3D constraints and finite-difference modeling of massive sulfide deposits: The Kristineberg seismic lines revisited, northern Sweden

Abstract

The Kristineberg mining area in the western part of the Skellefte ore district is the largest base metal producer in northern Sweden and currently the subject of extensive geophysical and geologic studies aimed at constructing 3D geologic models. Seismic reflection data form the backbone of the geologic modeling in the study area. A geologic cross section close to the Kristineberg mine was used to generate synthetic seismic data using acoustic and elastic finite-difference algorithms to provide further insight about the nature of reflections and processing challenges when attempting to image the steeply dipping structures within the study area. Synthetic data suggest processing artifacts manifested themselves in the final 2D images as steeply dipping events that could be confused with reflections. Fewer artifacts are observed when the data are processed using prestack time migration. Prestack time migration also was performed on high-resolution seismic data recently collected near the Kristineberg mine and helped to image a highamplitude, gently dipping reflection occurring stratigraphically above the extension of the deepest Kristineberg deposit. Swath 3D processing was applied to two crossing seismic lines, west of the Kristineberg mine, to provide information on the 3D geometry of an apparently flat-lying reflection observed in both of the profiles. The processing indicated that the reflection dips about 30°to the southwest and is generated at the contact between metasedimentary and metavolcanic rocks, the upper part of the latter unit being the most typical stratigraphic level for the massive sulfide deposits in the Skellefte district.

Seismic methods in mineral exploration and mine planning: A general overview of past and present case histories and a look into the future

“…Note that massive sulfides rich in pyrite (a noneconomic sulfide mineral) tend to have higher velocities (e.g., those reported from Lokken Verk in Norway), whereas massive sulfides rich in pyrrhotite (e.g., those reported from Kristineberg and Flin Flon in Sweden and Canada, respectively) tend to fall along the mixing lines between pure pyrrhotite and mafic host rocks (Figure 2). Case studies presented in this special section (e.g., Dehghannejad et al, 2012;Duff et al, 2012;Malehmir et al, 2012a; are consistent with this observation. Malehmir et al (2011) report that magnetite-rich (>40% Fe) iron deposits show a significant acoustic impedance contrast against almost all lithologies (see Figure 2).…”

“…Three-dimensional, and even 4D geologic modeling studies (e.g., Dehghannejad et al, 2012), based on regional and mining camp scales and, sometimes, mine scale information, will be very important in limiting exploration targets suitable for 3D surveys and/or downhole seismic studies. A complete and comprehensive data integration program combined with modeling will help to reduce speculative interpretation, especially at greater depths, and provide greater value to industry.…”

Seismic Reflection for Hardrock Mineral Exploration: Lessons from Numerical Modeling

“…They found that the ability to detect a clear signature of the ore was dependent on the mineralization type and the nature of the host rock. Dehghannejad et al (2012) carried out finite-difference elastic and acoustic modeling to better understand the observed reflections in a 2-D seismic survey in the Kristineberg mining area of Sweden. The synthetic data showed that processing artifacts produced steeply dipping events that could be confused with reflectors.…”

Integrated interpretation of 3D seismic data to enhance the detection of the gold‐bearing reef: Mponeng Gold mine, Witwatersrand Basin (South Africa)

“…, , , , ; Malehmir and Bellefluer ; Dehghannejad et al . , ; Bellefleur, Malehmir, and Müller ; Juhojuntti et al . ; Kukkonen et al .…”