北山造山带新元古代热事件及其构造意义:来自甘肃北山南带两期花岗质岩的地球化学和年代学证据  

Neoproterozoic thermal events and tectonic implications in the Beishan orogenic belt:Geochemical and geochronological evidence from two sets of granitic rocks from southern Beishan orogenic belt,Gansu Province

作　　者：李沅柏 李海泉 周文孝[2] 王波 常风 李树才[1] 杨欣杰 LI Yuanbai;LI Haiquan;ZHOU Wenxiao;WANG Bo;CHANG Feng;LI Shucai;YANG Xinjie(Cores and Samples Center of Natural Resources,China Geological Survey,Langfang 065201,Hebei,China;Institute of Geological survey,China University of Geosciences,Wuhan 430074,Hubei,China;Research Institute of Petroleum Exploration&Development,Sinopec Northwest China Petroleum Bureau,Urumqi 830011,Xinjiang,China;The Seventh Geological Brigade of Hubei Geological Bureau,Yichang 443100,Hubei,China;School of Earth and Space Sciences,Peking University,Beijing 100871,China)

机构地区：[1]中国地质调查局自然资源实物地质资料中心,河北廊坊065201 [2]中国地质大学(武汉)地质调查研究院,湖北武汉430074 [3]中国石油化工集团有限公司西北石油局勘探开发研究院,新疆乌鲁木齐830011 [4]湖北省地质局第七地质大队,湖北宜昌443100 [5]北京大学地球与空间科学学院,北京100871

出　　处：《地质通报》2021年第7期1117-1139,共23页Geological Bulletin of China

基　　金：中国地质调查局项目《实物地质资料汇集与服务》(编号:DD20190411);《天山-北山成矿带那拉提-营毛沱地区地质矿产调查(国土资源实物地质资料中心)》(编号:DD20160010);国家自然科学基金项目《东昆仑诺木洪地区榴辉岩的发现及其对东昆仑北早古生代俯冲带演化过程的制约》(批准号:41703024)。

摘　　要：北山造山带作为中亚造山带南缘一个重要的构造带,经历了长期、多阶段、多地体的增生-拼合过程。北山造山带内具有广泛的前寒武纪基底分布,且古生代地壳显著增生。因此,在前人工作的基础上,旨在进一步厘定北山造山带在新元古代这一重要历史时期的构造演化过程,研究北山造山带内前寒武纪基底的归属,探讨其在古亚洲洋演化乃至更大尺度构造演化中的地位。在甘肃北山南带铜矿道班—红沟山—大湾铁矿厂一带分别采集了似斑状黑云二长花岗岩和流纹岩,并对2套样品进行岩相学、地球化学和锆石U-Pb年代学研究。样品的主量元素均具有高硅、富碱、富钾、过铝质、低镁、低钙特征。稀土元素均表现出明显的轻、重稀土元素分异现象,以及负Eu异常的特征。微量元素均表现出Nb、Ta元素等高场强元素亏损,Sr、Ba等大离子亲石元素富集的特征。岩石的U-Pb测年结果非常接近,似斑状黑云二长花岗岩的锆石年龄加权平均值为892.3±5.1 Ma,流纹岩的年龄加权平均值为870.4±4.5 Ma。所有证据表明,似斑状黑云二长花岗岩为S型花岗岩,形成于碰撞环境,且源岩(浆)来自于古老地壳沉积物质再循环;流纹岩则具有A 2型花岗岩的特征,形成于后碰撞伸展环境,且源岩(浆)来自于深部地壳物质部分熔融。这2套岩石的形成表明,北山造山带在890~870 Ma经历了板块碰撞-后碰撞的构造转换过程。约890 Ma之前的板块碰撞代表了对罗迪尼亚(Rodinia)超大陆汇聚的响应,约870 Ma的伸展则代表了古亚洲洋在该区域内开始孕育,且这次伸展作用可能与罗迪尼亚超大陆裂解有关。As an important tectonic terrane in the southern margin of Central Asian Orogenic Belt(CAOB),the Beishan orogenic belt has undergone the accretion and stitching process of long-time and multi-stage,where Precambrian basements were universally distributed and Paleozoic crust was remarkably accreted.Therefore,based on the previous works,it is necessary to reconstruct the tectonic evolution of this belt in Neoproterozoic,research the ascription of basements,and discuss its role in the evolution of Paleo-Asian Ocean and even larger-scaled tectonic evolution.Two set of samples were collected from porphyritic biotite monzogranite and rhyolite in Daoban copper-Honggoushan-Dawan iron mine in the southern Beishan belt,Gansu Province,which were used for the study of petrography,geochemistry and zircon U-Pb geochronology.The samples are characterized by high silicon,rich alkali and potassium,peraluminous,low magnesium and calcium.The rare earth elements(REE)are characterized by differentiation of light and heavy rare earth elements and the negative anomaly of Eu.Trace elements manifest depletion of high field strength elements(HFSE)such as Nb and Ta,and enrichment of large ion lithophile elements(LILE)such as Sr and Ba.U-Pb dating of porphyritic biotite monzogranite yields the weighted average age of 892.3±5.1 Ma,and that of rhyolite yields 870.4±4.5 Ma,which shows similar geochronology.Typically featuring S-type granite,the porphyritic biotite monzogranite was formed in collision environment,and its magmatic source was generated from recycling of ancient crustal sediments.Characterized by A 2-type granite,the rhyolite was formed in post-collisional extensional environment,and its magma was originated from partial melting of deep crustal material.The formation of two types of intrusives indicates that Beishan orogenic belt experienced a tectonic transformation from collision to extension.The collision before 890 Ma indicates its response to Rodinia supercontinental converging.The extensional event at 870 Ma reflects the b

关 键 词：花岗岩 地球化学 U-Pb年龄 北山造山带 古亚洲洋 罗迪尼亚超大陆 

分 类 号：P534.3[天文地球—古生物学与地层学] P597[天文地球—地质学]