Advanced Applied Geology

Advanced Applied Geology

Investigation of the Relationship between Tectonic Activities and Hydrothermal-Magmatic Iron Mineralization in the Razan area, Hamadan

Authors
1 Department of Geology, Payame Noor University, Tehran, Iran
2 Department of Geology, Faculty of Basic Sciences, Bu-Ali Sina University, Hamadan, Iran
Abstract
Iron mineralization in the Razan area occurs as quartz–iron oxide veins (mainly hematite and magnetite) that are closely linked to fractures and reactivated faults within a right-lateral transpressional system. The principal veins strike approximately N35°E and reach a minimum thickness of 0.5 m. Geometric and kinematic analysis of faults, joints, dikes, and mineralized veins, together with shear-sense indicators and brittle C/S fabrics, demonstrates that the regional structures developed under a right-lateral transpressional stress field. In this field, the dominant shortening direction was northeast–southwest, while extension was oriented northwest–southeast. Reverse faults predominantly strike NW–SE, whereas normal and strike-slip faults, dikes, and a substantial portion of the mineralized veins are concentrated between N15°E and N45°E. This arrangement indicates that the ore-bearing veins formed along fractures that were favourably oriented for dilation under the extensional component of the transpressional regime. Consequently, structural control on mineralization is governed more by the creation and maintenance of open spaces than by fault trends alone. The spatial coincidence of these structures with monzodioritic and monzogabbroic intrusions and associated hydrothermal alteration points to the role of the intrusive bodies in supplying heat and driving the fluid system. Iron mineralization is therefore interpreted as the product of hydrothermal fluid focusing into dilational fractures related to right-lateral transpression, developed in conjunction with intrusive activity. Based on the results of this study, identifying open fractures may help delineate zones favourable for hydrothermal fluid concentration and iron mineralization associated with intrusive bodies.
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