{ "currentVersion": 10.91, "id": 160, "name": "gtk_self_potential", "type": "Feature Layer", "description": "Omapotentiaalimenetelmässä (SP, Self Potential) mitataan suoraan maankamaran luonnollisia sähköisiä potentiaalieroja. Potentiaalierot ovat seurausta tiettyihin puolijohdemineraaleihin liittyvistä sähkökemiallisista ilmiöistä sekä myös muista taustailmiöistä, kuten esim. maankamaran elektrolyyttien väkevyyseroista ja pohjaveden virtauksesta huokoisessa väliaineessa. Tausta-arvoon nähden mitatut häiriöt (anomaliat) ovat aina negatiivisia. Suuruudeltaan mineralisaatiopotentiaalit voivat olla jopa 1 000 mV anomalioita. Alueet joilla kallion pinta on pohjavesipinnan yläpuolella, ovat otollisia omapotentiaalikentän syntymiselle. Tämän vuoksi suot jossain määrin haittaavat menetelmän käyttöä.\nSP mittauksia on tehty hajaprofiilimittauksina ja systemaattisina mittauksina. Hajaprofiilimittaukset ovat yksittäisiä lähinnä tunnusteluluontoisia mittauksia. Systemaattisissa mittauksissa on yleisesti käytetty 50-100 metrin linjaväliä ja 10-20 metrin pisteväliä ja mittauslinjojen suunta on valittu paikallisen geologian mukaan. Mittauksia on tehty eri puolilla Suomea lähinnä malminetsinnän tarpeisiin. \nOmapotentiaalimenetelmää voidaan käyttää malminetsinässä ja kallioperäkartoituksessa johtavien kiisu- ja grafiittimuodostumien kartoittamiseen ja luokitteluun. Hydrogeologisissa tutkimuksissa menetelmällä voidaan kairanrei\u2019issä paikallistaa savitäytteisiä rakopintoja ja veden virtauskohtia.\n/\nThe self potential (SP) method is a direct measurement of the natural differences in the electrical potential of the ground. Potential differences are the result of electrochemical phenomena associated with certain semiconducting minerals, and other background phenomena, such as differences in the concentration of certain electrolytes in the soil and the flow of ground water in a porous medium. Compared to the background value, the anomalies are always negative. Mineralisations can cause anomalies of up to 1 000 mV. Self potential fields most commonly emerges in areas where the bedrock surface is above the water table. As a result, bogs interfere with the method to some extent.\nSP measurements have been conducted as individual profile measurements and systematic measurements. Individual profile measurements are mostly individual tentative measurements. Systematic measurements commonly used a line interval of 50-100 metres and a point interval of 10-20 metres. The direction of measurement lines was selected on the basis of local geology. The measurements have been conducted in various locations in Finland mostly for ore exploration purposes. \nThe self potential method can be used in ore exploration and bedrock surveys to map and classify conductive pyrite and graphite deposits. 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