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Geomagnetic signature of the Sabzevar ophiolite belt in north-eastern Iran

S.H. Hosseini, S.M. Ghiasi, S. Ghanbarifar, M. Abedi and A. Afshar


Ophiolite zones in Iran are capable of bearing precious minerals, which indicates the importance of undertaking investigations into ophiolite belts. Although the north-eastern ophiolites of Iran cover a vast area, they should be better recognised in terms of geophysical features and properties. The Sabzevar ophiolite area is an orogenic and subducted zone with typical ophiolite series, including sedimentary, crustal and mantle sequences. This study sets out to characterise the auspicious igneous and ophiolite zones in the frame of large-scale and tectonic conditions, geometrical shapes, expansions, and deep susceptibility features through novel magnetic synthesis interpretation techniques. In order to study the mentioned area, airborne magnetometry data over 60,000 km2 have been utilised. Thus, geophysical research has been conducted to define the tectonic and ophiolite zones of the Sabzevar area by means of magnetic methods including edge detection techniques and 3D susceptibility models. In this research, newly developed edge-detection filters of MNTHD and MNTDR are applied to the aeromagnetic data to identify the shape and boundary of the anomalies at the Sabzevar ophiolite. In addition, edge detection would facilitate dividing the study area into smaller sectors, as proper targets, for running 3D inversion schemes precisely. This study uses qualitative analysis to gain insights into the subsurface structure status. The simultaneous interpretation of edge detection results and 3D inverted models would lead the way to dependable outcomes. The study area consists of six ophiolite sections, pre-identified by geological and geochemical approaches. These are the basis for this research which primarily studies the Sabzevar ophiolitic area. In order to conduct a detailed investigation into the study area, seven blocks were considered for the inverse modelling procedure. Consequently, the 3D susceptibility models matched the edge detection results accurately. Finally, as a multidisciplinary geophysical investigation over a large-scale ophiolite belt, the inverted susceptibility models of the whole area were overlaid with the geological and magnetic edge detection maps, unifying a solid view of the deep underground structures.