摘要
晚中生代是华北克拉通破坏的关键时期,定量约束晚中生代岩石圈厚度对理解华北克拉通破坏过程具有重要意义。本文研究了辽东晚白垩世(~81 Ma)曲家屯玄武岩的全岩和橄榄石化学组成。结果显示,曲家屯玄武岩为碱性玄武岩,具有洋岛玄武岩的微量元素特征(Nb-Ta正异常,明显的K和Pb负异常)和亏损的Sr-Nd同位素特征(^(87)Sr/^(86)Sr(i)=0.704053~0.704098和ε_(Nd)(t)=1.75~2.00),指示其岩浆源区为软流圈。橄榄石斑晶的Fo值为84.02~86.20,Ni、Ca和Mn含量分别为(977~1823)×10^(-6)、(1234~1667)×10^(-6)、(1345~1833)×10^(-6),Fe/Mn、10000×Zn/Fe和Mn/Zn值分别为66.91~81.29、7.36~8.66和16.6~19.8,与橄榄岩熔体中的橄榄石成分相似。全岩的FC3MS和FCKANTMS值与橄榄岩熔体相近,表明其熔融源区为橄榄岩。根据曲家屯玄武岩浆形成时的地幔温压条件(1298~1325℃和2.50~2.67 GPa),估算其形成时的岩石圈厚度为82~90 km,略厚于该地区早白垩世的岩石圈厚度(40~60 km),表明从早白垩世至晚白垩世,华北克拉通东部岩石圈可能经历了增生和增厚过程,克拉通破坏已经结束。
The Late Mesozoic is a critical period for the destruction of North China Craton,and quantitative constraints on lithospheric thickness during this phase is critical to understand destruction process of North China Craton.The whole-rock and olivine chemical compositions of Late Cretaceous(~81 Ma)Qujiatun basalts in eastern Liaoning is reported.The results show that Qujiatun basalts are alkalic basalts with trace element composition charactevistics similar to that of oceanic island basalts(positive anomalies of Nb-Ta and negative anomalies of K and Pb),and depleted Sr-Nd isotopic signatures(^(87)Sr/^(86)Sr(i)=0.704053-0.704098 andε_(Nd)(t)=1.75-2.00),indicating their asthenospheric orgin.The olivine phenocrysts have Fo values of 84.02-86.20,Ni(977-1823)×10^(-6),Ca(1234-1667)×10^(-6),Mn(1345-1833)×10^(-6),as well as Fe/Mn,10000×Zn/Fe and Mn/Zn ratios of 66.91-81.29,7.36-8.66 and 16.6-19.8,respectively,similar to those in peridotite-derived melts.Together with their whole-rock FC3MS and FCKANTMS values comparable to the corresponding values of peridotite-derived melts,these geochemical characteristics support their source lithology of peridotite.Based on the mantle temperature and pressure conditions(1298-1325℃and 2.50-2.67 GPa)during the formation of Qujiatun basaltic magma,the lithospheric thickness is estimated at 82-90 km,slightly thicker than the Early Cretaceous lithosphere in this region(40-60 km).This suggests that the lithosphere of the North China Craton may have undergone processes of accretion and thickening,and its destruction had probably ended from the Early to Late Cretaceous.
作者
尹焕秋
王丹
张银慧
洪路兵
张乐
贺鹏丽
YIN Huanqiu;WANG Dan;ZHANG Yinhui;HONG Lubing;ZHANG Le;HE Pengli(College of Earth Sciences,Guilin University of Technology,Guilin 541006,China;Guangxi Key Laboratory of Hidden Metallic Ore Deposits Exploration,Guilin University of Technology,Guilin 541006,China;Collaborative Innovation Center for Exploration of Nonferrous Metal Deposits and Efficient Utilization of Resources in Guangxi,Guilin University of Technology,Guilin 541006,China;Guangzhou Institute of Geochemistry,Chinese Academy of Sciences,Guangzhou 510640,China)
出处
《桂林理工大学学报》
北大核心
2025年第3期294-306,共13页
Journal of Guilin University of Technology
基金
广西科技计划项目(桂科AD22035160,桂科AD23026332)
国家自然科学基金项目(42172053,42002057)。
关键词
玄武岩
地球化学
矿物化学
源区性质
辽东曲家屯
华北克拉通破坏
basalts
geochemistry
mineral chemistry
source characteristics
Qujiatun in eastern Liaoning
destruction of North China Craton
作者简介
尹焕秋(1998-),女,硕士研究生,研究方向:地球化学,3183884097@qq.com;通讯作者:洪路兵,博士,副研究员,honglubing@glut.edu.cn。
