| Based on the systematic analysis of the styles of tectonic deformation , volcanic activities , sequence stratigraphical framework, sediment filling sequence, sediment provenance and clastic fabric et al. since Mesozoic in western Hunan-Hubei and the adjacent areas, added with the studies on Qinling-Dabie and Jiangnan orogenic belts, this paper mainly focuses on the characteristics of the regional tectonics and its evolution, the main structure styles and geodynamics of their formation, tectonic geothermal events and the influence on hydrocarbon formation in the area, from the view of lithosphere scale, crust-mantle interaction and basin-range coupling. In combination with the studies on petroleum geology, this paper proposed the potential exploration prospects in this area, and the main conclusions are as the followings:1. Particular tectonic setting, longtime evolution of the platform, stable deposition of platform-type favor the formation of hydrocarbon. Experiencing tectonics of multiple stages and directions which resulted in heterogeneous crustal evolution, this area is characterized by multiple structure styles. Forming during Yanshanian period and influenced by the basement tectonics, the main structure styles in the research area are subdivided into three types—compressive fault block, extensional fault block, and thrust fold. The crustal evolution experienced three stages: a) stage of platform development, which occurred geosynclinal structural layer during early to late Proterozoic, and whole stable subsidence of Yangtze block from Sinian to Silurian period; b) stage of post platform, which occurred Yangtze block extension, splitting, depressing, and forming marine deposit in Devonian to middle Triassic; and c) stage of tectonic activization, which occurred differential blocks restricted by faults since late Triassic.2. The age of geothermal evolution that ranged from 198.4±10.4 to 58.0±7.6Ma, indicates that at least three obvious tectonic thermal events have respectively occurred since Mesozoic: 198 Ma (Indosinian), 154Ma (Yanshanian), and 70 Ma (early Tertiary), which accordingly represented the ages of tectonic reconstruction since Indosinian-Yanshanian.3. Based on the comprehensive analysis and evaluation of the generation-reservoir-caprock, preservation and the structural conditions, the lower assemblage (Sinian to Silurian system) is thought to be the dominant source rock. Huaguoping synclinore, Sangzhi-Shimen synclinore and Yidu-Hefeng anticliorium are the three favorite structural units. Furthermore, two different types of the hydrocarbon reservoir are also proposed in this paper. The hydrocarbon preservation system is composed of two assemblages (A and B, vertically). The system includes four preserving unit series, which generally distribute in three preservation areas. To the north of Xuan'en in Huaguopin synclinore is the best unit for hydrocarbon preservation, and Wufeng, Miaoling, and Huangchang-Qiaotou zones take the second place.4. Numerical simulation shows that the evolution of basin-range system since Mesozoic is controlled by the uniform geodynamic system, and is the result of the coupling of the uniform geodynamics at different geological periods: Indosinian-early Yanshanian compressive stage was mainly controlled by the collision of North China and South China blocks, and late Yanshanian-Himalayan extensional stage mainly controlled by the subduction of Pacific Plate and the succedent mantle readjustment.5. According to the studies on petroleum geology and tectonic reconstruction, this paper proposed that the potential hydrocarbon exploration prospects in Lower Paleozoic in western Hunan-Hubei should focus in Huaguoping synclinore, Yidu-Hefeng anticliorium, Sangzhi-shimen synclinore, Zigui synclinore.
|
PDF Full Text Request