The gravity field evidence of the existence of a group of NNW-SSE trending fracture structures on the western margin of Qaidam Basin

Abstract：The western margin area of Qaidam Basin is close to the juncture between Altun orogen and Qimantag orogen of East Kunlun, where the tectonic movement is very complex. Based on a study of the newest data obtained from 1∶250000 gravity survey, the authors recognized a group of new NNW-SSE trending faulted structures, in addition to NEE-trending Altun fractures and NWW-nearly EW-trending South Kunlun, Central Kunlun and North Kunlun fractures. In this paper, the authors provided gravity evidence for the existence of a group of NNW-SSE trending fractures in this region. Based on an analysis of their characteristics and origins, the authors consider that these fractures are a group of newly rifted strike-slip structures, which have high-angle right-lateral fractures characterized by small fault displacement and long stretches, and they pass through the high-angle right-lateral fractures, belonging to a group of NEE and NWW-nearly EW trending fault zones. Further studies show that these fractures are a group of new faulted zones related genetically to NE-trending movement of the whole Tibetan Plateau. The new findings may have some significance for the understanding of the tectonic movement (especially the new tectonic movement ) and the mineral research in Qaidam western margin area.