9th International Symposium „Topical Problems in the Field of Electrical and Power Engineering“ Pärnu, Estonia, June 14-19, 2010 The geological perspectives for Paleozoic carbonate raw material mining in Harjumaa County, Estonia Angela Notton Tallinn University of Technology [email protected] Ylo J. Systra Tallinn University of Technology [email protected] Abstract building materials grew very quickly and reached maximal level, 1800 000m3, in 2007 (Fig.1). After Harjumaa County surrounds a capital-city Tallinn the Ida-Virumaa County with its oil shale mining for and has the highest density of population, more electric power stations about 15 million tons yearly, than 121 residents per 1 km2 .At the same time here Harjumaa County is keeping the second place in is going active mining, mostly different building total mining and the first in raw building material materials: limestone, gravel and sand are mining. In Harjumaa County in 2008 were extracted extracted. At dense population, network roads and carbonate raw materials 1746 000m3 and 49 800m3 railways there are very few places for new quarries, pure limestone for technological use, 289 700m3 of because the places of mineral resources of good building gravel, 1956 700m3 of building sand and quality are occupied by different settlements. By 49 000m2 of sand for fillings. The bigger part of the Estonian laws underground resources belong them was used in civil, industrial and road building. to government and may be easily and without harm The renewing of road network and railways needs to environment extracted. Mined territories after many million tons of building stone, gravel, sand put in order may be returned to owners. In many and other materials. cases the soil conditions after mining is better than At the dense population the best places for quarries before. In this paper are discussed the problems of are occupied by towns, settlements, villages and the Ordovician bedrock mineral resources using, farm houses, so it is the main problem to find places development and their quality in the Harjumaa for new quarries. The local people are very clever to County. In paper are shown volumes of mining, find reasons, why the mineral resources (which by some demands to limestone and dolostone material Estonian laws belong to government) must not be and their properties in some different deposits. mined on their domains and home places. They are involved into expertise foreign specialists, who after receiving rich “compensation” will find Keywords “underground rivers” in every place, wherever it is Carbonate bedrock, Paleozoic, Ordovician, building needed. If there were no protected rare plants, it is stone, limestone, dolostone, technological material, easy to seed them from other areas, only not to give rights for mining. The situation needs to be more chemical composition, compressive strength carefully studied and it is possible, that will be found other territories with needed quality of mineral resources, where the mining is not so painful for Introduction local people. It was the main reason for initiating Harjumaa County covers 4333km2 and is the biggest this doctoral study of different mineral resources in by territory and population in Estonia. Including the the Quaternary sediments and Paleozoic bedrocks capital-city Tallinn with more than 400 000 residents for their economical and more effective usage in the here in 2008 lived 523 400 people or 38.5% of all Harjumaa County. This paper deals only the part of population of Estonia. Ordovician carbonate rock. In Tallinn are concentrated transport junctions to Europe and Russia, industry, education, culture, the Geological setting main harbors and airfield. After receiving back independency and joining the European Union in Harjumaa County is located in the northwestern 2004 was initiated renovation of all types of Estonia, on the southern shore of the Finnish Gulf, transport, road- and railways, airfields and harbors. about 80km to south from Helsinki, Finland. This action was financially supported by EU. For Geologically this area belongs to the southern slope building were needed special materials: aggregate, of the Fennoscandian shield, where the Precambrian gravel, sand etc. From 2001 extracting of different Early Proterozoic crystalline rocks of age 2.0-1.3Ga 1 2750 2500 2250 2000 1750 1500 1250 1000 750 500 250 0 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 Figure1. Volumes of mined carbonate building stone (in thousands m3) in the Harjumaa County (light columns) and total in Estonia (dark columns) Vasalemma, Harku, Nabala, and Väo are listed as from 1994 to 2009 (data about all country are not deposits of all-country importance. As sources of received yet) local importance are registered deposits near Jägala, Kernu, Maardu, Määra, Rummu, Sookaera, Valkla (Lehtinen et al, 2005) are covered by sequence of and Sõrve (Rannamõisa). the Ediacaran and Paleozoic sedimentary rocks with In 5 deposits: Munalaskme, Tuula, Rummu, age between 600Ma and 359Ma in Estonia. The Paeküla-Kõmmaste and Vasalemma are registered surface of the Precambrian basement together with also reserves of pure limestone of technological all sedimentary layers is slightly inclined to south, quality (Table1). about 3m per 1km. The sedimentary bedrock cover become thicker to south, it thickness near the Historical using of carbonate rocks in northern seashore is only 100-140m and grows at the southern boundary of county up to 250-280m. The Estonia bedrocks are covered by thin, 5-20m Quaternary cover, usually less than 5m. The first using of local bedrock were fixed at the end The oldest sedimentary bedrocks of Estonia belong of younger Bronze Age, when plate-like carbonate to Ediacaran system, represented here by 630- stones removed from fields and put in piles or a low 542Ma old Vendian complex (Nestor et al, 2007). stone wall around the fields (Perens, Kala, 2007). This time was going Rodinia’s breakup and ancient Some hundred years before our era a limestone wall continent Baltica became the newly independent, but was built on Saaremaa Island to protect the fortified was located near the southern pole (Cocks, Torsvik, settlement of Asva. In ninth-eleventh centuries local 2005). In such very cold climate conditions was limestone was used for building of 7-10m high walls impossible to form carbonate sediments, and it was surround the Valjala and Varbola strongholds. The the reason that Vendian complex as well as all length of Varbola wall is 580m. Both forts had deep Cambrian and Lower Ordovician series are here limestone-mantled wells, which are preserved up to represented by sandstones, siltstone and claystone now. From limestone were built graves in the North (Mens, Pirrus, 1997). Only in the beginning of the Estonia, also in the Harjumaa County. After invasion Middle Ordovician 471.8 ± 1.6 Ma Baltica reached of Danish king Valdemar II in 1219 the building of the limestone castle-citadel was at once initiated. more warm latitudes and in shallow continental sea th carbonate sediments began to form (Nestor et al, The works finished in 1227. The 13 century was 2007). The Middle and Upper Ordovician section the time for building numerous limestone churches reaches in the Kerguta (565) drill core, Central in Tallinn, Saaremaa etc. Later the limestone became Estonia, 185m. The whole sequence is represented common as a local building stone. by limestone, dolostone, marl and dolomitic marl. The bedrocks contain iron or phosphorite ooliths Demands to carbonate stone, crushed sometimes and in the Kukruse Stage of Upper and grinded material Ordovician the kerogenous and K-bentonite interbeds are common (Põldvere, 2006). Limestone and dolostone is easy to handle, therefore In the Harjumaa County there are being registered it has been used in buildings fore many hundred 16 carbonate stone deposits, four of them: years. Limestone in road construction is needed in 2 many different stages, aggregate of many fractions cement. Limestone in agriculture is widely used to for layers forming, lime powder as a filler in asphalt improvement of composition and properties of soils, etc. The white road-marking mixture also contains for animal feeds, lime filter drains and garden lime. the limestone powder. Very important are quicklime and slaked lime in Building limestone must be strong to pressure and environmental care for purifying drinking water and resistant to weather and frost, which usually is 25 flue gases, cleaning waste water and industrial waste cycles, in clayey limestone only 15 and in more water, sludge and biological waste treatment, liming strong types of rock reaches 35 cycles (Perens, Kala, of waterways, treatment of contaminated soil, for 2007). As a rule the compressive strength of the covering of landfills, production of heat (Nordkalk, Estonian Ordovician limestone is between 600-800 2007, 2009). For technological limestone demands kg/cm2 (65-85MPa), in more strong types rising up Table 1. Limestone deposits in the Middle (O2) and are very high to quality and impurities, CaO content Upper Ordovician (O3) succession of the Harjumaa must exceed 52%. County: (DEP- not in use) and (PiW open pits in Pure technological dolostone is needed for glass work). Numbers show next listed in registry production (not less than 18% MgO), for making deposits: 1–Sõrve, 2–Harku, 3–Väo, 4–Maardu, 5– fireproof materials (MgO not less than 19%, CaO Jägala, 6–Valkla, 7–Paeküla-Kõmmaste, 8– not more than 33%, SiO2 not more than 1%, sum of Määra, 9–Rummu, 10–Vasalemma No 1, 11– Al2O3, Fe2O3, Cr2O3 not higher than 2%). Abrasive Vasalemma No 2, 12–Tuula, 13–Sookaera, 14– products for polishing glass, nickel, cupper, pearl Munalaskme, 15–Nabala, 16–Kernu and other soft materials made from dolostone need very pure bedrock: MgO > 19,5%, CaO < 32,5%, to 1200kg/cm2 (about 120MPa) and in clay-rich insoluble remnants not more than 2%.