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- for biotites of the Ramberg pluton and the Delitzsch plutonite massif 295 and 303 Ma, respectively.The K/Ar-age data presented above shows evidence for a tectonometamorphic evolution of the border area Rhen ohercynian -Sax oth uringian: The oldest early- Variscan, very low metamorphic overprint appears in Cambrian sediments of the Saxothuringian basin and also in Ordovician sediments of the Northern Phyllite Zone with an early Lower Carboniferous age of 350 Ma.Because of the combination of white mica polytype determinations in the fine mineral fractions it was possible for the first time to prove and separate polyp hase overprinting.Combined use of illite crystallinity measurements with polytype determinations made it possible to estimate the influence of detrital white micas on the K Ar-ages of the fine fractions, thus leading to a better interpretation of these ages.Therefore, the final stacking of the Wippra Metamorphic Zone took place after the youngest overprint with an age of 320 Ma.The age data obtained from the Wippra Metamorphic Zone suggest a metamorphic overprint prior to the SW -part of the Northern Phyllite Zone (S-Hunsrück, S-Taunus).The source area assigned is Gondwana or a related terrane.
The different ages of metamorphism in the various series of the Wippra Metamorphic Zone prove that they were not in the present geotectonic position at the time of their individual overprinting.
The different ages of metamorphism from Hunsrückffaunus and the Wippra Metamorphic Zone allows two possible interpretations: Either the data from the Wippra Metamorphic Zone indicate an earlier beginning of collision, and therefore, of metamorphism in the SE-Harz region or at least parts of the Wippra Metamorphic Zone do not belong to the Rhenohercynian but to the accretionary wedge of the overriding Saxothuringian latter could be the proof of an earlier beginning of deformation of the rocks in the accretionary wedge and their continuous deformation until c10sure of the ocean.
The ages of metamorphism in the northern Middle Harz Mountains (Rhenohercynian shelf) with Ma (Namur-Westfal) confirm the assumption that the metamorphic overprint is caused by nappe thrusting with simultaneous low grade metamorphism.
The nappe thrusting is possibly connected with the final stacking of the Wippra Metamorphic Zone.
n the Upper Harz Mountains the ages of overprinting indicate a slightly later passing of thevariscan orogenic wave at about 310 Ma in the Westphalian.