内蒙古东乌旗北部晚侏罗世A型花岗岩的厘定及其构造意义  

Defination of Late Jurassic A-type granite in the north Ujimqin Banner,Inner Mongolia and the tectonic implications

作　　者：赵鸿燕 朱德胜[3] 邱庆伦 常秋玲 吕际根 刘家橘[3] ZHAO Hongyan;ZHU Desheng;QIU Qinglun;CHANG Qiuling;LV Jigen;LIU Jiaju(Henan Acedemy of Territorial Spatial Survey and Planning,Zhengzhou 450053,China;Key Laboratory for Dynamic Monitoring of Land and Resources in Henan Province,Zhengzhou 450053,China;Henan institute of geological research,Zhengzhou 450001,China)

机构地区：[1]河南省国土空间调查规划院,郑州450053 [2]河南省国土资源动态监测重点实验室,郑州450053 [3]河南省地质研究院,郑州450001

出　　处：《地质找矿论丛》2023年第4期457-467,共11页Contributions to Geology and Mineral Resources Research

基　　金：中国地质调查局项目“内蒙古东乌旗北部塔尔根敖包边防连等8幅1∶5万区域地质调查”(编号:1212010881219)资助。

摘　　要：内蒙古东乌旗北部地区分布有大量的晚侏罗世花岗岩,且有早中晚三次侵入。本文对东乌旗塔尔根敖包边防站一带的晚侏罗世三次花岗岩侵入岩体开展了岩石化学、微量稀土元素地球化学及岩体锆石SHRIMP U-Pb年龄测试研究。研究结果表明:晚侏罗世三次花岗侵入岩岩石化学方面具有高硅、过铝、高钾钙碱性特点。岩体微量元素均明显富集大离子亲石元素Rb、Th、U、K和Ph,但Ba和Sr相对亏损;在高场强元素中,Nb、Ta、Ti亏损明显,Zr和Hf相对富集。岩体稀土元素含量均较高,球粒陨石标准化配分模式图曲线呈“海鸥”型,Eu负异常明显。花岗岩Na 2O-K 2O图解显示样品投影点均落入A型花岗岩区,且10000×Ga/A1值高,属于铝质A型花岗岩。花岗岩锆石SHRIMP U-Pb测年显示,第二次侵入花岗岩岩浆结晶年龄162.8 Ma±1.8 Ma,第三次侵入花岗岩岩浆结晶年龄159.4 Ma±2.1 Ma;综合分析认为,该区铝质A型花岗岩形成于侏罗纪晚期(早燕山晚期),三次侵入的花岗岩——粗中粒多斑状二长花岗岩、细中粒少斑状正长花岗岩、细中粒含斑状正长花岗岩,属于同一个岩浆演化旋回,应该为古太平洋板块向西北俯冲后伸展作用的产物。塔尔根敖包一带早燕山晚期铝质A型花岗岩是在东乌旗北部首次确定出的具有可靠年代学资料的燕山期A型花岗岩。Late Jurassic granite is widely spread in the north East Ujimqin Banner,Inner Mongolia.The granite is with three episodic(early,middle and late)intrusion.Study on petrochemistry,trace element and REE geochemistry and zircon SHRIMP U-Pb age dating of the three-episode-intruded granite in Taergenaobao frontier station area is carried out.The granite characterized 159.4 Ma±2.1 Ma by high Si,pera-aluminous and high K-Ca alkaline property,enrichment of large ionic lithophile element Rb、Th、U、K and Ph but relative depletion of Ba and Sr,obvious depletion of high strong field elements of Nb、Ta、Ti but relative enrichment of Zr and Hf,relative high REE content,the seagull-shaped chondrite-normalized REE pattern with obvious negative Eu anomaly.Projection points of the granite fall in field of A type granite in w(Na 2O)-w(K 2O)plot,159.4 Ma±2.1 Ma and high value of 10000×Ga/A1 of the granite suggest that it belongs to aluminous A type granite.Zircon SHRIMP U-Pb age of 162.8 Ma±1.8 Ma is crystallization age of the secondly intruded granitic magma.Zircon SHRIMP U-Pb age of 159.4 Ma±2.1 Ma is crytallization age of thirdly intruded magma.The firstly intruded coarse-medium grained spotted monzonitic granite,the secondly intruded less spotted fine-medium grained orthoclase granite and spotted fine-medium grained orthoclase granite are of the same magmatic evolution cycle formed in Late Jurassic period(late period of Yanshan movement)and the product of stretching movement after NW subduction of pacific plate.Aluminous A type granite in Taergenaobao area in the north East Ujimqin Banner is the first one with reliable age dating data.

关 键 词：铝质A型花岗岩 SHRIMP U-Pb年龄 伸展环境 晚侏罗世 东乌旗 内蒙古 

分 类 号：P588.121[天文地球—岩石学] P597.1[天文地球—地质学]