GEUS Bulletin (Geological Survey of Denmark and Greenland)
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The north-east Baffin Bay region, offshore Greenland – a new frontier petroleum exploration region
No full textIn recent years the Arctic has come into focus for hydrocarbon exploration, and areas offshore both West and East Greenland have been evaluated as promising frontier hydrocarbon provinces. Seven hydrocarbon exploration and exploitation licenses were awarded in 2007–2008 offshore the Disko–Nuussuaq region (Fig. 1), and two more have been awarded in the open-door region offshore south-western Greenland. In 2007, an extensive amount of new seismic and aeromagnetic data was acquired by the TGS-NOPEC Geophysical Company in the north-eastern Baffin Bay region. Geophysical mapping has been initiated by the Geological Survey of Denmark and Greenland (GEUS) in the Melville Bugt region offshore North-West Greenland (Fig. 1) with the purpose of evaluating the hydrocarbon prospectivity. Initial interpretation of seismic and gravity data suggests the presence of deep sedimentary basins separated by structural highs. Geological information on source rock, reservoir rock and seal intervals from surrounding regions suggest that the Melville Bugt region is likely to have a significant petroleum potential. The study is based on public domain magnetic and gravity data, and all proprietary and public 2-D seismic data (Fig. 1) acquired before 2003. Seismic horizons from the ‘seismic basement’ to ‘base Quaternary’ are being interpreted regionally. Based on the seismic interpretation, a structural element map, depth-structure maps and isopach maps will be produced in order to assess the prospectivity of the Melville Bugt region
A multi-disciplinary study of Phanerozoic landscape development in West Greenland
No full textThe western margin of the Greenland craton has been much less stable in the Phanerozoic than previously thought. This new insight has come from close integration of independent datasets: geomorphological analysis of large-scale landscapes, apatite fission track analysis (AFTA), onshore and offshore stratigraphy and analysis of onshore fault and fracture systems. Each data set records specific and unique parts of the event chronology and is equally important to establish a consistent model. A key area for understanding the Mesozoic– Cenozoic landscape evolution and into the present is the uplifted part of the Nuussuaq Basin, where remnants of planation surfaces cut across the Cretaceous to Eocene sedimentary and volcanic rocks. Our integrated analysis concluded that the West Greenland mountains were formed by late Neogene tectonic uplift (Fig. 1) and also provided new insight into early Phanerozoic development. To understand our model, we present the different methods and the results that can be deduced from them
Gold-hosting supracrustal rocks on Storø, southern West Greenland: lithologies and geological environment
No full textA gold prospect on central Storø in the Nuuk region of southern West Greenland is hosted by a sequence of intensely deformed, amphibolite facies supracrustal rocks of late Mesoto Neoarchaean age. The prospect is at present being explored by the Greenlandic mining company NunaMinerals A/S. Amphibolites likely to be derived from basaltic volcanic rocks dominate, and ultrabasic to intermediate rocks are also interpreted to be derived from volcanic rocks. The sequence also contains metasedimentary rocks including quartzites and cordierite-, sillimanite-, garnet- and biotite-bearing aluminous gneisses. The metasediments contain detrital zircon from different sources indicating a maximum age of the mineralisation of c. 2.8 Ga. The original deposition of the various rock types is believed to have taken place in a back-arc setting. Gold is mainly hosted in garnet- and biotite-rich zones in amphibolites often associated with quartz veins. Gold has been found within garnets indicating that the mineralisation is pre-metamorphic, which points to a minimum age of the mineralisation of c. 2.6 Ga. The geochemistry of the goldbearing zones indicates that the initial gold mineralisation is tied to fluid-induced sericitisation of a basic volcanic protolith. The hosting rocks and the mineralisation are affected by several generations of folding
Two tectonically significant enclaves in the Nordre Strømfjord shear zone at Ataneq, central West Greenland
No full textThe Nordre Strømfjord shear zone is a 1.8 Ga zone of largescale, transcurrent and sinistral ductile shear (Sørensen et al. 2006) within the Nagssugtoqidian Mobile Belt (NMB) of central West Greenland. It has been hypothesised that the NMB is a suture between two Archaean continental masses (Kalsbeek et al. 1987). During field work in 2005 along the Nordre Strømfjord shear zone in the fjord Ataneq (Fig. 1), some unusual rock types were discovered that preserve evidence of magmatic and metamorphic processes not previously reported in the area. These observations include the first indication of high-pressure (HP) metamorphism in West Greenland and the first reported occurrence of a cumulate of giant orthopyroxene. The tectonic telescoping of these features together within the Nordre Strømfjord shear zone has important implications for reconstructing the Palaeoproterozoic history of this region, and provides evidence that processes typical of Phanerozoic continent–continent collision zones (e.g. the Caledonian and Alpine systems) operated at least as far back as 1.8 Ga ago
Seismic hazard assessment of Greenland
No full textEarthquake activity in Greenland has been registered and mapped since 1907 (Larsen et al. 2006) and thus a long (albeit relatively sparse) record of seismic activity is available for evaluation of seismic hazard and risk. Seismic hazard assessment is carried out by judging the probability of future earthquakes in a given region and is based on statistic treatment of earthquake data. The determination of the seismic hazard is the first step in an evaluation of seismic risk, i.e. the possible economic costs and loss of human life after an earthquake. The motivation for this seismic hazard study is the registration of four significant earthquakes in Greenland in 2005. The Geological Survey of Denmark and Greenland (GEUS) received reports of all four earthquakes from residents who had felt the shaking. The 2005 earthquakes were located at or near Qeqertarsuaq on 30 March, Sisimiut on 23 July, Station Nord on 30 August and Attu on 23 October (Fig. 1), with magnitudes on the Richter scale of 4.3, 4.1, 5.1 and 2.5, respectively. The earthquake in Attu led to the inhabitants fleeing in their boats
Shallow groundwater quality in Latvia and Denmark
No full textExperience and results from the Danish groundwater monitoring programme that has been carried out systematically since 1990, have been used in a co-operative project between Latvia and Denmark. The main objective of the project was to obtain more detailed knowledge of the shallow Latvian groundwater, to optimise the Latvian groundwater monitoring programme and to support the implementation of European legislation such as the Water Framework Directive, the Nitrate Directive and the Groundwater Directive in Latvia. Comprehensive summaries describing the methodology of groundwater quality monitoring as well as the major results from the Danish groundwater monitoring network can be found in GEUS (2005) and Stockmarr (2005). Until recently only few data on Latvian groundwater quality were available, but in a project running from 2003 to 2006, 800 samples from groundwater, springs and drains have been analysed for a large number of components resulting in a comprehensive overview of the status of Latvian groundwater (Fig. 1; Gosk et al. 2006). The project Agricultural influence on groundwater in Latvia was carried out by the State Geological Survey of Latvia and the Geological Survey of Denmark and Greenland (GEUS) and was supported by the Danish Environmental Protection Agency within the framework of the DANCEE programme (Danish Co-operation for Environment in Eastern Europe). As a spin-off of the project this paper compares groundwater quality in the two countries
Pre-metamorphic hydrothermal alteration with gold in a mid-Archaean island arc, Godthåbsfjord, West Greenland
No full textRecently discovered volcaniclastic rocks of andesitic composition form major parts of the mid-Archaean, amphibolite facies supracrustal belts at Qussuk, on Bjørneøen and on part of Storø in western Godthåbsfjord (Fig. 1). These rocks are interpreted as an island arc that represents the onset of the magmatic accretion of the Akia terrane 3070 Ma ago; this terrane is the north-westernmost of several Archaean tectono-stratigraphic terranes in the Nuuk region, which were all amalgamated by 2720 Ma (cf. Hollis et al. 2006). The presence of the arc in the Akia terrane points to similarities between high-grade orthogneiss-amphibolite associations in West Greenland and lower-grade granite-greenstone terrains of other Archaean cratons e.g. in Canada and Western Australia. Volcaniclastic rocks belonging to the ancient arc have been subject to intense synvolcanic, hydrothermal alteration associated with gold-copper mineralisation especially in parts of the Qussuk area. Another important gold prospect occurs on central Storø, which is currently being explored by NunaMinerals A/S (Knudsen et al. 2007 – this volume). This contribution presents new field observations from some of the best preserved parts of the ancient arc at Qussuk and on Bjørneøen, while it remains unclear if the volcano-sedimentary associations and their gold mineralisation at Qussuk, Bjørneøen and the nearby Storø share a common mid-Archaean geological history
Development of marine landscape maps for the Baltic Sea and the Kattegat using geophysical and hydrographical parameters
No full textThe Baltic Sea is one of the largest brackish water bodies in the world (Segerstråle 1957) with a number of basins varying from almost fresh water in the northern part of the Bothnian Bay via the more brackish conditions in the southern part to the saline waters of the Kattegat. The Baltic Sea is subject to severe environmental degradation caused by commercial and leisure activities, including fisheries, dredging, tourism, coastal development and land-based pollution sources. This causes severe pressures on vulnerable marine habitats and natural resources, and a tool for aiding marine management is therefore strongly needed. The marine landscape concept presented by Roff &Taylor (2000) is based on the use of available broad-scale geological, physical and hydrographical data to prepare ecologically meaningful maps for areas with little or no biological information. The concept, which was elaborated by Day & Roff (2000) was applied in UK waters (Connor et al. 2006) before it was adopted by the BALANCE project described here. The aim of developing marine landscape maps is to characterise the marine environment of the Baltic Sea region (the Baltic Sea together with the Kattegat) using geophysical and hydrographical parameters. Such maps can be applied, for example, to an assessment of the Baltic-wide network of marine protected areas, and thus provide a sustainable ecosystem-based approach to the protection of the marine environment from human activities, and contribute to the conservation of marine biodiversity. The BALANCE project is based on transnational and cross-sectoral co-operation with participants from nine countries surrounding the Baltic Sea as well as Norway (Fig. 1), and is partially financed by the European Union through the BSR INTERREG IIIB programme
Provenance of Cretaceous and Paleocene sandstones in the West Greenland basins based on detrital zircon dating
No full textThe extensive and very deep ?Jurassic/Cretaceous–Palaeogene sedimentary basins offshore West Greenland have a significant petroleum exploration potential. This is particularly true for the offshore region west of Disko and Nuussuaq where a live petroleum system has been documented for many years. At present, stratigraphic knowledge in this area is almost nonexistent and analogue studies from onshore areas and offshore exploration wells to the south are therefore crucial to understanding the distribution and quality of possible reservoir rocks in the Disko–Nuussuaq offshore area. One of the main risk parameters in petroleum exploration in this region is the presence of an adequate reservoir rock. Tectonostratigraphic considerations suggest that several sand-prone stratigraphic levels are probably present, but their provenance and reservoir quality are at present poorly known both onshore and offshore. A sediment provenance study including zircon provenance U-Pb dating and wholerock geochemical analysis was therefore initiated by the Geological Survey of Denmark and Greenland (GEUS) in preparation for the Disko West Licensing Round 2006 (Scherstén et al. 2007). The main aims of this study were to: 1. Characterise the source areas and dispersal patterns for the various sandstone units of Cretaceous–Paleocene age in the Nuussuaq Basin and compare these with sandstone units in selected West Greenland offshore exploration wells (Figs 1, 2), employing advanced zircon provenance U-Pb dating using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS; cf. Frei et al. 2006). 2. Detect possible changes in sediment source with time, e.g. local versus regional sources. Zircon as a provenance tool is receiving increasing attention and has proven to be a powerful indicator of clastic sediment sources, a tracer of the Earth’s oldest materials, and a tracer of continental crust-forming processes (Froude et al. 1983; Williams & Claesson 1987; Dodson et al. 1988; Fedo et al. 2003; Hawkesworth & Kemp 2006). Zircon is common in continental rocks and it is assumed that its distribution in sediments will normally represent the source rocks. Although there are several complications, the sediment zircon U-Pb age frequency should in general terms mirror the relative proportions of different source materials. This assumption is particularly important if exotic components can be identified, as their frequency will provide an estimate of the exotic influx: it may also be essential in tracing sediment paths that affect the detrital compositions and subsequent diagenetic history of possible hydrocarbon reservoir rocks