Faults act as conduits for large-scale fluid movements, often hosting multiple circulation events within their brecciated structures.

In the Alps, particularly along the Penninic Frontal Thrust within the ‘Briançonnais Zone’, a mineral assemblage of calcite and hematite has been observed in the breccias of the High-Durance normal Fault System (HDFS). Recent geological investigations have utilized a multidisciplinary approach, including petrological analysis, geochemical examination of calcite (involving stable isotopes and clumped isotopes analysis), and U-Th-Pb dating.

U-Pb dating on calcite provided dates ranging from 5.3 to 2.3 Ma and Hematite (U-Th)/He dating from 13.3 to 0.2 Ma. All ages indicates the onset of transtensional fault activation and the transition from the previous compressional tectonic regime in the Middle Miocene with a westward migration of the extension. The onset of the HDFS extensional regime thus appears to be contemporaneous with the development of the fold and thrust belt of the western Alpine foreland.

Two isotopic signatures (Δ₄₇) of the calcites suggest an open fluid system with (1) crystallization temperatures around 130°C related to deep fluids and (2) a meteoric fluid signature (36°C) associated to a 1900m precipitation altitude, indicating that similar altitudes were present around 2 My ago. This coincides with the transition from a Mediterranean climate to a colder, glacier-dominated climate, leading to valley formation during this period.

Upper Neoproterozoic sedimentary rocks anchored in the literature as greywackes are exposed in Saxo-Thuringia and represent the main sedimentary part of the Cadomian basement of the region with sedimentation ages between 540 and 570 Ma based on the youngest detrital zircon ages (e.g., Linnemann et al. 2000, Geol. Soc. Spec. Publ., 179, 131–153). Previous Nd model ages give a uniform old cratonic source of 1.5–1.9 Ga for the Neoproterozoic greywackes (Linnemann & Romer 2002, Tectonophysics, 352, 33–64). This study aims to re-examine the Cadomian greywackes of Saxony and adjacent areas by combining analytical methods, such as whole-rock Sm–Nd isotopic studies and detrital zircon U–Pb dating using LA-ICP-MS. The investigations have also been carried out comprehensively at locations not previously studied. Some Carboniferous greywackes were also sampled as a reference due to their similar appearance in the field and local uncertainties in their stratigraphic position. The new data are used to validate existing models of basin development and sedimentary provenance. The sedimentation of a large part of the Saxo-Thuringian clastic rocks along the periphery of Gondwana adjacent to the West African Craton in the Late Neoproterozoic could be proven. However, the youngest detrital zircons of around 490 Ma indicate that some units were deposited during the Late Cambrian to Early Ordovician and do not belong to the Cadomian rock units. Carboniferous samples show in addition Late Devonian zircon ages and Nd model ages younger than 1.5 Ga which points toward a different sedimentary provenance.

This talk presents radiometric ages and mineral sizes of detrital zircons and apatites representing six sediment samples from three different recent rivers of the eastern Erzgebirge: The Wilde Weißeritz, the Freiberger Mulde and the Müglitz. We took one sample from the upper and one from the lower reaches of each river.

The objectives were, (1) to find evidence for thermal, magmatic events in the apatites, (2) to record the U-Pb-spectrum of zircons for each sample, and (3) to improve insight into the transport behaviour and sediment composition of the studied rivers.

The apatites showed thermal overprinting of their U-Pb ages, which varied between ca. 306 Ma and ca. 328 Ma. Therefore, small, local thermal events seem to be more likely than one large event affecting the entire study area. The older ages are interpreted to represent the end of the Variscan Orogeny and the beginning of the post-Variscan magmatism. The younger ages are interpreted as later thermal overprinting by local magmatic events, possibly caused by heating events along the margins of the Erzgebirge Block at the beginning of the Permian magmatism.

The U-Pb-ages of the zircons represent the rocks of the hinterland of the specific rivers and show mainly Cadomian ages derived from the gneisses combined with (post-)Variscan ages from the igneous rocks. Therefore, the spectrum of zircons found at the sampling sites is dominated by the local rocks.

Interestingly, the detrital minerals analysed do not allow interpretation of very long sedimentary fluvial transport.

Recently, new age data have been published for the Variscan magmatism as well as for times of ore formation in the Erzgebirge (e.g., Breitkreuz et al., 2021; Burisch et al., 2019; Meyer et al., 2024; Leopardi et al., 2023; Löcse et al., 2020; Reinhardt et al., 2022; Tichomirowa et al. 2019, 2022). Förster and Romer (2010) wrote in their compilation on Carboniferous Magmatism that two major periods of magmatic activity occurred in the Erzgebirge. During the first period (327 - 318 Ma) most of the large plutons in the Western Erzgebirge were formed and probably also the volcano-plutonic rocks of the Altenberg-Teplice Caldera (ATVC) in the Eastern Erzgebirge (Förster and Romer, 2010). The second major period of magmatic activity was assigned by these authors to small subsurface granites and various subvolcanic rhyolithic dykes and microgranites (305 – 295 Ma). New high-precision dating of the major plutons in the Western Erzgebirge slightly shifted the proposed time interval for the first magmatic period (323-314 Ma; Tichomirowa et al., 2019). Based on new high-precision ages it was shown that the magmatic activity in the Western and Eastern Erzgebirge was diachronic and that the first volcanites in the Eastern Erzgebirge were already formed at ca. 322 Ma (Tichomirowa et al., 2022). We present new high precision age data for the second magmatic period from the Western and Eastern Erzgebirge and compare the age data of Variscan magmatic activity with the data for ore formation.

The early post-Variscan evolution of central Europe was characterized by the formation of numerous volcano-sedimentary Rotliegend (Late Carboniferous–early Permian) basins. Recent dating attempts in the Thuringian Forest Basin have shown that the precision and accuracy of zircon CA-ID-TIMS dating (< 0.1 %) is crucial to discriminate the sedimentation ages of successive formations. The correlation between different basins will be most successful by a combination of high-precision age dating with the existing extensive knowledge about biostratigraphic correlations.

Here, we present new zircon U-Pb CA-ID-TIMS data of three volcanic rocks from the Unkersdorf, Niederhäslich, and Bannewitz formations of the Döhlen Basin (Saxony, Germany) and of two tuff samples of the Manebach and the Goldlauter formations of the Thuringian Forest Basin (Thuringia, Germany). Our data indicate that all four formations of the Döhlen Basin were deposited during ≤ 1.8 Myr and are within errors coeval with the Manebach and Goldlauter formations of the Thuringian Forest Basin. The Niederhäslich Formation of the Döhlen Basin and the Manebach and Goldlauter formations of the Thuringian Forest Basin contain fossil-rich lacustrine horizons, which have been correlated to a variety of formations in other European basins through the use of insect, amphibian, or conchostracan assemblage zones. Our new data thus provide new absolute age constraints for different fossil assemblage zones, and thereby can be extrapolated to other basins in central Europe.

The Graissessac-Lodève Basin (southern France) contains a thick and very well preserved record of Late Carboniferous to Permian continental sediments. These sediments are remnants of a complex erosional history of the Variscan orogen and post-orogenic extension, as well as a record of the local geotectonic history of southern France. The use of original isotopic detrital zircon and apatite data revealed the provenance of the siliciclastic strata. The detrital zircon age populations and sandstone compositions in the Permian strata, which reflect the rapid exhumation and unroofing of the Montagne Noire dome, are determined by the ages and compositions of units forming the Montagne Noire metamorphic core complex to the west of the basin. The Cambrian to Archean zircon ages are most likely recycled detritus derived from the Early Paleozoic sedimentary cover and Neoproterozoic to Early Cambrian shales that formerly covered the Montagne Noire dome. Ordovician detrital zircon ages may indicate orthogneiss units of the dome. The youngest detrital zircon suite, ranging in age from ca 285 to 320 Ma, reflects erosional products of Carboniferous to Permian granites of the Montagne Noire axial zone. The latter zircon population is absent from Carboniferous-aged strata, but was found throughout the studied Permian strata. These results suggest that the young granite suite was exposed during early Permian time, reflecting uplift of the southern Montagne Noire during post-orogenic extension. Detrital apatite data from the Permian strata show that the last thermal event in the hinterland of the Graissessac-Lodève basin occurred in the Upper Carboniferous.