摘要
【研究目的】以兴安地块南段马拉格复式岩体作为研究对象,进一步解读蒙古-鄂霍茨克洋、古太平洋两大构造体系对东北地区影响的时空范围。【研究方法】对该岩体不同岩性系统采集样品,进行岩相学、锆石U-Pb定年、岩石地球化学分析研究。【研究结果】研究表明,马拉格复式岩体由2期花岗岩组成,早期为石英二长岩、二长花岗岩、碱长花岗岩的岩性组合,形成于晚三叠世(225±2~220±2 Ma);晚期为花岗斑岩,形成于早白垩世晚期(124±1 Ma)。2期岩体属于高钾钙碱性Ⅰ型花岗岩,区别在于分异程度不同,均具有(Rb、Ba、K)大离子亲石元素及轻稀土元素(LREE)明显富集、(Ta、Nb、P、Ti)高场强元素及重稀土元素不同程度亏损、稀土元素总量偏低(ΣREE为34.25×10^(-6)~217.91×10^(-6))、中等负Eu异常(δEu=0.40~0.84)的特点。【结论】结合区域构造演化,马拉格复式岩体2期岩体指示:晚三叠世兴安地块南段已受到蒙古-鄂霍茨克洋俯冲的远程影响;早白垩世晚期区域上处于伸展背景,推断为蒙古-鄂霍茨克洋闭合后伸展、古太平洋俯冲后撤的共同作用,尤其与后者联系密切。
[Objective]This study investigates the Malage composite pluton in the southern Xing'an Block to clarify the spatiotemporal influence boundaries of two tectonic systems(Mongolia-Okhotsk Ocean and Paleo-Pacific)in Northeast China.[Methods]We conducted systematic sampling of lithologic units within the pluton,followed by petrographic analysis,zircon U-Pb geochronology,and whole-rock geochemical characterization.[Results]The Malage complex pluton comprises two granite phases.The early-stage assemblage(quartz monzonite diorite,monzogranite and alkali-feldspar granite)emplaced during the Late Triassic(225±1 Ma and 220±2 Ma),and granite porphyry intruded in the late Early Cretaceous(124±1 Ma).Both phases represent high-K calc-alkaline I-type granites,though the Cretaceous porphyry exhibits higher differentiation.They are both characterized by enrichment of large ion lithophilic elements(Rb,Ba,K)and light rare-earth elements(LREE),different degrees of loss(Ta,Nb,P,Ti)in high field strength elements(HFSE)and heavy rare-earth elements(HREE),low total rare earths(ΣREE=34.25×10^(-6)~217.91×10^(-6)),variable negative Eu anomalies(δEu=0.40~0.84).[Conclusions]Integrated geological evidence suggests that Late Triassic Mongolian-Okhotsk Ocean subduction influenced the southern Xing'an Block,and late Early Cretaceous magmatism occurred under an extensional regime driven jointly by post-collisional relaxation after Mongolia-Okhotsk Ocean closure and Paleo-Pacific Plate rollback,with predominant control from the latter.
作者
李猛兴
王丽娟
李珍
王权
李娟
LI Mengxing;WANG Lijuan;LI Zhen;WANG Quan;LI Juan(Xi'an Center of Mineral Resources Survey,China Geological Survey,Xi'an 710100,Shaanxi,China;Institute of Hydrogeology and Environmental Geology,Chinese Academy of Geological Sciences,Shijiazhuang 050061,Hebei,China;Shanxi Institute of Geological Survey Co.,Ltd.,Taiyuan 030006,Shanxi,China;Shandong Yantai No.11 Middle School,Yantai 264000,Shandong,China)
出处
《地质通报》
北大核心
2025年第6期1087-1105,共19页
Geological Bulletin of China
基金
中国地质调查局项目《1∶5万勃洛浑迪幅(L50E011020)等四幅区调》(编号:1212010781033)
自然资源部研究项目《我国典型地区大气水-地表水-地下水资源综合评估与水平衡研究——以滹滏平原为例》(编号:B201905)。
