华北克拉通北缘凉城基性岩墙成因及古地理的重建意义  

Petrogenesis and paleogeographic reconstruction significance of mafic dykes in Liangcheng,northern margin of the North China craton

作　　者：连光辉 任云伟 施建荣 徐仲元[1,2] LIAN Guanghui;REN Yunwei;SHI Jianrong;XU Zhongyuan(College of Earth Science,Jilin University,Changchun,Jilin 130061,China;Key Laboratory of Mineral Resources Evaluation in Northeast Asia,Ministry of Natural Resources,Changchun,Jilin 130061,China;Tianjin Center,China Geological Survey,Tianjin 300170,China;Precambrian Geological Research Centre,China Geological Survey,Tianjin 300170,China)

机构地区：[1]吉林大学地球科学学院,吉林长春130061 [2]自然资源部东北亚矿产资源评价重点实验室,吉林长春130061 [3]中国地质调查局天津地质调查中心,天津300170 [4]中国地质调查局前寒武纪地质研究中心,天津300170

出　　处：《地质学报》2023年第4期1295-1314,共20页Acta Geologica Sinica

基　　金：国家自然科学基金项目(编号41872203、41872194);中国地质调查项目(编号DD20190035)联合资助的成果。

摘　　要：为揭示华北克拉通北缘凉城基性岩墙的形成时代、岩石成因、构造背景及对罗迪尼亚超大陆重建的意义,本研究借助激光烧蚀多接收器等离子质谱(LA-MC-ICP-MS)锆石U-Pb定年、Hf同位素及全岩地球化学研究手段,对凉城桃花沟岩墙开展了系统研究。研究结果显示,凉城桃花沟岩墙为新元古代早期(903±15 Ma)基性岩浆活动的产物,归属拉斑岩石系列,具有较高的TFeO(12.78%~16.30%)及TiO2(2.59%~3.31%)含量、较低的MgO(2.87%~3.83%)、Cr(32.7×10^(-6)~42.0×10^(-6))、Ni(11.6×10^(-6)~14.5×10^(-6))含量及Mg^(#)值(29~38),富集轻稀土元素(LREE)、Rb、Pb、Zr及Hf元素,亏损Ba、Sr、Nb、Ta、Ti及Eu(Eu/Eu*=0.74~0.83)元素。锆石原位εHf(t)范围为2.4~13.4,单阶段Hf模式年龄(tDM1)范围为1357~892 Ma。综合研究显示,凉城桃花沟岩墙形成于陆内裂谷构造背景,母岩浆来源于较深(~80 km)的软流圈地幔,并且源区有辉石岩组分参与;岩浆经历了橄榄石、单斜辉石、斜长石、铁钛氧化物及磷灰石的分离结晶并遭受了地壳混染作用的影响。地球化学数据表明华北克拉通新元古代早期基性岩浆作用记录了从陆内裂谷向大陆裂解的转换过程。地质及古地磁资料支持新元古代早期华北克拉通与劳伦古陆相邻,其是否与圣弗朗西斯科-刚果克拉通相邻需要更多古地磁证据来检验。In this paper,we undertook laser ablation-multicollector-inductively coupled plasma-mass spectrometer(LA-MC-ICP-MS)investigations on zircons for U-Pb geochronology,zircons in-situ Hf isotopic and whole-rock geochemical analysis on the Taohuagou dyke in Liangcheng,northern margin of the North China craton(NCC).Based on the newly obtained data,we identified the emplacement age,petrogenesis,and tectonic setting of the mafic dykes in Liangcheng and further discussed their implications for the reconstruction of the Rodinia supercontinent.The results show that the Taohuagou dyke was the product of mafic magmatism in the early Neoproterozoic(903±15 Ma),belonging to tholeiitic series,with high TFeO(12.78%~16.30%)and TiO_2(2.59%~3.31%)contents,and low MgO(2.87%~3.83%),Cr(32.7×10^(-6)~42.0×10^(-6)),Ni(11.6×10^(-6)~14.5×10^(-6))contents,and low Mg^(#)values(29~38).They are enriched in light rare earth elements(LREEs),Rb,Pb,Zr,and Hf elements,and depleted in Ba,Sr,Nb,Ta,Ti and Eu(Eu/Eu~*=0.74~0.83)elements.The zircon in-situε_(Hf)(t)of Taohuagou dyke ranges from 2.4 to 13.4,with single-stage Hf model(t_(DM1))ages ranging from 892 to 1357 Ma.The comprehensive study shows that the Taohuagou dyke in Liangcheng was formed in an intracontinental rift tectonic setting.The parent magma originated from the deep(~80 km)asthenospheric mantle,and pyroxenite components were involved in the source area.The magma experienced the fractional crystallization of olivine,clinopyroxene,plagioclase,Fe-Ti oxides and apatite,and was contaminated by the continental crust during emplacement.Geochemical data show that the early Neoproterozoic mafic magmatism in the NCC recorded the transition from intracontinental rifting to continental breakup.Geological and paleomagnetic data support that the NCC was adjacent to Laurentia in the early Neoproterozoic.However,further paleomagnetic research is needed to clarify whether it was adjacent to the S2o Francisco-Congo craton.

关 键 词：新元古代早期 基性岩墙 华北克拉通 陆内裂谷 罗迪尼亚超大陆 古地理重建 

分 类 号：P532[天文地球—古生物学与地层学] P588.124[天文地球—地质学]