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Taking Maogongpu iron mine in Fushun, Liaoning Province, as the object, the study carries out the high-precision gravity and magnetic survey, with non-equidistant, non-equal-ratio IP sounding and wide-audio-frequency magnetotelluric (MT) sounding in key areas. The survey adopts small point distance of 5 m for key sections, and large point distance of 20 m for other sections in single profile. The maximum interval of non-equal-ratio pole distance induced polarization(IP) sounding is less than 200 m, and the widest frequency of wide-audio-frequency MT sounding is 0.1 Hz. The gravity and magnetic data are processed by multi-software, multi-parameter and multi-method, with multiple transition maps for comprehensive research and selection of effective key areas. Conventional sounding methods with unconventional parameters are applied in key areas. Besides, multi-parameter and multi-method data processing and inversion methods are used to accurately characterize the deep electrical characteristics, which are finally verified by drilling project. The results show that the high-precision gravity survey can assist high-precision magnetic survey with iron deposit exploration. The gravity anomaly can better represent the surface projection position of anomaly geological body. Electromagnetic sounding is an effective method for vertical division. Parameters such as resistivity and polarizability of IP sounding can be used to classify and detect the boundary of alteration, structure and rock mass better. The multiple electrical parameters of IP sounding can make up for the shortage of single electrical parameters of MT sounding, and help to identify water body, polymetallic mineralization, altered body, structure and fracture zone. The working procedure from region to area, from area to point and from point to depth is effective. The drilling results show that the integrated methods have a good performance in the iron deposit exploration, especially in the determination of spatial occurrence parameters of iron orebody, such as buried depth, dip direction, dig angle and shape. A set of effective iron deposit exploration technology model is established with this method. [ABSTRACT FROM AUTHOR]

The comparative study places the geological characteristics and evolution of Mongolia-Okhotsk fold system into the macroscopic framework of Paleo-Asian Ocean and peri-Pacific tectonic domains. It shows that the Mongolia-Okhotsk tectonic belt belongs to composite fold system. According to the main characteristics, the fold system can be divided into two parts. In the western part, the geological characteristics of Hangay-Kent-Daur fold belt in Late Neoproterozoic-Late Paleozoic are similar to the evolution characteristics of Paleo-Asian Ocean tectonic domain, with its tectonic evolution in Early Mesozoic related to the continental disintegration after the plate convergence of Paleo-Asian Ocean tectonic domain and large-scale strike slip and thrust superimposed in Late Mesozoic. While in the east, the main fold system is part of the Mesozoic tectonic evolution of peri-Pacific active continental margin, with the Mesozoic continental arc basin system and large strike-slip fault zone in its western sectiont superimposed on the paleo-Eurasia Plate and Paleozoic fold belt and the Middle Late Jurassic-Early Cretaceous Uda-Murga continental margin fold-thrust belt in its eastern section cut obliquely and covered by Late Cretaceous Sikhot-Alin and Okhotsk-Chukchi continental margin volcanic belt. [ABSTRACT FROM AUTHOR]

By reprocessing the gravity and magnetic data in Northeast China, the paper discusses the location of suture zone between North China Plate and Siberia Plate, which has been controversial for long, and gains a new understanding. It is considered that, in Northeast China, the suture is with an approximately equal width about 240 km, starting from north Chaoyang-south Tongliao in the west with NEE trend, turning SEE through north Shenyang- north Changchun, to north Tonghua-south Hunchun. Such understanding mainly comes from the comprehensive analysis of regional gravity and magnetic data, including the primary data, vertical and horizontal derivatives, horizontal gradient mode, different upper continuation heights, several filtering such as wavelet, small subdomain and interpolation, and anomaly characteristics reflected by various processing like signal extraction and enhancement. There are obvious differences in gravity and magnetic anomaly between the south and north, inside and outside of the zone, commonly showing anomaly dislocation, curve distortion, trend change, scale difference and feature interaction between inside and outside. For example, the Songliao Basin has undergone significant changes in the north-south width, and even the terrains and mountains are differentiated due to the existence of the suture zone. [ABSTRACT FROM AUTHOR]