摘要
基于研究区早白垩世早中晚三次岩体岩石化学和地球化学研究及和锆石SHRIMP年龄[(137.7±2.2)Ma、(130.5±1.6)Ma和(129.6±1.7)Ma]结果分析,内蒙古东乌旗塔尔根敖包边防连一带存在早白垩世岩体A型花岗岩。各期次岩体均具有高硅,早白垩世从早到晚三次侵入的SiO 2平均质量分数分别为73.59%、75.33%和75.93%,具有逐渐增加的趋势;富碱,由早到晚,全碱平均质量分数分别为8.22%、8.48%和8.39%,逐渐增加;由早到晚,铝指数平均值分别为1.05、1.05和1.04,均呈过铝质的特点。各期次岩体微量元素均明显富集大离子亲石元素Rb、Th、U、K和Ph,但Ba和Sr相对亏损,同样在高场强元素中,Nb、Ta和Ti亏损明显,Zr和Hf相对富集,而且从早到晚三次侵入岩体微量元素含量均具有逐渐变少的趋势。稀土元素含量均较高,球粒陨石标准化分布模式呈“海鸥”型;Eu负异常明显,从早到晚三次侵入δEu平均值为0.42、0.33和0.30,异常逐渐加强。综合研究表明,在成因类型上,早白垩世,则由早中期的A 1型逐渐向晚期的A 2型演化。区内早白垩世岩浆旋回应该是太平洋板块西北向俯冲后地壳伸展的产物。
Based on the research of petological,geochemical characteristics on Late Jurassic granite and SHRIMP U Pb dating of(137.7±2.2)Ma,(130.5±1.6)Ma and(129.6±1.7)Ma of the first,the second and the third intrusions during Early Cretaceous respectively,confirm there have three intrusions of A type granite during Early Cretaceous in Taergenaobaobianfanglian area of East Ujimqin Banner,Inner Mongolia.They are all characterized by high silica,from early to late in the Early Cretaceous,the SiO 2 average mass fraction of granite is 73.59%,75.33%and 75.93%respectively,and shows gradually increased trend.All granite of research area characterized with Alkali abundance,and from early to late,the ALK average mass fraction of Early Cretaceous is 8.22%,8.48%and 8.39%respectively,shows increased trend gradually.From early to late,the average value of A/CNK index is 1.05,10.5 and 1.04 respectively,all show peraluminous characteristic.All granite are characterized by enriched LIVE(Rb,Th,U,K),and some HFSE(Zr,Hf),relatively depleted Ba,Sr,and strongly depleted Nb,Ta and Ti,and from early to late,trace element content of Early Cretaceous granite show gradually reduced trend.ALL intrusions of A type granite have high∑REE content,and show“sea-gull”type rare earth element pattern,as well as,have obvious negative Eu anomaly,and from early to late,the average ofδEu about Early Cretaceous granite is 0.42,0.33 and 0.30 respectively,and the Eu anomaly strengthens gradually.Integrated research indicates that,from early to late,the Early Cretaceous granite type changes from A 1 type to A 2 type gradually.These three intrusions of A type granite from research area should be the result of stretching setting that related to the subduction of Pacific Plate during Early Cretaceous.
作者
赵鸿燕
邱庆伦
朱德胜
ZHAO Hongyan;QIU Qinglun;ZHU Desheng(Henan Acedemy of Territorial Spatial Survey and Planning,Zhengzhou 450053,Henan,China;Key Laboratory for Dynamic Monitoring of Land and Resources of Henan Province,Zhengzhou 450053,Henan,China;Henan Academy of Geology,Zhengzhou 450001,Henan,China)
出处
《吉林地质》
2023年第3期1-13,共13页
Jilin Geology
关键词
铝质A型花岗岩
SHRIMP年龄
伸展环境
早白垩世
东乌旗
Aluminous A type granite
SHRIMP U Pb dating
stretching setting
Early Cretaceous
East Ujimqin Banner,Inner Mongolia
