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Based on the latest compiled 1/100 million aeromagnetic map data, the Curie point depth was estimated by power spectrum method. The calculation obtained 8004 Curie point depth values in Chinese continent. Eventually, we completely compiled the Chinese continental Curie point isotherm map. This map first fully shows the characteristics of Chinese continental Curie point depth. The study shows that Curie point isotherm is characterized by depression inside the stable blocks with the depth of 28~45 km, such as the Tarim Basin, Junggar Basin, Qaidam Basin, Hoh Xil-Bayan Har Depression area, the Yangtze Basin area, North China basin area, Songliao Basin, Erlian Basin, Bayan-Wuwei-Chaoshui basin, Pearl River Estuary-southeast Hainan basin. The Curie depth of North China basin area is shallower than Tarim continent block and Yangtze continent block, which may be related to the fact that North China block suffered a complex post-transformation which resulted in the asthenosphere upwelling and lithospheric thinning. Hoh Xil-Bayan Har block is a NWW trending Curie point isotherm depression area in northern Tibetan Plateau, where developed a large area of Triassic sedimentary strata and experienced less magmatism. The stable blocks all have uplifted Moho and depressed Curie point isotherm. Conversely, the Curie point isotherm of active orogenic belt is characterized by uplift at the depth of 18~26 km, such as the Mountain (Mtn.) area of northeast and northwest China, Qinling-Dabie area, West Kunlun-Tibet-Sanjiang-Kangdian area, the southeast coastal areas and so on. The uplift reflects the geothermal gradient difference caused by tectonic and magmatic activities. A collection of 816 heat flow data from published literatures are used to study the relationship between Curie point isotherm and heat flow. The results show that there is not a simply linear relationship between the depth and heat flow. When the depth is greater than 30 km, the heat flow values are less than 100 mW·m-2. While the Curie point depth is less than 30 km, the heat flow values vary in a wide range. The high heat flow values are mostly found in the east coast of China, southern Tibet-Sanjiang area, Qinling-Dabie area, and the east of Liaoning province, which are all characterized by uplift of Curie point isotherm. These areas are important for future geothermal exploration.

Extremely complicated fault structures characterize Xizang and the Sanjiang (Jinsha River, Lancang River, Nujiang River) region in southwest China. In spite of many years' study, different recognitions to this issue remain present. Based on new aeromagnetic data and gravity data, and from the view of combining gravity and magnetic characteristics with geological structure, we compile a new map of fault structures in Xizang and the southwestern Sanjiang region. The results show that the deep faults along the Jinsha River, Lancang River and Nujiang River are independent NW-striking faults which extend from the south to the northwest, not connecting with the arc-like faults in Xizang which extend from the east to the west. These faults are newly discovered NW-striking faults in the Tethys fault system and belong to a different fault system relative to EW-striking faults in Xizang. This opinion is different from the previous view that the suture zones of Jinsha River, Lungmu Co-Lancang River and Bangong Co-Nujiang River extend towards NW and EW in arc distribution. This discovery of the faults has changed the recognition of fault structure framework of Xizang-Sanjiang areas, which lends light on the geotectonic research in the future. In this paper, the west extending characteristics of deep fault belt developed in Xizang and southwest Sanjiang River area are mainly explained, and the intersection relationship of faults between the Sanjiang River and Xizang is also discussed, which indicates that gravity and magnetic data are significant for the research on fault structures.

The relief of the metamorphosed basement of the Precambrian and the thickness variation of the overlying sedimentary cover are very important for geology and exploration of energy and resources. The magnetic difference between these two layers permits geophysicists to estimate the magnetic basement depth using aeromagnetic data. The work is based on such data acquired by AGRS's aero geophysical surveys for more than 30 years over China mainland, covering more than 30 basins and areas. Our purpose is to compile the magnetic basement depth map for China mainland on a scale 1:1000000 with the data converted into the same coordinate system and scale. The resultant map shows that using E105° line as a boundary, the covers are thick in sedimentary depression areas of western China, mainly distributed in the Tarim basin, Junggar basin, Qaidam basin and Tibet area. While, in east China, mainly distributed in the Songliao basin, Erlian basin, Ordos, southern North China, Sichuan basin, and South Yellow Sea-Subei basin, such covers are relatively thin in sedimentary depression areas, of which the largest thickness is located in the southwest of the Sichuan basin and the western edge of the Ordos basin. These characteristics are associated with the metamorphosed basement of Precambrian and depth changes of irruptive rocks body with certain scales, and reflect sedimentary covers' thickness and status. They allow us to intuitively observe depths and sizes of various types of sedimentary basins and sedimentary depression areas, and provide direct evidence for exploration of oil and gas reservoirs on the basements.

The temperature experiment and lithologic analysis were conducted on the samples obtained in the underground coal spontaneous combustion areas to study the mechanisms how rock magnetism changes with temperature. The samples were tested at different temperatures to analyze the characteristics and changing rules of the magnetic value, iron-containing oxide percentage and structure. The results show that temperature change can cause variation of magnetism, which is very small below 400°C, and increases with temperature before it reaching the Curie temperature. Magnetism of the samples vanishes when the temperature is beyond the Curie temperature. Magnetism of samples increases obviously when they are cooled below the Curie temperature, and is higher than being heated before. The changes of magnetism are primarily related with mineral content and structure in iron-containing oxides, such as pyrite, hematite, siderite, and limonite. The content of ferromagnetic mineral in rock samples increases obviously by heating samples to 700°C and cooling it to normal temperature. The structure of mineral is variable in the experiment and the size of particle is smaller than the before as well. Generally, the particle size is 10∼150 μm which belongs to multi-domain structure (MD), some of which belongs to single-domain structure. The main reason for magnetism enhancement is that new ferromagnetic minerals (pyrite, hematite, siderite, limonite etc.) are created from few iron-contained minerals when the temperature is increased. The research results above are significant to explain magnetic anomalies in coal spontaneous combustion areas.

This paper takes the South Yellow Sea as an example to show a new method for comprehensive geological-geophysical research such as residual basin and tectonolayering using airborne gravity and magnetic data in China. Based on airborne gravity and magnetic data, by measuring and analyzing stratigraphic density and susceptibility, the depths to the pre-Sinian magnetic basement top, the pre-Jurassic top and the Cenozoic bottom, are obtained by forward and inverse methods constrained by seismic and drilling data; and furthermore, the residual thicknesses of the Sinian–Triassic, the Jurassic–Cretaceous and the Cenozoic are calculated. Based on airborne gravity and magnetic anomalies, the faults in the pre-Sinian magnetic basement, the Jurassic-Cretaceous and the Cenozoic are respectively interpreted by the qualitative and quantitative methods. On the basis of the above study, and combining regional important tectonic events, four tectonolayers are divided in the vertical succession in South Yellow Sea, namely the pre-Sinian magnetic basement, the Sinian-Triassic, the Jurassic-Cretaceous and the Cenozoic. The result shows that there are thick Cenozoic and Jurassic-Cretaceous strata and thin residual Sinian-Triassic strata in the Suzhong-Huangnan depression area, but there are thin or only sporadic Mesozoic-Cenozoic terrestrial strata and thick Sinian-Triassic marine strata reserved in Subei-Huangzhong uplift area and Sunan-Wunansha uplift area. The four tectonolayers are very different in structures as well as distributions in plane.

The airborne gravimetry was an important leap and innovation in the world's history of geophysical exploration. China's first test of the airborne gravity geological survey in the onshore-offshore transitional area of the western and southern part of the Bohai Sea was successful and effective in geology. Based on the airborne gravity data, and combining previous ground gravity, seismic and drilling data etc., we carried out the geological interpretation by forward and inverse methods. The result shows that the airborne Bouguer gravity anomaly was clear, the fracture interpretation was reliable, and the inversion depth of the main geological interfaces was relatively accurate. This airborne gravity geological survey not only filled the exploring gaps in the onshore-offshore transitional area, and realized the geological and tectonic junction between the sea and the land, but also discovered four local gravity anomalies, 11 fractures and three sags or subsags, and so on. The good geological effect of airborne gravimetry not restricted by terrain condition shows that it can be served as a new geophysical method in the exploration of complex terrain physiognomy area such as mountain, jungle, desert, marsh, onshore-offshore transitional area and so on, and has an extensive application prospect in China in the future.