对内蒙古北山造山带洋-陆转换认识的新思考——来自大红山南泥盆纪弧花岗岩的证据  

A new thinking on the process of ocean-continent transition in Beishan orogenic belt of Inner Mongolia:Evidence from the Devonian arc granite in the south of Dahong Mountain

作　　者：闫涛 辛后田 卫彦升 杨五宝 李拯宇 YAN Tao;XIN Houtian;WEI Yansheng;YANG Wubao;LI Zhengyu(Shanxi Institute of Geological Survey,Taiyuan 030006,Shanxi,China;Tianjin Center,China Geological Survey,Tianjin 300170,China;North China Center for Geoscience Innovation,Tianjin 300170,China)

机构地区：[1]山西省地质调查院,山西太原030006 [2]中国地质调查局天津地质调查中心,天津300170 [3]华北地质科技创新中心,天津300170

出　　处：《地质通报》2020年第9期1341-1366,共26页Geological Bulletin of China

基　　金：中国地质调查局项目《阴山成矿带小狐狸山和雅布赖地区地质矿产调查》(编号:DD20160039);《内蒙古1∶5万大红山等六幅区域地质矿产调查》(编号:12120114064401)。

摘　　要：报道了红石山-百合山蛇绿构造混杂岩带南侧大红山地区发现的一套泥盆纪弧花岗岩,并论述其地质特征、岩石学、地球化学、年代学及其岩石成因和构造背景。该套弧花岗岩由英云闪长岩、花岗闪长岩及石英二长岩组成,整体经历了强烈的区域动热变质作用,普遍发育透入性的新生面理构造。据岩石地球化学特征,该套弧花岗岩可分为钠质的T 1G 1(英云闪长岩+花岗闪长岩)和钾质的QM(石英二长岩),T 1G 1具有高铝型TTG的特征(Al 2O 3平均15.22%,大于15%),QM则为一套高钾钙碱性系列岩石,属于低Sr高Yb的浙闽型花岗岩(Sr含量平均121.64×10-6,Yb含量平均2.95×10-6)。二者均具有轻稀土元素和大离子亲石元素明显富集、重稀土元素和高场强元素明显亏损,以及非常明显的“TNT”异常(Nb、Ta、Ti亏损)特征,指示该套弧花岗岩形成于成熟度较高的岛弧背景。锆石U-Pb测年结果显示,这套弧花岗岩的侵位时代为364~399 Ma。结合区域地质背景和时空演化配置,认为该套弧花岗岩为北山造山带雀儿山岛弧(D)的残留。该发现为北山造山带北带古生代弧-盆演化体制的研究提供了新的证据和线索。This paper reports a set of Devonian arc granites firstly found on the south side of Dahong Mountain,the southern side of ophiolite tectonic mélange zone in Hongshi Mountain-Baihe Mountain.This set of arc granites are composed of tonalite,granodiorite and quartz monzonite.The rocks on the whole experienced intense thermodynamic metamorphism and developed permeable mylonitic texture.According to the geochemical characteristics of rocks,the arc granite assemblage can be divided into sodic T 1G 1(tonalite+granodiorite)and potassium to potash QM(quartzite).The combination of T 1G 1 shows the characteristics of the high aluminum(the average content of Al 2 O 3:15.22%,>15%),and the QM is a set of high potassium calc-alkaline rocks which belong to Zheming type granite with low Sr and high Yb(the average content of Sr is 121.64×10-6,and the average content of Yb is 2.95×10-6).Both of them have the characteristics of obvious enrichment of light rare earth elements(LREE)and large ion lithophile elements(LILEs),obvious depletion of heavy rare earth elements(HREE)and high field strength elements(HFSEs)and obvious"TNT"anomaly(Nb,Ta,Ti depletion).The overall results show that the arc granite assemblage was formed in the background of island arc with high maturity.Besides,zircon U-Pb dating shows that this set of arc granites was emplaced in the Devonian period between 364 Ma and 399 Ma.Combined with the overall spatial and temporal configuration of the region,it is held that this set of arc granites may be the remnant of the Que’ershan island arc(D)in the northern belt of Beishan Mountain.This discovery provides new evidence and clues for the Paleozoic arc-basin evolution system in the north belt of northern Beishan Mountain.

关 键 词：北山造山带 弧花岗岩 泥盆纪 大红山 雀儿山岛弧 

分 类 号：P542[天文地球—构造地质学] P588.12[天文地球—地质学]