The Coupling Relationship Between Early Paleozoic Sedimentary and Tectonic Events at the Northern Margin of the Qaidam Basin

Key words: 
• northern margin of Qaidam /
• Early Paleozoic /
• event deposit /
• coupling relationship

Abstract: The North Qaidam Orogenic Belt experienced a complicated ocean-land transformation process in the PanAfrican-Qilian period,and developed a trench-arc-basin system in the convergent margin in the Cambrian-Early Or-dovician. Consequently,the NWW-SEE trending Tanjianshan island arc belt and the South Oulongbuluq back-arc ba-sin formed along the North Qaidam Orogenic Belt,and developed a set of carbonate-clastic-volcanic sedimentary for-mations. During this time,a basin-scale coupling system was formed between sedimentary evolution of the southern margin of the Oulongbuluq microcontinent and convergence forces between it and the Qaidam block,triggering a se-ries of geological events. They are linked by a series of genetic mechanisms,which have a common macroeconomic background. In the Early Paleozoic era a tectonic shift from passive to active continental margin occurred at the south-ern margin of the Oulongbuluq microcontinent,as a consequence of northward subduction by the North Qaidam Ocean. This induced multi-period volcanic eruption events,and formed numerous sets of volcanic rocks,pyroclastic rocks and intercalated metamorphic clasolite in the Tanjianshan island arc belt. Meanwhile,the southern margin of Oulongbuluq microcontinent changed from a shallow water carbonate platform to deep water slope,and regularly de-veloped concentrated event deposits such as carbonate gravity flow deposits (submarine fan,turbidite,etc.) and slumping deposits. In addition,a mass of island-arc material and uplifted continental crust basement caused by subse-quent collision between the Tanjianshan island-arc belt and the Qaidam block provided important provenance for sub-sequent sandy debris flow and clastic turbidite deposition in the South Oulongbuluq back-arc basin. The isotopic chro-nology data shows that the development time of these event deposits is consistent with the relatively most active period of tectonism at the northern margin of the Qaidam Basin area and early in the Paleozoic. Therefore,these stable-distri-bution volcanics and gravity flow deposits with concentrated and regular distribution formed in the aftermath of sub-duction and arc-continent collision, and there is a coupling relationship between them.