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王金芳,李英杰,李红阳,董培培.内蒙古西乌旗努和特早白垩世A型花岗岩LA-ICPMS锆石U-Pb年龄及其地质意义[J].地质通报,2017,(8):1343-1358.
内蒙古西乌旗努和特早白垩世A型花岗岩LA-ICPMS锆石U-Pb年龄及其地质意义    点此下载全文
王金芳  李英杰  李红阳  董培培
河北地质大学资源学院, 河北 石家庄 050031
基金项目:国家自然科学基金项目《内蒙古西乌旗迪彦庙蛇绿岩年代学、地球化学及大地构造意义》(批准号:41502211)、中国地质调查局项目《内蒙古1:5万沙日勒昭等四幅区域地质矿产调查》(编号:1212011120701)、《内蒙古1:5万高力罕牧场三连等四幅区域地质矿产调查》(编号:1212011120711)和河北省教育厅项目《白音布拉格蛇绿岩岩石学和地球化学研究》(编号:ZC20165013)
DOI:
摘要:
      内蒙古西乌旗努和特A型花岗岩位于贺根山缝合带内,侵位于晚石炭世梅劳特乌拉蛇绿岩带、中二叠统哲斯组和晚石炭世英云闪长岩中,岩性为正长花岗岩。努和特A型花岗岩富硅、富钾、富碱、贫Al2O3、CaO、MgO、TiO2、P2O、Sr、Ba、Eu、Ti和P,具有较高的Ga/Al、(Na2O+K2O)/CaO、K2O/MgO、TFeO/MgO、Rb/Nb、Y/Nb、Sc/Nb值,稀土元素配分曲线为海鸥式分布,δEu值为0.25~0.54,负Eu异常明显,地球化学特征明显不同于I、S和M型花岗岩,为铝质A型花岗岩。在地球化学分类判别图解上,努和特A型花岗岩显示后造山A2型花岗岩特征,反映其形成于后造山伸展环境。LA-ICP-MS锆石U-Pb测年表明,该花岗岩的侵位年龄为130.4±1.2Ma和130.4±1.4Ma,其形成时代为早白垩世。根据蛇绿岩、俯冲-岛弧型-碰撞型和后造山型岩浆岩的时空分布与演化特征,贺根山缝合带在早白垩世可能处于后造山伸展阶段。
关键词:铝质A型花岗岩  LA-ICP-MS锆石U-Pb定年  早白垩世  后造山伸展环境  内蒙古西乌旗
LA-ICP-MS zircon U-Pb dating of the Nuhete Early Cretaceous A-type granite in Xi Ujimqin Banner of Inner Mongolia and its geological significance    Download Fulltext
WANG Jinfang  LI Yingjie  LI Hongyang  DONG Peipei
School of Natural Resources, Hebei GeoUniversity, Shijiazhuang 050031, Hebei, China
Fund Project:
Abstract:
      Located along the Hegenshan collisional orogenic suture zone in Xi Ujimqin Banner of Inner-Mongolia, the Nuhete Atype granite intruded into Late Carboniferous Meilaotewula ophiolite,Middle Permian Zhesi Formation and Late Carboniferous tonal-ite and consists mainly of syenogranites. The granite is geochemically characterized by high SiO2(72.92%~76.18%), K2O(4.1%~5.03%) and absolute alkali values (Na2O+K2O=8.01%~8.64%), low Al2O3, CaO, MgO, TiO2, P2O5, Sr, Ba, Eu, Ti, P values, and relatively high Ga/Al, (Na2O +K2O)/CaO, K2O/MgO, TFeO/MgO, Rb/Nb, Y/Nb, Sc/Nb ratios. It is characterized by a slightly right-inclined gull-wing shaped REE patterns with negative Eu anomalies (δEu=0.25~0.54). The Nuhete syenogranite exhibits the typical geochemi-cal characteristics of aluminous A-type granites, being significantly different from I, S and M type granites in geochemistry. According to the chemical subdivision diagrams of the A-type granitoids, the Nuhete A-type granite belongs to aluminous A2-type granitoid formed and emplaced in a post-orogenic extension setting. The LA-ICP-MS zircon U-Pb dating shows that the age of the granite is 130.4 ±1.2 Ma and 130.4 ±1.4Ma, suggesting early Cretaceous. According to the temporal and spatial distribution and evolution charac-teristics of the ophiolites, subductional arc granitoids, collisional granites and post orogenic granitoids in the Hegenshan collisional oro-genic suture zone, the authors hold that the Hegenshan suture zone was in a post orogenic extension stage in the Early Cretaceous period.
Keywords:aluminous A-type granite  LA-ICP-MS zircon U-Pb dating  Early Cretaceous  post orogenic extension setting  Xi Ujimqin Banner  Inner Mongolia
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