Blymalmen vid Laisvall, dess geologi och en jämförelse med några utländska förekomster

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Abstract
Title: The lead ore at Laisvall, its geology and a comparison with some foreign deposits. Laisvall is situated at the eastern border of the Caledonides only some 10 km S of the Arctic Circle. The deposit was found in 1939 by the Boliden Mining Co. Production was started in 1943 and the output is now 325 000 tons of lead ore per year with 4–5 % Pb. The ore reserve is about 16 mill. tons. The deposit occurs as disseminations in authoctonous Eocambrian sandstones lying between impounding beds of a mudstone and covering Cambrian shales. The shales are cut by overthrusted nappes. The paragenesis of the ore consists of galena, sphalerite, pyrite, barite, calcite, fluorite, and scricite. The mineralization is especially located around faults, fissures, and crushed zones caused by the overthrust movements. The mineralizing solutions have followed such structures and have migrated into the sandstone from them. The mineral deposition has preferably occurred in quartzitic layers while beds rich in clay have been more or less impermeable and only seldom contain any lead. The mineralization is supposed to have been caused by hydrothermal solutions of low temperature originating from palingenic zones in the inner parts of the Caledonides. Decreasing temperature and pressure at the border of the orogenie zone seem to have played an important role in the ore deposition. Compared with foreign deposits Laisvall is most similar to Mechernich-Maubach in Germany but there are also many similarities with the lead-zine ores of Touissit— Bou Beker in Morocco, the North Pennine lead deposits in Great Britain and the ores of the Tri State district in USA.

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