云岗盆地晚中生代沉积-火山充填序列及其构造意义

Late Mesozoic sedimentary-volcanic filling record in Yungang basin and its tectonic implications

利用凝灰岩夹层及安山岩的锆石U-Pb同位素测年,对云岗盆地晚中生代地层充填序列的关键时限进行了限定。结合地层接触关系、安山岩的地球化学特征,分析了重点地质界面的构造意义。取得了以下主要认识:(1)早中侏罗世,盆地为一套湖进序列的连续沉积,以大同组含煤地层为代表,暗示着区域拉张的构造背景;(2)盆地整体缺失了晚侏罗世(160.4±1.1)Ma至早白垩世(130.1±0.7)Ma的沉积地层,其发生的动力学背景可能与古太平洋、西伯利亚、特提斯同时向东亚大陆汇聚产生的远程效应有关;(3)旧高山安山岩形成于早白垩世(130.1±0.7)Ma大陆板内裂谷的构造背景,与华北克拉通破坏的动力学背景紧密相关。研究成果对旧高山安山岩时代归属提出了新的认识,并不归属于上侏罗统髫髻山组,而相当于下白垩统张家口组。

Based on regional stratigraphic correlation and using zircon dating method of tuff layer and andesite rocks in the LateMesozoic stratigraphic sequence, the authors defined the key time of the sedimentary-fill record. According to the formation contactrelationship and the geochemical characteristics of the andesite, the authors also analyzed the tectonic significance of the keygeological interface. Some conclusions have been reached： （1） During the Early- Middle Jurassic, the sedimentary sequence wascharacterized by a suite of lake transgression sequence with the coal- bearing strata of Datong Formation, indicating the tectonicsetting of the regional extension; （2） These strata had no sedimentary record from Late Jurassic （160.4±1.1 Ma） to Early Cretaceous （130.1±0.7 Ma）, which was dynamically associated with far field effects produced by synchronous convergences toward the eastAsia continent of different plates （Siberia, Paleo- Pacific, Tethys）; （3） The andesite of Jiugaoshan was developed in the tectonicsetting of the continental rift during the Early Cretaceous, which might have been associated with the destruction of the North ChinaCraton. The andesite age of Jiugaoshan was defined in the study. It does not belong to the Tiaojiashan Formation, but corresponds tothe Zhangjiakou Formation in Yanshan area.