安徽金寨岩体地质和地球化学特征及LA-ICP-MS锆石U-Pb年龄  

Geological and Geochemical Characteristics and LA-ICP-MS Zircon U-Pb Ages of the Jinzhai Intrusion in Anhui Province

作　　者：陈芳[1,2] 彭智[1,2] 邱军强[1,2] 董婷婷[1,2] 柳丙全[1] 

机构地区：[1]安徽省地质调查院,合肥230001 [2]安徽省大陆成矿作用研究中心,合肥230001

出　　处：《地质学报》2016年第5期879-895,共17页Acta Geologica Sinica

基　　金：中国地质调查局地质调查工作项目(编号1212011220547)资助成果

摘　　要：安徽金寨岩体为一钾长花岗岩体,位于大别造山带北淮阳构造带,LA-ICP-MS锆石U-Pb定年获得岩体侵位年龄为129.7±1.5Ma,属早白垩世岩浆活动产物。岩体周边发现有数个铅锌多金属矿点,与区域岩浆作用及其矿化一致。岩体富硅(SiO_2=72.47%~77.80%)、富碱(K_2O+Na_2O=7.48%~8.16%)、贫钙(CaO=0.15%~1.47%);稀土配分曲线呈现"海鸥式"分布特征,显示强烈的Eu负异常(δEu=0.18~0.40);微量元素特征显示具有较高的Ga(21.68×10^(-6)~24.12×10^(-6))、Zr(127.68×10^(-6)~196.75×10^(-6))、Nb(33.31×10^(-6)~60.53×10^(-6))和Y(14.57×10^(-6)~27.51×10^(-6))含量,较低的Sr(8.15×10^(-6)~138.52×10^(-6))、Ba(23.04×10^(-6)~332.63×10^(-6))含量,在微量元素原始地幔标准化蛛网图上显示明显的Ba、Sr、P、和Ti的负异常。以上特征表明金寨钾长花岗岩为A型花岗岩,可能是下地壳源岩部分熔融的产物。金寨钾长花岗岩是形成于造山后伸展环境下的板内A1型花岗岩,不是形成于非造山大地构造背景下的碱性花岗岩。The Jinzhai moyite intrusion is located in the north Huaiyang tectonic zone of Dabie orogenic belt.LA-ICP-MS zircon U-Pb dating yields an age of 129.7±1.5 Ma by,suggesting it may be the product of the early Cretaceous magmatism.Several lead-zinc mineralization occurrences are found to distribute around the Jinzhai intrusion,and to be consistent with the regional magmatism and mineralization.The intrusion is characterized by high SiO_2 content（SiO_2=72.47%~77.80%）,high alkali contents（K_2O＋Na_2O=7.48%~8.16%）,but low CaO content（0.15%~1.47%）.REE district patterns of the moyite show a shape of＂sea-gull＂and relatively significant negative Eu anomalies with δEu ranging from 0.18 to 0.40.Trace element analysis indicates that the rocks have high contents of Ga（21.68×10^（-6）~24.12×10^（-6））,Zr（127.68×10^（-6）~196.75×10^（-6））,Nb（33.31×10^（-6）~60.53×10^（-6））and Y（14.57×10^（-6）~27.51×10^（-6））,but low content of Sr（8.15×10^（-6）~138.52×10^（-6））and Ba（23.04×10^（-6）~332.63×10^（-6））,with Ba,Sr,P,Eu and Ti exhibiting distinct negative anomalies on the primitive mantlenormalized trace element diagram.All this characteristics indicate that the Jinzhai moyite is A-type granite and might be the product of partial melting of lower crust source rock.The Jinzhai moyite is the intraplate A1-type originating in the post orogenic extension environment,but not the alkaline granite generating in anorogenic tectonic background.

关 键 词：A型花岗岩 地球化学 LA-ICP-MS锆石U-PB测年 构造环境 金寨 

分 类 号：P597.3[天文地球—地球化学] P588.12[天文地球—地质学]