This ongoing study focuses on the reprocessing of the historical BABEL (Baltic and Bothnian Echoes from the Lithosphere, 1989) seismic lines in the Bay of Bothnia in preparation for the acquisition of a 400 km long onshore reflection and refraction profile in central part of Sweden. The main aim of the project is to increase the understanding of the tectonic evolution of the mineral-rich Bergslagen region both offshore and onshore. The seismic data have been recovered and currently being reprocessed using up-to-date processing methods and preliminary results show promising outcome from this work.

Of the different types of REE mineralisation known from the Fennoscandian shield, the Palaeoproterozoic apatite-iron oxide ores of Kiruna type represent one resource type with significant potential. Here we describe an REE-rich apatite-magnetite mineralisation from the classic Bergslagen ore province in south central Sweden. Associated with moderately to weakly REE-enriched magnetite mineralisation of banded and vein types, the most apatite-rich occurrence at Kopslahyttan shows REE enrichment that is similar in both magnitude and pattern to other Kiruna type deposits. Yet, the present REE mineralogy is wholly dominated by monazite-(Ce), allanite-(Ce) and LREE-enriched epidote, the latter two often occurring as zoned crystals or aggregates. Minor xenotime-(Y) also occurs, and titanite locally hosts minor Y+HREE. The abundant fluorapatite is suggested to have been an additional, original host for REE, prior to fluid-mediated alteration leading to wholesale remobilisation of REE from the apatite. This remobilisation included dissolution-reprecipitation processes that lead to the nucleation of monazite in fluorapatite, but probably also further transport and precipitation as e.g. allanite/REE-epidote, through reactions with locally common silicates. In addition, we suggest that very coarse grained, variably Th-bearing monazite present in the mineralisation may have been a primary REE phase, in marked contrast to most other deposits of this type.

We have conducted a reflection seismic investigation over the apatite-iron deposit at Grangesberg in central Sweden. At the time of closure in 1989, the mine was operated using the sublevel caving method down to approximately a 650-m depth. This mining technique caused subsidence and generated a network of faults that propagated from excavated zones at depth up to the surface. The Grangesberg deposit is the largest iron oxide mineralization in central Sweden and is planned to be mined again in the coming years. It is therefore imperative to have a better understanding of the ore geometry and the fault network. A reconnaissance survey consisting of two seismic lines with a total length of 3.5 km was carried out to address these issues. The profiles intersect the Grangesberg deposit and open pit, as well as the major mining-induced fracture zone present in this area. A drop-hammer source mounted on a hydraulic truck was used to generate seismic signals; cabled and wireless receivers were used for the data recording. Preprocessing of the data first required the cable-and wirelessrecorded data sets to be merged before stacking all data available at each shot point. Source gathers exhibit reflections from the near surface, probably generated at lithological boundaries hosting the iron mineralization and other geologic structures. Deeper reflections were also observed. The metavolcanic assemblage hosting the mineralization and the anthropogenic fault network were depicted in the stacked sections, bringing in new elements to refine the geologic model of the area. This study also illustrated the ability of reflection seismic methods to delineate mining-induced structures in hard-rock environments. Low-velocity anomalies from the open pit and adjacent structures were depicted in tomographic sections along the two lines, which showed good agreement with known geologic features and the reflection seismic results.

Mine dumps the abundant by-products of centuries of mining in Europe have potential to become sources of a wide range of metals and minerals. Despite their variable volumes and the geometallurgical challenges involved, they are a raw material resource to include among other, not least in the context of the present societal demand to increase recycling. Until the mid-1900s the applications and therefore the markets for many metals were limited. Additionally, many were difficult to identify, and thus often missed. In numerous mining districts this resulted in rocks hosting such metals to end up as waste, that is, on the mine dumps. The present pilot project is aimed at testing the potential for such secondary resources in the classic and ancient Bergslagen ore province in south central Sweden, with a special focus on metals presently identified as "critical" for industry. The Bergslagen province, with its 1000-year-history of mining is a suitable testing ground to find out what may actually be out there. Results so far include the detection and mineralogical characterisation of variable amounts of precious and critical as well as base metal minerals, along with the main ore commodity in many old mining fields.

Reflection seismic investigation has been conducted on the Grängesberg apatite iron deposit. At the timeof closure in 1989, the mine was operated at about 650 m below the surface. Mining activities might beresumed in the next years, which require better understanding of (1) the ore geometry and (2) the faultnetwork which has developed up to the surface from excavated zones at depth. Two E-W orientedreflection lines with a total length of 3.5 km were acquired. The seismic lines intersect the Grängesbergore body and open pit, as well as several of the mining-induced faults. A weight drop mounted on anhydraulic bobcat truck was used as a seismic source; both cabled and wireless receivers were used for thedata recording. Preprocessing of the data first required the cable- and wireless- recorded datasets to bemerged before stacking all data available at each shot point. The dataset exhibits several shallowreflections which are likely to occur on steep lithologic or tectonic structures. Other deeper reflections arerecorded; careful processing will be carried out in order to preserve such events in final stacked sectionsand help with refining the geological model of the area.

The rare palladium mineral sudburyite occurs as a Te-Cu-rich variety [(Pd,Cu)(Sb,Te,Se,S)] in the classic selenide-rich carbonate vein deposit Skrikerum, located in the southernmost extreme of the Bergslagen ore province in south-central Sweden. This is the first observation of a platinum-group element-(PGE)-bearing mineral in this complex Cu-Ag-Tl selenide mineralisation, and to our knowledge, the first occurrence of sudburyite in a selenide vein-type deposit. Here, we report on its assemblage and mineral chemistry, based on optical, scanning electron microscope and field emission electron microprobe studies. The Te-Cu-rich sudburyite occurs at Skrikerum as euhedral to subhedral, often atoll-like, ca. 5-30 mu m-sized crystals in a selenide fracturefilling hosted by vein calcite. Based on electron microprobe analyses, its empirical formula normalised to ideal stoichiometry is (Pd0.915Cu0.132)(Sigma 1.047)(Sb0.795Te0.152Se0.004S0.002)(Sigma 0.953). The complex host assemblage comprises athabascaite (Cu5Se4), berzelianite (Cu2Se), crookesite [Cu-7(Tl,Ag)Se-4], Cu-bearing clausthalite [(Pb,Cu)Se], eucairite (CuAgSe), Se-Cu-bearing hessite [(Ag,Cu)(2) (Te,Se)], sabatierite (Cu6TlSe4) and umangite (Cu3Se2), as well as unidentified Te-Pd-Ag-Cu-bearing, most likely oxidised compounds. The associated hessite represents the first substantiated observation of a telluride in this deposit. Sudburyite from Skrikerum is Cu-, Te-, Se-and S-bearing, but in contrast to the type locality, it does not contain measurable quantities of e.g. Ni and Bi. The Skrikerum sudburyite contains highly variable amounts of Te, from ca. 2.7 wt% to over 15 wt%. Electron microprobe data show a very good correlation between Sb and Te contents (R = 0.95), which is consistent with Te substituting for Sb, forming part of an extensive but seemingly incomplete solid-solution series towards borovskite and merenskyite in the ternary Pd-Sb-Te system. Based on the general paragenesis of the deposit and the studied assemblage, we observe that the comparatively high temperatures of formation for sudburyite suggested from other studies are not applicable here. We also report previously unpublished mineral chemical data of sudburyite from another Swedish locality, Njuggtr skliden.

Iron is the most important metal for modern industry and Sweden is by far the largest iron-producer in Europe, yet the genesis of Sweden's main iron-source, the 'Kiruna-type' apatite-iron-oxide ores, remains enigmatic. We show that magnetites from the largest central Swedish 'Kiruna-type' deposit at Grangesberg have delta O-18 values between -0.4 and +3.7%, while the 1.90-1.88 Ga meta-volcanic host rocks have d18O values between +4.9 and +9%. Over 90% of the magnetite data are consistent with direct precipitation from intermediate to felsic magmas or magmatic fluids at high-temperature (delta O-18(mgt). > +0.9 parts per thousand, i.e. ortho-magmatic). A smaller group of magnetites (delta O-18(mgt) <= +0.9 parts per thousand), in turn, equilibrated with high-delta O-18, likely meteoric, hydrothermal fluids at low temperatures. The central Swedish 'Kiruna-type' ores thus formed dominantly through magmatic iron-oxide precipitation within a larger volcanic superstructure, while local hydrothermal activity resulted from low-temperature fluid circulation in the shallower parts of this system.