摘要
松嫩-张广才岭地块位于我国东北兴蒙造山带东段,受古亚洲洋构造域及濒太平洋构造域叠加转换的影响,该区构造演化十分复杂,因此,对区内花岗岩进行研究能够有效反演该区的构造演化历史。德裕花岗岩体位于松嫩-张广才岭地块东缘张广才岭岩浆岩带北段,样品岩性为二云二长花岗岩,主要由石英、斜长石、钾长石、黑云母、白云母、角闪石等矿物组成。锆石U-Pb定年结果显示其侵位时代为254±1Ma,形成于晚二叠世。岩石具有高硅(71.26%~75.34%),中铝(12.23%~14.71%),低镁(0.33%~0.52%)的特点,K2O/Na2O为0.85~1.17,铝饱和指数A/CNK为0.99~1.05,属于弱过铝质高钾钙碱性岩石。样品稀土元素含量较低(∑REE=54.7×10-6~82.0×10-6),轻稀土富集而重稀土亏损(LREE/HREE=8.49~10.46),显示负Eu异常(δEu=0.69~0.80)。样品岩石学特征和地球化学特征暗示其为Ⅰ型花岗岩。德裕花岗岩样品的Nb/Ta值为10.42~15.12,Zr/Hf值为33.77~46.45,结合Sr-Nd同位素分析结果及两阶段模式年龄(TDM2(Ma)为1330~1375Ma),显示该花岗岩体起源于松嫩-张广才岭地块的中元古代物源区。微量元素特征显示高场强元素Th、U、Zr、Hf为正异常,Ta、Nb、P、Ti相对亏损,显示活动陆缘弧特征,在构造环境判别图解中位于俯冲与碰撞交汇部位,结合本区及相邻地区同时代岩浆岩及变质岩的研究,认为德裕花岗岩为东北地区古亚洲洋俯冲行将结束时岩浆活动的产物。
The Songnen-Zhangguangcai Range Massif is located in the eastern Xing’an-Mongolian Orogenic Belt.Influenced by the superimpositon and transformation of the Paleo-Asian Ocean and Paleo-Pacific tectonic system,the tectonic evolution of this area is extremely complicated.Hence,further study of the granite can help understand the tectonic evolution history of the Songnen-Zhangguangcai Range Massif.The Deyu fine-grained granite at the northern margin of the Zhangguangcai Range magmatic rock belt is composed mainly of quartz,plagioclase,K-feldspar,biotite,muscovite and amphibole,etc.Zircon LA-ICP-MS U-Pb dating yielded an age of 254±1 Ma,suggesitng that the emplacement occurred in Late Permian.The granites from the Deyu pluton have high SiO2(71.26%~75.34%),moderate Al2O3(12.23%~14.71%),low MgO(0.33%~0.52%),with K2O/Na2O of 0.85~1.17 and A/CNK of 0.99~1.05,suggesting that they belong chemically to weak peraluminous,high fractionated high-K and Ca alkaline Ⅰ-type granites.The grantie has the low REE content(∑REE=54.7×10-6~72.8×10-6)and distinctive differentiation of LREE and HREE(LREE/HREE=8.49~10.46),and obvious positive Eu anomalies(δEu=0.69~0.8).The Nb/Ta(10.42~15.12),Zr/Hf(33.77-46.45),combined with the Sr-Nd isotopes(TDM2(Ma)=1330~1375 Ma),indicate that the granite derived from the Mesoproterozoic source area in lower crust.Trace element characteristic shows enrichment of Th,U,Zr,Hf,and relative depletion of Ta,Nb,P and Ti,suggesting an active enviroment of continental margin arc.The tectonic discrimination diagram shows a convergence part between subduction and collosion.Combined with study of contemporary granite and metamorphic rocks in the area and neighboring areas,it can be concluded that the Deyu granite was the product of Late Permian magmatism at the end of the subduction of the PaleoAsian Ocean.
作者
李韶凯
刘金龙
周永恒
刘二情
LI Shaokai;LIU Jinlong;ZHOU Yongheng;LIU Erqing(Institute of Geomechanics,Chinese Academy of Geological Sciences,Beijing 100081;School of Earth and Space Sciences,Peking University,Beijing 100871;Shengyang Geological Survey Center,China Geological Survey,Shenyang 110034;Hebei regional geological survey institute,Langfang 065000)
出处
《地质学报》
EI
CAS
CSCD
北大核心
2020年第2期450-466,共17页
Acta Geologica Sinica
基金
中国地质调查局项目(编号DD20190438)资助成果.
