Abscherungen sind charakteristische Strukturen yon Kollisions-Orogenen. Sie sind das Ergebnis yon Verkiirzung und Scherung verschieden kompetenter Gesteine infolge intrakontinentaler Subduktion und Krusteniiberlagerung. Zu unterscheiden sind l)berschiebungen oberer Zonen, wie in den Randgebirgsbereichen ohne bedeutende innere Deformation, yon internen metamorphen Zonen mit Schieferung und PI~ttung. In den tiefen Krusrenzonen und im KrustenMantelbereich gehen sie einher mit hochgradiger Metamorphose, allgemein in der Granulitfazies.Beispiele der mittleren und tiefen Zonen sind gut erschlossen im paleozo[schen Orogen Zentratchinas und im Variszikum Europas und belegt sowohl dutch die Geologie wie tiefenseismische Profile. Diese Beispiele zeigen mehr uad mehr, daf~ geschieferte Gebirgsstockwerke mit an der Oberfl~che steilstehender Schieferung yon flachen Abscherungen unterlagert werden.Die typische Erscheinung einer seismisch gut geschichteten Strukturierung der Unterkruste k6nnte in dieser Hinsicht als Deckenbahnen interpretiert werden. AbstractDecollements are conspicuous features of collision belts as a resutt of shortening and shearing of rocks of different competencies in response to intracontinental subducdon and crustal stacking. When these decollements occur at upper levels, the classical thin skin tectonics of the foredeeps without important internal strain results; at mid crustal levels slaty cleavage and foliation development occurs. In the more internal parts of the chains, in the lower crust, near the crust mantle boundary, the more severe conditions (granulitic metamorphism) result in ductile deformation in the deepest parts of the mountain belts. Examples of middle and lower crust are well documented in Central China and the Variscan Belt of Europe from fidd evidence and deep seismic profiling.

Abstract-The data acquisition mode of Multi-channel transient electromagnetic method (MTEM) is similar to that of seismic method, it is significant to research pseudo-seismic wave-field extraction technology for MTEM data. Basing on singular value decomposition method and regularized method, we propose correlation stacking method to extract pseudo-seismic wavefield of MTEM data. Firstly extracting pseudo-seismic wave-field of whole-time-domain MTEM data with regularized method, then extracting pseudo-seismic wavefield of each time quantum determined with the same method. Finally, stacking the pseudo-seismic wavefield data according to their correlation, and regard the stacked result as the final extraction result. The extraction result of measured MTEM data with correlation stacking method is more smooth than that of singular value decomposition method and regularized method.

Grounded electric source Borehole TEM is introduced in this paper to find the deep conductive ore body, particularly in areas where the ability of surface TEM to define a target is limited either by large depths or by interfering conductive bodies such as overburden shallow sulphides and peripheral mineralized horizons. In this method the grounded electric transmit system is deployed on the surface and receive the three-component TEM response along borehole. As receiver is nearer to ore body through the borehole than on surface, more reliable TEM response of ore bodies can be obtained. Researches show that the detection depth of grounded electric source system is deeper and more suitable for complex terrain area deep prospecting than magnetic source system. Considering there is no conventional explanation method for the grounded electric source borehole TEM, global apparent resistivity is introduced in this paper to provide a reliable explanation method. Global apparent resistivity is defined by the inverse function relationship between induction magnetic field and resistivity of half space. Numerical model calculation results show that underground information can be showed reliably by global apparent resistivity curves along borehole. The application of this study can provide strong support for the deep prospecting in mining area.

The Qingchengzi orefield is an important polymetallic ore concentration zone in the northern margin of the North China Craton (NCC). The region has significant metallogenic potential for deep mining. Many areas with gold mineralization have been found in the shallow area of Taoyuan–Xiaotongjiapuzi–Linjiasandaogou in the east of the Qingchengzi orefield. To assess the distribution of mineralization levels, we carried out deep exploration using the transient electromagnetic method (TEM). A superconductive quantum interference device (SQUID) magnetometer and a conventional induction coil were used for field data acquisition. The SQUID data inversion results reflect the bottom interface of the high-conductivity area, the fold state of the underlying dolomite marble stratum, and the deep structural characteristics of the syncline. Secondary crumples appear in the inversion results of the southern segment of TEM, which is inferred as a favorable area for deep gold mineralization. Negative values appear in the SQUID data of some stations, to varying degrees. This induced polarization phenomenon may be related to deep gold mineralization.

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