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Geology and mineral resources of the Lövstrand Pb(-Zn) mineralization, Dorotea area, north-central Sweden
2008 (English)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

The Dorotea district is situated in North Central Sweden and is the host of many small sized sandstone-hosted lead-zinc deposits such as Lövstrand, Bellviksberg and Granberget. The mineralized areas were discovered during the 1930s through an extensive exploration campaign along the Caledonian Front. Boliden Mineral AB has investigated the Lövstrand zone for about ten years (from 1947 to 1958) but even with X drill-holes and a mine-testing excavation, the mineralization was estimated to contain too low lead grades and too limited tonnage to be considered economic. The present study aims to improve the knowledge about the Lövstrand mineralization. The Lower Cambrian Sandstones, deposited in a fluvial dominated deltaic system and rich in organic matter, were involved in thrusting during the Scandian Event 425 million years ago. They are now included in the Lower Allochthonous Unit of the Tåsjön Décollement and host a stratabound galena-(sphalerite) mineralization at Lövstrand. The organic matter (indicating a high probability of sulfide presence due to high authigenic pyrite content) associated with intergranular clayey minerals, together with a lower alteration of the porosity, are the most likely causes for the precipitation of the sulfides in the sandstones. Because of the high rock fracturing due to the thrusting process, the mineralization has been partly remobilized and spread along faults, lowering the grades to sub-economic levels. The lead content in mineralized rocks is strongly correlated with silver. The high-grade parts of zinc mineralization are spatially separated from the lead even though both still seems to be linked to the same mineralizing event. The latter is likely to be of same nature as the mineralizing event described in Laisvall. The resource estimation indicates that the Lövstrand mineralization contains X Mt of inferred resources with an average of X % lead and X % zinc. In addition, the area contains a potential mineralization estimated at X Mt with an average of X % lead and X % zinc. Using the correlation between lead and silver, the silver grade has been estimated to be around X g/t. The observation of the spatial separation between high zinc grades and high lead grades, together with the low number of zinc assays, indicates the possibility of further zinc mineralization.

Place, publisher, year, edition, pages
Keyword [en]
Life Earth Science, Caledonides, Dorotea, Lövstrand, sandstone-hosted lead/zinc, deposit, galena, sphalerite, resource estimation
Keyword [sv]
Bio- och geovetenskaper
URN: urn:nbn:se:ltu:diva-46746ISRN: LTU-PB-EX--08/055--SELocal ID: 45d87324-ef75-4a9f-bcfc-076643217bbdOAI: diva2:1020061
Subject / course
Student thesis, at least 30 credits
Educational program
Geosciences, master's level
Validerat; 20101217 (root)Available from: 2016-10-04 Created: 2016-10-04Bibliographically approved

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