ALBERT

Description: The data set contains VNIR and SWIR raw and reference hyperspectral imaging data of the Apliki mine open cut and of samples from the surface of the mine measured in the laboratory. It is con-nected to the published spectral library and chemical analyses of 37 different surface materials from the copper-gold-pyrite mine Apliki in the Republic of Cyprus (Koerting et al., 2019). The field outcrop scan was acquired in March 2018 in cooperation with the Geological Survey Department of the Republic of Cyprus (GSD) and the German Research Centre for Geosciences (GFZ). The laboratory sample scan presented in this document is a collection of hyperspectral scans compiled in one large dataset. The hyperspectral data in the field and the lab were acquired with the HySpex sys-tem in a range of 414 – 2498 nm. The field data is shared as one VNIR and one SWIR radiance and reflectance data cube each. The laboratory data is shared as one full VNIR-SWIR (414 – 2450nm) reflectance data cube that was processed and corrected for the detector jump, data spikes and the last 8 SWIR bands were clipped due to a low signal to noise ratio (SNR). The data and the samples originate from fieldwork in the Republic of Cyprus and laboratory work at the GFZ Potsdam. A detailed description of the data acquisition and processing can be found in Koerting (2021).

Description: The data set contains LIBS (Laser-Induced Breakdown Spectroscopy) emission spectra of 18 lithium-bearing minerals and their corresponding hyperspectral reflectance spectra. The data were collected within the research project LIGHTS (Lightweight Integrated Ground and Airborne Hyperspectral Topological Solutions, http://lights.univ-lorraine.fr/) which aims at developing a new exploration process for Li targets combining drone-borne hyperspectral data and field observations. Hyperspectral data were acquired with the HySpex system in a wavelength range of 414 - 2498 nm and are presented in a spectral library. Detailed information about the samples and area of spectral retrieval is presented in the data sheet below. The spectral library presented here expands the collection of spectral libraries including samples from rare-earth minerals, rare-earth-oxides (Koerting et al., 2019a) and copper-bearing minerals (Koellner et al., 2019) which are fully described in Koerting et al. (2021). These libraries aim to give a spectral overview of important resources and deposit mineralizations. 18 samples taken partly from the collections of the University of Potsdam (UP) and the Federal Institute for Geosciences and Natural Resources (BGR) and partly in the field during previous measurement campaigns were hyperspectrally measured and geochemically analysed by using a LIBS handheld analyzer. A description of the HySpex system in lab use can be found in Koerting et al. (2021). The lithium-bearing mineral samples were measured without prior sample preparation as the surface of the minerals and the influence of the mineral structure were of interest (Figure 1). Figure 1 shows one HySpex scan of four lepidolite samples (Lep1, Lep2, Lep3, Lep4) displayed as a true color RGB image in order to show the untreated samples and the white reflectance (WR) panel needed for the hyperspectral measurements (WR 90%).

Description: The data set contains chemical analyses of 32 different surface materials from the Bajoca feldspar mine in Portugal and their corresponding hyperspectral reflectance spectra. The field samples were collected in May 2019 within the LIGHTS (Lightweight Integrated Ground and Airborne Hyperspectral Topological Solutions) project. The goal in this project is to develop tools for hybrid data analysis of remote sensing data from different scales, geochemical and geological data for Li target area exploration (LIGHTS; Cardoso-Fernandes et al. (2020a,b & 2021) & Fabre et al. (in prep.)). The hyperspectral data were acquired in the laboratory with the HySpex system in a range of 414 – 2498nm and on-site with the Spectral Evolution PSR+ 3500 handheld spectroradiometer (short “PSR+”) in a range of 350 – 2500nm. The sample spectra of 32 different surface samples are presented for both sensors systems. The resulting HySpex reflectance data are scaled from 0 – 10000, the PSR+ reflectance data are scaled from 0-1. Detailed information about the samples and geochemistry is presented in the data sheets.

Description: Geophysical exploration and in particular active-source seismic imaging of geothermal fields is important to assess and optimize the exploitation of natural heat sources for energy production and direct use. The first multi-offset (moving-source) vertical seismic profiling (VSP) experiment over the high-temperature geothermal field in Krafla (Iceland) was carried out in spring 2014 with the aim to test whether VSP is a suitable method to map volcanic stratigraphy, fractures, dykes, steam zones and magmatic bodies at this site and for volcanic environments in general. In this study, we present a workflow for processing the sparse Krafla VSP dataset recorded with receivers in either of two boreholes. The analysis involved first-arrival traveltime inversion and seismic reflection processing. The seismic velocity model obtained by traveltime tomography reveals structural information between the two boreholes and can be linked to an existing geological model, showing that the seismic velocities are mainly controlled by lithology. The zero-offset seismic reflection data were processed into two corridor stacks. Walk-away VSP reflection data were migrated with a novel multicomponent Kirchhoff migration algorithm that includes P- and S-wave isolation to obtain separate PP, PS and SS migrated images. The reflections imaged in the corridor stacks can be linked to the main lithological units known from borehole logging information. Migrated images from the walk-away data reveal reflectors below and to the sides of the two boreholes. Considering à priori information, such as hypocenter locations from earthquake seismology studies, the reflectors can be related to changes in lithology, fault zones, dykes and possibly the top of the Krafla magma chamber. We found that VSP is potentially a useful method to image the key lithological boundaries and volcanic stratigraphy in the complex magmatic environment at Krafla, but à priori information proved to be essential to constrain the processing and interpretation of the sparse array dataset.

Description: The Krafla geothermal area in northern Iceland comprises one of the best studied examples of a high temperature geothermal field associated with an active volcanic rift zone. Of key importance to improved resource exploration and development in volcanic areas such as Krafla, is the interpretation and understanding of the subsurface geology. Within this study we present results from an integrated analysis of the downhole volcanic stratigraphy from the K-18 borehole within the Krafla caldera based on combined wireline, ditch cuttings, and zero-offset VSP (vertical seismic profile) analyses. This study presents the first published sonic log velocity data from a high temperature geothermal borehole in Iceland and clearly demonstrates the importance of borehole velocity data for improving volcanic facies interpretations. The shallow subsurface geology of the K-18 site from c. 0–380 m comprises an inter-layered sequence of sub-aerial basaltic lavas, hyaloclastites and tuffaceous lithologies of both felsic and basic composition, which are progressively replaced by basaltic sheet intrusions with increasing depth. An interval of variably basic to more evolved mixed tuffaceous facies is identified based on cuttings analysis, gamma and sonic velocities between c. 790–1120 m depth. Discrete high sonic Vp units cut the lower c. 100 m of this interval and are interpreted as either sheet intrusions or lava interiors. At c. 1800 m, a sharp increase in P-wave velocity from c. 4.5 to c. 5.5 km/s, represents the transition from a mixed lava and sheet intrusion dominated sequence, into a dense basic intrusion forming the local basement that persists to the bottom of the borehole at c. 2215 m. Reduced travel time analysis of processed zero-offset VSP results reveal good correspondence with the major stratigraphic boundaries in the borehole, supporting the potential for VSP studies to robustly characterize complex volcanic stratigraphy in high temperature geothermal fields. Finally, the application of percentage-based ditch cuttings analyses methods for volcanic facies analysis in geothermal boreholes is tested and assessed to have future potential.