额尔古纳地块北段霍洛台地区辉绿岩锆石U-Pb定年、岩石地球化学特征和构造背景  

Zircon U-Pb dating,petrogeochemical characteristics and tectonic setting of diabase in Huoluotai area,northern segment of Erguna Block

作　　者：孙永刚 李碧乐[2] 谢实学 靳皇玉 凌世伟 李焕纪 SUN Yonggang;LI Bile;XIE Shixue;JIN Huangyu;LING Shiwei;LI Huanji(School of Resources and Civil Engineering,Suzhou University,Suzhou 234000,Anhui,China;College of Earth Sciences,Jilin University,Changchun 130061,China;Geological Survey Institute of Jilin Province,Changchun 130102,China)

机构地区：[1]宿州学院资源与土木工程学院,安徽宿州234000 [2]吉林大学地球科学学院,长春130061 [3]吉林省地质调查院,长春130102

出　　处：《世界地质》2025年第1期22-34,共13页World Geology

基　　金：2024年度安徽省教育厅高校自然科学重点科研项目(2024AH051826);宿州学院2022年博士科研启动基金项目(2022BSK009);宿州学院2023年博士后科研启动基金项目(2023BSH001)。

摘　　要：为探讨大兴安岭地区早白垩世大规模岩浆活动形成的地球动力学机制,笔者选取大兴安岭额尔古纳地块北段霍洛台地区辉绿岩为研究对象,通过对霍洛台地区辉绿岩进行岩石地球化学特征及锆石U-Pb定年的研究,查明其形成时代、岩石成因和构造背景。LA-ICP-MS锆石U-Pb定年分析结果表明霍洛台地区辉绿岩的加权平均年龄为(135.1±3.6)Ma,代表辉绿岩的结晶年龄为早白垩世。全岩地球化学数据显示,霍洛台辉绿岩具有低w(SiO_(2))(48.84%~52.11%),高w(MgO)(5.13%~6.85%)和w(Fe_(2)O_(3))(7.45%~8.60%)的特征;其Eu异常不明显或具有弱的负异常特征(δEu=0.83~1.06),富集大离子亲石元素(如Ba、Sr和K),亏损高场强元素(如Zr、Ta、Nb和Th)。霍洛台地区辉绿岩受到分离结晶、地壳混染和堆晶作用的影响有限。Nb/Yb-Th/Yb图解显示霍洛台地区辉绿岩落在俯冲改造的岩石圈地幔起源的原始镁铁质熔体区域,Th/Nb-Ba/Th和Th/Yb-Ba/La图解显示霍洛台地区辉绿岩的岩浆源区被板片流体改造,La/Nb-La/Ba图解显示霍洛台地区辉绿岩的岩浆源区为岩石圈地幔源区。上述地球化学特征表明霍洛台地区辉绿岩起源于俯冲板片流体交代的岩石圈地幔源区。结合前人研究成果,认为大兴安岭额尔古纳地块北段霍洛台地区辉绿岩的形成与古太平洋板块的回卷过程密切相关。To explore the geodynamic mechanisms of the large-scale magmatic activity during Early Cretaceous in Da Hinggan Ling(Mts.),the authors focused on diabase in Huoluotai area in northern segment of Erguna Block,Da Hinggan Ling(Mts.),through the study of petrogeochemical characteristics and zircon U-Pb dating of diabase in Huoluotai area,aimed to determine its formation age,petrogenesis,and tectonic setting.Zircon LA-ICP-MS U-Pb dating results show that the weighted average age of diabase in Huoluotai area is(135.1±3.6)Ma,indicating that the crystallization age of diabase is Early Cretaceous.Whole rock geochemical data reveal that diabase in Huoluotai area is characterized by low w(SiO_(2))(48.84%-52.11%),high w(MgO)(5.13%-6.85%)and w(Fe_(2)O_(3))(7.45%-8.60%).The Eu anomaly of diabase is insignificant or exhibits a weak negative anomaly(δEu=0.83-1.06).The diabase is enriched in large ion lithophile elements(such as Ba,Sr,and K),and depleted in high field strength elements(such as Zr,Ta,Nb,and Th).Diabase in Huoluotai area is only minimally influenced by fractional crystallization,crustal contamination,and accumulation processes.The Nb/Yb-Th/Yb diagram shows that diabase in Huoluotai area falls within the area of primitive mafic melts derived from subduction-modified lithospheric mantle.The Th/Nb-Ba/Th and Th/Yb-Ba/La diagrams indicate that the magma source of diabase in Huoluotai area was modified by fluids derived from subducted slabs.The La/Nb-La/Ba diagram reveals that the magma source of diabase in Huoluotai area is from the lithospheric mantle.The above geochemical characteristics indicate that diabase in Huoluotai area originated from a lithospheric mantle source metasomatized by fluids derived from subducted slabs.Combined with previous research,it is concluded that the formation of diabase in Huoluotai area in northern segment of Erguna Block,Da Hinggan Ling(Mts.)is closely related to the rollback process of the Paleo-Pacific Plate.

关 键 词：辉绿岩 地球化学特征 构造背景 锆石U-PB定年 早白垩世 霍洛台地区 额尔古纳地块 

分 类 号：P595[天文地球—地球化学] P[天文地球—地质学]