Natural Resources of the Kärdla Impact Structure, Hiiumaa Island, Estonia
2002; Springer Nature; Linguagem: Inglês
10.1007/978-3-662-05010-1_12
ISSN2365-0710
Autores Tópico(s)Astro and Planetary Science
ResumoThe about 455 Ma (Late Ordovician, Caradoc period) Kärdla impact structure on Hiiumaa Island, Estonia (58°59´N; 21°47´E), has a 4 km rim-to-rim diameter and was formed in a shallow epicontinental sea. Several natural resources are spatially related to the Kärdla structure: 1) at the rim wall crystalline building stone is found; 2) above the rim wall chemically pure micritic (cryptocrystalline) Ordovician limestones crop out; 3) in the north-eastern part of the crater, on the slopes of the crater rim, chemically pure organodetrital (cystoid) grainstones are exposed; 4) on the slopes, dolomitized limestones of the crater rim contain galena and sphalerite mineralization is discovered; 5) outside the crater, hydrocarbons in the form of diffused patches in limestones, liquid oil in pores, asphalt and asphaltite in fissures and pores are widespread; 6) within the crater, at depths of 270–815 m, mineral water of Cl—Na—Ca composition with a total content of dissolved salts of 2–6 gl−1 is found; 7) around and inside the crater, the Ordovician artesian basin is directly related to the structures of the buried impact crater; 8) in the crater proper and in the surrounding area, glaciolacustrine clays are distributed; 9) on the south-eastern slope of the crater rim there are considerable reserves of gravel and sand.Except the crystalline building stone, these resources were formed after the impact. They are largely related to the morphological features caused by the impact. Sulphide precipitation and hydrocarbon impregnation were facilitated by rock jointing and brecciation caused by the impact. The processes directly related to the impact have not induced any ore mineral concentrations.
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