The Muschelkalk and its lead-zinc mineralization in the eastern Netherlands

Abstract

The Muschelkalk of the eastern Netherlands, as exposed in quarries east of Winterswijk, is made up of sequences of dolomitic lime-mudstones. These are interpreted as stromatolites, particularly because of their characteristic algal growth patterns around mudcracks which show evidence of intermittent cracking and sealing. Rare, intercalated skeletal packstone layers with cyclic grain-size grading are thought to represent storm layers deposited within the high intertidal to supratidal algal mat environment. Pyrite, marcasite, sphalerite and galena occur widely dispersed in the limestone but have been concentrated more conspicuously in the storm layers and mudcrack fillings. A widespread occurrence of algal mats could account for initial concentration of considerable amounts of base metals. These probably did not derive from the deeper portions of the main Triassic basin to the north but are more likely of southern provenance, transported in meteoric water draining the emerged Variscan massifs. Secondary concentration of metals during dolomitization and compaction has demonstrably occurred, preferably in coarser-grained fabrics. Supergene enrichment is inferred from high strontium, lead and zinc values below a red bed interpreted to be a paleosol. A further analysis of the metal distribution is required. The area investigated is considered immature as regards economic mineral concentration. However, a place for base metal exploration is advocated in the course of the systematic investigation of the Netherlands subsurface.