Structural deformation and mineralization on the ore deposits in the Wondong area, Gangwon, Korea

The basement around the study area is Cambrian, Ordrovician and Carboniferous sedimentary rocks forming a part of the Taebaeksan Basin in NE Korea, and it is intruded by Crataceous igneous rocks. The most dominant structural feature is the ENE-WSE trending Wondong thrust, which is a SE-directed thrust. To clarify the tectonic evolution of the study area, structural elements such as faults, folds, joints, and dykes, have been kinematically analyzed and their maximum compressive or extensional stress axes inferred. At least three deformation events are recognized in the study area. The first phase of deformation is characterized by the NE-SW trending normal faults and N-S trending folds. The second phase of deformation is N-S trending conjugate faults, NW-SE trending right-lateral strike-slip faults and E-W trending folds. The last phase of deformation is only recognized by NE-SW trending joints. These deformation events indirectly indicate the clockwise rotation of maximum compressive stress axes from E-W or ENE-WSE to NE-SW. We have also investigated the W mineralization along the structural elements. Based on the field survey, we detected the scheelite on the NE-SW and NW-SE trending normal faults and fractures. It indicates that the mineralization is closely related with the first and second phases of deformation. For understanding the distribution of the scheelite, we conducted the drilling on the studied sites. Consequently, the mineralization was mainly concentrated on the NE-SW trending faults and fractures. It demonstrates that the mineralization have been occurred after first or second phases of deformation.