Zircon age data as gathered from literature and GEUS samples

Exploration companies are obliged to report their activities to the Ministry of Minerals and Resources (MMR). Now reports are delivered in digital format, but were previously delivered in paper, to the Geological Survey of Denmark and Greenland (GEUS). They are scanned and released reports are available under Reports. Digital restoration The data that the reports hold is thus available, but stored as images in scanned pdf?s. The geochemical data of 4 reports (Allen & Harris, 1980; Coppard et al., 1992; Harris et al., 1992 and Pearson & Joudrie, 1995) have been digitized. I.e. the reports have be optically characterised and the sample locations georeferenced. The matching of the sample locations and geochemically referenced samples does not always match. Meaning that a sample that has coordinate may not have geochemical results, and a sample with geochemical measurements might not have coordinate. The reporting of the analytical facilities and precision is sparse. Detection limits, analytical uncertainty and reliability are generally not reported. Analytical methods and analysed grain fractions of sediment samples also not reported. When all these issues have been listed, it should be noted that errors may occur. From the digital restoration of scanned paper to optically characterisation of the scanned text and numbers errors may be introduced. The user is cautioned to these issues. Upload to data base To make the data available on the web, upload to GEUS sample data base is required. To fit into the sample data base, some adjustments had to be made. Sample names modified, collector created etc., resulting in modified sample names, relative to the ones used in the reports. The reports from which the samples occur in are not mentioned in the data base. Hence the four reports and links to them are listed below:

Intrusions and magmatic complexes are central, when it comes to an assessment of the economic geological potential of a region. There are many of these in Greenland, and only a few of them have been examined in detail for their economic potential. In Nielsen (2002), tertiary intrusions and complexes in East Greenland were described, and later on information on intrusions and magmatic complexes in all of Greenland, were modelled based on the same methodology. The information has been compiled by GEUS geologists.

This view presents data from stream sediment geochemical mapping of West and South Greenland (Steenfelt, 2001a). Stream sediment samples were collected from 1979 to 1998 with as even coverage as possible from low-order streams and with a sampling density between 1 sample per 5 km2 and 1 sample per 50 km2, mostly around 1 sample per 30 km2. With few exceptions, the 0.1 mm grain size fractions of 500-g samples were analysed for major and trace elements by two or three methods. After careful quality control and elimination of bias between analytical values determined by different methods or at different times (calibration), the most reliable analytical data were selected as the final consistent dataset, containing data from 7122 samples analysed for up to 43 elements (see Steenfelt 1999, 2001b for details on data selection and calibration). Major element oxides and volatiles are determined by X-Ray Fluorescence Spectrometry (XRF) and loss on ignition, respectively. Loss on ignition mostly reflects the amount of organic material in stream sediment samples. As the aim is to show the regional variation in the chemistry of the minerogenic component of the stream sediment, volatiles are not included in the major element composition which is recalculated as volatile-free oxides. Instead, volatiles are listed in a separate column for documentation. Locally, high loss on ignition may be caused by high contents of carbonate in the stream sediment of streams draining rare occurrences of marble or carbonatites. For detailed or more accurate studies, the CO2 concentrations of the stream sediment samples should be measured, or the amount of carbonate minerals estimated by microscopy. Trace element data are from methods determining total concentrations (XRF, Instrumental Neutron Activation, Delayed Neutron Counting). The quality of the trace element data varies (see Steenfelt 1999, 2001b) In the present dataset, all values below lower detection limit are indicated by the digit 0. Sample location Before 1993, sample sites were originally marked on topographic maps at the scale 1:100,000 and their positions were later digitised and later again corrected, when a new topographic reference was introduced around year 2000. From 1993 onwards, GPS was used to determine sample positions.

The regional-scale gamma spectrometry data are associated with two collaboration projects involving the Geological Survey of Greenland (GGU) and the Danish Atomic Energy Commission’s Research Establishment. The projects' objectives were to outline areas with an elevated uranium potential in two regions of Greenland: The airborne radiometric surveys in southern and central West Greenland in 1975/76 and the SYDURAN project in South Greenland in 1979-1982. To acquire the data, four-channel gamma ray spectrometers were mounted upon an aircraft (1975/76 surveys) and a helicopter (SYDURAN project). The vehicles flew along shoreline and valley contour lines at low average terrain clearances of 100 and 50 m respectively. The data were recorded without GPS systems, and so positioning was estimated when known landmarks were passed. This means that the dataset is sparse and inhomogeneous, and the spatial accuracy remains low. The gamma-spectrometer had been calibrated at a pad facility at Risø, which enabled the conversion of recorded counts per second into simulated concentrations of radioactive components in the surface of the overflown terrain. Large parts of the data (surveys from 1975/76) were originally stored on magnetic tapes and data were transferred to datafiles in 2003 to make them digital accessible. Most data were retrieved and are now available as ASCII files.

The gravity compilation is based on data stored in the national/Nordic gravity data base at the DTU Space. This data base contains for Greenland data surveyed by DTU Space on behalf of the geodetic survey authorities “Danish Agency for Data Supply and Efficiency” (SDFE) and its predecessor agencies “National Survey and Cadastre” (KMS) and the Geodetic Institute (GI), with some data dating back to the 1950’s. Older data have been rectified into modern gravity datums (absolute gravimetry and IGSN71). The national data contains both surface, airborne and marine data, mainly in the coastal ice-free regions and offshore (Forsberg et al, 2001, Kenyon et al, 2008). Airborne, marine and land data from a number of external data sources are also included in the data base after a QC process, including high-level airborne data from the GAP91/92 campaigns (Brozena et al, 1993) and recent data from NASA OIB (MacGregor et al., 2021) and OMG projects (Fenty et al., 2016). Marine data in the Baffin Bay and Davis Strait and land data from the Geodetic Survey Division, Canada (Veronneau 2010, pers.comm.), and a number of other marine and land data from a large set of contributors have also been included in the compilation, including marine data from Alfred Wegener Institute (Germany), land and marine data from Orkustofnun (Iceland), and a number of released commercial data sources. In areas void of gravity data, satellite-derived altimetry data have been used as fill-in (DTU 15, Andersen et al. 2017). The compiled grids have been based on public domain and some proprietary data sources, and has been computed for the area 58-85°N, 78-7°W on a 0.02°x 0.05° grid, using rigorous downward continuation of airborne data to the terrain surface, with terrain corrections from a detailed digital terrain and ice sheet surface model, and long-wavelength satellite gravity data from GRACE and GOCE satellites (Forsberg and Olesen, 2010). The data are available as a free-air (Faye) anomaly grid as well as a derived terrain-corrected Bouguer anomaly grid (land and ice sheet areas only), computed in GRS80 with density 2.67 g/cm3. The ice sheet Bouguer anomaly data are derived using the ice sheet thickness model of Bamber et al., 2013. The free-air gravity grid (v1) have also have been used as the primary background data also for the latest geoid models of Greenland (GGEOID16).

A series of Aster band ratios highlighting mineral distributions. Band ratio color composite images to distinguish variability of lithology in the area. Preprocessing of the Aster scenes encompasses atmospheric, radiometric and topographic corrections before masking non-outcrop pixels and generating the final mosaic. The calibrated radiance data is converted to apparent surface reflectance using a radiative transfer program, Atmospheric and Topographic Correction (ATCOR-3), in rugged terrain mode. The ATCOR rugged terrain mode utilizes a surface elevation model to adjust illumination levels. Calibration and adjusting the apparent surface reflectance values from the ATCOR-3 processing was not feasible due to lack of ground-based reflectance measurements.

The Geological Survey of Denmark and Greenland has previously conducted sampling campaigns of heavy mineral concentrate in Greenland. The sampling methods are described according to their sampling years below. Unfortunately, not all the samples have reported as the campaigns in have not been undertaken on regional scale and therefore fallen under smaller projects or sampled under projects that have had other objects, and not all elements were considered relevant in the reports, translating to that metadata concerning the analyses are missing. All together there are geochemical analyses of 725 heavy mineral concentrate samples. The samples that are mentioned in reports below, are 319 in number, and do not comprise all heavy minerals samples collected the specified years. Samples collected in un-mentioned campaigns do occur in the full list. Use of data that is not mentioned here, needs caution and the quality should be weighed against other data. Years 1982-1986 A regional sampling campaign was conducted between 1982 and 1986, these samples are described in Appel 1989. These samples comprise the analysis batch numbers 10, 36 and 55. Numbers 10, 36 are analysed at Activation Laboratories and 55 analysed at Bondar-Clegg and Co. Ltd., both in Canada. In this campaign 210 samples were collected and are all sampled in the area around Nuuk. Sampling procedure: In the field: The coastal areas were accessed by boat while inland areas were accessed by helicopter. Four litres of coarse gravel and sand were collected and sieved through a 6 mesh of brass. The fines (c. 10 %) was panned and inspected in ultraviolet light and the scheelite grains counted. In the laboratory: The samples were dried and separated by bromoform, the heavy material was weighed and the scheelite grains counted again. A small splitter separated c. 0.5 gram of each sample for analysis of W, Mo, Pb, Cu, Cr, Co, V, Mn, Zr, Ni and Fe. During the years the sampling programme as well as the analysis methods changed. In 1983 the four litres were added up to five. In 1985 the material increased to 5-6 litres (or 10 kg). In 1986 a plastic sieve with 1 mm holes used and filled three times (5-8 kg) for each sample, the volume of fines was measured. C. 10 gram of each sample was analysed by Bondar-Clegg for (Sc, Cr, Fe, Co, Ni, As, Se, Rb, Mo, Ag, Cd, Sb, CS, BA, La, Eu, Tb, Yb, Hf, Ta, W, Ir, Au, Th and U) analyses. The reader should note that the analyses below detection limit is given as "0" (zero) and not analysed as "-1" for the samples collected in this campaign (year 1982-1986, i.e. batch numbers 10, 35 and 55). Year 1991 In 1991, 106 streams were sampled for heavy mineral concentrate, in the southern part of the Nuuk area, between 62°30?N and 64°N. Sample procedure was as follows: 5-10 litres of detrital material, < 5 cm, were collected, from 2-5 sub-localities in the stream bed. Wet sieving split the sample in less-than and bigger-than 0.5 mm, and the coarser fraction inspected for economic minerals. The fine fraction was heavy minerals concentrate was produced using a rotary panning device "goldhound" (see Erfurt et al., 1992 for reference). The heavy mineral concentrate was shipped to Denmark and dried and further spilt for analytical purposes. Activation Laboratories, Canada, analysed the samples for 35 elements including gold, with INAA and ICP-ES. Analyses batches are numbered 10 and 36. Unique samples number 103 for these two batches. In additional batch 41, has analysed Pb, Cu, Ni and Zn. Year 2004 The analyses batch no. 193 and 194 have been described in GEUS report 2004/42, and were sampled in 2003 in the Qaanaaq region in North-West Greenland. Six samples were collected in this campaign and sieving of 1.0 mm material on site and a pre-concentrate by panning of the fine fraction. In Copenhagen minerals with > 2.8 g/cm3 density was produced by heavy liquid separation. The rest The remaining 406 samples (analyses batch numbers: 10, 15, 21, 35, 36, 41, 55, 165, 166, 193, 194, 374, 375, 376, 1014, 1015, 1016, 1017, 1029, 1030, 1051, 1052, 1077 and 1078) have been analysed in addition to the laboratories mentioned above, at Risø National Laboratory in Denmark. As reports have not been available for writing up these analyses, the description is limited to the analyses. Chances are, however, that sampling procedures are similar to the descriptions above. The analyses below detection limits of the remaining 406 unique samples have not been consistent, but are presented as "0" or as negative values and elements that have not been measured as "0" or empty cells.

A summary geological description of 18 areas on Greenland containing mineral occurrences is provided with references. The information was provided by the Mining and Mineral Resources Authority of Greenland and represents the main geological features with respect to the formation of occurrences.

The map is based on selected seismic data up to 2001. The map shows the structural conditions at depth for the 'Top Kalk' surface, from the central to the eastern part of the Danish North Sea. 'Top Kalk' denotes the surface which forms the basis of the Tertiary deposits (except Denmark). The map is described in GEUS Bulletin No. 13. 2007.