甘肃北山大豁落南地区晚二叠世花岗闪长岩成因——锆石U-Pb年龄和岩石地球化学制约  

Petrogenesis of the Late Permian granodiorite in southern Dahuoluo area, Beishan,Gansu: Constraints from zircon U-Pb geochronology and geochemistry

作　　者：卜涛[1,2] 余吉远 过磊[1,2] 王国强 郭琳[1,2] 计波 BU Tao;YU Jiyuan;GUO Lei;WANG Guoqiang;GUO Lin;JI Bo(Research Center for Orogenic Geology/Xi'an Center of Geological Survey,CGS,Xi’an 710054,Shaanxi,China;MNR Key Laboratory for the Study of Focused Magmatism and Giant Ore Deposits/Xi'an Center of Geological Survey,Xi’an 710054,Shaanxi,China)

机构地区：[1]中国地质调查局造山带地质研究中心/西安地质调查中心,陕西西安710054 [2]自然资源部岩浆作用成矿与找矿重点实验室/西安地质调查中心,陕西西安710054

出　　处：《地质通报》2019年第2期254-265,共12页Geological Bulletin of China

基　　金：中国地质调查局项目<甘肃北山牛圈子地区1:5万K47E014003等6幅区域地质矿产调查>(编号:12120113046400);<北山图拉尔根-辉铜山地区区域地质调查>(编号:DD20190812);国家自然科学基金项目<甘肃北山泥盆纪高镁安山岩岩石成因及其地球动力学意义>(批准号:41703038)

摘　　要：对甘肃北山大豁落南地区花岗闪长岩进行了LA-ICP-MS锆石U-Pb测年及主量和微量元素地球化学分析。结果表明,花岗闪长岩的结晶年龄为259.7±1.5Ma。花岗闪长岩SiO_2含量介于63.10%～69.69%之间,Al_2O_3介于14.86%～15.48%之间,平均15.21%,MgO含量为0.96%～3.59%,平均2.69%,岩石强烈富集轻稀土元素,(La/Yb)N为18.60～50.91,具弱Eu异常(δEu=0.83～1.06),高Sr(454×10^(-6)～862×10^(-6))、高Sr/Y值(Sr/Y=44.95～60.35),具有埃达克岩的地球化学特征。花岗闪长岩富钾、贫钠,具有较高的Cr、Ni含量和Mg~#(50.31～66.75)值,结合区域地质背景,认为花岗闪长岩是碰撞后板内热隆伸展环境壳幔交互作用的产物,暗示晚古生代北山地区地壳为垂向增生,与以天山为主的中亚造山带大范围存在的二叠纪与幔源岩浆有关的花岗岩是同期构造岩浆事件的产物。This paper reports LA-ICP-MS zircon U-Pb ages and whole rock major and trace elements from granodiorite in southern Dahuoluo area of the Beishan region.Magma zircons from granodiorite yielded a weighted 206Pb/238U mean age of 259.7± 1.5Ma.Granodiorite is characterized by SiO2 ranging from 63.10% to 69.69%,Al2O3 ranging from 14.86% to 15.48%,15.21% on average,MgO ranging form 0.96%~3.59%,2.69% on average,strong enrichment of LREE,and(La/Yb)N values ranging from 18.60 to 50.91.In addition,Eu anomaly is not obvious,with Eu/Eu* values ranging from 0.83 to 1.06,Sr content is high(454× 10^-6~ 862 × 10^-6)and Sr/Y ratio is 44.95~60.35,rocks show geochemical characteristics of adakite.Granodiorite is enriched in K and depleted in Na,and has high Cr,Ni and Mg^#(50.31~66.75).Combined with regional geological background,the authors hold that granodiorite was formed after the collision,as a product of both intraplate thermal upwelling extension and crust-mantle interaction.It is suggested that,in Late Paleozoic,the crust in Beishan area was in vertical increment,and the granites associated with the Permian and mantle-derived magmas were in the form of synchronic tectonic magmatic events.

关 键 词：LA-ICP-MS锆石U-PB年龄 地球化学 埃达克岩 后碰撞 北山 甘肃 

分 类 号：P534.46[天文地球—古生物学与地层学] P588.121[天文地球—地质学]