Characteristics of the crustal magnetic anomaly and regional tectonics in the Qinghai-Tibet Plateau and the adjacent areas

Study of the characteristics of the crustal magnetic anomaly in the Qinghai-Tibet Plateau and the adjacent areas helps better understand the lithospheric structure and evolution, as well as the regional geodynamic processes. Here we analyze the distribution laws of the crustal magnetic anomaly and its vertical gradient, the decay characteristics of the anomaly, the contributions from different wavelength bands to the anomaly, and the relationship between the anomaly and the crustal regional tectonics in the plateau and nearby, based on a new and higher degree geomagnetic model NGDC-EMM-720-V3 constructed from the surface, aeromagnetic, marine and satellite survey data. The results reveal that the positive and negative anomalies in the Qinghai-Tibet Plateau are weak, while those of the surrounding areas are strong. The boundary agrees well with the border of the plateau regional tectonics. The anomaly is nearly east-west in the central and western plateau, arc-shaped in the southwestern and eastern, and nearly north-south in the southeastern, consistent with the tectonic trends. There are strong negative anomaly foci in the east and west syntaxis, whereas no significant differences exist among the Cenozoic blocks in the plateau interior. No direct correspondence exists between the anomaly and the crustal depth. On the background of a weak magnetic anomaly in the plateau, relatively stronger short wavelength fields from the shallower crust are overlapped in the Lhasa, Qilian, Qaidam, and Sichuan-Yunnan rhombic blocks. A strong negative anomaly in the east-west direction is distributed along the Himalayas, mainly caused by the middle and long wavelength bands in the deep and central crust. The magnetic structural layers are stable in the Sichuan and Tarim basins. The anomalies at different altitudes over the southern plateau vary strongly, showing a drastic variation in the magnetic structure from the deep crust to the shallow crust.

[1]  Nils Olsen,et al.  Extending comprehensive models of the Earth's magnetic field with Ørsted and CHAMP data , 2004 .

[2]  An Yin,et al.  Geologic Evolution of the Himalayan-Tibetan Orogen , 2000 .

[3]  M. Purucker,et al.  Curie isotherm map of Indian subcontinent from satellite and aeromagnetic data , 2009 .

[4]  N. Olsen,et al.  A Comprehensive Model of the Near-Earth Magnetic Field: Phase 3 , 2013 .

[5]  Cheng Xian-qiong.  3D structure and dynamic types of the lithospheric crust in continental China and its adjacent regions , 2007 .

[6]  Mioara Mandea,et al.  GRIMM: the GFZ Reference Internal Magnetic Model based on vector satellite and observatory data , 2008 .

[7]  Hermann Lühr,et al.  Fifth‐generation lithospheric magnetic field model from CHAMP satellite measurements , 2007 .

[8]  Z. An.  SPHERICAL CAP HARMONIC ANALYSIS OF THE GEOMAGNETIC RESIDUAL FIELD IN CHINA FOR 1950～1990 , 2003 .

[9]  S. Maus,et al.  Why no anomaly is visible over most of the continent–ocean boundary in the global crustal magnetic field , 2005 .

[10]  Mioara Mandea,et al.  CHAOS—a model of the Earth's magnetic field derived from CHAMP, Ørsted, and SAC‐C magnetic satellite data , 2006 .

[11]  Jafar Arkani-Hamed,et al.  Geophysical interpretation of the magnetic anomalies of China derived from Magsat data , 1988 .

[12]  Xiaoping Yang,et al.  Basic characteristics of active tectonics of China , 2003, Science in China Series D Earth Sciences.

[13]  Kang Guo-fa.  Global models of the Earth's crust magnetic anomalies , 2008 .

[14]  Dhananjay Ravat,et al.  National Geophysical Data Center candidate for the World Digital Magnetic Anomaly Map , 2007 .

[15]  X. Yuan.  ON CONTINENTAL BASAL STRUCTURE IN CHINA , 1995 .

[16]  Z. Chang.  The Magnetic Characteristics of Crust Beneath Xizang (Tibetan) Plateau Deduced from Satellite Magnetic Anomaly , 2002 .

[17]  P. Wasilewski,et al.  The Moho as a magnetic boundary revisited , 1992 .

[18]  S. Maus,et al.  A global lithospheric magnetic field model with reduced noise level in the Polar Regions , 2006 .

[19]  M. Hamoudi,et al.  GeoForschungsZentrum Anomaly Magnetic Map (GAMMA): A candidate model for the World Digital Magnetic Anomaly Map , 2007 .

[20]  J. D. Fairhead,et al.  EMAG 2 : A 2 – arc min resolution Earth Magnetic Anomaly , 2009 .

[21]  Mioara Mandea,et al.  Magnetic anomaly map of the world: merging satellite, airborne, marine and ground-based magnetic data sets , 2007 .

[22]  Liu Qiusheng.  A Review on the Moho Discontinuity beneath the Tibetan Plateau , 2004 .

[23]  Xiongwei Sheng.  The present situation and development of airborne gravity and magnetic survey techniques in China , 2009 .

[24]  Hermann Lühr,et al.  Resolution of direction of oceanic magnetic lineations by the sixth‐generation lithospheric magnetic field model from CHAMP satellite magnetic measurements , 2008 .

[25]  Hermann Lühr,et al.  Third generation of the Potsdam Magnetic Model of the Earth (POMME) , 2006 .

[26]  J. Teng,et al.  Study on crustal, lithospheric and asthenospheric thickness beneath the Qinghai-Tibet Plateau and its adjacent areas , 2007 .

[27]  K. Guo.  Distribution of the magnetic anomaly for the CHAMP satellite in China and adjacent areas , 2010 .

[28]  R. Gao,et al.  Matched‐Filter Analysis of Aeromagnetic Anomaly in Mid‐Western Tibetan Plateau and Its Tectonic Implications , 2007 .