A New Understanding on the Pattern of Deep Faults in Xizang and the Southwestern Sanjiang Area

Abstract

Extremely complicated fault structures characterize Xizang and the Sanjiang (Jinsha River, Lancang River, Nujiang River) region in southwest China. In spite of many years' study, different recognitions to this issue remain present. Based on new aeromagnetic data and gravity data, and from the view of combining gravity and magnetic characteristics with geological structure, we compile a new map of fault structures in Xizang and the southwestern Sanjiang region. The results show that the deep faults along the Jinsha River, Lancang River and Nujiang River are independent NW‐striking faults which extend from the south to the northwest, not connecting with the arc‐like faults in Xizang which extend from the east to the west. These faults are newly discovered NW‐striking faults in the Tethys fault system and belong to a different fault system relative to EW‐striking faults in Xizang. This opinion is different from the previous view that the suture zones of Jinsha River, Lungmu Co‐Lancang River and Bangong Co‐Nujiang River extend towards NW and EW in arc distribution. This discovery of the faults has changed the recognition of fault structure framework of Xizang‐Sanjiang areas, which lends light on the geotectonic research in the future. In this paper, the west extending characteristics of deep fault belt developed in Xizang and southwest Sanjiang River area are mainly explained, and the intersection relationship of faults between the Sanjiang River and Xizang is also discussed, which indicates that gravity and magnetic data are significant for the research on fault structures.