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Analysis Of Sedimentary Heavy Minerals In The Xining And Guide Basins And Its Tectonic Significance In Cenozoic

Posted on:2013-10-22Degree:MasterType:Thesis
Country:ChinaCandidate:X B WuFull Text:PDF
GTID:2180330467483978Subject:Paleontology and stratigraphy
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Sedimentary basins and orogenic belts are the two basic tectonic units in the continent, both they closely contact each other in space development and driving mechanism. The sediments in basins are the result of the orogenic belt rock weathering, denudation, transportation and deposition within drainage area. So, the sediments not only can record continuous information of the tectonics of the orogenic belts, but also reflect the climatic and environmental changes during the process of basin formation.In the NE Tibetan Plateau, the basins of Xining and Guide as the fold system convergence zone from the northern Qilian Mountains, Kunlun Mountains and the Qinling Mountains, are controlled by the Kunlun Mountains and Altun Mountains sinistral relative motion induced NW-trending dextral fault movement and NWW to the combined effect of L-fracture the formation of the plateau northeast of a typical basin and range landscape pattern in the northeastern Tibetan Plateau. The Cenozoic sediments from the Xining and Guide basins have completely recorded the tectonic movements within and around the basins. In order to reveal the processes of these two basin sediments, the surrounding mountain uplifts as well as the driving forcing, a series of profiles in Xining and Guide basins, including Xiejia, Ganjia, Gepiza, sections, are selected carefully for the heavy minerals analysis as well as considering the sedimentary characters (lithology, lithofacies, sedimentary characteristic components, contact relation, et al), space changing rule, paleocurrent direction, sedimentary facies based on the paleomagnetic age controls. We obtained three main conclusions as the following:1. In these two basins, detailed heavy mineral characteristics revealed five stages from old to young. They are:less stable mineral phase, a more stable mineral phase, unstable heavy mineral phase, relatively stable phase and very unstable heavy mineral phase.2. Based on these five heavy mineral stages and related sedimentary characteristics, five correlated tectonic stages are indicated, including i) the earliest tectonic uplift phase between Paleocene and Early Eocene, ii) steady stage of middle Eocene-Late Oligocene, iii) tectonic activity again during late Oligocene-Early Miocene, iv) tectonic clam stage in middle Miocene, and v) strong activity phases since Late Miocene.3. The Eastern Kunlun Mountains uplifts and the earliest Xining-Guide Basin formation at the northeastern Tibetan Pleteau are result from the early Indian-Eurasian plates collision. During the late Oligocene-early Miocene, the onset of deformation and rock uplift along the eastern part of the Laji Mountain, divided the Xining-Guide Basin into two subbasins, Xining Basin and Guide Basin. During the Late Miocene (possibly~8.5Ma), the Laji Mountain strongly deformed and uplifted, the Guide Basin recessed and became an intramontane basin.
Keywords/Search Tags:heavy mineral, basin evolution, Basin-range coupling, Qinghai-Tibet Plateau, New generation
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