粤北扶溪岩体成因及时代:来自矿物化学、岩石地球化学及LA-ICP-MS锆石U-Pb年龄证据  

Genesis and Age of Fuxi Granodiorite,Southern Zhuguang Mountain,Northern Guangdong Province:Constrain from Mineralogy Chemistry,Geochemistry and LA-ICP-MS Zircon U-Pb Dating

作　　者：于玉帅[1,2,3] 戴平云[1,2] 郭福生[3] 谢小占 鲍波 

机构地区：[1]中国地质调查局武汉地质调查中心,武汉430205 [2]中国地质调查局花岗岩成岩成矿地质研究中心,武汉430205 [3]东华理工大学,南昌330013 [4]广东省核工业地质局291大队,广州510800

出　　处：《地质科技情报》2017年第6期71-82,共12页Geological Science and Technology Information

基　　金：国家重点研发计划"深地资源勘查开采"重点专项(2016YFC0600205);中国地质调查局地质调查二级项目(DD20160134;121201009000150007)

摘　　要：分析了粤北扶溪地区花岗闪长岩角闪石、黑云母矿物化学组成,全岩岩石地球化学及LA-ICP-MS锆石U-Pb年龄。结果显示,花岗闪长岩中角闪石属镁角闪石,黑云母属镁质黑云母。岩石硅含量较高,w(SiO_2)为63.86%~66.19%;富碱,w(K_2O)为4.07%~4.71%,w(Na_2O)在2.42%~2.76%;铝质量分数中等,w(Al_2O_3)为14.27%~15.02%。稀土元素总量w(ΣREE)为183.22×10^(-6)~283.31×10^(-6),稀土元素配分模式右倾,中等强度负Eu异常(0.62~0.80),富集Rb、K、Th、Sr、Pb、Nd等大离子亲石元素,亏损Th、U、Zr、Hf、Nb、Ta、Ti等高场强元素。LA-ICP-MS锆石U-Pb年龄为(440.7±3.3)Ma(MSWD=2.4,n=18)。上述分析结果表明花岗闪长岩为I型花岗岩,是早志留世岩浆活动产物,岩浆主要来源于地壳物质的部分熔融,在温度777~802℃、压力316~442 MPa和氧逸度约lgf(O_2)=-14条件下侵位结晶。This paper presents results from mineralogy, whole-rock geochemistry and LA-ICP-MS zircon U-Pb geochronology of Fuxi granodiorite pluton. The analyzed amphiboles are magnesiohornblende and the studied micas are Mg-rich biotites. The granodiorite is characterized by high SiO2 content （63.86%- 66.19%）, high alkali content （K2O of 4.07%-4.71% ;Na2O of 2.42%-2.76%）, and moderate AlzO3 content （14.27 %-15. 02%）. The bulk REE contents of the granodiorite specimens range from 183 × 10-6 to 283 × 10-6 , with right oblique chondrite-normalized REE pattern and obvious negative Eu anomaly （Eu =0.62-0.80）. The ＂spider＂ diagram of primitive mantle normalized trace elements shows that this plu- ton is enriched in LILEs （Rb,K,Th,Sr,Pb and Nd） but depleted in HFSEs （Th,U,Zr, Hf,Nb,Ta and Ti）. Zircon LA-ICP-MS U-Pb dating for granodiorite yields the age of （440.7±3.3）Ma （MSWD=2.4,n = 18）. Results above indicate that Fuxi granodiorite belongs to I-type graniteand that the parental magma is generated by partial melting of the crust. In addition, the Fuxi pluton is crystallized from the shallowly emplaced parental magma at the condition of 777-802℃, 3.16 ×108 -4.42 × 108 Pa and log fo2 =- 14.

关 键 词：花岗闪长岩 矿物化学 地球化学 LA-ICP-MS锆石U-PB测年 扶溪 诸广山南部 

分 类 号：P588.12[天文地球—岩石学]