关键词: 构造变革期, 区域不整合面, 构造沉降, 岩浆活动, 周缘板块事件, 板内变形, 克拉通盆地, 鄂尔多斯盆地

Abstract: Ordos Basin is a typical intracratonic basin, rich in mineral resources such as oil and gas, coal, salt, and uranium. Studying the periods, sequences and attributes of tectonic movement of the basin will not only lay the foundation for revealing the origin and evolution process of the craton basin, but also provide a basis for exploring the internal occurrence mechanism of the multiple energy and mineral resources. Based on high-resolution reflection seismic profile and deep-well data in recent years, in combination with the analysis of peripheral geological outcrops, this paper establishes a spatio-temporal framework of basin evolution by determining the key tectonic evolution periods of Ordos Basin. Studies have shown that there are 10 regional unconformities developed from bottom to top in the Ordos Basin, namely the basal unconformities in the Changchengnian, the Jixianian, the Sinian, the Cambrian, the Ordovician, the Carboniferous, the Triassic, the Jurassic, the Cretaceous and the Quaternary. Six tectono-stratigraphic sequences developed in the Mesoproterozoic, the Cambrian to Ordovician, the Upper Carboniferous to Triassic, the Jurassic, the Lower Cretaceous and the Cenozoic in the basin. The formation and evolution of Ordos Basin was controlled by the tectonization of the peripheral plates. It experienced the continental breakup in the early and middle period of the Mesoproterozoic, the development of passive continental margin during the Cambrian to the Middle Ordovician, the formation of active continental margin and collision orogeny in the Late Ordovician, the periphery breakup during the Late Carboniferous to the end of the Permian, the development of large-scale intracontinental depressions during the Early Mesozoic and intracontinental foreland basins during the Middle to Late Mesozoic, and peripheral fault depressions during the Cenozoic and other evolution processes. Tectonism in the deep lithosphere of Ordos Basin is relatively active. The basin is subjected to four periods of intermediate-acid or mafic-intermediate volcanic activities in the Middle Ordovician, the Middle and Late Triassic, the Early Cretaceous, and the Late Miocene, especially much extensive in the late period of the Early Cretaceous. Further, through analyzing the tectonic events of peripheral plates, intrabasin magmatic activity and basin subsidence-uplifting process, it is believed that Ordos Basin has experienced five key tectonic modification periods of the Neoproterozoic, the Late Ordovician, the Middle to Late Triassic, the Late Jurassic to Early Cretaceous, and the Cenozoic. These tectonic modification periods control the tectonic evolution and geological architecture of the basin, and have a profound impact on the distribution of oil and gas in Ordos Basin.

Key words: tectonic modification period, regional unconformity, tectonic subsidence, magmatism, peripheral plate events, intraplate deformation, cratonic basin, Ordos Basin