内蒙古温都尔庙地区早二叠世岛弧型花岗闪长岩的发现：对古亚洲洋闭合的时限约束  

Discovery of Early Permian Island-Arc Type Granodiorites in Wenduermiao Area, Inner Mongolia:Constraints on Timing of Closure of Paleo-Asian Ocean

作　　者：高征西 王继春[2,3] 周路路 赵鑫[2,3] 秦江东 王沛东 吴艳君 汪岩 宝音乌力吉[2,3] Gao Zhengxi;Wang Jichun;Zhou Lulu;Zhao Xin;Qin Jiangdong;Wang Peidong;Wu Yanjun;Wang Yan;Baoyin Wuliji(School of Earth Resources,China University of Geosciences,Wuhan 430074,China;Inner Mongolia Key Laboratory of Magmatic Mineralization and Ore Prospecting,Huhhot 010020,China;Geological Survey Institute of Inner Mongolia Autonomous Region,Huhhot 010020,China;Anhui Natural Gas Development Co.,Ltd.,Hefei 230051,China;Shenyang Center of Geological Survey,China Geological Survey,Shenyang 110034,China)

机构地区：[1]中国地质大学资源学院,湖北武汉430074 [2]内蒙古自治区岩浆活动成矿与找矿重点实验室,内蒙古呼和浩特010020 [3]内蒙古自治区地质调查院,内蒙古呼和浩特010020 [4]安徽省天然气开发股份有限公司,安徽合肥230051 [5]中国地质调查局沈阳地质调查中心,辽宁沈阳110034

出　　处：《地球科学》2019年第10期3178-3192,共15页Earth Science

基　　金：中国地质调查局项目（No.12120115030401）;内蒙古地质勘查基金项目（No.2018-01-YS01）;内蒙古1:5万白音敖包（L50E024024）、兴隆地（K50E001024）、北岗台（K50E002024）幅区域地质调查项目（No.DD20190039-05）;内蒙古自然科学基金项目（No.2019BS04002）

摘　　要：研究区位于西伯利亚板块与华北板块之间的关键部位,可能代表了古亚洲洋最终闭合的位置.在嘎顺地区首次识别出花岗闪长岩,通过对岩石地球化学、锆石U-Pb年代学和Lu-Hf同位素分析,获得LA-MC-ICP-MS锆石U-Pb年龄为294.8±2.7 Ma,形成于早二叠世.SiO2含量介于64.69%~67.64%;Al2O3含量介于15.00%~15.52%;MgO含量介于1.14%~1.77%;Na2O含量介于1.41%~3.61%;K2O含量介于3.25%~3.98%.ΣREE值介于157.89×10^-6~174.43×10^-6;LREE值介于147.86×10^-6~149.55×10^-6;HREE值介于9.34×10^-6~11.8×10^-6;右倾稀土配分曲线,呈轻度负Eu异常,轻重稀土元素分馏程度大,轻稀土相对于重稀土明显富集.明显富集Rb、K,亏损Ba、Sr大离子亲石元素(LILE);富集Th,亏损Nb、Ta、Ti等高场强元素(HFSE).锆石176Hf/177Hf值介于0.282673~0.282791;εHf(t)值介于2.7~7.0,其二阶段模式年龄TDM2介于861~1129 Ma,176Lu/177Hf值介于0.000486~0.000734,结合岩石地球化学特征,认为该套岩石形成于岛弧岩浆作用,证实了早二叠世古亚洲洋仍未闭合.The study area is located in the key part between the North China and the Siberia plates,which may represent the final closure of the Paleo-Asian Ocean.Granodiorites were recognized in the Gashun area for the first time.According to petrogeochemistry,zircon U-Pb geochronology and Lu-Hf isotope analysis,the granodiorites yield an LA-MC-ICP-MS zircon UPb age of 294.8±2.7 Ma,suggesting that they were formed in the Early Permian.The rocks have SiO2=64.69%-67.64%,Al2O3=15.00%-15.52%,MgO=1.14%-1.77%,Na2O=1.41%-3.61%,and K2O=3.25%-3.98%.The content ofΣREE varies from 157.89×10^-6 to 174.43×10^-6,the content of LREE varies from147.86×10^-6 to 149.55×10^-6,and the content of HREE vary from 9.34×10^-6 to 11.8×10^-6.The rocks display rightly-inclined REE distribution curves,slightly negative Eu anomalies,highly fractionated LREE/HREE,and more enriched LREE relative to HREE.In the rocks,Rb and K were obviously enriched,and Ba and Sr(LILE)were depleted;Th was enriched and Nb,Ta and Ti etc.(HFSE)were depleted.Zircon 176Hf/177Hf changes from 0.282673 to 0.282791,andεHf(t)varies from 2.7 to 7.0.The two-stage model ages(TDM2)vary from 861 Ma to 1129 Ma,and 176Lu/177Hf ranges from 0.000486 to 0.000734.Combined with petrogeochemical characteristics,this set of granodiorites is considered to be formed by island-arc magmatism,confirming that the Paleo-Asian Ocean was still open in the Early Permian.

关 键 词：岛弧型花岗闪长岩 古亚洲洋 温都尔庙 岩石学 

分 类 号：P581[天文地球—岩石学]