柴达木地区晚古生代沉积构造演化

Sedimentary and tectonic evolution of Qaidam areas in Late Paleozoic

依据野外采集的古流向数据和上古生界火山岩地球化学资料对柴达木地区晚古生代沉积构造演化特征进行研究。结果表明:盆地东部地区物源总体来自北部,海侵方向由南向北,沉积中心在盆地南部地区;构造背景晚泥盆世为后碰撞期的板内拉伸,早石炭世为陆内拉张构造环境,晚石炭世二叠纪以洋陆俯冲构造背景为主;晚泥盆世开始,柴达木地块周围普遍因拉张而发生裂陷,形成一系列狭长状的地堑式断陷盆地或海槽,柴达木中央隆起(牛鼻子梁古陆)的雏形形成;石炭纪沉积盆地是在海西运动产生的晚泥盆世裂陷槽基础上形成的差异性沉降盆地,具有坳、隆相间的古地理格局,海侵广泛,以台型沉积为主的浅海相碳酸盐岩裂谷盆地,在古陆边缘附近形成了海陆过渡相的泻湖、扇三角洲(或辫状河三角洲)及沼泽相含煤沉积;二叠纪基本保持了石炭纪的海域,仍处于陆缘裂陷盆地的构造背景,属于稳定型浅海相沉积的碎屑岩—碳酸盐岩建造。

According to the restoration of paleocurrent data collected in the field and the study on geochemical behavior of Neopaleozoic volcanic rocks,sedimentary and tectonic evolution features of Qaidam areas in Late Paleozoic were studied. The results show that the land sources of the eastern part of the basin generally come from the north,which reflects that the direction of transgression is from south to north and the deposition center lies in the southern part of the basin. The tectonic settings were intraplate tension in later stage of collision in Late Devonian,intracontinental tension in Early Carboniferous and ocean-continent underthrust in Late Carboniferous. The Qaidam Basin Block Mass developed a series of slim graben-like basin or ocean trough and formed the prototype of Qaidam Basin central uplift （ Niubiziliang ancient land） because of tension from Late Devonian. The Carboniferous depositional basin,with a depression and uplift palaeogeographic framework,is a differential subsidence basin,formed by Hercynian movement on the basis of Late Devonian rift trough. It was a rift basin deposited with neritic facies carbonate rocks and was extensivly transgressed. Lagoon,fan dalta （ or braided river dalta） of transitional facies and coal-bearing deposition of paludal facies were formed around the ancient land. Permian Period had the same sea area as that of Carboniferous Period,which still located in epicontinental faulted depression and belonged to clasolite-carbonate construction with stable shallow marine deposition.