The Late Carboniferous deeply eroded Tharandt Forest caldera–Niederbobritzsch granite complex: a post-Variscan long-lived magmatic system in central Europe

Abstract Samples and documentation of outcrops drillings, facies analysis, whole rock geochemistry radiometric ages have been employed to re-evaluate the Late Carboniferous Tharandt Forest caldera (TFC) co-genetic Niederbobritzsch granite (NBG) in eastern Erzgebirge near Dresden, Germany. The c. 52 km 2 TFC harbours strongly welded ignimbrites with a preserved minimum thickness 550 m. Composition initial fallout tephra at base fill, comprising lithics rhyolitic basic lava, silica-rich pyroclastic rocks, suggests bimodal volcanic activity area prior climactic eruption. lower part fill comprises quartz-poor ignimbrites, overlain by quartz-rich apparently without depositional break. Landslides originating from collapse collar plunged into still hot producing monolithic gneiss mesobreccia clasts ≤ 1 m matrix. Aphanitic porphyritic magma formed ring- radial dykes, subvolcanic bodies centre TFC. Whole geochemical data indicate high silica (most samples > 73 wt% SiO ) composition magma, similar granodiorite–granitic for NBG. Based on drillings extent, volume 22 3 is preserved, original assumed about 33 . This estimate translates denudation least 210 during Paleozoic pre-Cenomanian. Telescopic subsidence took place two, perhaps three stages. A possible outflow has completely eroded distal tuff not recognized neighboring basins. New CA-ID-TIMS measurements two gave mean zircon 313.4 ± 0.4 Ma 311.9 Ma; NBG resulted 318.2 0.5 319.5 Ma. In addition, one sample ring dyke an age ca. 314.5 obtained. These ages, together field relations, allow model long-standing evolution upper crustal magmatic system (~ 5 Ma?), where pulses injection doming alternate quietness erosion. Together Altenberg–Teplice Volcanic Complex, located some 10 southeast, TFC–NBG Complex represents early post-Variscan central Europe.