Fission-track analysis of uplift times and processes of the Weibei Uplift in the Ordos Basin

Abstract

The Weibei Uplift which is located in the transition zone between an active belt (the Qinling Orogenic Belt) and a stable block (the Ordos Block), is in a unique and important structural position. Understanding of the timing and processes of uplift of the belt is of great significance for research on basin-mountain relationships, basin dynamic evolution, and hydrocarbon accumulation. In this study, apatite fission-track analysis, zircon fission-track, and geothermal simulation were used to study the low-temperature thermochronology of the Weibei Uplift. The results show that the processes of uplift and cooling were markedly different. The cooling event took place much earlier in the south than in the north. The uplift of the Ordovician to lower Permian sequence in the south of the area during the late Early Cretaceous (102-107 Ma), much earlier than in the northern part of the area in which uplift occurred during the Cenozoic (65 Ma), especially during the late Eocene (40 Ma). The Weibei Uplift experienced two episodes of rapid uplift, which began in the late Early Cretaceous (102-107 Ma) and during the late Eocene (40 Ma), the main period of rapid uplift took place at 40 Ma. The results of the thermal evolution simulation indicate that the Weibei Uplift experienced rapid uplift during the period from 125 to 100 Ma, slow uplift between 100 and 40 Ma, and further rapid uplift and cooling after the late Eocene (40 Ma), particularly from 5 Ma until the present. The timing of the rapid uplift since 40 Ma in the Weibei Uplift and the timing of uplift of the Qinling Orogenic Belt are consistent, The overall rapid uplift in the Weibei Uplift since 40 Ma shows good correlation with the rapid subsidence of the Weihe basin during the Cenozoic.