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辽东黑沟地区古元古代碱长花岗岩年代学、地球化学、Hf同位素 特征及其地质意义
投稿时间:2019-07-21  修订日期:2019-09-21  点此下载全文
引用本文:
DOI:10.19762/j.cnki.dizhixuebao.2020020
摘要点击次数: 39
全文下载次数: 44
作者单位E-mail
杨玉伟 辽宁省物测勘查院有限责任公司 478033166@qq.com 
余超 辽宁省地质矿产调查院有限责任公司 286149526@qq.com 
王广伟 辽宁省地质矿产调查院有限责任公司  
苏特 辽宁省地质矿产调查院有限责任公司  
杨新宇 辽宁省地质矿产调查院有限责任公司  
张天元 辽宁省地质矿产调查院有限责任公司  
基金项目:中国地质调查局基础地质调查项目
中文摘要:华北克拉通东部造山带内古元古代中期(2.1~2.2Ga)岩浆记录了造山带早期重要的地壳演化信息,对探讨辽吉造山带古元古代地质演化过程具有十分重要的意义。本文选择了辽东黑沟地区古元古代碱长花岗岩进行岩石学、地球化学、锆石U-Pb年代学和Hf同位素研究。黑沟碱长花岗岩LA-ICP-MS锆石U-Pb测年结果为2186.5±6.5Ma,形成时代为古元古代。岩石属碱性、弱过铝质A型花岗岩,岩石富硅、碱,贫钙、镁、铝,极度富钠贫钾,富集Hf、Zr、Nb、Y等高场强元素,亏损Rb、K、Ba等大离子亲石元素,具有较高的(K2O+Na2O)/Al2O3、FeOT/MgO、Ga/Al比值,负的Eu异常,稀土元素配分曲线呈右倾海鸥型配分模式。锆石饱和温度介于857~884℃之间,同时具有非常低Sr高Yb特征,指示岩石形成于低压高温的伸展构造背景。锆石εHf(t)值为-0.96~+4.58, 二阶段模式年龄tDMc=2476~2821Ma,明显大于花岗岩的成岩时代 ,结合岩石地球化学特征指示黑沟碱长花岗岩岩浆源于太古宙TTG质片麻岩在地壳浅部伸展条件下的部分熔融。综合区域已有的岩石学、地球化学和同位素特征等资料,辽吉地区在古元古代早期可能处于大陆弧后盆地构造环境,黑沟碱长花岗岩是弧后盆地伸展环境下的产物。
中文关键词:古元古代  辽吉造山带  Hf同位素  A型花岗岩  弧后盆地
 
Chronology,Geochemistry and Zircon Hf Isotopes of the Paleoproterozoic Alkali Feldspar Granite from Heigou Area in the Eastern Part of Liaoning Province and Its Geological Significance
Author NameAffiliationE-mail
YANG Yuwei Geophysical Measuring Xeploration Institute of Liaoning Province,Shenyang 478033166@qq.com 
YU Chao Liaoning Survey Academy of Geology and Mineral Resources InvestigationShenyang 286149526@qq.com 
WANG Guangwei Liaoning Survey Academy of Geology and Mineral Resources InvestigationShenyang  
SU Te Liaoning Survey Academy of Geology and Mineral Resources InvestigationShenyang  
YANG Xinyu Liaoning Survey Academy of Geology and Mineral Resources InvestigationShenyang  
ZHANG Tianyuan Liaoning Survey Academy of Geology and Mineral Resources InvestigationShenyang  
Abstract:The magma in the middle Paleoproterozoic(2.1~2.2Ga) in the eastern orogenic belt of the north China craton recorded important crustal evolution information in the early stage of the orogenic belt,which is of great significance for the Paleoproterozoic geological evolution in the Liaoning-Jilin orogenic belt.In this paper,we have studied petrology,geochemistry,zircon U-Pb chronology and Hf isotope characteristics of Paleoproterozoic alkali feldspar granite in Heigou area,eastern Liaoning province.The zircon U-Pb dating result of the granite by LA-ICP-MS was 2186.5±6.5Ma,and the formation age was Paleoproterozoic.The rocks belong to the alkaline and weakly peraluminous A-type granites.The rocks are high in Si and rich in alkali,while poor in Ca,Mg and Al,and also extremely rich in sodium and poor in potassium,at the same time rich in HFSEs(such as Hf,Zr,Nb,Y) and deficit in LILEs(such as Rb,K,Ba),and also with high(K2O+Na2O)/Al2O3,FeOT/MgO,Ga/Al ratios,and with negative Eu anomaly,and the rare earth elements distribution curve shows the right-leaning seagull pattern. The saturation temperature of zircon ranges is between 857℃ and 884℃,and it has a very low Sr and high Yb characteristic,indicating that the rock is formed in the extensional tectonic background of low pressure and high temperature. εHf(t) values of zircons in the granites range from -0.96~+4.58,and two-stage Hf model ages (tDMc) are 2476~2821Ma,which are significantly older than the zircon U-Pb ages of the granites.Combined with lithogeochemical characteristics,it is indicated that the Paleoproterozoic granites are derived from partial melting of Archean TTG gneisses under an extensional environment at shallow crustal level.Based on the data of petrology,geochemistry and isotopic characteristics,the Liaoning-Jilin region was likely to be in the tectonic environment of continental back-arc basin in the early Paleoproterozoic,and the Heigou alkali feldspar granite is the product of the extensional environment of back-arc basin.
keywords:Paleoproterozoic  Liao-Ji Orogen  Zircon Hf Isotopes  A-type granites  back-arc basin
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