2D Reflection Seismic Imaging of Sparse 3D Data in the Zinkgruvan Mine, Central Sweden

Abstract: Zinkgruvan mining area in the southern Bergslagen mineral district of central Sweden holds over 30 million tons of massive sulphide mineralization. The ever-increasing global demand for mineral/metal resources, together with metal consumption growth especially for high-tech purposes has made the exploration of these resources of particular importance. In this thesis work, as a part of the larger research-industry SIT4ME project, Seismic Image Techniques for Mineral Exploration, project sponsored by the EIT Raw Materials, three 2D-crooked reflection seismic profiles were extracted from a sparse 3D dataset in the Zinkgruvan mining area and processed in a combination since approximately 600 receivers simultaneously recorded 368 shots along these three different profiles. One of the profiles (P1) was acquired using 10 m receiver and source intervals, while the other two profiles (P3 and P4) were acquired using 20 m receiver and 10 m source intervals. The data show notable reflections on several shot gathers presenting reasonable quality, although parts are severely contaminated with electricity grid noise from a major powerline crossing the profiles. The study mainly aims at providing information applicable for near surface structural imaging in this complex geological setting. Three different combinations of CDP lines for every two different profiles were binned and processed together in order to examine 3D nature of reflections and their corresponding geological origins. Through a number of tests and careful parameter selections, reflections in the raw shot gathers were enhanced. The final sections (both unmigrated and migrated stacks) show clear reflections associated with important geological units. This thesis presents the acquisition setup, reflection seismic processing procedure, results obtained and the interpretation of the three cross profiles in conjunction with available geological data from the site. The sections show a good correlation with the available borehole data from the site.