华北克拉通胶莱盆地马山地区粗面英安岩磷灰石U-Pb年代学及其地质意义  

Apatite U-Pb Geochronology of the Trachy Dacite in Mashan Area,Jiaolai Basin,North China Craton,and Its Geological Significance

作　　者：朱拓 何登洋 黄雅琪 邱昆峰[1,2,3] ZHU Tuo;HE Dengyang;HUANG Yaqi;QIU Kunfeng(School of Earth Sciences and Resources,China University of Geosciences(Beijing),Beijing 100083,China;State Key Laboratory of Geological Processes and Mineral Resources,Beijing 100083,China;Frontiers Science Center for Deep-time Digital Earth,China University of Geosciences(Beijing),Beijing 100083,China)

机构地区：[1]中国地质大学(北京)地球科学与资源学院,北京100083 [2]中国地质大学地质过程与矿产资源国家重点实验室,北京100083 [3]中国地质大学(北京)深时数字地球前沿科学中心,北京100083

出　　处：《现代地质》2024年第1期117-127,共11页Geoscience

基　　金：国家自然科学基金项目(42261134535);中国地质大学(北京)创新创业训练计划项目(S202211415007);山东省深部金矿探测大数据应用开发工程实验室项目(SDK202211,SDK202214);深时数字地球前沿科学中心项目(2652023001);高等学校学科创新引智计划项目(BP0719021)。

摘　　要：五莲—青岛—烟台断裂是胶莱盆地重要的控盆断裂之一,控制了盆地的形成与演化,主要由牟平—即墨断裂和桃村断裂等多条NNE向断裂组成。前人研究表明,五莲—青岛—烟台断裂运动学转换历史先后可划分为晚侏罗世左旋走滑、早白垩世伸展断陷和晚白垩世—古新世右旋走滑三个阶段,但其新生代右旋走滑事件的持续时间仍存在争议。已有研究表明,区域上同尺度断裂走滑运动温度为550~650℃,显著高于磷灰石U-Pb体系封闭温度(350~550℃),因此磷灰石可能是记录五莲—青岛—烟台断裂右旋走滑的理想对象。本文选取胶莱盆地马山粗面英安岩中的磷灰石进行U-Pb年代学研究,拟约束五莲—青岛—烟台断裂的右旋走滑持续时间。磷灰石U-Pb年龄为(64.1±3.7)Ma,明显晚于早白垩世寄主粗面英安岩锆石U-Pb年龄(119.3±1.6)Ma,表明自早白垩世以来磷灰石至少经历了一次热事件导致其U-Pb同位素体系重置。早白垩世以来,由于印度板块和欧亚板块的碰撞,以及古太平洋板块由NWW向俯冲转变为NW向俯冲,导致了古新世胶莱盆地N—S向拉分和牟平—即墨断裂右旋走滑。因此,本文认为马山粗面英安岩磷灰石U-Pb年龄记录了五莲—青岛—烟台断裂右旋走滑热事件,表明其右旋走滑可能持续到古新世。The Wulian-Qingdao-Yantai fault(WQYF)is one of the most important basin-controlling faults in the Jiaolai basin,where the fault dominates the formation and evolution of the basin.This fault is mainly composed of abundant NNE faults,such as Muping-Jimo fault and Taocun fault.The WQYF experienced sinistral strike-slip movement in Late Jurassic,extensional rift in Early Cretaceous,and dextral strike-slip movement during Late Cretaceous-Paleocene.However,the most key question that the duration of the Cenozoic dextral strike-slip movement still remains unclear.Previous studies suggested that temperature of strike-slip movement in this region is about 550-650℃,which is higher than the closure temperature,350-550℃,of the apatite U-Pb system.Therefore,in this case apatite can be an ideal candidate to investigate the dextral strike-slip of the WQYF.In this study,we conducted U-Pb dating of apatite from the Early Cretaceous trachy-dacite in the Mashan area and obtained the U-Pb age of 64.1±3.7 Ma.The measured magmatic age of apatite is different from the crystallization age of the Mashan trachy-dacite,indicating that at least there was one geothermal event which reset the apatite U-Pb isotope system in Early Paleocene.Since Early Cretaceous,the collision between the Indian plate and Eurasian plate,and the switch of subduction direction of the paleo-Pacific plate from NWW to NW result in a north-south extension of the Jiaolai basin and the dextral strike-slip of the Muping-Jimo fault.Therefore,we propose that the apatite U-Pb age of the Mashan trachy-dacite documented the dextral strike-slip thermal event of the WQYF,and indicates that the dextral strike-slip may continue until Paleocene.

关 键 词：磷灰石U-Pb年代学 粗面英安岩 五莲—青岛—烟台断裂 古新世右旋走滑 

分 类 号：P597[天文地球—地球化学]