吉林中部后倒木中侏罗世花岗质岩石的成因:对中亚造山带东部元古宙大陆地壳生长的启示  

Petrogenesis of Middle Jurassic granitoids in Houdaomu,Central Jilin Province:Implications for the growth of Proterozoic continental crust in the eastern CAOB

作　　者：张立仕[1] 孙丰月[1,2] 钱烨 张雅静[1,2] 王力 王琳琳[1] ZHANG LiShi;SUN FengYue;QIAN Ye;ZHANG YaJing;WANG Li;WANG LinLin(College of Earth Sciences,Jilin University,Changchun 130061,China;Key Laboratory of Mineral Resources Evaluation in Northeast Asia,Ministry of Natural Resources,Changchun 130061,China)

机构地区：[1]吉林大学地球科学学院,长春130061 [2]自然资源部东北亚矿产资源评价重点实验室,长春130061

出　　处：《岩石学报》2021年第7期2051-2072,共22页Acta Petrologica Sinica

基　　金：国家重点研发计划项目(2017YFC0601304);国家自然科学基金项目(41402060)联合资助。

摘　　要：中亚造山带属于地球上最大的增生型造山带其中之一,中亚造山带东部正是我国东北地区,而该地区的地壳增长时间与地壳增长机制仍然有待于进一步深入的研究。本研究选取中亚造山带东部后倒木地区的花岗质岩石为研究对象,进行岩石学、岩石地球化学、同位素年代学等研究,结合前人的研究成果,探讨其成因岩石学、构造背景以及对地壳增生的指示意义。通过同位素测年研究,发现后倒木地区的花岗岩类岩石就位于175-171Ma;全岩地球化学结果显示SiO_(2)含量为66.58%-76.73%,Al_(2)O_(3)含量为12.21%-16.03%,MgO含量介于0.09%-2.07%之间,显示出高钾钙碱性特征;后倒木地区花岗岩类岩石富集大离子亲石元素,同时亏损高场强元素;Sr-Nd-Hf同位素显示:ISr值介于0.7063-0.7077之间,εNd(t)值介于+2.38-+3.95之间,具年轻的tDM2年龄(639-768Ma),岩浆锆石εHf(t)值介于+4.1-+9.0之间,同样具有年轻的二阶段模式年龄tDM2(554-806Ma),揭示岩石重熔的下地壳物质可能是花岗岩类岩石的源区。综合研究表明,古太平洋板块俯冲导致区域下地壳熔融,形成该类花岗质岩石,而模式年龄揭示新元古代为中亚造山带重要的地壳生长期。The Central Asian Orogenic Belt(CAOB)is one of the largest accretionary orogenic belts in the world.Northeast China is located in the eastern part of the CAOB,and its crustal growth time and mechanism need to be further explored.In this study,we selected the granitoids from Houdaomu area in the CAOB as the research objects,and studied their petrology,LA-ICP-MS zircon U-Pb geochronology,petrochemistry and Sr-Nd-Hf isotope geochemistry.Combined with the previous research results,we discussed their petrogenesis,tectonic setting and the indication of crustal accretion.The zircons from granitoids yield U-Pb concordant ages 175-171Ma.These granitoids are characterized by SiO_(2)(66.58%-76.73%),Al_(2)O_(3)(12.21%-16.03%),and MgO(0.09%-2.07%)contents,showing the characteristics of high potassium calc alkaline;the rocks are enriched in LILE and depleted in HFSE,which is consistent with the trace elements of arc igneous rocks.The Sr-Nd-Hf isotopes show that the ISr values range from 0.7063 to 0.7077,theεNd(t)values range from+2.38 to+3.95,and the corresponding tDM2 ages are 639Ma to 768 Ma,the zirconεHf(t)values range from+4.1 to+9.0,and the two-stage model age tDM2 varying from 554Ma to 806Ma,suggesting that the rocks are derived from the remelting of the lower crust.The comprehensive study shows that the subduction of the Paleo Pacific Plate resulted in the melting of the regional lower crust and the formation of this kind of granitoids.The model age indicates that the Neoproterozoic was an important period of crustal growth in the CAOB.

关 键 词：中亚造山带 地壳生长 后倒木 锆石U-Pb年龄 岩石地球化学 SR-ND-HF同位素 

分 类 号：P588.121[天文地球—岩石学] P597.3[天文地球—地质学]