碱性-高钾钙碱性岩浆系列,岩石轻重稀土分馏不明显,富集Rb、Ba、K等大离子亲石元素,亏损高场强元素P、Hf等,岩石相对富集Nd同位素,εNd(t)值介于-1.6~2.6,(176Hf/177Hf)i比值变化于0.281497~0.281612之间,εHf(t)值变化于2.2~6.3之间,模式年龄tDM1(Hf)值介于2.25~2.33 Ga.多种特征元素地球化学图解显示辉长岩具有E-MORB特征,与裂谷构造环境中产出的MORB和OIB不同.研究认为胶辽吉造山带在~2.1 Ga已存在洋壳俯冲,并可能已存在古岛弧,造山带演化过程中存在弧陆碰撞.The meta-gabbro,distributed in the Longchang area,eastern part of the North China craton,yields a zircon U-Pb age of 2113±15 Ma by LA-ICP-MS.Detailed geochemistry analyses,whole rock Nd isotope and zircon U-Pb and in-situ Hf isotope analyses were made to confine tectonic settings of the Jiao-Liao-Ji orogenic belt and other crucial problems.The gabbro samples studied show calc-alkaline to high potassic alkaline series features with weak alteration and also low content of TiO2(<1.31%),moderate content of MgO(6.88%-7.62%),FeOT(11.91%-14.25%)and K2O(0.85%-1.23%).The studied samples are characterized with low REE content and show weak REE fractionation and depletion in high field strength elements like P and Hf.The samples also show enrichment in large ion lithophile elements like Rb,Ba and K,and enrichment in Nd isotope content,withεNd(t)values of-1.6 to 2.6.(176Hf/177Hf)i of zircon from the meta-gabbro samples ranging from 0.281497 to 0.281612,and the calculatedεHf(t)values ranging from 2.2 to 6.3.The calculated Hf modal ages are 2.25 to 2.33 Ga.Several crucial diagrams from meta-gabbro sample analysis results show far distance from MORB or OIB both of which are typical basalts distributed in a rift geological setting.E-MORB with continental crust component mixed in may be the exact origin of the meta-basalts in the Longchang area.It can be concluded that there was ocean crust subduction in^2.1 Ga within the Jiao-Liao-Ji orogenic belt,with possible paleo-arc and the evolution model of the Jiao-Liao-Ji orogenic belt is more like an arc-continental collision model.

关 键 词：华北克拉通 胶辽吉造山带 隆昌地区 古元古代 变质辉长岩 地球化学 

分 类 号：P595[天文地球—地球化学]