Numerical simulations of tectonic stress fields for Late Mesozoic-Paleogene extensional tectonics in western Shandong

Extensional tectonics in the West Shandong Uplift were examined and geological models were established using field geological survey data of the western Shandong and the geophysical data of the Jiyang Depression. Based on a finite element method, we adopted the Ansys12.0 software to carry out a 3D tectonic stress field numerical simulation of the extensional tectonic evolution of the study area from the Late Mesozoic to Paleogene, which fit well with the actual geological conditions. The results indicated that the tectonic stress field evolved from strong to weak from the Late Mesozoic to Paleogene, and the maximum principal stress axis transferred from NW-SE to NWW-SEE, and then to NE-SW, which was a major shift. Paleocene-Early Eocene was a transitional period with its stretching orientation transformed from NE-SW to NS, and Eocene-Oligocene was a significant phase for uplift-depression differentiation when the West Shandong Uplift and the Jiyang Depression became separated and evolved separately. This evolution regularity had an important control on the migration and accumulation of oil and gas in the Jiyang Depression and the enrichment of metallic minerals in the West Shandong Uplift. The essential factors leading to the tectonic evolution were the changes of the Pacific Plate subduction, the strike slipping motion along the major boundary fractures, and the magma under plating.