昌宁—孟连结合带北端癞痢头山岩体地球化学特征及其对成岩成矿作用的启示  

GEOCHEMICAL CHARACTERISTICS OF LAILITOUSHAN PLUTON AT THE NORTHERN END OF CHANGNING-MENGLIAN JUNCTION ZONE AND ITS IMPLICATIONS FOR PETROGENESIS AND MINERALIZATION

作　　者：徐恒 豆松 姜永果 刘文佳 李晓峰[2] 齐武福[3] 张金学 Xu Heng;Dou Song;Jiang Yongguo;Liu Wenjia;Li Xiaofeng;Qi Wufu;Zhang Jinxue(Yunnan Geological Bureau of Nonferrous Metals,Kunming 650051,Yunnan,China;Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China;Vocational College of Yunnan Territorial Resources,Kunming 650217,Yunnan,China;No.310 Geological Party,Yunnan Geological Bureau of Nonferrous Metals,Dali 671000,Yunnan,China)

机构地区：[1]云南省有色地质局,云南昆明650051 [2]中国科学院地质与地球物理研究所,北京100029 [3]云南国土资源职业学院,云南昆明650217 [4]云南省有色地质局三一〇队,云南大理671000

出　　处：《矿物岩石》2021年第3期16-28,共13页Mineralogy and Petrology

基　　金：第二次青藏高原综合科学考察研究项目(编号:2019QZKK0802);云南省技术创新人才培养对象项目(编号:202105AD160003)。

摘　　要：位于昌宁—孟连结合带北端的癞痢头山岩体,主要由中粗晶花岗闪长岩(MGG)和细晶花岗闪长岩(FG)组成,形成于中三叠世(232 Ma)。MGG和FG岩相学特征相似,无明显空间分带关系,呈过渡渐变关系。它们具高硅(w(SiO_(2))=66.2%-68.2%,平均67.0%),富钾(K_(2)O/Na_(2)O=1.04-2.59,平均1.64),贫碱(w(Na_(2)O+K^(2)O)=5.45%-7.31%,平均5.99%)、低钠(w(Na_(2)O)=1.54%-3.58%,平均2.38%),高镁值(Mg^(#)=47.3-58.7,平均51.5)和过铝质(A/CNK=1.41-2.17,平均1.65)特征,属过铝质高钾钙碱性系列。二者轻、重稀土元素含量比值介于6.91-12.1,表现为轻稀土元素相对富集、重稀土元素相对亏损。岩石富集w(Rb)(54.7-176×10^(-6)),w(U)(1.10-4.77×10^(-6)),w(Th)(9.33-35.30×10^(-6))等大离子亲石元素,亏损w(Ta)(1.22-1.51×10^(-6)),w(Nb)(14.9-18.5×10^(-6)),w(Zr)(78.4-171.0×10^(-6))等高场强元素,以及δEu(0.35-0.57)和"TNT"负异常特征,表明初始岩浆以陆壳成分为主并有幔源组分的加入。癞痢头山岩体样品具有较高的A/CNK值(1.41-2.17)和刚玉分子含量(1.87%-8.67%),以及Nb/Ta比值(11.03-13.76)和Zr/Hf比值(23.13-47.85)分别与平均地壳和壳源岩石相应比值一致,显S型花岗岩特征。综合分析,认为癞痢头山岩体属于S型花岗岩,起源于古老地壳物质(贫黏土的古老杂砂岩)部分熔融岩浆和底侵作用带入的幔源岩浆的混合岩浆,是保山—思茅地块陆陆后碰撞阶段力学性质由挤压向伸展转化动力学背景下的产物,具备成矿作用发生的物质基础,有一定的找矿潜力。The Lailitoushan pluton occurred in the northern end of the Changning-Menglian suture zone is mainly composed of middle Triassic(232 Ma)medium-coarse grained granodiorite(MGG)and fine-grained granodiorite(FG).The petrographic characteristics of MGG and FG are similar,without obvious spatial zonation relation.Both rock bodies are rich in silicon(w(SiO_(2))=66.2%-68.2%,average 67.0%)and potassium(K_(2)O/Na_(2)O=1.04-2.59,average 1.64),poor in alkali(w(Na_(2)O+K_(2)O)=5.45%-7.31%,average 5.99%)and sodium(w(Na_(2)O)=1.54%-3.58%,average 2.38%),with high magnesium value(Mg^(#)=47.3-58.7,average 51.5)and peraluminous value(A/CNK=1.41-2.17,average 1.65),belonging to peraluminous high K calc-alkaline series.The ratios of LREE and HREE range from 6.91 to 12.1,indicating that LREE is relatively enriched and HREE is relatively depleted.The rocks are enriched in large ion lithophile elements such as w(Rb)(54.7-176.0×10^(-6)),w(U)(1.10-4.77×10^(-6)),and w(Th)(9.33-35.3×10^(-6)),depleted in high field strength elements such as w(Ta)(1.22-1.51×10^(-6)),w(Nb)(14.9-18.5×10^(-6))and w(Zr)(78.4-171.0×10^(-6)),with negative anomalies ofδEu(0.35-0.57)and"TNT",indicating that the initial magma is mainly composed of continental crust material with the addition of mantle-derived components.The Lailitoushan rock body has high values of A/CNK(1.41-2.17),corundum(1.87%-8.67%),Nb/Ta(11.03-13.76)and Zr/Hf(23.13-47.85)ratios,which are consistent with the average crust and crust-source rocks,showing the characteristics of S-type granite.Through comprehensive analysis,it is considered that the Lailitoushan rock body belongs to S type granite rock mass,which is originated in partial melting of ancient crust material(graywacke poor in clay)mixed with mantle-derived magma and produced under the dynamic background of mechanical properties transforming from compression to extension in the post-continental collision stage of Baoshan-Simao massif.Therefore,the rock body has the material basis for mineralization and has certain prospecting potent

关 键 词：花岗闪长岩 岩石地球化学 构造环境 成岩成矿作用 昌宁 

分 类 号：P588[天文地球—岩石学] P597[天文地球—地质学]