Seismic constraints on the geological evolution of the McArthur River region in view of the tectonics of the Eastern Athabasca Basin, Northern Saskatchewan.

摘要

The principal objective of this investigation was two-fold: (1) analysis of 2D and 3D high-resolution and related regional seismic reflection data and (2) critical assessment of seismic methods as exploration tools within the Athabasca Basin of Northern Saskatchewan. The original data were collected as a part of the the multidisciplinary EXTECH-IV project. During the winter of 2000, both regional and high-resolution 2D and 3D seismic data were acquired at McArthur River, the world's largest high-grade uranium deposit. The main focus of the present study was to process and interpret the high-resolution dataset. Specifically, the objectives of the high-resolution seismic study are: (1) to define the basement structure underlying this part of the basin, (2) to define the stratigraphic architecture of the sedimentary rocks within the basin, (3) to map the sandstone/basement unconformity, (4) to locate and image faults controlling the ore deposits, and (5) to establish possible spatial and temporal relationships between subsurface geology and high-grade uranium mineralization. Although the raw data contains elevated noise levels, the acquisition geometry is irregular and the subsurface geology is complex the applied processing sequence resulted in good quality 2D and 3D data. The unconformity surface, brittle faults as well basement shear zones were successfully mapped throughout the survey area. It has been established that brittle faults are kinematically linked to pre-existing ductile shear zones of the basement. Reflectivity variations within the metamorphic basement permitted distinction of Archean and Paleoproterozoic assemblages. It has been shown that high-grade uranium deposits are located at the intersection of the main P2 trend and high-angle transcurrent faults. Recognition of this particular structural setting is fundamental for providing a predictive model for other unexplored uranium deposits. Integration of the high-resolution and regional seismic data offered the opportunity to extend structural analysis from local to regional scale. Synthesis of seismic and currently available geological data provided new constraints on the structural evolution of the western Trans-Hudson Orogen. The seismic method emerges as an important exploration tool for future investigations in the deeper parts of the Athabasca Basin.