摘要
包括辽东半岛在内的华北克拉通北缘早白垩世早期岩浆活动极其稀少,研究程度较低,导致该时期的地质背景限定缺乏直接证据.对辽东半岛三股流地区新发现的花岗伟晶岩开展了岩石学、锆石U-Pb年代学、锆石阴极发光(CL)成像技术、锆石微量元素、全岩地球化学和锆石Lu-Hf同位素等方面的研究,以期为研究区早白垩世早期构造背景提供制约.花岗伟晶岩锆石阴极发光微弱甚至不发光,大多数锆石内部结构为斑杂状分带或海绵状分带,少见岩浆震荡环带,Th/U<0.1,其锆石稀土元素特征也与岩浆锆石明显不同,显示出热液锆石特征.锆石U-Pb年代学结果表明花岗伟晶岩的形成年龄为144.3±2.7 Ma,属早白垩世早期.花岗伟晶岩以富Si、Al、碱,贫Fe、Mg,富集大离子亲石元素,亏损高场强元素,以及显示出一定的四分组效应为特征.其εHf(t)为-27.4^-24.7,二阶段模式年龄为2.91~2.74 Ga,与五龙中晚侏罗世花岗岩Hf同位素组成相类似.综合以上研究,认为三股流花岗伟晶岩经历了较高程度的分异结晶,与五龙中晚侏罗世花岗岩存在成因联系,其成岩介质为富含热液的岩浆-热液共存体系.辽东半岛早白垩世早期岩浆活动形成于伸展背景,该伸展背景可能与蒙古-鄂霍茨克洋后碰撞伸展和太平洋俯冲相关.
The early stage of Early Cretaceous magmatic activity in the Liaodong Peninsula was extremely rare and the research has been inadequate,which leads to the lack of direct evidence for constraints on the tectonic setting.Here,it presents new petrological,whole-rock geochemical,zircon U-Pb geochronological,cathodoluminescence(CL)imaging,trace element and LuHf isotopic data for granitic pegmatite of the Sanguliu region,Liaodong Peninsula.Most of the zircon grains show very weak cathodoluminescence,with few oscillatory zoning,low Th/U ratios(<0.1),and the zircon REEs are also markedly different from magmatic zircons,which is typical of hydrothermal zircon.Zircon U-Pb dating shows that the granitic pegmatite was formed at144.3±2.7 Ma.The granitic pegmatite is characterized by enrichment in Si,Al and alkali,and depletion in Fe and Mg.In addition,the granitic pegmatite is enriched in lithophile elements and depleted in high-field strength elements,with REE tetrad effect.The zircon grains from the granitic pegmatite haveεHf(t)values of-27.4 to-24.7,with two-stage Hf model ages ranging from 2.91 to 2.74 Ga,which is similar to the Wulong Middle-Late Jurassic granites.It can infer that Sanguliu granitic pegmatite may have genetic relationship with Wulong Middle-Late Jurassic granites,and Sanguliu granitic pegmatite may be originated from the hybrid of hydrothermal fluid and magma after the highly fractional crystallization of parental magma.By combining these findings with the previous research results,this study proposes that the early stage of Early Cretaceous magmation was formed at extension setting in the Liaodong Peninsula,which is related to the post-collision of the Mongol-Okhotsk Ocean and the back-arc basin of the Pacific plate subduction.
作者
李锦毓
钱烨
李予晋
孙金磊
赵昌吉
孙丰月
沈艳杰
Li Jinyu;Qian Ye;Li Yujin;Sun Jinlei;Zhao Changji;Sun Fengyue;Shen Yanjie(College of Earth Sciences,Jilin University,Changchun,130061,China;Key Laboratory of Mineral Resources Evaluation in Northeast Asia,Ministry of Natural Resources,Changchun,130061,China)
出处
《地球科学》
EI
CAS
CSCD
北大核心
2020年第11期4054-4071,共18页
Earth Science
基金
科技部深地专项(No.2018YFC0603804)
吉林省教育厅“十三五”科学技术项目(No.JJKH20200946KJ)
自然资源部东北亚矿产资源评价重点实验室自主基金项目(Nos.DBY-ZZ-19-13,DBY-ZZ-19-15)
吉林省自然科学基金项目(No.20170101201JC)。
关键词
花岗伟晶岩
伸展背景
蒙古-鄂霍茨克洋
太平洋板块
辽东半岛
矿床学
granitic pegmatite
extension setting
Mongol-Okhotsk Ocean
Pacific plate
Liaodong Peninsula
mineral deposits
