银川拜寺口剖面黄旗口组LA-ICP-MS碎屑锆石U-Pb年代学特征及其地质意义  

Chronology characteristics of detrital zircons U-Pb dating with LA-ICP-MS from Huangqikou Formation of Baisikou Section,Yinchuan and its geological significance

作　　者：李琳静[1,2] 胡明毅 吕奇奇[1] 舒爽[3] 王铜山 宋到福[5] 张严[1] LI Linjing;HU Mingyi;LYU Qiqi;SHU Shuang;WANG Tongshan;SONG Daofu;ZHANG Yan(School of Geosciences,Yangtze University,Wuhan,Hubei 430100,China;Hubei Geological Survey,Wuhan,Hubei 430034,China;No.8 Oil Production Plant of Changqing Oilfield Branch Company Limited,PetroChina,Xi'an,Shaanxi 710000,China;Research Institute of Petroleum Exploration&Development,PetroChina,Beijing 100083,China;State Key Laboratory of Petroleum Resources and Prospecting,China University of Petroleum(Beijing),Beijing 102249,China)

机构地区：[1]长江大学地球科学学院,湖北武汉430100 [2]湖北省地质调查院,湖北武汉430034 [3]中国石油长庆油田分公司第八采油厂,陕西西安710000 [4]中国石油勘探开发研究院,北京100083 [5]中国石油大学(北京)油气资源与探测国家重点实验室,北京102249

出　　处：《东北石油大学学报》2022年第4期24-36,47,I0003,共15页Journal of Northeast Petroleum University

基　　金：国家科技重大专项(2016ZX05004-001-004);油气资源与探测国家重点实验室开放课题(PRP/open-1804)。

摘　　要：黄旗口组为贺兰山古老结晶基底之上的第一个沉积盖层,其时代归属问题存在争议。利用LA ICP MS方法,对银川拜寺口剖面黄旗口组深灰色含海绿石石英细砂岩进行碎屑锆石U Pb测年分析。结果表明:黄旗口组锆石颗粒以椭球状居多,短柱状次之,外形多呈次圆状和次棱角状,粒径多介于40~130μm;锆石Th/U介于0.12~1.81,其中Th/U大于0.40的占85.3%,以具震荡环带结构的岩浆成因锆石居多,部分锆石后期可能受变质事件改造影响;锆石^(207)Pb/^(206)Pb年龄数据分布范围为1680~2606 Ma,存在明显的1890 Ma主峰值年龄和2345、2514、2576 Ma次级峰值年龄,最小碎屑锆石年龄为(1680±40)Ma。2700~2450、2040~1950、1950~1800、1800~1680 Ma锆石年龄分布对应华北克拉通新太古代克拉通化事件、研究区新生陆弧花岗质岩体主要形成时期、阴山陆块与鄂尔多斯陆块发生碰撞而形成华北西部陆块时期、华北克拉通中元古代基底隆升与陆内裂谷事件。黄旗口组为中元古代长城系晚期沉积,华北克拉通北缘西段孔兹岩带为主要物源区,新太古代晚期(约2500 Ma)陆壳物质和太行—吕梁基性岩墙群为次要物源区。该结果为研究区地层对比和年代地层格架建立提供新的年代学资料。The Huangqikou Formation,the first sedimentary cover over the ancient crystalline basement of Helan Mountains,is subject to controversy over the issue of its age.By using the method of LA ICP MS,the U Pb date of detrital zircons from dark-gray glauconite-bearing fine quartz sandstones in the Huangqikou Formation of Baisikou Section,Yinchuan was carried out.The results showed that the zircon particles were mostly ellipsoidal,followed by short prismatic,subrounded and subangular in shape,with particle sizes ranging from 40 to 130μm.Zircons are mostly magmatic origin with concussive annulus structures.The Th/U ratio of zircon ranges from 0.12 to 1.81,most of which are larger than 0.40,most of thezircons are magmatic origin with oscillatory zoning structure,and part of them may be affected by metamorphic events;the age of ^(207)Pb/^(206)Pb data ranges from 1680 to 2606 Ma,with the apparent main peak of 1890 Ma and several other secondary peak(2345,2514 and 2576 Ma)in the age spectrum.The age of the youngest detrital zircon was(1680±40)Ma.The analysis of the age peaks and composition of detrital zircon shows that:the zircon age of 27002450,20401950,19501800,18001680 Ma correspond to the Neo-Carcinogenic event of the North China Craton,the formation of the Neogene continental arc granitoids in the study area,the formation of the Western North China Block due to the collision between the Yinshan Block and the Ordos Block,and the Middle Proterozoic basement ascendant and intracontinental rift events of the North China Craton.The Huangqikou Formation belongs to Middle Proterozoic Changcheng System;the khondalite series in the northern margin of the North China Craton is the main provenance,and the continental crust material and the Taihang-Lyuliang basic dyke in Late Neoarchean(about 2500 Ma)are the secondary source areas.Providing new chronology data for further establish the contact relationship of Changcheng System and underlying Palaeoproterozoic.

关 键 词：碎屑锆石 U-PB测年 华北克拉通 黄旗口组 长城系 拜寺口剖面 贺兰山 

分 类 号：TE122.2[石油与天然气工程—油气勘探] P534.3[天文地球—古生物学与地层学]