辽东地区中生代花岗岩的侵位时代:锆石和独居石U-Pb年代学  

Emplacement Ages of Mesozoic Granites in Liaodong Area:Constraints from Zircon and Monazite U-Pb Dating

作　　者：胡国辉[1,2] 张琪琪 李建锋 张拴宏[1,2] Hu Guohui;Zhang Qiqi;Li Jianfeng;Zhang Shuanhong(Institute of Geomechanics,Chinese Academy of Geological Sciences,Beijing 100081,China;Key Laboratory of Paleomagnetism and Tectonic Reconstruction,Ministry of Natural Resources,Beijing 100081,China)

机构地区：[1]中国地质科学院地质力学研究所,北京100081 [2]自然资源部古地磁与古构造重建重点实验室,北京100081

出　　处：《地球科学》2020年第11期3962-3981,共20页Earth Science

基　　金：国家重点研发计划(No.2018YFC0603802)。

摘　　要：辽东地区中生代岩浆活动强烈,伴随着大规模的金成矿作用.五龙金矿是该地区规模最大的典型石英脉型金矿床,金矿体主要赋存于侏罗纪片麻状花岗岩和早白垩世花岗闪长岩中.因此,该地区中生代岩浆活动对金成矿作用具有显著的制约.选择辽东五龙金矿区片麻状花岗岩和三股流岩体进行岩相学、锆石和独居石U-Pb年代学研究.3个片麻状花岗岩的岩性均为黑云母二长花岗岩,矿物发生强烈的韧性变形,呈定向排列,锆石U-Pb年龄分别为159.2±1.8 Ma、160.2±1.8 Ma和156.1±1.2 Ma,三股流黑云母二长花岗岩样品的锆石U-Pb年龄为123.8±1.2 Ma.花岗岩样品中的独居石矿物学特征和化学组成显示均为岩浆成因,3个片麻状花岗岩的独居石年龄分别为158.1±1.9 Ma、157.5±1.4 Ma和153.5±1.4 Ma,三股流岩体的独居石U-Pb年龄为123.4±1.5 Ma.晚侏罗世片麻状花岗岩的独居石年龄比锆石年龄略小1.1~2.7 Ma,其中2个样品的冷却速率分别为55.56℃/Ma和57.69℃/Ma,表明晚侏罗世岩浆在高温阶段为一快速冷却作用过程,可能经历了快速的地壳抬升事件.锆石和独居石的U-Pb年龄结果表明片麻状花岗岩和三股流岩体分别形成于侏罗纪晚期和白垩纪早期,结合已有研究资料,辽东五龙矿集区主要发生了晚侏罗世和早白垩世两期岩浆活动,与古太平洋板块向欧亚大陆俯冲作用有关,并伴随着早白垩世金矿的形成.The Mesozoic magmatic activities extensively developed in East Liaoning Province accompanied by large-scale gold mineralization.Wulong gold deposit is a representative largest quartz-vein type gold deposit,and the gold ore bodies mainly hosted in Jurassic gneiss biotite granite and Early Cretaceous granodiorite.Therefore,Mesozoic magmatism has a significant genetic relation with the gold mineralization.In this paper,it presents zircon and monazite U-Pb dating of gneiss granite and Sanguliu rock mass in Wulong gold ore-concentrated district to constrain their emplacement ages.The gneiss granite is dominated by biotite monzogranite,the minerals of which show strong ductile deformation and are oriented.Their zircon U-Pb ages are 159.2±1.8 Ma,160.2±1.8 Ma,and 156.1±1.2 Ma,respectively.Zircons from Sanguliu biotite monzogranite yield a U-Pb age of123.8±1.2 Ma.Mineralogical characteristics and chemical compositions of monazites from four granitic samples suggest a magmatic origin.New LA-ICP-MS dating of monazites from three gneiss granite samples yielded U-Pb ages of 158.1±1.9 Ma,157.5±1.4 Ma,and 153.5±1.4 Ma,respectively,and 123.4±1.5 Ma for Sanguliu biotite monzogranite.Monazite ages of Late Jurassic gneiss granite are 1.1-2.7 Ma younger than their zircon ages,two of which have high cooling rate of 55.56℃/Ma and57.69℃/Ma,suggesting a rapid cooling process and crustal uplift.Both zircon and monazite U-Pb ages indicate that the gneiss granite and Sanguliu rock mass formed during Late Jurassic and Early Cretaceous,respectively.In combination with the available data,Wulong gold ore-concentrated district mainly developed Late Jurassic and Early Cretaceous magmatic activities,which were closely related to the subduction of Paleo-Pacific plate to Eurasia continent,accompanied by Early Cretaceous gold mineralization.

关 键 词：辽东 中生代花岗岩 锆石和独居石U-Pb定年 金矿 地质年代学 

分 类 号：P597[天文地球—地球化学]