Sparse 3D Seismic Imaging in the Kylylahti Mine Area, Eastern Finland: Comparison of Time Versus Depth Approach

Minerals

Sanna Juurela¹  Emilia Koivisto²  Suvi Heinonen³  Stefan Buske⁴  Olaf Hellwig⁴  Felix Hloušek⁴  Michał Malinowski⁵  Michał Chamarczuk⁵  Brij Singh⁵ 

[1] Boliden FinnEx, Polvijärventie 22, FI-83700 Polvijärvi, Finland;Department of Geosciences and Geography, University of Helsinki, PL 68, 00014 Helsinki, Finland;Geological Survey of Finland, Vuorimiehentie 5, P.O. Box 96, FI-02151 Espoo, Finland;Institute of Geophysics and Geoinformatics, TU Bergakademie Freiberg, Gustav-Zeuner-Str. 12, D-09599 Freiberg, Germany;Institute of Geophysics, Polish Academy of Sciences, Księcia Janusza 64, 01-452 Warsaw, Poland;

关键词: 3D seismic;    pre-stack depth migration;    hardrock seismic exploration;   

DOI  :  10.3390/min9050305

来源: DOAJ

【 摘 要 】

A 10.5 km² 3D seismic survey was acquired over the Kylylahti mine area (Outokumpu mineral district, eastern Finland) as a part of the COGITO-MIN (COst-effective Geophysical Imaging Techniques for supporting Ongoing MINeral exploration in Europe) project, which aimed at the development of cost-effective geophysical imaging methods for mineral exploration. The cost-effectiveness in our case was related to the fact that an active-source 3D seismic survey was accomplished by using the receiver spread originally designed for a 3D passive survey. The 3D array recorded Vibroseis and dynamite shots from an active-source 2D seismic survey, from a vertical seismic profiling experiment survey, as well as some additional “random” Vibroseis and dynamite shots made to complement the 3D source distribution. The resulting 3D survey was characterized by irregular shooting geometry and relatively large receiver intervals (50 m). Using this dataset, we evaluate the effectiveness of the standard time-imaging approach (post-stack and pre-stack time migration) compared to depth imaging (standard and specialized Kirchhoff pre-stack depth migration, KPreSDM). Standard time-domain processing and imaging failed to convincingly portray the first ~1500 m of the subsurface, which was the primary interest of the survey. With a standard KPreSDM, we managed to obtain a good image of the base of the Kylylahti formation bordering the extent of the mineralization-hosting Outokumpu assemblage rocks, but otherwise the image was very noisy in the shallower section. The specialized KPreSDM approach (i.e., coherency-based Fresnel volume migration) resulted in a much cleaner image of the shallow, steeply dipping events, as well as some additional deeper reflectors, possibly representing repetition of the contact between the Outokumpu assemblage and the surrounding Kalevian metasediments at depth.

【 授权许可】

Unknown