摘要
为探讨内蒙古中部察哈尔右翼后旗一带晚古生代构造--岩浆事件演化背景和过程,对该地区石英二长岩进行了岩相学、地球化学和年代学研究。结果显示,石英二长岩年龄为(269.1±4.6)Ma,属中二叠世,并可进一步分为高钾钙碱性系列和钾玄岩系列。前者主要为粗粒--似斑状石英二长岩,富集FeO^(T)、MgO、CaO、P_(2)O_(5)、Th、U和轻稀土元素(LREE),极度富Sr、F,亏损Rb、Ba等大离子亲石元素(LILE)、Zr、Hf、Nb、Ta、Ti等高场强元素(HFSE)和重稀土元素(HREE),具弱到中等负Eu异常;钾玄岩系列主要为中粗粒石英二长岩,富K、Rb、Th和轻稀土元素,贫FeO^(T)、MgO、CaO,亏损Zr、Hf、Nb、Ta、Ti、U等高场强元素和重稀土元素,极度亏损P、Sr,具较强的Eu负异常。上述特征显示,察哈尔右翼后旗石英二长岩属伸展背景下的后碰撞花岗岩,与华北板块北缘加厚地壳的底侵拆沉等壳幔相互作用有关,并为区内古亚洲洋早—中二叠世闭合提供了约束。
In order to discuss the evolution setting and processes of tectonic-magmatic events during Late Paleozoic in Chahar Right Back Banner,central Inner Mongolia,the petrology,geochemistry and geochronology study has been conducted for quartz monzonite in the area.Results show that the quartz monzonite was emplaced in the Middle Permian(269.1±4.6)Ma,which can be further divided into high-K calc-alkaline and shoshonitic series.The former consists of coarse-grained to porphyritic quartz monzonite,rich in FeO^(T),MgO,CaO,P_(2)O_(5),Th,U and light rare earth elements(LREE),extremely high in Sr,F,depleted in large ion lithophile elements(LILE,e.g.Rb,Ba),high field strength elements(HFSE,such as Zr,Hf,Nb,Ta,Ti)and heavy rare earth elements(HREE),with weak to moderate negative Eu anomalies.The shoshonitic series is mainly composed of medium and coarse-grained quartz monzonite,featured by K,Rb,Th and LREE enrichment,FeO^(T),MgO,CaO,HFSE(such as Zr,Hf,Nb,Ta,Ti,U),and HREE depletion,extreme deficiency of P,Sr,with strong Eu negative anomalies.The above characteristics indicate that the quartz monzonite in Chahar Right Back Banner belongs to post-collisional granitoid formed in a lithospheric extension setting,related to crust-mantle interaction caused by underplating and delamination of the thickened crust at the northern margin of the North China plate.It also provides a constraint for the closure process of the Paleo--Asian Ocean during Early--Middle Permian in the study area.
作者
陈岩滨
夏立元
王翔
王耀
CHEN Yanbin;XIA Liyuan;WANG Xiang;WANG Yao(Geological Survey of Anhui Province(Anhui Institute of Geological Sciences),Hefei 230001,China)
出处
《世界地质》
CAS
2022年第4期689-702,共14页
World Geology
基金
内蒙古自治区地质勘查基金管理中心项目(NMKD2013-19)。
关键词
石英二长岩
锆石U-PB定年
后碰撞花岗岩
华北板块北缘
察哈尔右翼后旗
quartz monzonite
zircon U-Pb dating
post-collisional granitoid
northern margin of the North China plate
Chahar Right Back Banner
