Seminar

The Cathaysia Block is characterized by a widespread magmatic belt, prominent NE-striking fault zones and numerous rifted basins filled by Cretaceous-Eocene sediments. The geology denotes a transition from an active to a passive margin, which led to rapid modifications of crustal stress configuration and reactivation of older faults in the Cathaysia Block.

Numerical geodynamic modeling of the subduction zone indicates that slab roll-back of the paleo-Pacific Plate during Late Cretaceous could be the main driving force of the compression-extension regime transition in the Cathaysia Block. This stress regime inversion could explain the concurrent volcanic rocks found in some sedimentary basin formations. The zircon fission-track dating shows differential exhumation of the Yunkai-Nanling region from Middle Jurassic to Late Cretaceous, which is considered as a result of Jurassic-Early Cretaceous magmatism in the Nanling Range. The apatite fission-track analysis, together with numerical models of crustal extension, implies that the faults in the marginal areas of the Cathaysia Block were reactivated from south to north. The timing of the transition is suggested to have taken place at ~ 92 Ma, according to a rapid cooling as revealed by the thermal history modeling of AFT length data. Another rapid cooling occurring at ~59 Ma is probably evidence for the opening of the proto-South China Sea.