Abstract:

Tectonic evolution of the Ordos faultblock was reconstructed, which could be separated into five main stages, namely, Archean-Paleoproterozoic, Meso-Neoproterozoic, Early Paleozoic, Late Paleozoic and Meso-Cenozoic，and the tectono-sedimentary frameworks of each stage were explored. The roles of controlling basin development of the fractures with varied strikes, including the W-E and NE-striking fractures in the basement, were analysed, which emphasized that the neogenic structures of N-S orientation appearing in Mesoproterozoic and NW-striking forming in Early Ordovician played an important part in the fault-block's  evolution and oil-gas accumulation. In the light of basin-orogeny coupling theory, an organic relation between the neogenic structures as well as the W-E fracture and the neighbouring orogenic occurring was discussed. The inheritance development of the N-S and NW structures in Meso-Cenozoic, instead of younger neogenic structures appearing in Meso-Cenozoic, resulted in a tectonic stability of the Ordos fault-block. The N-S fracture further developed and became a boundary fault of the block during Cretaceous-Eogene, when the thrusting controlled the oil-gas reservation or adjustment. The NW-striking neogenic structure, which was firstly put forward and systimatically described in this paper, didn't reactivate in Late Mesozoic and Cenozoic. Based on the example, the characteristics of neogenic structural inheritance activities were analysed, which underlined the significance of NW structure in constraining later sedimentary framework and oilgas formation. The Ordos fault-block supported a case that the key of structural analysis for marine oil-gas exploration should be inheritance developing of neogenic structures

Key words: basin-orogeny coupling, neogenic structure, inheritance development, oil-gas exploration, the Ordos fault-block