Cenozoic tectono-thermal evolution of the Weihe Basin, Central China

Abstract

ABSTRACT As a passive rift basin in the Cenozoic, the formation and evolution process of the Weihe Basin has not been well explained. Here we estimate the stretching factor and basal heat flow for each rift period along four geological profiles using a 2D multi-stage finite extension model. The modelling is based on a reconstruction of pre-rift crustal and lithospheric thicknesses, and is calibrated with the current heat flow. The Xi’an Depression had the biggest stretching factor while the Pucheng Uplift had the smallest throughout the Cenozoic period, which saw a range of stretching factors from 1.02 to 2.06. The basal heat flow in the Weihe Basin exhibits a corresponding change. At the end of the Oligocene, Miocene, and Pliocene periods, the basal heat flow varied between 58.5 ~ 64.0 mW·m−2, 59.2 ~ 67.0 mW·m−2, and 59.6 ~ 78.7 mW·m−2, respectively. Increasing stretching factor and basal heat flow indicate that the Weihe Basin is currently in a state of sustained extension. The formation and development of the Weihe Basin are analysed in the context of larger tectonic changes, and it is considered that the Weihe Basin is controlled by pre-existing faults, and formed in a regional tectonic context of sliding and pulling apart first, and tensioning and lifting up later. Since the late Miocene (7.3 Ma), anomalously rapid subsidence has occurred, induced by a new phase of rifting and depth-related lithospheric extension. The thermal genesis of the geothermal system in the Weihe Basin is also thought to be closely related to the latest phase of extension.