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A prototype electromagnetic vibrator, referred to here as E‐Vib, was upgraded and developed for broadband hardrock and mineral exploration seismic surveys. We selected the iron oxide mine in Blötberget, central Sweden, for a test site in 2019 for the newly developed E‐Vib because of the availability of earlier seismic datasets (from 2015 to 2016) for verification of its performance for hardrock imaging purposes. The two‐dimensional data acquisition consisted of a fixed geometry with 550 receiver locations spaced at every 5 m, employing both cabled and wireless seismic recorders, along an approximately 2.7 km long profile. The E‐Vib operated at every second receiver station (i.e. 10 m spacing) with a linear sweep of 2–180 Hz and with a peak force of 7 kN. The processing workflow took advantage of the broadband signal generated by the E‐Vib in this challenging hardrock environment with varying ground conditions. The processed seismic section shows a set of reflections associated with the known iron oxide mineralization and a major crosscutting reflection interpreted to be from a fault system likely to be crosscutting the mineralization. The broadband source data acquisition and subsequent processing helped to improve signal quality and resolution in comparison with the earlier workflows and data where a drophammer seismic source was used as the seismic source. These results suggest new possibilities for the E‐Vib source for improved targeting in hardrock geological settings. [ABSTRACT FROM AUTHOR]

Measuring the degree of organic matter (OM) alteration caused by uranium (U) irradiation is important in the effective evaluation of the hydrocarbon potential and thermal maturity of U-rich source rocks. This study investigates OM alteration in the Baltoscandian U-rich, lower Paleozoic Alum shale obtained from three research wells in the thermally immature parts of eastern Sweden and western Estonia. The results show a marked increase in the proportion of refractory, non-generative organic carbon (NGOC) in the U-rich shale. Fluorescence spectrometry of unicellular alginites and lamalginites show a reduction of up to 95.6% in fluorescence relative intensity (RI) with increase in U content from 29 to 401 ppm. Fluorescence spectra of the liptinites exhibit a marked "red shift" as expressed by increase in red(R)/green(G) quotients. This change in fluorescence properties of the liptinites is associated with up to 77.6% decrease in hydrogen index (HI) and hence loss of hydrocarbon generation potential. Furthermore, organic molecules show significant loss of aromatic moieties as well as aliphatic constituents resulting in a more condensed macromolecular structure. The measured random reflectance of solid bitumen (BR o) appears to be significantly elevated in micro scale proximity to the U-containing minerals. The heterogeneous distribution of U-containing minerals and the contact with solid bitumen attributes to the wider range of BR o values and lead to the overall increase in mean BR o in samples with high U contents. In contrast, R o values of zooclast macerals (GR o , e.g., graptolite, chitinozoans and vitrinite-like fragments) appear to be less influenced by U irradiation and hence are a more reliable maturity indicator in U- rich lower Paleozoic shales. • Uranium (U) irradiation is responsible for alteration of organic matter, manifested by red shift in fluorescence spectra of liptinites (Red/Green quotient) and increase in solid bitumen (thucholite) reflectance (BR o). • U irradiation attribute to hydrogen index (HI) decrease, relative non-generative organic carbon (NGOC) increase and parent macromolecule condensation. • Zooclast fragments (GR o , Graptolite, Chitinzoan and vitrinite-like particles) are more reliable maturity indicators in U-rich rocks. [ABSTRACT FROM AUTHOR]

Population growth, together with overall improvement of life standards, greater level of environmental awareness and energy transition towards green technologies, result in globally increasing demand for mineral resources on a yearly basis. Considering that most of the shallow large-scale deposits have likely already been explored and mined out (or are being mined), there is a great interest to explore for deeper-seated deposits. For this purpose, the SIT4ME project, through EIT Raw Material Program was established, aiming to promote, improve and further establish seismic methods for mineral exploration in hard rock environments. In November 2018, a multi-method seismic dataset was acquired in the Zinkgruvan mining area in the Bergslagen mineral province of Sweden. Both active (32t seismic vibrator truck as source) and passive data were acquired using a combination of sparse 3D grid and dense 2D profiles in an area of approximately 6 km2 enabling reasonable 3D subsurface illumination. For the data acquisition, a total of 1300 receivers were used across the study area, distributed along ten 2D-crooked-seismic lines and in a 3D mesh. This provided us with a comprehensive dataset, which would be used for a multitude of processing and imaging approaches. The objectives are to image any deep (> 500 m depth) massive sulphide mineralization and structures hosting them within this complex three-dimensionally deformed hard rock setting. Here, we present the acquisition setup, preliminary reflection seismic processing results obtained from active part of the dataset. [ABSTRACT FROM AUTHOR]