大兴安岭中部扎赉特旗晚三叠世A型花岗岩的发现及其地质意义  

Discovery and Geological Significance of Late Triassic A–Type Granite in Jalaid Banner,Middle of Great Xing’an Range

作　　者：孙巍[1,2] 许逢明[1,2] 吴大天[1,2] 赵院冬[1,2] 秦涛[1,2] 马永非[1,2] 臧延庆 司秋亮[1,2] 付俊彧[1,2] 宋维民[1,2] SUN Wei;XU Fengming;WU Datian;ZHAO Yuandong;QIN Tao;MA Yongfei;ZANG Yanqing;SI Qiuliang;FU Junyu;SONG Weimin(Shenyang Center of China Geological Survey,Shenyang 110034,Liaoning,China;Northeast Science&Technology Innovation Center of China Geological Survey,Shenyang 110034,Liaoning,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]中国地质调查局东北地质科技创新中心,辽宁沈阳110034

出　　处：《西北地质》2023年第2期80-91,共12页Northwestern Geology

基　　金：中国地质调查局项目“塞尔维亚铜金资源调查”(DD20201162);“内蒙古1∶5万五家户、孟家沟、莫利根屯、扎赉特旗、巴彦高勒五幅区域地质调查”(DD20160048-03);“东北基础地质综合研究与片区总结”(1212011220435);“中国大地构造演化和国际亚洲大地构造图编制”(DD20190360)联合资助。

摘　　要：大兴安岭中部在三叠纪叠加了古亚洲洋和蒙古−鄂霍茨克洋的影响,其构造背景存较大争议。笔者对大兴安岭中部扎赉特旗中粗粒正长花岗岩进行岩石学、岩石地球化学、锆石LA−ICP−MS U−Pb测年和Lu−Hf同位素分析。结果显示:锆石U−Pb年龄加权平均值为(228.5±2.0)Ma(MSWD=2.8);岩石高Si、富Fe、高K、低Sr和Eu,相对富Nb和富Zr,高10000×Ga/Al(3.0~3.1);全岩锆饱和温度平均值为805℃;综合判定该套花岗岩为铝质A型花岗岩。该岩体的εHf(t)值为+5.28~+8.00,二阶段Hf模式年龄(TDM2)为683~832 Ma,指示花岗岩可能形成于新增生地壳物质的部分熔融。综合区域已有研究成果,表明扎赉特旗地区的古亚洲洋残余洋盆在二叠纪闭合并进入碰撞造山阶段,晚三叠世A型花岗岩的出现,标志着本区进入造山后伸展阶段。The middle of Great Xing’an Range superimposed the influence of the Paleo–Asian ocean and the Mongol–Okhotsk ocean in the Triassic,and its tectonic setting remains controversial.Taking the medium-coarse grained texture syenogranite in Jalaid Banner,middle of Great Xing’an Range as research object,the study on petrology,geochemistry,zircon LA–ICP–MS U–Pb age and Lu–Hf isotope compositions have been carried out.The results show that the weighted average zircon U–Pb age of the granite is(228.5±2.0)Ma(MSWD=2.8);The rocks are high in Si,Fe and K,depleted in Sr and EU,relatively rich in Nb and Zr,and high in 10000×Ga/Al(3.0~3.1);The average of zircon saturation temperature is 805℃;It is comprehensively determined that the granite is considered to be the aluminous A-type granite.The graniteεHf(t)values range from+5.28 to+8.00,and the TDM2 range from 683 Ma to 832 Ma,indicating that the granite may have been formed by partial melting of neoaccretionary crustal materials.Based on the regional research results,this paper holds that the residual ocean basin of the Paleo-Asian ocean in the Jalaid Banner closed and entered the collision orogeny stage in the Permian,and the appearance of A-type granite in the Late Triassic indicates that the area entered the post-oro-genic extension stage.

关 键 词：地球化学 晚三叠世 A型花岗岩 古亚洲洋 扎赉特旗 大兴安岭中部 

分 类 号：P581[天文地球—岩石学]