【摘要】 内蒙古达茂旗南部北口子片麻状花岗闪长岩位于华北克拉通北缘集宁地块, 该地区记录了两期（～2. 7Ga 和～2. 5Ga） 非常重要的新太古代—早古元古代岩浆构造热事件。 尽管地质学家对该地区做了大量的工作, 但是对～2. 5Ga 时期地壳形成机制仍存在较大争议: 地壳增生还是地壳再造? 为了解决上述争议问题, 对北口子地区的片麻状花岗闪长岩进行了年代学以及Hf 同位素研究工作。 锆石U-Pb 测年结果显示, 片麻状花岗闪长岩的原岩形成年龄为2572. 8Ma, 且经历了2520. 6Ma 的变质作用改造。 锆石Hf同位素结果显示, 大部分ε_Hf（t） 值位于球粒陨石线之上 （-0. 4～ +3. 15, 平均值为+1. 34）,Hf 同位素单阶段模式年龄 (T_DM) 范围为2752～2885Ma,Hf 同位素二阶段模式年龄(T^C_DM) 介于2864 ～ 3082Ma,表明达茂旗南部北口子地区的该期岩浆作用代表着一期地壳再造事件。 结合华北克拉通Hf 同位素特征,认为华北克拉通～2. 5Ga 岩浆作用既有地壳增生作用也有地壳改造作用。更多还原

【Abstract】 _The Block,（～ 2. 7Beikouzi gneissic Proterozoic granodiorite is located in thermal Jining events still northern Ga margin of Ga）North are China recorded crustal Craton.in Two area.important Although Neoarchean—Early geologists magmatic-tectonic and about～ 2. 5the this region,order mechanism:have or done a lot of work in this In there solve is the controversy～2. 5paper Ga carried that formation crustal isotope gneissicε_Hf （t）of reconstruction?gneissic issues,dating accretion research crustal the to Beikouzi undergone controversial Zircon this results Ma.out Geochronology protolith and age most model Hf of on granodiorite Ma,in has area.U-Pb show Zircon the isotope Hf formation show granodiorite values is above from2572. 8the and metamorphism ofε_Hf （t）2520. 6values(T^C_DM)Hf results isotope that（-0. 4～ +3. 15,and+1. 34）,range(T_DM)that are meteoroid line Ma,Beikouzi average is single-stage ages suggesting Ma,isotope range～2. 5China2752Ma to in2the885Hf two-stage represents model crustal ages from2Combined864Ma with to Hf both3082the North crustal Ga magmatism Craton,a Ga reconstruction magmatism event.North characteristics crustal of and it is considered that the～ 2. 5of the China Craton has accretion transformation.更多还原