华北克拉通南缘中-新元古代沉积地层对比研究及其地质意义  

Meso-Neoproterozoic sedimentary formation in the southern margin of the North China Craton and its geological implications

作　　者：胡国辉[1,2] 赵太平[1,3] 周艳艳[4] 王世炎[5] 

机构地区：[1]中国科学院广州地球化学研究所矿物学与成矿学重点实验室,广州510640 [2]中国科学院大学,北京100049 [3]西北大学大陆动力学国家重点实验室,西安710069 [4]中国科学院地质与地球物理研究所,北京100029 [5]河南省地质调查院,郑州450001

出　　处：《岩石学报》2013年第7期2491-2507,共17页Acta Petrologica Sinica

基　　金：国家基础研究发展计划(973项目)(2012CB416606);西北大学大陆动力学国家重点实验室科技部专项经费联合资助

摘　　要：华北克拉通南缘新太古代-古元古代变质结晶基底之上不整合覆盖着巨厚的中-新元古代陆源碎屑岩-碳酸盐岩沉积盖层,根据沉积建造特征,将其划分为三个不同的地层分布小区,分别为嵩箕地层小区、渑池-确山地层小区和熊耳山地层小区。嵩箕小区位于熊耳裂谷盆地东北缘,以硅质碎屑岩(砂岩)为主,渑池-确山地层小区位于熊耳裂谷盆地北缘,以硅质碎屑岩-碳酸盐岩(白云岩)过渡相为主,熊耳山地层小区位于熊耳裂谷盆地南缘,以碳酸盐岩为主。本文通过对三个地层小区的沉积地层剖面和岩石学特征进行研究,认为华北南缘从中元古代开始处于河流相-浅海相的沉积环境,从南向北,海水由深变浅。根据地层的岩性、沉积构造及其组合特征,将其划分为低水位、海侵和高水位沉积体系,最大海侵时期为青白口系早期。通过对熊耳山地区的官道口群的岩相学和地球化学分析,并结合其已有的碎屑锆石年龄和另外两个地层小区的五佛山群和汝阳群的碎屑锆石年龄以及它们的地球化学特征,表明三个地层区的沉积地层在中元古代均处于被动大陆边缘环境,而新元古代则可能处于与大陆岛弧相关的沉积盆地,这一结果表明从中元古代到新元古代华北南缘可能受到秦岭造山带早期微陆块俯冲碰撞的影响,由被动大陆边缘向活动大陆边缘过渡的过程。三套地层最年轻的碎屑锆石207Pb/206Pb年龄基本上在1600Ma左右,从而限定了其最大沉积时代不早于1600Ma。其锆石年龄大多数都分布于古元古代(1700～2400Ma),太古代的年龄极少,说明其物源区以古元古代的地质体为主,且碎屑锆石年龄峰值为～1.93Ga,反映了华北南缘在～1.93Ga发生过重要的构造-热事件,与华北克拉通古元古代中期发生的变质作用时间(～1.91Ga)一致。三套沉积地层的碎屑锆石εHf(t)值变化较大(-20～+6),表明既有新生地壳物�Meso-Neoproterozoic terrigenous clastic and carbonate rocks cover the metamorphic crystalline basement with angular unconformity in the southern margin of the North China Craton （ NCC） ,which can be divided into Songshan-Jishan,Mianchi-Queshan and Xiong’ershan stratigraphic provinces. The Songshan-Jishan stratigraphic province,in the northeast of the Xiong’er basin,is composed of siliceous clastic rocks. The Mianchi-Queshan province,in the northern margin of the Xiong’er basin,consists of the transitional facies of siliceous clastic-carbonate rocks. The Xiong’ershan province,in the southern margin of the basin,is mainly composed of carbonate rocks. Based on their stratigraphic and petrologic characteristics,these sedimentary sequences formed in typical fluvial-marine environment with water depth shallowing from south to north. They can be divided into low sea depth,transgression and high sea depth depositional system accordingly. The petrologic and geochemical signatures show that these sedimentary rocks sourced from post-Archean felsic components with minor basic rocks and formed in a passive continental margin during Mesoproterozoic. However,the Neoproterozoic sequences formed in sedimentary basin related to a continental arc. It implies that more crustal activities and distinct changes in tectonic settings from passive to active continental margin from Mesoproterozoic to Neoproterozoic,a possible effect of the early tectonic events of the Qinling Orogenic Belt. Laser ablation ICP-MS U-Pb dating of detrital zircons from these sedimentary sequences yields ages ranging from ca. 1. 50Ga to 2. 70Ga with most Paleoproterozoic ages （ 1. 70 ～ 2. 40Ga） and minor Archean ages,indicating the detritus mainly sourced from Paleoproterozoic geologic bodies. The youngest ages at the bottom of the sequences of ～ 1600Ma can constrain the maximum age of deposition. The pronounced age peak at ～ 1. 93Ga corresponds to the significant Early Precambrian metamorphic event of the NCC. All detrital zircons have ob

关 键 词：华北克拉通 五佛山群 汝阳群 官道口群 地层对比 物源区 

分 类 号：P588.1[天文地球—岩石学]