华南造山带上泛非期岩浆活动证据的发现及地质意义  

A direct evidence of Pan-African magmatism:Discovery of Wutong pluton and geological significance

作　　者：张素梅 汪洋[3] 任纪舜[4] 朱俊宾[4] 张敏杰 苏天瑞 王霄汉 于延秋 王诗琪 ZHANG Sumei;WANG Yang;REN Jishun;ZHU Junbin;ZHANG Minjie;SU Tianrui;WANG Xiaohan;YU Yanqiu;WANG Shiqi(Hebei Key Laboratory of Strategic Mineral Resources,College of Earth Sciences,Hebei GEO University,Shijiazhuang,Hebei 050031,China;Hebei Collaborative Innovation Center for Strategic Critical Mineral Research,Shijiazhuang,Hebei 050031,China;College of Earth Science and Resources,China University of Geosciences,Beijing 100083,China;Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037,China)

机构地区：[1]河北地质大学地球科学学院,河北省战略性关键矿产资源重点实验室,河北省石家庄050031 [2]河北省战略性关键矿产研究协同创新中心,河北石家庄050031 [3]中国地质大学(北京)地球科学与资源学院,北京100083 [4]中国地质科学院地质研究所,北京100037

出　　处：《地质学报》2025年第1期209-223,共15页Acta Geologica Sinica

基　　金：中国地质调查局地质调查项目(编号DD20221646,DD20240075);河北省骨干人才项目(编号B2024015);河北省青年科学基金项目(编号D2022403023)联合资助的成果。

摘　　要：由于华南造山带缺乏早古生代初岩浆活动的直接证据而导致华南造山带与扬子地块碰撞拼合完成时间、早古生代初的大地构造背景、是否属于冈瓦纳一部分等科学问题的研究争议不断,因此寻找泛非期岩浆岩成为解决以上问题的关键。本次研究主要通过岩相学、锆石U-Pb年代学、全岩地球化学及Lu-Hf同位素等手段来分析诸广山复式岩基中北部的梧桐岩体的年代学、岩石地球化学等方面的特征。研究表明,梧桐岩体主体由黑云母二长花岗岩构成,黑云母二长花岗岩的成岩年龄为494.4 Ma,具有高硅铝(SiO_(2)=59.93%~71.31%,Al_(2)O_(3)=13.43%~19.20%)、高碱(K_(2)O=3.35%~5.93%,Na_(2)O=2.33%~6.21%)、高铁(TFe_(2)O_(3)=2.09%~6.20%)、低镁(MgO=0.44%~2.18%),富集Rb、Th、U、Nb和轻稀土元素,亏损Ba、Sr、P、Ti等特征,其岩浆物质主要来源于下地壳物质的重熔或多次重熔,岩浆侵入过程中可能存在少量地幔物质加入。梧桐岩体的发现暗示华南造山带与扬子地块中部可能在早古生代(520~480 Ma)完成碰撞拼合,且与冈瓦纳大陆关系密切,极有可能是冈瓦纳大陆的一部分,它为进一步厘清泛非造山运动作用于华南造山带乃至华南地区的时限、作用范围、岩浆成因、大地构造背景特征等科学问题提供了典型研究对象。The absence of direct evidence for early Paleozoic magmatic activity within the South China orogenic belt has sparked considerable debates.These debates center around,the timing of the collisional amalgamation between the South China orogenic belt and the Yangtze block,the early Paleozoic tectonic setting,and the belt's potential affiliation with Gondwana.Consequently,the discovery of Pan-African magmatic rocks has become crucial in resolving these questions.This paper focuses on the petrographic characteristics,zircon U-Pb geochronology,whole-rock geochemistry,and Lu-Hf and Sr-Nd isotopic signatures of the Wutong pluton,located north of the Zhuguangshan batholith.The results reveal that the pluton primarily consists of biotite monzogranite with a crystallization age of about 494.4 Ma.Geochemically,it exhibits high silica and alumina content(SiO_(2)=59.93%~71.31%,Al_(2)O_(3)=13.43%~19.20%),high alkali content(K_(2)O=3.35%~5.93%,Na_(2)O=2.33%~6.21%),and high iron content(TFe_(2)O_(3)=2.09%~6.20%),while displaying low magnesium content(MgO=0.44%~2.18%).The rock mass is enriched in Rb,Th,U,Nb,and LREE,and depleted in Ba,Sr,P,and Ti.These geochemical features suggest that the magmatic source material was mainly derived from the remelting of lower crustal rocks,potentially involving the multiple remelting events.A minor contribution from mantle-derived material during magma intrusion is also evident.This discovery suggests that the collisional amalgamation between the South China orogenic belt and the Yangtze block occurred during the early Paleozoic(520~480 Ma),likely along the margin of the central part of Gondwana.This study provides valuable insights into the timing,characteristics,magma genesis,and tectonic setting of the Pan-African orogenic event in the South China orogenic belt and may contribute to a better understanding of the region's geological history.

关 键 词：华南造山带 梧桐岩体 泛非期 锆石U-PB年龄 

分 类 号：P588.11[天文地球—岩石学]