云开造山带北段侏罗纪花岗岩年代学、地球化学特征及其地质意义  

Chronological,Geochemical Characteristics and Geological Significance of Jurassic Granites in the Northern Segment of Yunkai Orogenic Belt

作　　者：崔倩倩 杨启军[1,2] 黄浩峰 CUI Qianqian;YANG Qijun;HUANG Haofeng(Earth Science College,Guilin University of Technology,Guilin,Guangxi 541006,China;Guangxi Key Laboratory of Concealed Metal Mineral Exploration,Guilin University of Technology,Guilin,Guangxi 541006,China)

机构地区：[1]桂林理工大学地球科学学院,广西桂林541006 [2]桂林理工大学广西隐伏金属矿产勘查重点实验室,广西桂林541006

出　　处：《铀矿地质》2025年第2期314-331,共18页Uranium Geology

基　　金：广西找矿突破项目(编号:桂核办[2019]4号)资助。

摘　　要：南渡-杨梅岩体产于桂东南岑溪地区水汶盆地的北缘,为云开造山带北段的侏罗纪花岗岩。文章通过对南渡-杨梅岩体岩石学、年代学及地球化学等方面研究,厘定了该岩体的成岩时代、源区性质及其形成的构造背景。研究表明,杨梅-南渡岩体是经历系统演化的复式岩体,杨梅岩体侵位于南渡岩体中。南渡岩体由辉石闪长岩、二长岩和正长岩组成,结晶年龄为156.8~156.2 Ma,杨梅岩体由二长花岗岩和末期的花岗斑岩组成,花岗岩结晶年龄为156.3~155.3 Ma,年龄基本一致。在地球化学特征上,南渡岩体属于钾玄质A型花岗岩,而杨梅岩体为钙碱性A型向S型过渡型花岗岩,两者都具有轻、重稀土元素分异明显,富集大离子亲石元素和高场强元素的特征,但杨梅岩体更加富集稀土元素,且Eu的负异常特征更加强烈,南渡岩体甚至出现Eu的正异常,这些特征表明南渡岩体岩浆有幔源物质的参与,而杨梅岩体来源于壳熔。根据花岗岩大地构造环境判别图解,南渡岩体具有板内花岗岩特征,而杨梅岩体为板内花岗岩向活化过渡特征。结合中生代区域构造演化历史,认为南渡-杨梅岩体是晚侏罗世的复式岩体,南渡岩体A型花岗岩特征代表印支板块控制的特提斯构造域向太平洋构造域的转换完成于早、中侏罗世,同碰撞型杨梅岩体S型花岗岩的形成代表太平洋板块对云开造山带的控制作用已经开始。Nandu-Yangmei pluton is located in the northern margin of the Shuiwen Basin in the Cenxi area of southeastern Guangxi.It is the Jurassic granite in the northern segment of the Yunkai orogenic belt.The pluton is composed of Nandu granitic pluton(so-called Nandu pluton)and Yangmei granitic pluton(so-called Yang pluton).Through the study of petrology,chronology,and geochemistry of rocks,we has determined the diagenetic age,source region characteristics,and the forming tectonic setting of the pluton.The results indicates that the Nandu-Yangmei pluton is a complex which expernced systematic evolution.Nandu pluton is composed of pyroxene diorite,monzonite and syenite,and the zircon U-Pb dating by LA-ICPMS suggest the pluton was crystallized in 156.8-156.2 Ma.The Yangmei pluton is composed of monzonitic granite and late granite porphyry and crystallized in 156.3-155.3 Ma,while the late granite porphyry was formed in 152 Ma.Therefore the plutons were crystallized nearly in the same age,indicating that these plutons emplaced in the same period by diferrent phase.In terms of geochemical characteristics,Nandu pluton belongs to shoshonitic A-type granite,while Yangmei pluton belongs to calc-alkaline A-type to S-type transitional granite.Both of them have obvious differentiation of light and heavy rare earth elements,and are enriched in large ion lithophile elements and high field strength elements.However,Yangmei pluton is more enriched in rare earth elements,and the negative anomaly of Eu is more intense.Nandu pluton even has positive anomaly of Eu,indicating that the magma of Nandu pluton was participated with mantle source material,while Yangmei pluton was derived from crust melting.The Nandu pluton has the characteristics of intraplate granite,while the Yangmei pluton has the characteristics of transition from intraplate to activation.In conclusion,Yangmei-Nandu granite is a late Jurassic complex pluton formed under the conversion setting from the Tethys tectonic domain to the Pacific tectonic domain in the early and mid

关 键 词：云开造山带 侏罗纪 南渡-杨梅岩体 岩石地球化学 年代学 

分 类 号：P619.14[天文地球—矿床学]