| East China Sea Shelf Basin is in a special location, which is among Eurasian Plate, Pacific Plate and Philippine Plate. So the beginning of Okinawa trough had effected on East China Sea Shelf Basin. Its tectonic evolvement is a hot debate in many geologists from different country. Because of the high sensitive matter and low exploration degree, tectonic evolvement and background of East China Sea Shelf Basin is not clear and have lots of unsolved problems. Characteristic and distribution of Mesozoic basement are not fully revealed; the late Eocene tectonic movement and its mechanism were rarely mentioned by other people, the characteristic and dynamic source of inversion structure in Xihu Depression is controversial. These three hard questions of evolvement in Mesozoic-Cenozoic are answered after study, and the background and dynamic resource of development in study area is revealed in this thesis which may help oil and gas exploration in the field. Through analyzing concrete geological data and contrast between basins, these difficult issues were dissected.Connected by many important development moments, rock thin sections are observed, main and trace elements samples is analyzed, zircon U-Pb dating experiment is analyzed, seismic sections and logging data are studied, while the documentation of southeast land of china, Subei Basin, Okinawa Trough are collected and read. The changing of various sedimentary and tectonic characteristics in different areas is analyzed, which is used to reveal its tectonic background and dynamic resource during evolving of East China Sea Shelf Basin. The following results and achievements are obtained:1. Various basement rock samples experiments in Lishui Depression show that the rock thin sections have typical granite structure, the main and trace elements are found to come from the upper crust in land environment which formed in the same period with orogenic collision, U-Pb zircon ages for 194-243Ma and mainly generated in 205Ma and 220Ma. This is the first time early Mesozoic basement igneous rock has been found in East China Sea Shelf Basin.2. Contrasting sedimentary rocks and magmatic rocks between Mesozoic sea basin and land shows strong similarity. Paleozoic metamorphic rocks and gravity-magnetic characteristics indicate that both sea and land are above the same basement. Jurassic and Cretaceous strata in two places have the same type of sedimentary deposits and formation. The type and development situation of Mesozoic igneous rocks are the same too. Therefore, two places come through three phases of evolution together in Mesozoic, and the sea basin is a little bit behind.3. Through tectonic, sedimentary and paleontology study in Xihu Depression and Subei Basin, the late Eocene tectonic movement is find out to affect a wide range of area which from eastern land China to east edge of ancient east china, and cause stratigraphic unconformity or missing. In different tectonic environments, eastern land China and East China Sea Shelf Basin in the late Eocene tectonic uplift transformation have different performance. This tectonic movement is caused by subduction of the Pacific Plate.4. Xihu Depression in East China Sea Shelf Basin developed comprehensive structural inversion in late Miocene. Different intensity inversion structure can be divided into four categories:wide fold, narrow fold, wide fold with reverse fault, narrow fold with reverse fault. The inversion structure in Xihu Depression characterized to be belted from east to west and blocked from south to north. Three parameters which are reverse displacement of inversion fault, amplitude of inversion fold and compression ratio in Central Uplift Belt are statistical studied and the result shows that inversion structure in North Central Uplift Belt is strong, but limited; while inversion structure in Middle central Uplift Belt is very strong or weak; South Central Uplift Belt comprises strong inversion in some places, but weak mostly. In vertical, reverse displacement of inversion faults are mostly developed in the lower part, but inversion folds are more likely to develop on the top strata. And inversion structure enhanced from bottom to top over all.5. The evolvement of East China Sea Shelf Basin can obviously divided into many stages. In early Mesozoic, it is in inner land tectonic environment with Southeast China Land, and the dynamic is from the collision of blocks. The continental margin back-arc stretching background is developed in both land and sea in Late Mesozoic, and the dynamic comes from subduction of Pacific Plate. In late Eocene, China eastern land and sea have been separated, the East China Sea Shelf Basin is in extensional back-arc environment, the subduction of Pacific Plate cause general uplift structure in the eastern China. Most part of East China Sea Shelf Basin is margin depression basin in late Miocene, but Xihu Depression develop inversion structure caused by the westward pushing of Okinawa Trough, the power source comes from the subduction of Philippine Plate. |
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