caa a22 4500 475827902 CHVBK 20180406123833.0 cr unu---uuuuu 170329e20000301xx s 000 0 eng 10.1007/s005310050308 doi (NATIONALLICENCE)springer-10.1007/s005310050308 Schaltegger U. Department of Earth Sciences, Federal Institute of Technology ETH, CH-8092 Zurich, Switzerland Tel.: +41-1-6326616 Fax: +41-1-6321179 e-mail: schaltegger@erdw.ethz.ch, CH aut U-Pb geochronology of the Southern Black Forest Batholith (Central Variscan Belt): timing of exhumation and granite emplacement [Elektronische Daten] [U. Schaltegger] Some granites, granitoid dykes and volcanic rocks of the Southern Black Forest were dated by U-Pb techniques using zircon and monazite. An effusive rhyolite, which is interbedded in upper Visean sedimentary sequences of the Badenweiler-Lenzkirch zone, was dated at 340 ±2 Ma. This weakly metamorphic zone of supracrustal rocks borders high-grade gneiss terrains in the north and the south, which are intruded by a series of granitoid intrusions: the strongly sheared Schlächtenhaus granite is dated by monazite at 334±2 Ma and the hypothesis of a Devonian emplacement is therefore discarded. The emplacement of all other granites, crosscutting dykes and of an ignimbrite were all within analytical uncertainty: St. Blasien granite 333±2 Ma; Bärhalde granite 332±3 Ma; Albtal granite 334±3 Ma; and a porphyry dyke at Präg 332+2/-4 Ma. Deformation and thrusting of the basement units near the Badenweiler-Lenzkirch zone occurred after the emplacement of the Schlächtenhaus granite, but before the intrusion of the other granitoids, and may therefore be constrained to the time period unresolved between 334±2 and 333±2 Ma. The ignimbritic rhyolite of Scharfenstein was deposited in a caldera 333±3 Ma ago. This age coincides within error limits with published U-Pb monazite and Rb-Sr small slab ages of mimatitic gneisses, Ar-Ar hornblende ages of metabasites and Sm-Nd mineral isochron ages of eclogitic rocks in the underlying basement. This suggests that exhumation and cooling of this basement unit must have been active at rates of approximately 20 km and a few 100°C per million years. The silicic melts are interpreted to be of hybrid crust/mantle origin and their formation was most likely linked to these exhumation tectonics. A phase of mantle upwelling and heat advection into the crust is proposed to be the reason for this short-episodic magmatic pulse. Springer-Verlag Berlin Heidelberg, 2000 Key words Granite nationallicence U-Pb nationallicence Geochronology nationallicence Exhumation nationallicence Crustal melting nationallicence Variscan nationallicence https://doi.org/10.1007/s005310050308 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/s005310050308 text/html Onlinezugriff via DOI NATIONALLICENCE 100 1- Schaltegger U. Department of Earth Sciences, Federal Institute of Technology ETH, CH-8092 Zurich, Switzerland Tel.: +41-1-6326616 Fax: +41-1-6321179 e-mail: schaltegger@erdw.ethz.ch, CH aut Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer