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 pro...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 distri- bution laws of the crustal magnetic anomaly and its vertical gradient, the decay characteristics of the anomaly, the contribu- tions from different wavelength bands to the anomaly, and the relationship between the anomaly and the crustal regional tec- tonics 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 south- western and eastern, and nearly north-south in the southeastern, consistent with the tectonic trends. There are strong negative anomaly loci 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 lay- ers 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.展开更多
基金sponsored by National Natural Science Foundation of China (Grant Nos. 40464001 and 40864002)
文摘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 distri- bution laws of the crustal magnetic anomaly and its vertical gradient, the decay characteristics of the anomaly, the contribu- tions from different wavelength bands to the anomaly, and the relationship between the anomaly and the crustal regional tec- tonics 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 south- western and eastern, and nearly north-south in the southeastern, consistent with the tectonic trends. There are strong negative anomaly loci 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 lay- ers 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.
