Auswahl der wissenschaftlichen Literatur zum Thema „Frimurarbarnhuset i Kristineberg (Sweden)“

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 high-amplitude, 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.

Abstract. Structural analysis of the Palaeoproterozoic volcanogenic massive sulfide (VMS) hosting Kristineberg area, Sweden, constrained by existing magnetotelluric (MT) and seismic reflection data, reveals that the complex geometry characterized by non-cylindrical antiformal structures is due to transpression along the termination of a major high-strain zone. Similar orientations of the host rock deformation fabrics and the VMS ore lenses indicate that the present-day geometry of the complex VMS deposits in the Kristineberg area may be attributed to tectonic transposition. The tectonic transposition was dominantly controlled by reverse shearing and related upright to overturned folding, with increasing contribution of strike-slip shearing and sub-horizontal flow towards greater crustal depths. Furthermore, the northerly dip of the previously recognized subsurface crustal reflector within the Kristineberg area is attributed to formation of crustal compartments with opposite polarities within the scale of the whole Skellefte district. The resulting structural framework of the main geological units is visualized in a 3-D model which is available as a 3-D PDF document through the publication website.

Abstract. Structural mapping and 3-D-modelling with constraints from magnetotelluric (MT) and reflection seismic investigations have been used to provide a geological synthesis of the geometrically complex Kristineberg area in the western part of the Palaeoproterozoic Skellefte district. The results indicate that, like the south-eastern parts of the Skellefte district, the area was subjected to SSE-NNW transpressional deformation at around 1.87 Ga. The contrasting structural geometries between the Kristineberg and the central Skellefte district areas may be attributed to the termination and splaying of a major ESE-WNW-striking high-strain zone into several branches in the northern part of the Kristineberg area. The transpressional structural signature was preferentially developed within the southern of the two antiformal structures of the area, "the Southern antiform", which exposes the deepest cut through the crust and hosts all the economic volcanogenic massive sulphides (VMS) deposits of the area. Partitioning of the SSE-NNW transpression into N–S and E–W components led to formation of a characteristic "flat-steep-flat" geometry defining a highly non-cylindrical hinge of for the Southern antiform. Recognition of the transpressional structural signatures including the "flat-steep-flat" geometry and the distinct pattern of sub-horizontal E–W trending to moderately SW-plunging mineral lineations in the deeper crustal parts of the Kristineberg area is of significance for VMS exploration in both near mine and regional scales. The 3-D-model illustrating the outcomes of this study is available as a 3-D-PDF document through the publication website.

The Skellefte district, 1.90 to 1.80 Ga, is one of the most important base metal mining districts of Sweden with over 85 volcanic-hosted massive sulfide (VHMS) deposits. The study area focuses on the western part of the Skellefte district which contains volcanic, metasedimentary and intrusive rocks. In 2003, seismic data acquisition was carried out in the western part of the Skellefte district in the vicinity of the Kristineberg mine. Two parallel seismic lines were acquired about 8 km apart from each other. Profile 1 is about 22 km long and selected for the re-processing and interpretation in this thesis. The acquisition geometry, low fold coverage, the complex tectonic history and fewer outcrops in the area make the data processing and interpretation quite challenging and required a careful processing design to obtain interpretable seismic image. The re-processed Profile 1 is correlated with two other newly acquired seismic lines in the area for the purpose of possible 3D visualization and interpretation. The re-processing work includes a careful velocity analysis along with a series of iterations in residual statics, poststack and prestack migrations and cross dip analysis. The re-processed seismic section clearly shows a north dipping reflector which truncates against the Revsund Granites at depth. The possible interpretation for this reflector is a structural basement to the Skellefte Group constituting Bothnian Basin or a fault zone within the Viterliden intrusion. The Kristineberg mine is situated on the northern limb of a synform structure with prominent southwards dipping reflections. The major lithological contacts between different rock units are series of latest thrust faults. The prominent reflectivity within and at the contact with the Viterliden intrusion may suggest deep seated mineralized horizons. The cross dip analysis helps finding the eastward dipping component for the shallow horizons. The re-processed image is also compared with the previous processed seismic section and improvements in reflectors are evident.
VINNOVA 4D

Remediation of mine waste by the application of till cover is one of the more common methods used in Sweden to prevent oxidation of sulphide-rich minerals. Although the general conclusion from Swedish state-of-the-art field studies is that dry covers may be effective, they are expensive to construct. Further investigations are also needed to understand the processes occurring in till covered waste deposits. The Kristineberg mining area has been chosen as the main field site for the research program MiMi (Mitigation of the environmental impact of mining waste) funded by the Foundation for Strategic Environmental Research (MISTRA). MiMi focuses on finding new and improved methods to mitigate the environmental problems related to mining operations and disposal of mining waste. An extensive sampling programme was carried out in Kristineberg during 1998 and 1999. The Kristineberg mine is a Boliden mine, located within the Skellefte ore field. It is a Zn-Cu deposit developed in the 1940s and still in production. This thesis consists of three papers outlining the geochemical conditions prevailing in tailings Impoundment 1 at the Kristineberg mine, after remediation by applying till cover. The impoundment investigated was in use until the early 1950s and it was remediated in 1996. Two different remediation methods have been used; in the area with a shallow groundwater table 1.0 m of till was used to raise the groundwater table above the tailings. In other areas, with a deeper groundwater table, a sealing layer consisting of a 0.3 m thick layer of a compacted clayey till underlying a 1.5 m thick protective cover of unspecified till was used. Field studies include sampling of solid tailings, saturated tailings pore water as well as pore water from the vadose zone. Laboratory investigations consist of a five-step sequential extraction on solid tailings samples. Pre-remediation oxidation has resulted in a zonation of the tailings with an upper oxidised zone above unoxidised tailings. Just below the oxidation front, there is a secondary enrichment of especially Cu but also of other elements. Metals released by sulphide oxidation were thus secondarily enriched. Tailings remediated by the combination of a till cover and a raised groundwater table, resulted in a remobilisation of metals around and a few metres below the former oxidation front. Although the concentrations of several elements still are high in the pore water, they are lower than before the remediation. The general conclusion is that the remediation has succeeded in preventing further oxidation in this part of the impoundment. Sequential extractions performed on selected samples from the drilling of the impoundment show that most of the remaining sulphide-associated trace elements in the oxidised zone still belong to the sulphide fraction. At the level of the peaks of metal concentrations in the pore water (and the solid secondary enrichment) substantial concentrations of the trace elements Cd, Co, Cu, Ni, and Zn is present in the adsorbed/exchangeable/carbonate fraction. Other trace elements are retained with other secondary formations such as amorphous or crystalline iron oxyhydroxides e.g., As, Ba, and Pb. Especially the adsorbed/exchangeable/carbonate fraction is easily dissolved and the raised groundwater table remobilise these trace elements into the pore water, as could be seen from the pore water extractions. In Impoundment 1, where the sealing layer was applied, sampling of the infiltrating water was performed by tension lysimeters. Tension lysimeters were installed in the protective till cover, in the oxidised tailings, in the uppermost unoxidised tailings and at an intermediate depth. The groundwater at the same location was also sampled. The tension lysimeters in the till protective cover contained relatively low concentrations of most elements. Elements such as Al, Cd, Co, Cu, Fe, Mn, Ni, S, Si, and Zn had the highest concentrations in the second tension lysimeter in the tailings. Between the second and the third tension lysimeters the concentration of most elements decreased. The increase between the first and the second tension lysimeters can be explained by remobilisation of secondarily retained oxidation products. The decrease between the second and the third tension lysimeters is interpreted as co-precipitation with different iron oxyhydroxides as well as adsorption onto secondarily formed minerals and primary mineral surfaces. Between the deepest tension lysimeter and the groundwater table, the element concentrations decrease further. Most of the pre-remediation oxidation products that are secondarily retained below the oxidation front and are released by the small amount of infiltrating water, is tertiarily retained during continued downward transport. Thus, if the depth to the groundwater table is large enough, the metals released by infiltrating water do not reach it.
Godkänd; 2000; 20070317 (ysko)