LEAD-ISOTOPE SYSTEMATICS OF EPIGENETIC LEAD-ZINC MINERALIZATION IN THE WESTERN PART OF THE RHEINISCHES SCHIEFERGEBIRGE, GERMANY

In the western part of the Rheinisches Schiefergebirge three different types of epigenetic lead-zinc vein mineralization in Paleozoic rocks can be distinguished: 1. Syntectonic Variscan veins, 2. post-Variscan (Saxonian) veins mainly in Paleozoic siliceous elastic rocks, 3. post- Variscan carbonate-hosted mineralization in the Aachen-Stolberg area. Ore impregnations occur in the Triassic Buntsandstein (Bunter sandston e) and Muschelkalk of the Maubach-Mechernich triangular depression cov ering the Paleozoic rocks. Data points define two distinct populations in both lead isotope diagrams and thus indicate two major Variscan an d post-Variscan mineralization events. The lead isotope pattern of the Paleozoic sedimentary rocks bears good evidence that this thick rock sequence may be the main source of metals for the mineralization. The metals were mobilized at deeper levels by saline fluids at different t imes. There are no direct indications for remobilization of the older Variscan vein ore deposits. The sandstone- and carbonate-hosted ore im pregnations of Maubach-Mechernich have a similar lead isotope pattern to the post-Variscan mineralization in the Paleozoic sedimentary basem ent.