Geological Survey of Denmark and Greenland Bulletin 33, 2015, 37-40 37© 2015 GEUS. Geological Survey of Denmark and Greenland Bulletin 33, 37–40. Open access: www.geus.dk/publications/bull Assessment of the mineral raw material potential in Denmark – methods and major findings Jakob Kløve Keiding, Per Kalvig, Claus Ditlefsen, Steen Lomholt and Peter Roll Jakobsen Aggregates and other mineral raw materials are important prerequisites for the continual development of the infra- structure and economic growth of a country. Th e 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 popu- lated 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 fi rst time includes Danish resources both on land and at sea and summarises some of the main fi ndings of this analysis. Th e importance of availability of mineral raw materials such as sand, gravel, clay and limestone for a society cannot be overestimated: they are prerequisites for the development of the infrastructure and a wide range of products for the in- dustrial sector. Th e supply of these raw materials is the result of complex value chains, which in turn are based on indicated (see below) and exploited mineral resources from which the raw materials can be processed and turned into commercial materials and products. Globally, sand and gravel account for the largest volume of solid material extracted, with c. 15–25 billion m3 excavated annually, and demand increasing rap- idly (GEAS 2014). Th e Danish mineral industry includes exploitation of loose aggregate, limestone and chalk, diff erent types of clay, salt and granite, and amounted to c. 35 million m3 in 2012 of which aggregate alone accounted for c. 90% (Statistics Den- mark 2012a, b). According to a recent forecast, the demand for sand and gravel in 2036 will be c. 40 million m3 (Region- ernes Videncenter for Miljø og Ressourcer 2014). Th e greater part of the sand and gravel excavated in Den- mark is used as aggregate and fi ller for concrete and other construction purposes. Limestone is mainly used for ce- ment production as industrial fi ller and as soil conditioner. Th e clay industry is fairly diversifi ed and uses clay for bricks, insulation stones, membranes and special products such as absorbents and ion-exchange media. Salt is mainly used for de-icing of roads and in the food and chemical industries. About 35 000 persons were employed in the primary and secondary sectors of this part of the Danish industry in 2013 with a turnover of about 3500 million DKK (Statistics Den- mark 2012a, b). Exploitation of mineral resources in Denmark takes place at designated sites and the administration is controlled by the Danish Nature Agency for the marine resources and the Danish Regions for the resources on land. Th ere are about 630 onshore sites for excavation of sand, gravel, clay, lime- stone and granite, and about 100 off shore dredging sites for sand and gravel. Are there suffi cient mineral resources in Denmark to cover the future demand? Sometimes it is postulated that Denmark is endowed with abundant sand and gravel depos- its, and aggregates are thus oft en considered an essentially unlimited resource that will be available for exploitation in the foreseeable future. Th is is an oversimplifi ed assumption because (1) aggregates cover a diverse group of commodities and not all qualities and types are equally abundant, (2) the distribution of mineral raw materials refl ects the local geol- ogy and aggregates are geographically unevenly distributed and oft en have to be transported over considerable distances from the excavation site to the end-use location, and (3) there are many diff erent and oft en competing landuse interests particularly in a densely populated country like Denmark; exploitation of raw materials does not necessarily have the highest priority. An assessment of the aggregate resources in terms of their size, type and location – in conjunction with an evaluation of possible areas of confl ict with other interests – is crucial for both future resource and landuse planning. On this back- ground the Center for Minerals and Materials (MiMa) con- ducted the fi rst comprehensive Danish raw material resource assessment comprising both onshore and off shore areas. Additional work on mapping the value chains related to the Danish raw material sector is in progress. Methods Th is assessment covers the following resources: aggregates (sand, gravel and pebble); limestone and chalk; clay (clay for bricks and tiles; bentonitic clay; diatomite); salt and gran- ite. Aggregates cover a large and diverse group of materials that can be divided into diff erent quality classes according 3838 to their composition. Traditionally, quality classes applied to marine and terrestrial resources are diff erent. In order to compare the marine and terrestrial inventories this assess- ment uses the classifi cation used for exploitation of marine deposits. It discriminates between six commercial classes (Fig. 1): Sand 0, Sand 1, Gravel 2, Pebble 3, Filler sand 4 and Sand X (unspecifi ed quality). It is beyond the scope of this short paper to describe the defi nition of the various classes and qualities in detail but they refl ect diff erence in grain size, grain size distribution, as well as an assessment of the pet- rographic composition (i.e. the content of reactive, unstable and porous mineral grains). For further details see Ditlefsen et al. (2015). Th is survey is based on data available to the Geological Survey of Denmark and Greenland (GEUS) as per October 2014. Th e evaluation of land-based resources is based on previous investigations, including mapping of raw materials reported to or conducted by GEUS, as well as new resource assessments conducted by regional authorities within the present extraction areas. Borehole data and geological maps were also used. For the fi rst time we also incorporated data from geophysical surveys conducted for hydrogeological mapping. Th is allowed us to screen large parts of the terres- trial area for potential undiscovered raw material resources. Th e resources addressed in this paper are classifi ed by reliability of the resource data and are divided into three classes, namely measured, indicated and inferred. Th e cri- teria for assigning the resources to the diff erent categories were described by Larsen (1994) and Ditlefsen et al. (2015). In essence, the measured resources encompass raw materi- als that are mapped in detail and have well-known quality parameters. Th eir characterisation thus has a high degree of certainty (± 20%). Indicated resources are oft en based on shallow geophysical surveys and a small number of boreholes and have a lower reliability. Inferred resources are based on geophysical data only, or on relatively sparse geological data, regional-scale mapping, etc. To compile the nation-wide as- sessment, data from the communes (98 in total) and from 41 marine study areas were amalgamated. Fig. 1. Map of Denmark showing the location and areal extent of the different quality classes of aggregate mineral resources used in this assessment. The map illustrates the combined resources of measured and indicated resources. 5 0 k m 10°E 55°N 57°N 55°N 57°N Sweden Germany S a n d 0 S a n d 1 G r ave l 2 Pe b b l e 3 F i l l e r s a n d 4 S a n d X , u n s p e c i f i e d q u a l i t y German waters Swedish waters Norwegian waters Bornholm Jylland Copenhagen 15°E 55°N Based on an assessment of the prof- itable excavation depth, the compila- tion assesses the volume of raw mate- rials that is available within the top 25 m below surface, except for salt, which is exploited from deeper-seated salt diapirs and therefore considered to a depth of 500 m below terrain surface. Based on the same reasoning, we excluded areas with more than 5 m thick layers of soil or other mate- rial (overburden) covering the sought- aft er resource. When evaluating areas with limestone and chalk, only de- posits with less than 10  m of over- 39 burden were considered. Data for aggregates were compiled for both marine and terrestrial areas, whereas the remaining raw material groups were only considered on land since at sea they occur under a thick sedimentary cover and are therefore of no interest for exploitation. All areas with resources were screened with respect to commonly occurring confl icting interests (here referred to as ‘no-go’ fi lters). Th is assessment thus specifi es both gross volumes, comprising the total volume of the resources and net volumes, taking into account the eff ect of ‘no-go’ fi lters. Th e latter are calculated by subtracting volumes underlying areas that are claimed for other landuse from the total min- eral resource fi gures. Th e ‘no-go’ fi lter areas include nature protection areas (Natura 2000 areas, historical monuments, state-protected areas, etc.), major built-up and paved areas, and marine waters less than 6 m deep where exploitation is prohibited according to present-day jurisdiction, but areas less than 0.01 km2 in size are excluded. Since this is not a full list of areal restrictions, the available area for mineral extrac- tion as well as the extractable net volumes will be smaller due to other local pre-existing priorities. Results and conclusions Th e mineral assessment presented here covers about 40% of the Danish marine and terrestrial areas. Possible resource oc- currences have been indicated in about 10% of the surveyed areas. Th e calculated gross and net mineral resources are summarised in Table 1, and Fig. 1 shows the geographical distribution of the various resource types and qualities of ag- gregates, the largest commodity group apart from salt. Salt is the dominant resource in terms of volume for all three classes and comprises 89% of the measured net resource volumes (Table 1). Salt, however, is a special raw material that Table 1. Summary (in million cubic metres) of calculated gross and net mineral resources in Denmark Aggregates Granite Clay Chalk and limestone Salt Total Gross resources Measured 4603 38 46 293 34 669 39 649 Indicated 10 747 0 68 89 809 230 820 134 Inferred 80 064 3175 1190 9192 489 671 583 292 Net resources Measured 4073 38 46 293 34 669 39 119 Indicated 9621 0 66 89 809 230 819 006 Inferred 68 888 2020 1029 7048 489 671 568 656 Sum 95 414 3213 1304 9574 1 333 570 1 443 075 Sum 82 582 2058 1141 7430 1 333 570 1 426 781 Table 2. Calculated net volumes (million cubic metres) of aggregate resources in Denmark * unspecified quality. Sand 0 Sand 1 Gravel 2 Pebble 3 Filler sand 4 Sand X Total Marine resources Measured 184 2273 207 77 111 2852 Indicated 1214 6334 739 135 94 8516 Inferred 497 1183 106 13 418 2217 Terrestrial resources Measured 191 656 18 191 165 1221 Indicated 259 554 10 178 104 1105 Inferred 43 96 0 13 66 519 66 671 * Total assessment Measured 184 2466 863 95 302 165 4073 Indicated 1214 6593 1293 145 272 104 9621 Inferred 497 1226 202 13 431 66 519 68 888 Total sum 1895 10 283 2358 253 1005 66 788 82 582 Sum (marine) 1895 9790 1052 225 623 13 585 Sum (land) 493 1306 28 382 66 788 68 997 4040 diff ers from the other mineral resources in several ways: (1) a fundamentally diff erent extraction method is used, (2) it is only found at great depths and (3) and it is regulated by the Danish Subsoil Act (Undergrundsloven) in contrast to the other resources assessed here that are regulated by the Raw Materials Act (Råstofl oven). On a national scale, the measured resources of aggregates account for c. 10% of the registered mineral resources, fol- lowed by chalk and limestone (c. 1%; whereas the volumes of clay and granite account for less than 1%). For all the fi ve types of raw material considered, the volume of the inferred resource class is enormous (Table 1). However, only minor fractions of these volumes will be available for exploitation due to confl icting landuse interests. Aggregates mainly come from either glaciofl uvial depos- its or from Late- and Postglacial marine deposits. Marine deposits are more mature than glaciofl uvial deposits and usually contain smaller amounts of reactive grains that are harmful to constructions. In addition, older deltaic and fl uvial deposits of pure quartz sand are found in central Jyl- land and on and around the island of Bornholm. Granites in Denmark are confi ned to Bornholm where they are part of the Precambrian basement that is exposed or just covered by thin Quaternary deposits on the northern two thirds of the island. Clay is mainly of glaciolacustrine or marine origin, while limestone and chalk are marine formations of Creta- ceous and early Cenozoic age. Th e salt resources in Denmark are Permian in age and related to evaporates from the Zech- stein basin. Most salt deposits are found at more than 3 km depth, and are of no economic interest. Locally, however, the salt has been mobilised and is found in shallower diapirs at depths of 200–300 m. Sand X (unspecifi ed quality) is the largest class in the ag- gregate group and comprises c. 81% of the total volume of all aggregates (Table 2). Th e resources in this class are currently based only on geophysical screening and require a more thor- ough characterisation with respect to grain size, grain-size distribution, petrographic composition as well as better con- straints on the spatial distribution. However, this class off ers unique possibilities to focus future exploration for aggregates in relevant areas. Sand 1, Gravel 2, Pebble 3 and Filler sand 4 are the present commercial classes. Th ese qualities are not equally distributed, hence about 95% of the Sand 1 resources are located off shore, and about 88% of the Pebble 3 resources are found onshore (measured resources, Table 2). Within the onshore areas, the sand and gravel resources are unevenly dis- tributed, for example, very limited proven gravel resources are indicated close to the city of Copenhagen. Th ese obser- vations are important for long-term planning of how to ex- ploit the known resources. Th ere is an up to 19% diff erence between distribution of gross and net deposits for the various raw material qualities when looking at measured and indi- cated resource classes. Th e largest changes are seen for Pebble 3 (19%), Filler sand 4 (18%), Sand 1 (10%) and Sand 0 (7%). Th e eff ect of the ‘no-go’ fi lters is generally rather limited for most of the commodities and raw material classes due to a few very large deposits. Th is is in particular the case when including the inferred resources, which overshadows local- scale restrictions, and thus in places the fi lters have a major impact on the resulting resource fi gures. Also, a number of other constraints may be considered prior to designation of a resource resulting in substantial lower net resource fi gures. Th is survey shows that Denmark is endowed with enor- mous mineral resources of aggregates, clay and special clay, chalk and limestone, and salt and granite. However, to what extent these resources will be available as raw materials for the mineral industry is uncertain since it depends on local landuse and restrictions. Finally, this assessment shows that both off - and onshore aggregate deposits will have to be con- sidered in order to secure the supply of all quality classes. References Ditlefsen, C.B., Lomholt, S., Skar, S., Jakobsen, P.R., Kallesøe, A.J., Keiding, J.K. & Kalvig, P. 2015: Danske mineralske råstofressourcer. Kvantitativ analyse baseret på geologiske og geofysiske data. MiMa Re- port 2015/1, 61 pp. Copenhagen: Geological Survey of Denmark and Greenland. GEAS (Global Environmental Alert Service) 2014: Sand, rarer than one thinks. www.unep.org/pdf/UNEP_GEAS_March_2014.pdf Larsen, B. 1994: Material sammensætningen i submarine råstoff orekom- ster – et metodestudium. DGU Kunderapport 91, 51 pp. København: Danmarks Geologiske Undersøgelse. Regionernes Videncenter for Miljø og Ressourcer 2014: Fremskrivning af råstoff orbruget for 2013–2036. Region Syddanmark. Råstoff er 4, 27 pp. Statistics Denmark 2012a: Statistikbank – råstoff er indvundet fra havet. http://w w w.statisti kban ken.d k/statban k5a/SelectVarVa l/Define. asp?Maintable=RST3&PLanguage=0 Statistics Denmark 2012b: Statistikbank – råstoff er indvundet på land. http://w w w.statisti kban ken.d k/statban k5a/SelectVarVa l/Define. asp?Maintable=RST01&PLanguage=0 UEPG (Union Européenne des Producteurs de Granulats) 2014: Euro- pean Aggregates Association. A sustainable industry for a sustainable Europe. Annual Review 2013-2014. http://www.uepg.eu/uploads/ Modules/Publications/uepg-ar2013-2014_v28.pdf Authors’ address Geological Survey of Denmark and Greenland, Øster Voldgade 10, DK-1350 Copenhagen K, Denmark; E-mail: jkk@geus.dk www.unep.org/pdf/UNEP_GEAS_March_2014.pdf http://www.statistikbanken.dk/statbank5a/SelectVarVal/Define.asp?Maintable=RST3&PLanguage=0 http://www.statistikbanken.dk/statbank5a/SelectVarVal/Define.asp?Maintable=RST01&PLanguage=0 http://www.uepg.eu/uploads/Modules/Publications/uepg-ar2013-2014_v28.pdf << /ASCII85EncodePages false /AllowTransparency false /AutoPositionEPSFiles true /AutoRotatePages /PageByPage /Binding /Left /CalGrayProfile (Dot Gain 15%) /CalRGBProfile (sRGB IEC61966-2.1) /CalCMYKProfile (Coated FOGRA27 \050ISO 12647-2:2004\051) /sRGBProfile (sRGB IEC61966-2.1) /CannotEmbedFontPolicy /Warning /CompatibilityLevel 1.7 /CompressObjects /Off /CompressPages true /ConvertImagesToIndexed true /PassThroughJPEGImages false /CreateJobTicket true 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