华北克拉通减薄的岩浆浅表响应——来自大青山岩体的证据  

Magmatic response to lithospheric thinning of the North China Craton——evidence from the Daqingshan granite

作　　者：王丹阳 李猛兴 王权[1] 王丽娟[2] WANG Danyang;LI Mengxing;WANG Quan;WANG Lijuan(Shanxi Institute of Geological Survey Co.,ltd,Taiyuan 030006,Shanxi,China;The Institute of Hydrogeology and Environmental Geology,Chinese Academy of Geological Sciences,Shijiazhuang 050061,Hebei,China)

机构地区：[1]山西省地质调查院有限公司,山西太原030006 [2]中国地质科学院水文地质环境地质研究所,河北石家庄050061

出　　处：《华东地质》2024年第2期173-186,共14页East China Geology

基　　金：中国地质调查局“山西省1:25万大同市(K49C004004)、偏关县(J49C001003)幅区调修测(编号:基[2010]矿评01-11-07号)”;自然资源部“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)”项目联合资助

摘　　要：华北克拉通燕山期岩浆作用是研究克拉通破坏机理的理想载体。文章选择大青山岩体进行了LA-ICP-MS锆石U-Pb定年及岩石地球化学研究,探讨了岩石成因及其对华北克拉通中部北缘中生代构造-岩浆演化的启示。研究表明,该岩体为似斑状二长花岗岩,锆石U-Pb年龄为(139±1)Ma,为早白垩世早期岩浆活动的产物。岩石地球化学特征显示:岩体明显高硅、富碱且相对富钾,过铝质,贫镁钛磷铁钙;NK/A、全岩锆石饱和温度、P_(2)O_(5)含量、Zr值、FeO^(T)值等指标说明,岩体为过铝质、高钾钙碱性系列高分异I型花岗岩,且富集大离子亲石元素Rb、Th、K,亏损高场强元素Ba、Sr、P、Ti;稀土元素总量偏低,轻稀土元素相对重稀土元素分馏较强,负铕异常明显(δEu=0.08~0.56),具有稀土元素四分组特征;岩体具有明显地壳浅源特征,侵位时代与华北克拉通岩浆作用峰期一致,是克拉通减薄的岩浆浅表响应,与古太平洋板片后撤密切相关。The magmatic activities of the Yanshan period in North China Craton are an ideal carrier for studying the mechanism of craton destruction.In this paper,the Daqingshan granite was selected for LA-ICP-MS zircon U-Pb dating and geochemical analysis to investigate the rock genesis and its implications for the Mesozoic tectonic-magmatic evolution in the northern margin of the central North China Craton.The results show that the granite consists mainly of phenocryst adamellite,with a zircon U-Pb age of(139±1)Ma(MSWD=0.28,N=12),indicating an early Cretaceous magmatic event.The geochemistry of the genesis indicates that it is highly silicic,alkali-rich,relatively potassium-rich,peraluminous,and magnesium-titanium-phosphorus-calcium poor.The genesis was classified as a highly differentiated type I granite of peraluminous for the results of NK/A,saturation temperature of zircon and the value of P_(2)O_(5),Zr and FeO^(T).The granite is enriched in large ion lithophile elements(Rb,Th,K)and depleted in high field-strength elements(Ba,Sr,P,Ti).The total rare earth element contents are low(ΣREE ranges from 84.5×10-6 to 216.0×10^(-6)),with a strong fractionation between light and heavy rare earth elements and significant negative Eu anomalies(δEu=0.08~0.56),showing a four-group pattern.The genesis exhibits obvious characteristics of crustal source and intrusion age coincides with the peak period of magmatic activity in the North China Craton,representing a shallow magma response to craton thinning,closely related to the retreat of the ancient Pacific plate.

关 键 词：克拉通破坏 地球化学特征 岩石成因 大青山岩体 华北克拉通 

分 类 号：P581[天文地球—岩石学] P595[天文地球—地质学] P597