HR: 0800h
AN: T41A-1268    [Abstracts]
TI: Structure of the Dayangshu Basin in Northeast China Inferred from Magnetotelluric Data
AU: Cao, J
EM: jxcao@mit.edu
AF: MIT, Earth Resources Laboratory, Cambridge, MA 02142 United States
AU: Cao, J
EM: jxcao@mit.edu
AF: Chengdu University of Technology, 1 East 3rd Rd Erxianqiao, Chengdu, 610059 China
AU: * Sun, Y
EM: youshun@mit.edu
AF: MIT, Earth Resources Laboratory, Cambridge, MA 02142 United States
AU: Li, X
T41A-1268 AF: Chengdu University of Technology, 1 East 3rd Rd Erxianqiao, Chengdu, 610059 China
AU: Chen, S
T41A-1268 AF: Exploration & Production Research Institute, Daqing Oilfield Company Limited, Daqing, 163712 China
AB: The Dayangshu basin is a NNE trending fault-bounded basin, located at longitude 123°21' - 125°38' east and latitude 47°55' - 50°59' north within the southern part of the Xingan fold system. It is one of the largest sedimentary basins in Northeast China with an area of 15,460 km². The sedimentary rock in the basin is approximately 3,000 m thick, and is composed mainly of clastic rocks and volcanic rocks. The base of the basin consists mainly of Paleozoic low-grade metamorphic rocks. In the early 1990s, the Daqing Oilfield Company started petroleum exploration programs in the area. By the end of 1990s, gravity, magnetic, magnetotelluric (MT), and 2D seismic reflection measurements had been carried out in the basin and several prospects had been drilled. It has been determined that the majority, about 75%, of the basin is composed of volcanic rocks. However, the location and extent of the lava and main hydrocarbon source rock are still unclear. The distribution of these materials is very important for understanding the geological history and evaluating the petroleum resource capacity of the basin. The volcanic rocks within the basin are highly magnetic. The average susceptibility of the lava in the basin is about 0.18 SI units. It has been demonstrated that highly magnetic rocks significantly affect the MT response. By simultaneously inverting MT data for electric resistivity and magnetic susceptibility estimate, we develop a new approach for mapping magnetic strata. We apply the approach to the interpretation of MT data collected at 3,243 sites within the basin, and obtain a volcanic rock distribution model characterized by high susceptibility. The model shows that volcanic rocks are predominantly located at the boundary and middle of the basin. The volcanic rocks located at the middle of the basin cut the basin into southern, middle and northern sub-depressions. The hydrocarbon source rocks should be buried in the sub-depressions, and the lava close to the source rocks is potentially an oil or gas reservoir. The volcanic rock distribution mapped by the MT approach coincides with surface geological and magnetic surveys and drilling records.
DE: 8015 Local crustal structure
DE: 8169 Sedimentary basin processes
DE: 8180 Tomography (6982, 7270)
DE: 8409 Atmospheric effects (0370)
DE: 8429 Lava rheology and morphology
SC: Tectonophysics [T]
MN: Fall Meeting 2005