Lead isotope studies of strata-bound,vein-type,and unconformity-related Pb,Sb, and Bi ore mineralizations from the western edge of the Bohemian Massif (F.R. Germany) |
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| Authors: | A Höhndorf H Dill |
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| Institution: | (1) Federal Institute for Geosciences and Natural Resources, Stilleweg 2, D-3000 Hannover 51;(2) Geological Survey of Lower Saxony — Continental Deep Drilling Program of the Federal Republic of Germany, Project Management, Stilleweg 2, D-3000 Hannover 51 |
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| Abstract: | Specimens from strata-bound/stratiform  Kieslager , lineament-bound, and unconformity-related Pb occurrences from the NE Bavarian Saxothuringian and Moldanubian belts and samples from stibnite and polymetallic Sb-Au quartz veins were analyzed for their lead isotope composition.The strata-bound Pb at Bodenmais yielded an Upper Proterozoic 207Pb/206Pb model age which correlates with the assumed stratigraphic age of the host rock. Late Precambrian rift activity may have triggered the formation of this ore mineralization. This type of Pb was also found in the Kieslager at Waldsassen hosted by Early Paleozoic country rocks and in the fluorite veins at Kittenrain.The vein-type lineament-bound, and unconformity-related Pb occurrences show a similar isotopic pattern which suggests that this type of Pb originated from the same source. The 207Pb/206Pb model ages which are too old compared to the assumed age of formation and the accelerated 208Pb evolution indicate that the detritus of the source rock underwent a high-grade metamorphism in the Precambrian.The formation of the unconformity-related Pb concentrated in galena of fluorite-barite veins is correlated with late Variscan magmatic intrusions. The older model ages of about 100–150 Ma from the lineament-bound lead, located along deep-seated lineamentary fault zones, suggest an earlier separation of this type of Pb possibly triggered by the Caledonian A-subduction-related metamorphism. |
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