内蒙古狼山地区叠布斯格岩群锆石U-Pb年龄、Hf同位素特征及其对阿拉善地块构造演化的制约  

Zircon U-Pb age and Hf isotopic characteristics of the Diebusige Complex in Langshan area,Inner Mongolia,and its constraints on the tectonic evolution of the Alxa Block

作　　者：牛鹏飞 曲军峰[1] 张进[1] 张北航[1] 赵衡[1] NIU Pengfei;QU Junfeng;ZHANG Jin;ZHANG Beihang;ZHAO Heng(Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037,China)

机构地区：[1]中国地质科学院地质研究所,北京100037

出　　处：《地质通报》2022年第5期754-773,共20页Geological Bulletin of China

基　　金：中国地质调查局项目《狼山尔驼庙幅15万构造地质填图试点》(编号:12120115069601);《北方山系西拉木伦与贺根山基础地质调查》(编号:DD20190004);国家自然科学基金项目《阿拉善北部蛇绿混杂岩形成机制、变形过程与构造环境》(批准号:41972224)。

摘　　要：阿拉善地块位于华北克拉通西端,其早前寒武纪地质演化一直存在争议。选取阿拉善地块东北缘的叠布斯格岩群为研究对象,通过锆石U-Pb定年和Lu-Hf同位素分析,探讨阿拉善地块的性质和归属及华北克拉通早期地质演化。叠布斯格岩群主要由变质沉积岩和变质火山岩组成,包括高级变质的片麻岩、大理岩、石英岩、角闪岩,并被古元古代钾质花岗岩侵入。来自叠布斯格岩群3个副片麻岩样品的LA-ICP-MS锆石U-Pb定年结果显示,叠布斯格岩群副片麻岩中碎屑锆石的^(207)Pb/^(206)Pb年龄范围为2.60~2.10 Ga,变质锆石的年龄显示叠布斯格岩群经历了1.98~1.90 Ga和1.90~1.79 Ga的两组峰期变质作用,指示叠布斯格岩群原岩形成于2.10~1.98 Ga。研究区未发现有太古宙岩石出露,但不排除其下部地壳中存在太古宙基底岩石的可能。碎屑锆石的Lu-Hf同位素数据结果显示,叠布斯格岩群副片麻岩中碎屑锆石的εHf(t)均为负值,指示其成岩物质源于古—中太古代(3.42~2.79 Ga)古老地壳在新太古代晚期—古元古代早期的重熔或再造。通过对比叠布斯格岩群和阴山地块、孔兹岩带的岩浆-变质事件及Hf同位素特征,推测阿拉善地块前寒武纪基底在古元古代可能是孔兹岩带的一部分。The Alxa Block is located in the western part of the North China Craton(NCC),and its Precambrian geological evolution has been long controversial.In this study,the in-situ zircon U-Pb dating and the Lu-Hf isotope analysis were conducted on the Precambrian basement at the northeast margin of the Alxa Block,which called the Diebusige Complex.The Diebusige Complex consists mainly of metamorphic supracrustal rocks and metamorphic plutonic rocks,including high grade metamorphic gneiss,marble,quartzite,amphibolite and intruded K-felspar granite.LA-ICP-MS zircon U-Pb dating results of three paragneiss samples show that the detrital zircons from the Diebusige Complex yielded 207 Pb/206 Pb ages range from 2.60 Ga to 2.10 Ga,and the Diebusige Complex subjected to high grade metamorphic events at 1.98~1.90 Ga and 1.90~1.79 Ga,suggesting that the protoliths of the Diebusige Complex may be deposited at 2.10~1.98 Ga.There is no evidence of Archean rocks exposed in Langshan area,but the possibility of Archean rocks exist at deeper crustal levels cannot be ruled out.Zircon Lu-Hf isotopic data shows that the diagenetic material of the Diebusige Complex was originated from the reworking of Early-Middle Archean crust(3.42~2.79 Ga).Comparing the Diebusige Complex with the Yinshan Block and the Khondalite Belt in magmatic-metamorphic events and the Hf isotopic charateristics.We speculate that the Precambrian basements of the Alxa Block are probably part of the Khondalite Belt in Paleoproterozoic.

关 键 词：华北克拉通 阿拉善地块 叠布斯格岩群 古元古代 锆石U-Pb定年 HF同位素 地质调查工程 

分 类 号：P534.3[天文地球—古生物学与地层学] P588.3[天文地球—地质学]