Modeling of ground magnetic survey data over ultramaphic massifs

Abstract

Summary A ground-based magnetic survey was collected over two ultramaphic massifs of Albania, in response for mapping magnetic anomalies possibly connected with tectonic and cumulate sections, grade of horst rocks serpentinization and/or shallow chromite deposits of variable size. The results were contradictory. To improve them we have implemented a scheme and computer code for contouring rock surface with abnormal magnetization passing a small window over the analytic signal and fitting it with the transformed magnetic into the bell shaped field anomaly with so-called vertical, for the 2-D thin sheet model, within the window. Rapid estimations for the edge of the sources, depth, intensity and angle of total magnetization for the observed shallow anomalies surveyed-line data are obtained. As an alternative of filtering technique we have used the forward modelling of magnetic field intensity map of the area with constrained source parameters. The computed magnetic field anomaly map with magnetization vector collinear within the range revealed from chromite samples by laboratory measurements show characteristic, which, hardly notices in the survey magnetic anomaly map. The predicted magnetic data on an area 4 km 2 are well correlated with the shallow deposits or surface occurrences or controlled associated structures in the harzburgite host rocks. Image of total magnetization inclination data derived from ground magnetic survey acquired over a 30 km 2 resembles the geology than the total field magnetic anomaly map. These data show that the total magnetization of thick dunites, rich in basaltic impregnation, reveals an opposite direction data against the underlain harzburgite tectonic rock section.