华北板块北缘中段白马石沟岩体岩石成因及其地质意义  

Petrogenesis of the Baimashigou pluton in the middle segment of northern margin of the North China Block and its geological implications

作　　者：邹宇轩 聂逢君[2,3] 夏菲 严兆彬[2,3] 何剑锋 杨东光[2] 张鑫 李晓剑[1] ZOU YuXuan;NIE FengJun;XIA Fei;YAN ZhaoBin;HE JianFeng;YANG DongGuang;ZHANG Xin;LI XiaoJian(School of Earth Sciences,East China University of Technology,Nanchang 330013,China;State Key Laboratory of Nuclear Resources and Environment,East China University of Technology,Nanchang 330013,China;National Key Laboratory of Uranium Resources Exploration-Mining and Nuclear Remote Sensing,Nanchang 330013,China)

机构地区：[1]东华理工大学地球科学学院,南昌330013 [2]东华理工大学,核资源与环境国家重点实验室,南昌330013 [3]铀资源探采与核遥感全国重点实验室,南昌330013

出　　处：《岩石学报》2025年第4期1252-1278,共27页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(U2244205、U2067202);江西省教育厅科学技术研究项目(GJJ2200711);东华理工大学博士科研启动基金项目(DHBK2019029)联合资助.

摘　　要：华北板块北缘中段地表覆盖严重、基岩露头少,实物研究资料有限,制约了人们对中亚造山带东段构造演化的认识。本文对覆盖区钻孔揭露的白马石沟岩体进行了详细岩相学观测和岩石地球化学、锆石U-Pb年代学、锆石微量元素及原位Hf同位素分析。研究表明,白马石沟岩体形成于晚二叠世(254±0.7Ma),岩石富硅(SiO_(2)=69.13%~72.27%)、富碱富钾(K 2O+Na_(2)O=8.20%~9.51%、K 2O/Na_(2)O=0.98~2.52)、(弱)过铝质(A/CNK=0.98~1.10),属于未经分异的高钾过铝质S型花岗岩。进一步分析表明,其成因是碰撞造山过程中下行板片顶部贫黏土(CaO/Na_(2)O=0.27~0.38)、富含初生地壳碎屑(εHf(t)=-3.93~6.36)的变质杂砂岩在相对低温(612.9~799.8℃)、高压((Gd/Yb)_(N)=0.88~2.41、δEu=0.72~0.83、Sr=405.1×10^(-6)~545.6×10^(-6)、Y=11.13×10^(-6)~14.55×10^(-6)、Sr/Y=27.83~41.16)、高氧逸度(QFM~QFM+10)的环境下部分熔融形成的。结合前人研究成果,我们认为华北板块北缘中段在二叠纪末期之前已经进入碰撞造山阶段,白马石沟岩体是该区域古亚洲洋关闭、两侧板块碰撞拼合的直接岩浆岩证据。本项研究为进一步深入分析中亚造山带东段,尤其是覆盖区的地质结构和构造演化提供了重要线索。The middle segment of the northern margin of the North China Block is heavily covered by thick Quaternary strata,and as a result,only limited physical research data have provided restrict understanding of the tectonic evolution of this area and the neighboring eastern section of the Central Asian Orogenic Belt.This article presents detailed petrographic observations and rock geochemistry,zircon U-Pb dating,zircon trace elements,and in-situ Hf isotopic analysis of the Baimashigou pluton by drilling-core samples in the coverage area.The study shows that the Baimashigou pluton formed in the Late Permian(254±0.7Ma).The analyzed rock samples are characterized by high silicon contents(SiO_(2)=69.13%~72.27%),alkali and potassium-rich(K 2O+Na_(2)O=8.20%~9.51%,K 2O/Na_(2)O=0.98~2.52)and(weak)peraluminous(A/CNK=0.98~1.10),indicating they belong to high-K peraluminous unfractionated S-type granite.Furthermore,the geochemical characteristics of these samples also reveal that they are formed by the partial melting of metasandstone with low clay content(CaO/Na_(2)O=0.27~0.38)and rich in primary crustal debris(εHf(t)=-3.93~6.36)on top of the descending slab under a relatively low temperature(612.9~799.8℃),high pressure((Gd/Yb)N=0.88~2.41,δEu=0.72~0.83,Sr=405.1×10^(-6)~545.6×10^(-6),Y=11.13×10^(-6)~14.55×10^(-6),Sr/Y=27.83~41.16),and high oxygen fugacity(QFM~QFM+10)environment.Combined with previous research results,it is believed that the middle segment of the northern margin of the North China Block had entered the collision orogeny stage before the end of the Permian Period.The Baimashigou pluton provides direct petrological evidence of the plate collision and amalgamation.The study holds significant importance for further analyzing the geological structure and tectonic evolution of the eastern segment of the Central Asian Orogenic Belt,particularly within the coverage area.

关 键 词：S型花岗岩 同碰撞花岗岩 晚二叠世 华北板块北缘 HF同位素 锆石U-PB年龄 

分 类 号：P542[天文地球—构造地质学] P588.121[天文地球—地质学] P597.3