6533b826fe1ef96bd1284f54

RESEARCH PRODUCT

Timing of granitoid magmatism in the eastern mid-German crystalline rise

subject

description

Abstract The eastern parts of the mid-German crystalline rise (MGCR) are exposed in the Spessart, Ruhla and Kyffhauser crystalline complexes and known from boreholes in the region of Dessau. In this study we determined igneous formation ages of granitoid intrusives and orthogneisses from this part of the MGCR using the Pb/Pb single zircon dating technique. The intrusion ages of the granitoids range from ∼489 to ∼302 Ma (i.e. from lower Ordovician to upper Carboniferous). The grouping of these ages marks several distinct magmatic episodes during the Variscan orogeny, with a major peak at the end of the lower Carboniferous. We tentatively suggest the following geodynamic scenario for the origin of the granitoid magmas in the various parts of the MGCR. 1. In the Ordovician, Gondwana disintegrated. Remnants of this stage are preserved in the central and eastern part of the MGCR. 2. In the Silurian, granitoid magmatism was triggered by subduction underneath the MGCR from the North. Such magmatic rocks occur in the central part of the MGCR and to a lesser extent in the western part, but not in the northeast. 3. In the upper Devonian, magmatism originated in response to subduction of the Rhenohercynian Ocean underneath the MGCR from the North. This is only documented in the western part of the MGCR. 4. At the end of the lower Carboniferous, at ca. 330 Ma, subduction from the South generated voluminous granites in the entire MGCR. 5. In the upper Carboniferous, post-tectonic granitoids were formed in the central and eastern parts, documenting the end of the Variscan orogenic cycle.