3D lithospheric structure of western China and its enlightenment on petroleum prospecting

Abstrac：The 3D lithospheric structure of western China studied by using satellite gravity anomalies revealed that in the crust of western China there exist regular, distinct, parallel, linear basin-range structures. From north to south, there are: the Ertix basin belt, North Junggar uplift belt, North Tianshan basin belt, Tianshan uplift belt, Naomaohu -Olji basin belt, South Tianshan basin belt, Kuruktag- Beishan uplift belt, Altyn Tagh（Altun）-North Qilian belt (or South Tarim basin belt) and West Kunlun-Altyn Tagh-Qilian uplift belt, as well as the Qaidam basin belt and southern Tibet basin belt. These crustal basin belts formed by strong basal compression folding in the Indosinian-Yanshanian period. In the Himalayan period, northeast-directed subduction of the Indian plate resulted in uplift of the Borohoro-Qapqal -Ala Gou-Erben-Horo mountains, and they together with the Tianshan Mountains divide Xinjiang into the Tarim basin, Junggar basin, Tuha basin and Yining basin, forming the present-day geomorphology of Xinjiang. These NW-SE mountains and other NW-SE neotectonics have their corresponding satellite gravity anomalies in the lid of the lithosphere. Thus it is inferred that the dynamic force of the neotectonic movement was derived from the lithospheric mantle. In Tibet, the idea that the Tibetan Plateau is regarded as the superficial structure formed by a number of parallel faults such as the Yalung Zangbo fault, Bangong Co-Nujiang fault, Lanchang River fault and Jinsha River fault and the elongated blocks sandwiched therein does not conform to the crustal structure at ~15 to 18 km depth. This kind of elongated block structure and the southeast-directed escape structure only occur in the upper crust. Study also indicates that subduction of the Indian plate to the mantle only occurs in southwestern Tibet. In western Sichuan-eastern Tibet there exits a stable block which interrupts subduction of Indian plate beneath Tibet. The study provides the following enlightenment on petroleum prospecting: (1) petroleum prospecting in western China should not be restricted in Cenozoic basins; (2) in the study of the tectonic setting of basins in western China one should consider the structural control at depths; and (3) basic research may play an important role in petroleum prospecting and furnish clues leading to finding Paleozoic and Mesozoic oil/gas fields, and the research results may be used for reference in work arrangement, and especially we should carry out a systematic investigation and study of the whole deep aspects of the North Tianshan basin belt, South Tianshan basin belt, South Tarim basin belt, Qaidam basin belt and North Tibet basin belt and their control on the surface structures.