内蒙古阿拉善地块北缘雅布赖地区埃达克岩锆石U-Pb年龄、岩石成因和构造背景  

Zircon U-Pb age,petrogenesis and teceonic setting of the Yabulai adakite,northern Alxa Block,Inner Mongolia

作　　者：王凯垒 张学萌 李会恺 郑乐 张家兴 邢东雪 陈涛 侯占元 WANG Kailei;ZHANG Xuemeng;LI Huikai;ZHENG Le;ZHANG Jiaxing;XING Dongxue;CHEN Tao;HOU Zhanyuan(No.519 Geological Party,North China Geological Exploration Bureau,Baoding 071051,Hebei,China)

机构地区：[1]华北地质勘查局五一九大队,河北保定071051

出　　处：《地质通报》2021年第9期1443-1458,共16页Geological Bulletin of China

基　　金：中国地质调查局项目《阴山成矿带小狐狸山和雅布赖地区地质矿产调查》(编号:DD20160039)、《内蒙古1∶5万塔尔拜呼都格,白石头,红柳沟幅区域地质矿产调查》(编号:DD20160039-13)

摘　　要：雅布赖地区位于阿拉善地块北缘,埃达克岩岩石类型主要为闪长岩和石英闪长岩。用LA-ICP-MS方法测得埃达克岩中的锆石^(206)Pb/^(238)U年龄为275±1 Ma(MSWD=1.00,n=27,闪长岩)和277±2 Ma(MSWD=0.64,n=26,石英闪长岩),故认为雅布赖地区埃达克岩侵位年龄为275±1~277±2 Ma,形成时代为早二叠世。地球化学特征表明,该岩体具有较高的SiO_(2)(60.56%~63.41%)、Al_(2)O_(3)(15.86%~17.33%)、Sr(572×10^(-6)~758×10^(-6))含量,较低的MgO(1.45%~3.06%)、Y(11.10×10^(-6)~14.7×10^(-6))、Yb(1.06×10^(-6)~1.55×10^(-6))含量,富集大离子亲石元素K、Rb、Ba、Sr等,亏损高场强元素Ta、Nb、Ti、P等。岩石重稀土元素强烈亏损,轻、重稀土元素分馏明显,Eu异常较弱(0.81<δEu<1.04),Mg^(#)值较高(38~53),Y/Yb值为7.35~11.89,Na_(2)O/K_(2)O值为1.18~1.77,具有C型埃达克岩特征,为拆沉下地売部分熔融产生的流体与地幔橄榄岩相互作用形成的产物。结合前人研究,其可能形成于碰撞后伸展环境。Yabulai adakite is located in the western part of Yabulai-Nuorigong-Honggueryulin belt,northern Alxa Block.The main rock types of the Yabulai adakite are diorite and quartz diorite.The LA-ICP-MS zircon U-Pb dating results are 275±1 Ma(MSWD=1.00,n=27,diorite)and 277±2 Ma(MSWD=0.64,n=26,quartz diorite),which shows that the ages of the adakite are between ^(275)Ma and ^(277)Ma,suggesting a product of Early Permian.Geochemical characteristics show that the Yabulai adakite with high content of SiO_(2)(60.56%~63.41%),Al_(2)O_(3)(15.86%~17.33%),Sr(572×10^(-6)~758×10^(-6))and low content of MgO(1.45%~3.06%),Y(11.1×10^(-6)~14.7×10^(-6)),Yb(1.06×10^(-6)~1.55×10^(-6)),enrichment of large ion lithophile elements(such as K,Rb,Ba and Sr),and depletion of high field-strength elements(such as Ta,Nb,Ti and P).The Yabulai adakite is typical C-type adakite with high content of Mg^(#)(38~53),the ratio of Y/Yb is between 7.35 and 11.89,and Na_(2)O/K_(2)O is between 1.18 and 1.77;in addition,it exhibits significant fractionation between LREE and HREE and is depleted in HREE with slight Eu anomaly(0.81<δEu<1.04).The authors hold that the Yabulai adakite was formed by partial melting of delaminated lower crust and interaction with the mantle peridotite,and magmatic mixing was experienced during diagenesis.Combined with previous studies,the authors hold that the Yabulai adakite might have been formed in a post-collision extension stage.

关 键 词：埃达克岩 锆石U-PB定年 雅布赖 岩浆混合 阿拉善地块 

分 类 号：P581[天文地球—岩石学] P597.3[天文地球—地质学]