Aeromagnetic Survey In Tibetan Plateau And The Characteristics Of DAAZ Along Yarlung Zangbo River

The aeromagnetic survey in the middle and west Tibetan plateau was carried out during 1998-1999, which removed the absence of aeromagnetic data in Tibetan plateau and made the complete coverage of aeromagnetic data over the whole Chinese continent. Combining geological and other geophysical information, the research on the characteristics of the aeromagnetic anomaly over the Tibetan plateau and the Double-Aeromagnetic Anomaly Zone (DAAZ) along Yarlung Zangbo River have been done, and the main results are described bellow:1. Due to the close combination of the survey and scientific research during the Aeromagnetic survey, some key problems, such as previous processing system for aeromagnetic data and flight-height controlling, were overcome by the relative techniques.2. Based on some experiments, the ground magnetic diurnal variation net was established and the long term synchronized observation was firstly used in the extensive aeromagnetic survey with a huge and informative data set which was used to make corrections for the aeromagnetic data.3. The research on the high-resolution aeromagnetic data shows that two linear aeromagnetic anomaly zones(DAAZ), south and north characterize Yarlung Zangbo Suture, while the obvious difference of magnetic basements between Tarim basin and Tibetan plateau is defined by an arc-anomaly which marks the boundary between them. The NNE negative aeromagnetic anomaly, much clear after up-continuation, provides an information about the deep crust beneath the plateau.4. The result from the Magnetic Source Parameter. Imaging method reveals that the DAAZ along the Yarlung Zangbo River is caused by a hidden rock body, and this provides an inaccessible evidence for studying the property of the Yarlung Zangbo Suture.5. The DAAZ was calculated by forward and inversion methods with the constraints of gravity and seismic data, and the geometry of the northern anomaly zone in the DAAZ indicates that the anomaly inclines south with a continuity from west to east.6. The comprehensive research along Yarlung Zangbo River shows that the Yarlung Zangbo Suture is characterized by a high magnetic anomaly, high velocity of 6.0-6.2 km/s in upper crust and gravity gradient with a slight variation. This phenomenon is related to the rocks that are of high magnetism and high density, thus the anomaly is inferred as mafic or ultra-mafic rocks.