华北板块北缘东段泥盆纪伸展作用:来自辽北昌图碰撞后岩浆岩的证据  

Devonian extension of the eastern section of the northern margin of the North China Plate:Evidence from post-collision magmatic rocks in Changtu area,northern Liaoning Province

作　　者：张超[1,2] 权京玉 张丽 葛锦涛[1,2] 张立东 ZHANG Chao;QUAN JingYu;ZHANG Li;GE JinTao;ZHANG LiDong(Shenyang Center of Geological Survey,China Geological Survey,Shenyang 110034,China;Northeast Geological S&T Innovation Center of China Geological Survey,Shenyang 110034,China;Liaoning Institute of Geology and Mineral Resources Co.LTD,Shenyang 110016,China;College of Earth Science,Institute of Disaster Prevention,Sanhe 065201,China)

机构地区：[1]中国地质调查局沈阳地质调查中心,沈阳110034 [2]东北地质科技创新中心,沈阳110034 [3]辽宁省地质矿产研究院有限责任公司,沈阳110016 [4]防灾科技学院地球科学学院,三河065201

出　　处：《岩石学报》2022年第8期2345-2363,共19页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(42102271、42130305、41902234);中国地质调查局项目(DD20190042-03、DD20221632-02、DD20160048)联合资助。

摘　　要：华北板块北缘是研究古亚洲洋演化及其与华北克拉通北缘相互作用过程的关键地带,但其晚古生代特别是泥盆纪时期的构造演化一直存在争议,辽北地区出露的泥盆纪岩浆岩为解决这一科学问题提供了新的证据。本文以昌图地区新发现的祥子岭和夏家沟花岗质岩体以及红花店变流纹岩为研究对象,开展了岩相学、地球化学、年代学以及Lu-Hf同位素等研究,并对其岩石成因及构造环境进行了探讨。LA-ICP-MS锆石U-Pb测年结果显示,祥子岭黑云母二长花岗岩侵位年龄为389±2Ma,夏家沟二长花岗岩侵位年龄为377±7Ma,红花店变流纹岩年龄为385±2Ma,是泥盆纪岩浆活动的产物。这些岩石具有高硅(SiO_(2)=71.23%~77.39%)、富碱(K_(2)O+Na_(2)O=8.23%~10.25%),贫铁(FeO^(T)=1.17%~2.68%)、镁(MgO=0.01%~0.24%)、钙(CaO=0.40%~1.27%),以及准铝质-弱过铝质(A/CNK=0.84~1.03)的地球化学特征,并且富集Rb、Th、Pb和亏损Ba、P、Ti。结合较低的Zr+Nb+Ce+Y含量(109.4×10^(-6)~329.4×10^(-6))、10000×Ga/Al比值(0.57~3.59)和锆饱和温度(716~778℃),昌图泥盆纪岩浆岩表现出高分异I型花岗岩的特征。此外,样品的锆石ε_(Hf)(t)值皆为正值(6.4~14.6)且随着结晶年龄的年轻而显著升高,表明研究区泥盆纪岩浆岩是幔源基性岩浆与新生地壳再融熔体发生岩浆混合作用的产物,在岩浆演化过程中经历了结晶分离作用。结合区域资料分析,辽北昌图泥盆纪岩浆岩形成于伸展环境,与晚志留世末白乃庙弧与华北克拉通北缘发生弧-陆碰撞后的地壳伸展作用有关。The northern margin of the North China Plate is a key area for studying the evolution of the Paleo-Asian Ocean and its interaction with the northern margin of the North China Craton.However,the tectonic evolution of the North China Plate in the Late Paleozoic,especially in the Devonian Period,has been controversial.The Devonian magmatic rocks exposed in the northern Liaoning provide a new evidence for solving this scientific problem.In this paper,the petrography,geochemistry,chronology and Lu-Hf isotopes of the Xiangziling and Xiajiagou granitic bodies and the Honghuadian meta-rhyolite,which are all newly discovered in the Changtu area,are studied,and their petrogenesis and tectonic environment are also discussed.LA-ICP-MS zircon U-Pb dating results show that the Xiangziling biotite monzogranite is 389±2Ma,the Xiajiagou monzogranite is 377±7Ma,and the Honghuadian metamorphic rhyolite is 385±2Ma,which were the products of Devonian magmatic activity.These rocks are high in silicon(SiO_(2)=71.23%~77.39%),rich in alkali(K_(2)O+Na 2O=8.23%~10.25%),poor in iron(FeO^(T)=1.17%~2.68%),magnesium(MgO=0.01%~0.24%),and calcium(CaO=0.40%~1.27%).They also show geochemical characteristics of peraluminous to weakly peraluminous(A/CNK=0.84~1.03),with enrichment of Rb,Th,Pb and depletion of Ba,P,Ti.Given the aforesaid characteristics and low Zr+Nb+Ce+Y content(109.4×10^(-6)~329.4×10^(-6)),10000×Ga/Al ratio(0.57~3.59)and zirconium saturation temperature(716~778℃),the Changtu Devonian magmatic rocks exhibit the characteristics of highly fractionated I-type granites.In addition,the zirconεHf(t)values of the samples(6.4~14.6)are positive and increase significantly with the age of crystallization,indicating that the Devonian magmatic rocks in the study area were the product of the magmatic mixing between mantle-derived basaltic magma and the remelting of new crust,and experienced crystallization separation during the magmatic evolution.Based on the regional data analysis,the Changtu Devonian magmatic rocks were formed in an ext

关 键 词：泥盆纪 花岗岩 碰撞后伸展 昌图地区 华北板块北缘东段 

分 类 号：P588.121[天文地球—岩石学] P588.141[天文地球—地质学] P597.3