内蒙古达茂旗东北部比旗格淖复式岩体的形成年龄、地球化学特征及成因  

Formation age,geochemical characteristics and genesis of Biqigenao granitic complex in northeastern Damao Banner,Inner Mongolia

作　　者：张建超 朱孔阳[1] 杨波[1] 苏美霞 许立权 周飞 董传万[1] 沈忠悦[1] 吴艳君 孟晓玲 佘琳琳 ZHANG Jianchao;ZHU Kongyang;YANG Bo;SU Meixia;XU Liquan;ZHOU Fei;DONG Chuanwan;SHEN Zhongyue;WU Yanjun;MENG Xiaoling;SHE Linlin(Key Laboratory of Geoscience Big Data and Deep Earth Resources of Zhejiang Province,School of Earth Science,Zhejiang University,Hangzhou,310058;Inner Mongolia Survey Institute,Huhehot,010020)

机构地区：[1]浙江大学地球科学学院,浙江省地学大数据与地球深部资源重点实验室,杭州310058 [2]内蒙古自治区地质调查研究院,呼和浩特010020

出　　处：《地质论评》2024年第1期207-227,共21页Geological Review

基　　金：内蒙古自治区地质勘查基金资助项目(内蒙古白云鄂博地区深部软流体及其成矿作用,编号:2020-YS02)的成果。

摘　　要：达茂旗东北部比旗格淖复式岩体位于内蒙古中部,该岩体由两期侵入体组成,岩性分别为花岗闪长岩和二长花岗岩,前者为岩体主体岩性。主体花岗闪长岩主要由斜长石(An=14~30)、石英、钾长石和普通角闪石组成,内部发育暗色微粒包体;补体二长花岗岩主要由石英、钾长石和斜长石(An=12~23)组成。LA-ICPMS锆石U-Pb定年显示岩体形成于晚二叠世,形成年龄为259±2 Ma。主体花岗闪长岩SiO_(2)=66.37%-68.70%、为准铝质—弱过铝质(A/CNK=0.99~1.01),地球化学上显示出富集轻稀土、大离子亲石元素,亏损重稀土和高场强元素的特征,属于I型花岗岩;其中闪长质暗色微粒包体呈浑圆状或拉长扁平透镜状,年龄与寄主花岗闪长岩一致,为岩浆混合的产物;补体二长花岗岩,高硅(SiO_(2)=71.51%~73.09%)、富碱(Na_(2)O+K_(2)O=7.91%~8.61%),为弱过铝质—强过铝质(A/CNK=1.07~1.11),属分异I型花岗岩。比旗格淖复式岩体锆石εHf(t)分布范围为-3.0~3.4,对应的Hf同位素二阶段模式年龄为1473~1057 Ma。具有相对较低的[n(87Sr)/n(86Sr)]i值(0.704829~0.705327),εNd(t)值为-5.85~-8.86,对应的Nd的二阶段模式年龄为1.69~1.45 Ga。结合区域研究资料,认为比旗格淖复式岩体为亏损地幔组分与受其诱发的部分熔融的古老地壳物质混合形成,属于后碰撞型花岗岩,这类岩体的形成标志了古亚洲洋在兴蒙造山带南缘的闭合,并发生造山后伸展作用。The Biqigenao granitic complex in northeastern Darhan—Maoming’an Union Banner(Damao Banner)is composed of two phases of intrusions,the lithology of which is granodiorite and monzogranite,the former being the main lithology of the granitic complex.Granodiorite is mainly composed of plagioclase(An=14~30),quartz,alkali feldspar and amphibole,with mafic microgranular enclave inside;The monzogranite is mainly composed of quartz,alkali feldspar and plagioclase(An=12~23).Zircon U-Pb dating shows that the granitic complex was formed in the Late Permian,and its formation age is 259 Ma.The main granodiorite with SiO_(2)=66.37%~68.70%is aluminous—weakly peraluminous(A/CNK=0.99~1.01),which is characterized by enrichment of light rare earth and large ion lithophile elements,depletion of heavy rare earth and high field strength elements,belongs to I-type granite;mafic microgranular enclave is rounded or elongated flat lenticular,and the age is consistent with the granodiorite,which is the product of magma mixing;Monzogranite is high silica granite(SiO_(2)=71.51%~73.09%),alkali-rich(Na_(2)O+K_(2)O=7.91%~8.61%)and weakly peraluminous to strongly peraluminous(A/CNK=1.07~1.11),is a differentiated I-type granite.TheεHf(t)of Ziron distribution range is-3.0~3.4,and the corresponding Hf isotope two-stage model age is 1473~1057 Ma.It has relatively low(87 Sr/86 Sr)i value(0.704829~0.705327),εNd(t)value is-5.85~-8.86,and the corresponding Nd twostage model age is 1.69~1.45 Ga.Based on the regional research data,it is considered that the Biqigenao granitic complex is formed by mixing the depleted mantle component with the partially melted ancient crustal material induced by it,and belongs to the post-collisional granite.

关 键 词：兴蒙造山带 达茂旗 比旗格淖复式岩体 锆石U-Pb定年 锆石HF同位素 Sr—Nd同位素 后碰撞 

分 类 号：P597[天文地球—地球化学] P548[天文地球—地质学] P588.121