摘要
南蒙古额尔德尼(Erdene)花岗岩体位于整个东北亚巨量白垩纪花岗岩浆活动的西缘.本文对南蒙古额尔德尼地区花岗岩进行了锆石U Pb年代学、岩石地球化学和锆石Hf同位素研究,以确定其形成时代、岩石成因及大地构造背景.研究结果表明:额尔德尼地区花岗岩岩石类型主要为黑云母花岗岩.LA ICP MS锆石U Pb定年结果为(123.4±1.4)Ma,形成于早白垩世.岩石具有高硅(w(SiO_(2))为71.01%~72.66%)、富碱(w(Na2O+K_(2)O)为8.52%~8.90%)、贫磷(w(P2O5)为0.06%~0.11%)、贫镁钙(w(MgO)为0.27%~0.39%,w(CaO)为1.10%~1.27%)的特征,铝饱和指数A/CNK为1.05~1.07,属于弱过铝质岩石;富集Rb、U、Th等大离子亲石元素和Ta、Zr、Hf等高场强元素,亏损Nb、Sr、Ba等高场强元素,具有明显的Eu负异常(δEu=0.11~0.15),岩浆平均温度为816℃,属A1型花岗岩,形成于非造山的板内构造环境.岩石的εHf(t)值为2.54~7.92,TDM2变化于1016~673Ma之间,源区可能有少量年轻物质加入.结合区域伸展构造研究,认为额尔德尼花岗岩形成于大规模伸展减薄环境,与中下地壳减压熔融有关.
The Erdene granite in Southern Mongolia is located on the western margin of the massive Cretaceous magmatic granite in the whole Northeast Asia.The zircon U-Pb geochronology,rock geochemistry and zircon Hf isotopes in the Erdene region were studied to determine the formation age,petrogenesis,and tectonic setting.The main rock type is biotite granite.The zircon LA-ICP-MS U-Pb dating yields a weighted mean age of(123.4±1.4)Ma,indicating that it formed in the Early Cretaceous.The granite has high silicon(w(SiO_(2))=71.01%-72.66%),high alkali(w(Na2O+K_(2)O)=8.52%-8.90%),poor phosphorus(w(P2O5)=0.06%-0.11%),low magnesium and calcium(w(MgO)=0.27%-0.39%,w(CaO)=1.10%-1.27%),and A/CNK=(1.05-1.07),indicating that it belongs to the metaluminous-peraluminous rock.It is characterized by enrichment of LILE(such as Rb,U,Th),depletion of HFSE(such as Ta,Zr,Hf)and depletion of Nb,Sr,Ba elements,with obvious negative Eu anomalies(δEu=0.11-0.15).The average magmatic temperature is 816℃.It belongs to A1 type granite.TheεHf(t)of the rocks ranges from 2.54-7.92,and the TDM2 varies from 1016-673 Ma,indicating that a little young materials might have been added in the source region.Based on the regional extensional tectonics,it is believed that the large Erdene granite formed in an extensional thinning environment,which is related to the decompression and melting of the middle and lower crust.
作者
段思宁
童英
王文志
郭磊
Duan Sining;Tong Ying;Wang Wenzhi;Guo Lei(College of Earth Science and Resources,China University of Geosciences,Beijing 100083,China;Beijing SHRIMP Center,Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037,China;Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037,China)
出处
《吉林大学学报（地球科学版）》
CAS
CSCD
北大核心
2022年第3期917-929,共13页
Journal of Jilin University：Earth Science Edition
基金
国家重点研发计划项目(2018YFC0603702)。
