GEUS Bulletin (Geological Survey of Denmark and Greenland)
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Composition of ilmenite and provenance of zircon in northern Brazil
No full textThe mineral ilmenite (FeTiO3) is an important component of heavy-mineral placer deposits and constitutes the largest volume of valuable mineral in such deposits. The minerals zircon (ZrSiO4) and rutile (TiO2), which occur in lower concentrations than ilmenite in the deposits, have a greater value per ton – c. 1100 and 900 /ton depending on its composition. Other minerals such as staurolite, sillimanite, amphibole and garnet are generally also present in placer deposits, but are of minor or no commercial value and, e.g. amphibole needs to be separated from the valuable heavy minerals which adds to the production cost
Observed melt-season snowpack evolution on the Greenland ice sheet
No full textDue to recent warm and record-warm summers in Greenland (Nghiem et al. 2012), the melt of the ice-sheet surface and the subsequent runoff are increasing (Shepherd et al. 2012). About 84% of the mass loss from the Greenland ice sheet between 2009 and 2012 resulted from increased surface runoff (Enderlin et al. 2014). The largest melt occurs in the ablation zone, the low marginal area of the ice sheet (Van As et al. 2014), where melt exceeds wintertime accumulation and bare ice is thus exposed during each melt season. In the higher regions of the ice sheet (i.e. the accumulation area), melt is limited and the snow cover persists throughout the year. It is in the vast latter area that models struggle to calculate certain mass fluxes with accuracy. A better understanding of processes such as meltwater percolation and refreezing in snow and firn is crucial for more accurate Greenland ice-sheet mass-budget estimates (Van Angelen et al. 2013)
Reserves and resources for CO2 storage in Europe: the CO2StoP project
No full textThe challenge of climate change demands reduction in global CO2 emissions. In order to fight global warming many countries are looking at technological solutions to keep the release of CO2 into the atmosphere under control. One of the most promising techniques is carbon dioxide capture and storage (CCS), also known as CO2 geological storage. CCS can reduce the world’s total CO2 release by about one quarter by 2050 (IEA 2008, 2013; Metz et al. 2005). CCS usually involves a series of steps: (1) separation of the CO2 from the gases produced by large power plants or other point sources, (2) compression of the CO2 into supercritical fluid, (3) transportation to a storage location and (4) injecting it into deep underground geological formations
Relationship between groundwater chemistry and the Precambrian basement rocks on eastern Bornholm, Denmark
No full textBornholm is situated south of Sweden, in the Sorgenfrei–Tornquist Zone (Fig. 1). The Precambrian basement on northern and eastern Bornholm consists of different types of granitic and gneissic rocks with pegmatites, aplites and dolerite dykes (Callisen 1934). The age of the granite and gneiss is c. 1455 Ma (Waight et al. 2012)
Magma mixing, mingling and hybridisation at different crustal levels: snapshots from 1.9 billion years of magmatism in south-eastern Greenland
No full textDuring field work in 2014, we investigated a suite of igneous intrusions in south-eastern Greenland between 65° and 67°N. Many of the intrusions show widespread evidence for juxtaposition of different magmas in the liquid state and subsequent mixing, mingling and hybridisation. Here we present field evidence for these processes from three areas that differ in age and geological setting. We discuss the significance of mingling, mixing and hybridisation features in the field area, motivated by their abundance in the area, the morphological variation between intrusions that were emplaced at different crustal levels, the implications for magma genesis in collisional and rift settings, and the implications for the interior dynamics of igneous bodies
A quartz-wolframite-molybdenite vein and scheelite in amphibolite horizons from Thrudvang peninsula, Skjoldungen, SE Greenland
No full textDuring the South-East Greenland Mineral Endowment Task (SEGMENT) expedition in 2012, the possible mineral potential of the Skjoldungen region was investigated. The region is part of the Archaean North Atlantic Craton, and includes the Skjoldungen Alkaline Province (Nielsen & Rosing 1990; Blichert-Toft et al. 1995; Kolb et al. 2013). A quartz-wolframite-molybdenite vein with phyllic alteration was identified during the reconnaissance work in the northwestern part of the peninsula of Thrudvang, close to the Kangertikajik fjord (GGU 446946; Figs 1, 2). The c. 30 cm wide, subvertical vein is hosted in mafic granulite. However, the deformed nature of the vein and steep terrain did not allow us to establish its extent or general trend
Assessment of the mineral raw material potential in Denmark – methods and major findings
No full textAggregates and other mineral raw materials are important prerequisites for the continual development of the infrastructure and economic growth of a country. The production of these raw materials in Denmark amounted to c. 4.5 m3 per capita in 2012, which was 57% higher than the average in EU and EFTA countries (UEPG 2014). In this perspective, it is essential to locate and assess the Danish mineral resources in order to plan future exploitation, especially in densely populated regions where both spatial competition for landuse and demands for raw materials are high. Here we present the methods used in a recent resource evaluation that for the first time includes Danish resources both on land and at sea and summarises some of the main findings of this analysis
Follow-up on Ujarassiorit mineral hunt finds and outreach activities, South-East Greenland
No full textIn connection with field work in South-East Greenland in 2014, we took the opportunity to examine the geology associated with potentially valuable mineral occurrences found by local rock collectors. The initial finds were made by local collectors as part of Ujarassiorit, which is an annual mineral hunt competition where anyone in Greenland can submit samples of rocks they have found in the countryside for closer examination by the Ministry of Mineral Resources (see www.ujarassiorit.gl). In the Tasiilaq region, Ujarassiorit resulted in finds of corundum, precious metal and base-metal mineral occurrences. Our intention was to locate the original sample sites with help from the local rock collectors, describe the geological context and assess the potential for mineral exploration. Further work will include laboratory analyses of rock samples and geological reporting
Digital models based on images taken with handheld cameras – examples on land, from the sea and on ice
No full textGeological outcrops can be comfortably modelled in three dimensions in the office using images from a handheld digital camera. Recent developments within the imaging techniques of Structure from Motion (Lowe 2004; Snavely et al. 2008; Fonstad et al. 2013) and photogrammetry (Hirschmüller 2005; James & Robson 2012; Favalli et al. 2012) have made it easier and cheaper to construct so-called digital outcrop models using stereoscopic images from standard digital cameras. The digital outcrop model (Bellian et al. 2005) is a 3D representation of the outcrop surface and is often displayed in the form of a polygon mesh or a point cloud. In this paper we present three examples of such point clouds from images obtained with a handheld digital camera. The examples illustrate how outcrop topography or digital outcrop models can be constructed at different scales, with different accessibility and operational platforms. Two examples illustrate outcrop scales of metres to kilometres, with images obtained by walking along excavated exposures in the Faxe limestone quarry and from a boat sailing past the coastal cliff of Stevns Klint. The third example illustrates detailed micro-topography of ice and snow surfaces where the images were obtained from a snowmobile on an ice cap in A.P. Olsen Land, North-East Greenland
A hydrological early warning system for Denmark based on the national model
No full textThe rapidly increasing impacts of climate change are likely to require changes in relevant institutions (IPCC 2012). An example is the growing need for immediate information on the entire water cycle (Fig. 1), with quantitative assessments of critical hydrological variables and flow interactions between different domains, e.g. atmosphere, plant-soil, surface water, groundwater and the sea, as they take place