U-Pb LA-ICPMS geochronology of depositional carbonates demonstrated to be a potential chronostratigraphic tool for poorly time-framed sedimentary successions. However, not all carbonates are dateable. Evaluating the dating potential requires establishing the age accuracy and precision of various sedimentary and early diagenetic carbonates precipitated from the same system. This is of prime importance to boost future chronostratigraphic studies based on U-Pb LA-ICPMS analyses. The lacustrine Yacoraite Fm. (Maastrichtian-Danian, Salta rift, Argentina) was chosen to assess the dating potential of different co-precipitated carbonates, whose age was constrained by zircon U-Pb dating of interbedded ash layers. Results of analyses on 101 carbonate phases, including ooids microbialites and early cements, are presented. Criteria to discriminate preserved U-Pb depositional ages were proposed to construct a robust depositional age model. Statistical analysis of the preserved depositional ages and their relative uncertainties (2 sigma ex) point towards two factors that have partially controlled the carbonate U-Pb dating potential: the mineralogy and carbonate type that in turn reflect the dominant precipitation processes (chemical, induced or mediated by microbial activity), and textures (grain/crystal size and primary pore network). The highest dating potential is displayed by the early calcite cements precipitated via chemical processes and composed of coarse crystals with no micropores. Conversely, ooids and microbialites, especially those composed of dolomite, have lower dating potential. Results from this study provide insights regarding the sequestration of U and Pb in lacustrine carbonates and encourage to preferentially target early diagenetic calcite cements to apply U-Pb LAICPMS geochronology for chronostratigraphic studies.

The Koralpe–Saualpe–Pohorje Complex (KSPC) in the Eastern Alps represents a key segment of the Austroalpine basement and hosts the type locality of eclogite. Despite extensive study, its tectono-metamorphic evolution remains debated, particularly regarding a proposed NW–SE increase in pressure–temperature conditions and possible ultra-high-pressure metamorphism in the Pohorje unit. Structural analysis of the KSPC reveals four deformation phases recording a polyphase tectonic evolution: D1 pre-Alpine deformation with E–W-trending stretching lineation and isoclinal folding, D2 Alpine deformation with NW–SE-trending stretching lineation and isoclinal folding, D3 development of Plattengneis fabric with N–S foliation, and D4 late E–W open folding.We present new constraints from quartz-in-garnet elastic barometry, Zr-in-rutile thermometry, garnet diffusion modelling and in-situ U–Pb dating of garnet and rutile along a NW–SE transect from Koralpe to Pohorje. This study provides the first application of quartz-in-garnet barometry within the KSPC.Eclogite samples yield consistent maximum entrapment pressures of ~1.85 GPa across the entire complex, with no systematic spatial variation. Metasedimentary rocks record lower pressures of up to ~1.4 GPa. Zr-in-rutile thermometry indicates uniform peak temperatures of 640 ± 30 °C, likewise showing no thermal gradient. In addition, garnet diffusion modelling suggests short residence times at peak P–T conditions, consistent with rapid burial and exhumation.Garnet U–Pb ages cluster in the Early Cretaceous (~95–105 Ma), with eclogitic garnet from Koralpe yielding ~112 Ma. A Saualpe metasedimentary sample preserves Triassic garnet cores (~224 Ma) overgrown by Early Cretaceous rims (~115 Ma), indicating polymetamorphic overprinting. Rutile U–Pb ages range from ~98–80 Ma and are interpreted as cooling ages.Overall, the data suggest that the KSPC is best explained as consisting of several subnappes rather than a single coherent nappe. The absence of a systematic P–T gradient, together with uniform peak conditions, argues against the previously proposed NW–SE metamorphic gradient. Apparent pressure differences between lithologies are most plausibly attributed to fluid-assisted modification of quartz-in-garnet systems rather than primary metamorphic variations. Together with the identified four deformation phases, our results support a homogeneous peak metamorphic overprint within a polyphase tectonic framework.

Abstract The paucity of rocks from Earth’s first billion years (4.5–3.5 Ga) limits understanding of early felsic (continental) crust formation and craton development. We present zircon U–Pb, O- and Hf-isotope and whole-rock geochemical data from deformed and metamorphosed (ultra)mafic and felsic rocks of the Archaean Lewisian Gneiss Complex, NW Scotland. The felsic, MgO-rich hornblende-bearing tonalite gneisses contain magmatic zircon populations at c. 3.6, 3.5, and 2.8 Ga, as do enclosed hornblendite pods (>95 vol.% hornblende). Zircons from hbl-tonalite preserve median δ¹8O(zircon) of ~5.8‰, indicating limited supracrustal input. The hornblendites have high-MgO (~18 wt%), Cr (up to 5500 µg/g), and Ni (up to 2800 µg/g) concentrations and record slightly higher δ¹8O(zircon) median values (~6.3‰). Zircon εHf(zircon) from both lithologies implies a Hadean to early Archaean (c. 4.1–3.9 Ga) depleted mantle source variably modified by low-temperature surface-derived fluids and/or incorporation of Hadean continental crust. We argue that the hornblendites represent vestiges of a hydrated (proto)crust that contributed to the growth of the earliest Archaean continental nuclei.

Carbonatites are rare mantle-derived igneous rocks often economically enriched in rare earth and high field strength elements and are crucial archives of mantle and crustal processes. Zircon U-Th-Pb geochronology provides a powerful means of constraining their magmatic and hydrothermal evolution, but interpretation is often hindered by discordant data arising from open-system behavior. Discordant data are often dismissed as meaningless, yet hydrothermally recrystallized zircon can in fact record the timing of fluid-rock interaction, offering a means to date important orogenic-related or economic deposit-forming hydrothermal events. Here, we show that integrated U-Th-Pb geochronology, textural observations, trace element analysis, and Pb isotope data from the Mount Grace carbonatite and associated carbonatites and syenites in the southeastern Canadian Cordillera resolve both magmatic and hydrothermal histories. Four samples from meta-carbonatite and meta-alkaline rocks in the Monashee complex and Selkirk allochthon in the southern Omineca belt were studied to clarify the magmatic ages through new zircon U-Th-Pb geochronology. Concordant U-Pb zircon ages of ca. 360 Ma from the pyroclastic Mount Grace carbonatite confirm a Late Devonian depositional age for protoliths of the Monashee cover gneiss. Ca. 360 Ma magmatic ages for all four carbonatite-syenite samples expand the record of Late Devonian-Early Mississippian alkaline magmatism in the Monashee complex and Selkirk allochthon. Hydrothermally altered zircon domains that correspond with convolute zoning in cathodoluminescence and elevated light rare earth element contents yield a Th-Pb age of ca. 163 Ma from the Mount Grace carbonatite and U-Pb weighted mean and upper intercept ages of ca. 130 Ma from the Three Valley Gap carbonatite and syenite in the Monashee Complex and the Trident Mountain syenite in the Selkirk allochthon. Our data identifies a Jurassic hydrothermal event that affected carbonatites in both the Monashee complex and Selkirk allochthon, argued by some authors to have been tectonically separated until the Upper Cretaceous-Paleocene. Mineral Pb isotopic analyses from the same four carbonatites and syenites and one sediment-hosted magnetite-rich ore deposit reveal a highly radiogenic linear trend inconsistent with traditional closed-system models, likely indicating mixing between radiogenic Pb derived from clastic sedimentary sources and Pb in the alkaline bodies. This, along with the robust Late Devonian zircon age of the underlying Mt. Grace carbonatite, calls into question the validity of the shale curve model age for the Cottonbelt Pb-Zn deposit and helps resolve a longstanding age conundrum. Our findings refine the timing of Late Devonian carbonatite-alkaline magmatism along the western Laurentian margin, reveal a previously unrecognized Jurassic hydrothermal event that affected both the Monashee complex and Selkirk allochthon during Cordilleran orogenesis, and address a decades-old age conundrum in the Monashee complex leading to determination of a ca. 360 Ma maximum depositional age of the Monashee complex. More broadly, this study underscores the potential of hydrothermal zircon to date fluid-mediated events in carbonate-rich systems, offering a new framework for interpreting isotopically disturbed datasets in mineralized terranes.

Deformation microfabrics of anhydrite rock, collected from the Gorleben salt dome of northern Germany, revealed brittle-viscous deformation accommodated by fracturing, twinning, kinking, subgrain formation, straininduced grain boundary migration, and incongruent dissolution-precipitation creep (IDPC), which led to stylolites aligned oblique to bedding. IDPC along the stylolite planes is documented by magnesite, which developed as a new phase replacing anhydrite. U-Pb dating of large primary anhydrite crystals yielded 251 +/- 18 Ma interpreted as formation age. U-Pb dating of stylolite-magnesite, on the other hand, yielded Oligocene and Miocene ages, which reflect the time of deformation and stylolite formation after the main phase of diapir emplacement. Experimental deformation of a competent (brittle-viscous) anhydrite layer, embedded in incompetent viscous rock salt matrix, at temperature, T = 345 degrees C, strain rate, e(center dot) = 10-7 s- 1, and a shortening strain, eZ = -30%, led to boudinage of the anhydrite layer by tensile fracture. Primary fluids, trapped in fluid inclusions of anhydrite, became mobile during boudinage but were not able to escape through the enclosing rock salt, which acted as a sealing matrix. This sealing behavior explains the lack of stylolites in rock salt and is important for cavern industries and for the long-term safety of a repository for radioactive waste in salt structures. Moreover, the experimental deformation had a significant impact on the U-Pb isotopic system of both anhydrite and magnesite. Apart from one Miocene age of magnesite, with a large uncertainty, both yielded largely perturbed data, which cannot be used to calculate robust ages.

The age of the mylonite belts in the basement rocks of the Pyrenees is a subject of debate in the structural geology and petrology communities because of its potential implication on the regional tectonothermal history and on the tectonic evolution of SW Europe. Here we address when and how mylonitisation took place in two key areas of the Eastern Pyrenees, where shear zones are associated with Giant Quartz Veins (GQVs). We conducted zircon U-Pb and muscovite Ar-40/Ar-39 dating coupled with structural, textural, and crystallographic preferred orientation (CPO) analyses of mylonites from the Cap de Creus and Canig & oacute; Massifs. U-Pb zircon dating of a dacite porphyry dyke crosscut by GQVs and mylonitic bands yields a maximum shear zone and GQV formation age of ca. 292 +/- 3 Ma. Ar-40/Ar-39 analyses of muscovite within mylonitised GQVs yield initial crystallisation ages between ca. 164 and 188 Ma, as well as younger recrystallisation ages of ca. 110-118 Ma. A qualitative assessment of the GQV history is inferred from step-heating spectra of muscovite and quartz CPOs. The results indicate that GQV formation and mylonitisation were coupled, coeval, and long-lasting processes that took place from early Jurassic to early Cretaceous times. A comparative evaluation of quartz CPOs reveals inconsistencies regarding the strain distribution, quartz slip systems activity, and deformation temperatures depending on the deformed rock type. Quartz mylonites have stronger CPOs dominated by basal , prism , or prism slip systems, whilst phyllonites and granite mylonites show weaker fabrics mostly dominated by mixed slip. This apparently suggests higher deformation temperatures in quartz mylonites than those inferred from more reliable proxies, such as mineral assemblages, brittle behaviour of K-feldspar, and fluid inclusion data. We suggest that the water-weakening effect caused by coeval formation and deformation of GQVs enabled easier dislocation glide and creep, allowing strain localisation and transitions between slip systems at lower temperatures than commonly inferred due to enhanced ductility. U-Pb zircon dating further suggests the existence of an early Carboniferous (ca. 332 +/- 4 Ma; Visean) magmatic episode in the Pyrenees, in agreement with a cyclic, rather than a progressive, geodynamic history of the region during Variscan times. The present work challenges classical interpretations stating that Pyrenean mylonite belts developed during the retrograde stages of the Variscan Orogeny, highlighting that the structural evolution of this region during Mesozoic times deserves further investigation. Results have implications for interpreting deformation localisation mechanisms and conditions in crustal rocks, for the formation mechanisms of GQVs in worldwide orogenic belts, and for the tectonothermal history of the Pyrenees since late-Variscan times.

We integrate provenance, sedimentological and tectonic analyses to reconstruct sediment sources, transport pathways and hydroclimatic evolution of the Rotliegend Group in the Norwegian North Sea. The study also evaluates implications for basin development and reservoir quality in this key reservoir interval. Detrital zircon U-Pb geochronology from nine wells integrated with facies analysis, dipmeter- and image-derived palaeocurrent data and a palinspastic restoration reveals that sediment sources were closer to the basin than today and that inherited structural highs compartmentalized drainage and aeolian fields. Facies trends record a transition from arid dune fields to semi-arid mixed dune, interdune, flash-flood and playa-lake systems, reflecting increasing hydrological connectivity and base-level rise during the early Permian. Detrital zircon spectra define three main provenance domains with Caledonian-derived aeolian sand transported from the west-northwest, Sveconorwegian-sourced alluvial-fan systems along the eastern basin margin and hybrid basement-fed systems along northern and southern highs. Mixed zircon-age populations indicate substantial recycling of Devonian Old Red Sandstone basin fills and convergence of multiple sediment transport pathways within the basin interior. Converging transport pathways enabled interaction between long-distance and short-range detrital zircon input, whereas sustained pathway partitioning maintained distinct first-order provenance domains at basin scale. Provenance influences reservoir quality through its control on sediment composition, texture and depositional facies, with quartz-rich Caledonian-derived aeolian deposits retaining anomalously high porosities and feldspathic Sveconorwegian-derived alluvial-fan deposits displaying consistently lower porosity. Integrating provenance, facies, palaeocurrents and restored basin geometry therefore provides a predictive framework linking sediment transport, tectonic inheritance, and reservoir distribution in ancient continental basins.

Fluorite is a common mineral in low-temperature (<300 °C) hydrothermal environments and often occurs in mineral associations that are notoriously challenging for radiometric age dating. In this study, we apply both U-Pb LA-ICP-MS and Sm-Nd MC-ICP-MS isotope geochronology to two distinct generations of fluorite from the Niederschlag deposit in the Erzgebirge/Krušné Hory region in SE Germany. Two economically relevant and genetically distinct fluorite generations have been recognized at the Niederschlag deposit. The older generation is marked by small crystal sizes, distinct color banding and a close association with chalcedony. This is very distinct from the younger generation of fluorite that is typically coarse crystalline and associated with abundant barite and minor base metal sulfides. Stage I fluorite yields a Sm-Nd age of 289 ± 20 Ma and U-Pb LA-ICP-MS ages of 230 Ma -156 Ma. The 289 ± 20 Ma Sm-Nd age is consistent with a previously proposed magmatic-hydrothermal origin of this fluorite generation suggesting an affiliation with post-Variscan magmatism. Indeed, the 143Nd/144Nd versus 1/Nd relationships of the analyzed aliquots do not indicate isotopic mixing. The U-Pb dates of 230.2 ± 3.6 to 221.8 ± 6.8 Ma are analytically robust but significantly postdate regional magmatism. These younger dates do coincide with regional apatite fission track data and fluorite/zircon-derived U-Th/He ages that have previously been thought to date the cooling of the crust after crustal thinning and rifting during the Permo-Triassic period. Based on our petrographic observations and the thermal history of the region, we interpret the U-Pb ages for fluorite as cooling-related re-equilibration ages. The younger stage II fluorite mineralization was dated by Sm-Nd to 182 ± 33 Ma. A U-Pb LA-ICP-MS age could not be obtained due to unfavorable low U/Pb ratios. This Mesozoic age fits well into the framework of unconformity-related fluorite-barite-base metal mineralization that is found across Central and Western Europe. We conclude that U-Pb and Sm-Nd isotope records of polyphase fluorite mineralization at the Niederschlag deposit relate to three well-known large-scale geotectonic events. We further suggest that geochronological studies of vein-hosted fluorite mineralization should always consider more than one isotope system.

The dating of supergene copper minerals has been widely used as a proxy to investigate the evolution and onset of hyperaridity in the Atacama Desert. However, investigation of supergene copper mineralisation in the Atacama Desert has been restricted to two physiographic units favourable for the industrial extraction of copper: the Central Depression and the Precordillera. Furthermore, these studies dated the timing of supergene mineralisation by secondary non-copper minerals like alunite. In this study, we present new results of LA-ICP-MS U-Pb dating of chrysocolla from supergene deposits hosted in the western part of the Coastal Cordillera of northern Chile. The obtained U-Pb ages range from 8.0 +/- 1.2 to 0.045 +/- 0.027 Ma. Supergene mineralisation ages point to significantly reduced precipitation, necessary for leaching and mineral precipitation process, since the Late Miocene to Pleistocene in the Coastal Cordillera, later than the secondary supergene mineralisation ages from the Precordillera. The data point to repeated phases of sufficient moisture along the Coastal Cordillera that promoted chrysocolla mineralisation during the Pliocene and Pleistocene. We propose that due to the position of the study areas near the coastal escarpment, and the predominant hyperarid environment in this part of the Coastal Cordillera since at least the Mid-Miocene, pluvial periods and/or intensification of coastal fog events caused alternating phases of supergene activity.

Calcic garnet is a common component of skarns, alkaline igneous rocks and carbonatites. Recent studies report garnet laser ablation-ICP-MS U-Pb ages ranging from ca. 20 to 3100 Ma demonstrating the advantages of garnet for U-Pb geochronological studies. However, calibration using well-characterised matrix-matched reference materials is a critical issue for accurate age determinations. In this study we present the major and trace element compositions, and U-Pb systematics obtained from isotope dilution-TIMS and LA-ICP-MS measurements for Kovdor (Kovdor-GRT) andradite-shorlomite-morimotite garnet (Kola Alkaline Province, Kola Peninsula) as a potential reference material for LA-ICP-MS U-Pb dating. ID-TIMS gave 206Pb/238U, 207Pb/235U and 207Pb/206Pb Pbc-corrected weighted mean ratios of 0.06008 +/- 0.00018 (2s, MSWD = 4.5), 0.4495 +/- 0.0013 (2s, MSWD = 1.6) and 0.0542 +/- 0.0006 (2s, MSWD = 0.001), respectively. The weighted mean 206Pb/238U age is 376.50 +/- 0.9 Ma (MSWD = 1.3), the 207Pb/235U age is 376.5 +/- 0.62 Ma (MSWD = 0.83) and the 207Pb/206Pb age is 380.6 +/- 1.7 (MSWD = 0.27). The Concordia age of 376.6 +/- 0.86 Ma (MSWD = 0.79) for Kovdor-GRT, determined by ID-TIMS, is interpreted as the best estimate for its crystallisation age. The low common Pb (Pbc) content (Pbc/Pbt varies from 0.05 to 0.08), moderate U mass fraction (12.4-33.0 mu g g-1) and isotopically homogeneous composition allowed meaningful 206Pb/238U age determinations using various LA-ICP-MS systems. LA-ICP-MS measurement results are characterised by precisions fit for purpose and yield consistent 206Pb/238U ages indistinguishable from those obtained by ID-TIMS. The results highlight the potential of Kovdor garnet as a reference material for in situ U-Pb dating.

In situ garnet U-Pb geochronology by laser ablation-inductively coupled mass spectrometry (LA-ICPMS) is a powerful tool for rapid and high-spatial resolution dating of metamorphic pressure-temperature–time histories. Yet, the substitution of U and Pb into the structure of common pyralspite garnet and its influence on diffusion and potential age-resetting is poorly constrained. Studies by Mezger et al. (1989), Burton et al. (1995), and Dahl (1997) estimate U-Pb system closure temperatures in garnet of >800 °C. Similarly, Shu et al. (2024) proposed a closure temperature of >1100 °C but suggested that recrystallization may have reset some garnet U-Pb ages. However, there is little information on how dynamic processes, such as recrystallization, may impact the closure of the U-Pb system in garnet. Here we examine the impacts of garnet recrystallization on U-Pb ages by examining ultrahigh-temperature (UHT) crustal xenoliths from the southwestern USA and northern Mexico. These metapelitic granulites experienced isobaric heating at >900 °C between 36 and 30 Ma and UHT conditions were maintained until eruption at

Overridden continental margins preserve critical records of crustal growth, magmatic activity, and pre-orogenic topography, yet they are rarely accessible in situ. In the European Alps, the distal southern European margin is only exposed within the Tauern Window. An additional, unique archive of this margin basement is, however, provided by exotic granitoid blocks and boulders preserved in the Ultrahelvetic nappe system in the Alpine fold-and-thrust-belt. In the Ultrahelvetic slope setting at the passive margin, coarse-grained rock fall and debris flow material was deposited in pelagic sediments during opening and closure of the Penninic Ocean. These sedimentary successions were later accreted into the Alpine wedge and transported northwards, allowing the exotic basement clasts to escape subduction and pervasive Alpine metamorphism. As a result, Ultrahelvetic granitoid boulders preserve a unique record of the southernmost European basement.This archive forms the first sample suite and is complemented by sandstone samples hosting the boulders as well as drillcore samples from beneath the Alpine wedge. Whereas the drillcores sample the autochthonous basement adjacent to the Bohemian Massif, the samples from the Ultrahelvetic nappe system represent the most distal part of the European margin. To explore this largely hidden margin, we carried out U–Pb zircon dating on samples from all three archives.Drillcores from five basement samples beneath the northern Alpine wedge and the Molasse Basin range from Early Proterozoic orthogneisses (Mank drillcore) to Permian granodiorites (Moosbierbaum and St. Corona drillcores). Ordovician protolith ages (Großgraben and Oberndorf drillcores) correlate with known Bohemian Massif units, while late Variscan granites document post-collisional magmatism beneath the Molasse Zone.In contrast, the Ultrahelvetic exotic granitoid boulders provide direct information on the distal European margin. Previous geochronological data suggested exclusively Late Devonian ages and, in conjunction with geochemical analyses led to interpretation of these rocks as products of a marginal high (Frasl & Finger, 1988). Our new data reveal a much more differentiated record, with four magmatic pulses: Ordovician (~466–480 Ma), Late Devonian–earliest Carboniferous (~360–380 Ma), Carboniferous (~320–340 Ma), and Permian (~290–280 Ma). Following an Ordovician magmatic event, Late Devonian and Carboniferous ages record Variscan magmatism. Permian ages reflect post-Variscan extension preceding Jurassic rifting. We infer derivation of the exotic boulders from a topographically elevated marginal high, a characteristic feature of rifted passive margins. Notably, the exotic boulders are petrographically and geochronologically similar to the Zentralgneise of the Tauern Window, suggesting that this window exposes an equivalent distal margin basement.In sum, our Ultrahelvetic samples revealed that the crustal rocks at the southern European margin were formed by multi-stage magmatism between the Ordovician and the Permian. Reworked boulders of these rocks occur in Paleogene slope deposits and can be used as a proxy for crustal domains of the distal European margin, allowing us to reconstruct Penninic rifting, Variscan tectonics, and passive-margin architecture by effectively “lifting the orogenic lid.”Frasl, G., & Finger, F. (1988). The "Cetic Massif" below the Eastern Alps - characterised by its granitoids. Schweiz. Mineral. Petrogr. Mitt., 68, 433 - 439.

Early Jurassic volcanism was in the southern north Victoria Land portion of the Ferrar Large Igneous Province preceded by multiple phases of shallow-level intrusions of Ferrar sills into the 300 m thick cover of sedimentary rocks of the Triassic-Jurassic Victoria Group. Upward protrusions from sills into unconsolidated water-saturated sandstones triggered phreatomagmatic eruptions, forming discordant diatremes. Associated mafic volcaniclastic subaerial sediments are intercalated in the stratigraphic succession at two levels. Based on palynostratigraphy, their ages are late Pliensbachian and Early Toarcian, respectively. The matrix of the mafic volcaniclastic deposits is enriched in the individual minerals of the presently cemented fluviolacustrine country rocks. Clasts of the metamorphic and granitic basement are absent. The igneous clasts are comagmatic, comprising fragmented sill magma as well as scoriaceous juvenile lava shreds and bombs, some of which form welded deposits. All comagmatic and juvenile clasts, as well as those local pillows and lava flows embedded in the phreatomagmatic deposits, are of low-Ti andesitic composition (Cr < 80 ppm) and thus identical to the sills. Subsequent effusive volcanism (Kirkpatrick flows) started as low-volume lava flows and pillowed lava of more primitive low-Ti basaltic andesite composition (Cr > 100 ppm).

This paper provides a review of Late-Paleozoic skarns in the Erzgebirge/Krusne hory region (Germany/Czech Republic) with a particular emphasis on the Aue-Schwarzenberg and Geyer-Ehrenfriedersdorf Districts that host the most prolific skarn systems. Most skarns in the Erzgebirge replace carbonate units that occur intercalated with metamorphosed sedimentary and volcano-sedimentary host rock successions of pre-Variscan age. Skarn compositions range from calcic to magnesian, depending on the protolith. The timing of skarn formation is constrained by U-Pb ages of garnet and cassiterite, ranging from similar to 340 to similar to 295 Ma, broadly coinciding with different episodes of late- to post-Variscan magmatism. Textural and geochronological data implies that many of the skarns are multi-generational, with hiatuses between individual stages of up to 5 -10 Ma, indicating that they are the product of several magmatic-hydrothermal events. Early skarns are commonly characterized by skarnoid textures typical for heat-dominated metasomatism (rock-buffered), whereas younger skarns mainly show metasomatic textures and open space-infill typical for fluid-dominated metasomatism (fluid-buffered). We postulate that the relationship between timing and texture is related to uplift and exhumation of the Erzgebirge following the collisional phase of the Variscan orogeny. Most of the Sn mineralization is hosted in cassiterite, commonly intergrown with retrograde actinolite and chlorite. However, a significant portion of Sn remains locked within prograde calc-silicate phases (e.g., malayaite, Sn-bearing garnet), rendering it inaccessible for economic extraction. Indium mineralization is mainly hosted by sphalerite and less importantly other sulfides that are also associated with the retrograde stage. Scheelite is the main host of W, which shows a preferred affiliation to calcic skarns and occurs during the pro- and retrograde stage.

Transfer fault zones are commonly associated with volcanic activity. While geochronological methods such as the UPb and ArAr dating have been traditionally used to establish the absolute timing of volcanism, recent advances allow us the dating of fracture-filling minerals. However, integrated tectono-volcanic and geochronological studies of fault zones are scarce, limiting our ability to constrain accurately the evolution of fault-controlled volcanic zones.This paper reviews the tectono-volcanic history of northeastern Iberia through the geochronological and kinematic analysis of well-known examples of Neogene to Quaternary fault zones with associated volcanism along the Transverse Ranges. These fault zones are located at the northwestern tip of a NW-SE transfer zone that segmented the Liguro-Provençal Rift. We integrate available geological and geophysical data with new structural analysis of meter scale fractures across three fault zones and UPb dating of fracture-filling carbonates.The UPb dating of fracture-filling calcite reveals early Eocene strike-slip faulting at ∼49 Ma, during the Alpine compression, and synchronous strike-slip and extensional dip-slip faulting from ∼22 to ∼2 Ma, coinciding with the Liguro-Provençal rifting. We propose a new lithospheric-scale model in which faults acted as sub-vertical conduits for the ascent of magmas sourced from the lithosphere-asthenosphere boundary, based on the composition of recovered xenoliths. Our geochronological dataset supports the hypothesis that fault reactivation governs the timing, location and migration of volcanism in the Neogene to Quaternary Catalan Volcanic Zone, which was additionally influenced by lithospheric thinning and the development of transfer fault zones that potentially reflect the reactivation of Mesozoic structures. These processes share striking similarities with those observed in the western Mediterranean Region, the European Cenozoic Rift System, and other extensional systems worldwide, highlighting the role of inherited transfer fault zones in the evolution of volcanism.

Abstract. Advances in laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) have largely focused on improving spatial resolution through progressively smaller laser spot sizes. Here, we explore the opposite end of the analytical limits by investigating the lower concentration limits of in-situ U–Pb geochronology in garnet. Using a Neptune Plus multi-collector ICP-MS equipped with seven ion counters, we developed an analytical workflow specifically designed for metamorphic garnet with ultra-low U concentrations. The method was used to date garnet from a wide range of ages and geological settings, including granulites, eclogites and hydrothermal demantoids. Uranium concentrations were exceptionally low, even below 1 ng/g in some cases. At these concentrations, the total amount of uranium ablated during a single analysis is at femtogram levels, more than three orders of magnitude lower than that of a typical in-situ analysis of zircon. Despite these extremely low signal intensities, geologically meaningful ages were obtained for the analysed samples. Analytical precision depends on the U and radiogenic Pb concentrations, but we have obtained precisions of ca. 5–6 % for garnet containing less than 1 ng/g U. In garnet with higher U concentrations or ages as old as the Archean, internal precision of ca. 1 % may be achieved. These results expand the applicability of in-situ garnet U-Pb geochronology to the vast majority of metamorphic garnet, providing a powerful new tool for constraining garnet growth, prograde metamorphism, and deep crustal evolution.

The Bitlis-Pütürge Suture between Arabia and Eurasia records protracted Neotethys subduction, culminating in continental collision and the construction of the Southeast Anatolian collisional orogen and associated orogenic plateau. Here, we integrate detrital zircon, rutile, and apatite U-Pb geochronology with zircon Hf isotope analysis of Upper Miocene siliciclastic sediments from DSDP Sites 375/376 and ODP Site 968 in the northern Eastern Mediterranean to explore the offshore archive of detritus eroded from the Bitlis-Pütürge Suture and to reconstruct the tectono-magmatic evolution of Arabia-Eurasia convergence. Detrital age spectra are dominated by Late Cretaceous, Eocene, and Miocene populations and closely resemble those of coeval sediments in southern Anatolia and northern Cyprus, indicating a dominant source in the Southeast Anatolian Orogenic Belt and defining a regionally coherent sediment-routing system established during Arabia-Eurasia collision. Integration of the detrital record with published datasets from eastern Anatolia delineates four stages of convergence: (1) incipient convergence (∼105–90 Ma) marked by subduction initiation and juvenile arc magmatism; (2) peak subduction-accretion (∼90–70 Ma) characterized by evolved arc magmatism, high-grade metamorphism, slab rollback-driven upper-plate extension, rapid exhumation, and large-scale ophiolite obduction; (3) late subduction-extension (∼55–45 Ma) involving renewed subduction and rollback, juvenile back-arc magmatism, high-grade metamorphism, and rapid exhumation; and (4) orogenic climax (∼25–5 Ma) associated with continental collision, slab break-off and/or lithospheric delamination, syn- to post-collisional magmatism, orogen growth, plateau uplift, and enhanced sediment flux into the Eastern Mediterranean. Zircon Hf isotopes indicate long-term reworking of Cadomian crust with variable mantle input during Neotethys convergence. A marked increase in juvenile signatures after ∼13 Ma suggests enhanced mantle input and subcrustal processes contributing to Middle-Late Miocene uplift of the Eastern Anatolian Plateau. Collectively, the data define a ∼100 Ma-long orogenic cycle in the Neotethys and establish a refined tectonic framework for the western Arabia-Eurasia convergence system within the broader Alpine-Zagros-Himalaya orogenic realm.

The Arabian-Nubian Shield (ANS) is a classic example of Neoproterozoic crustal growth. Its prime and oldest crustal constituents are island-arc terranes, comprising principally Tonian, juvenile intra-oceanic magmatism. Herein we present a coupled U-Pb-Hf-O study of detrital zircons retrieved from Tonian metasedimentary sections storing island-arc detritus in the northern ANS (Eilat area, Israel), intended to explore ANS arcs juvenility and crustal reworking processes. Detrital zircon U-Pb geochronology places island-arc activity at ca. 1040-740 Ma, peaking between ca. 870-740 Ma. Juvenile arc crust formation is demonstrated by predominant positive epsilon Hf(t) values of +6 to +12 in zircons with mantle-like 518O (5.0-6.5%o), commencing at ca. 1040 Ma, thus designating one of the oldest uncontaminated magmatic phases in the ANS. The predominance of positive epsilon Hf(t) values, alongside only two Paleoproterozoic grains detected, precludes substantial incorporation of older crustal components in the (mainly) Tonian island-arc system. This confirms that the juvenile island-arc edifice was chiefly intra-oceanic, isolated from pre-Neoproterozoic continental margins during its entire history. Although constantly positive, zircon epsilon Hf(t) values temporally decline, implying continuous reworking of preceding juvenile island-arc crust. Reworking is further highlighted by abundant zircons with high 518O values (6.5-9.6%o) that indicate assimilation of 18O-rich supracrustal components, likely sediments, in arc magmas. Numerous zircons yielded both high epsilon Hf(t) and 518O values, suggesting their parent magmas assimilated juvenile, volcanogenic island-arc detritus. Mixing modeling indicates that as much as 10-40% of such sediments were assimilated into arc magmas between ca. 940 and 740 Ma, suggesting continuous cannibalization of juvenile sediments throughout most of the arc system's lifespan. Crustal reworking and sediment assimilation may have promoted crust maturation, resulting in declining epsilon Hf(t) values and culminating with quartzofeldspathic intrusions during the mid-Tonian. The present work therefore highlights the essential role of sedimentary assimilation and crustal reworking in the evolution of juvenile ANS island arcs.

Tectonic overprinting in polyorogenic zones hampers the reconstruction of the fracture and fluid history in basement rocks involved in successive tectonic events. In this regard, geochronological methods such as the U-Pb dating of fracture-filling carbonates enables the identification fractures formed during different orogenic cycles. In this study, we present 23 reliable U-Pb ages of fracture-filling carbonates crosscutting Carboniferous limestones within the Cabuerniga Fault System in the Cantabrian Mountains, incorporated into the Alpine Pyrenean-Cantabrian Orogen. Structural analyses of fractures of eight well-exposed fault zones reveal orientations comparable to E-W, NE-SW and NW-SE Variscan structures. The obtained U-Pb ages ranging from 280.8 f 2.7 Ma (Early Permian) to 4.71 f 2.59 Ma (Early Pliocene) are grouped into three main clusters: 1) Early Permian-Late Triassic (280.8 f 2.7 to 237.0 f 5.3 Ma), recording post-orogenic extensional collapse of the Variscan Orogen and the coeval onset of the North Iberian Rifting cycle (Kungurian to Carnian); 2) Early-earliest Late Cretaceous (144.5 f 5.2 to 107.5 f 5.9 Ma), corresponding to extension during the opening of the Bay of Biscay and coeval with Zn-Pb mineralization in faults and diapirs from the Cantabrian Zone and the overlying Basque-Cantabrian Basin (Berriasian to Albian); and 3) Early Oligocene-Middle Miocene (30.26 f 0.76 to 13.99 f 0.78 Ma), constraining the Alpine Orogeny compression during the Iberia-Eurasia collision (Rupelian to Langhian). The youngest Pliocene age of 4.71 f 2.59 Ma (Zanclean) records later extensional collapse of the Pyrenean-Cantabrian Orogen. The widespread occurrence of Mesozoic F-Ba and Pb-Zn mineralization across the Iberia reveals the critical role of Alpine Cycle extensional tectonics in driving large-scale fluid systems that played a crucial role in the Alpine tectonic overprinting of the Variscan basement. This tectonic event established hydraulic conductivity between the Paleozoic basement and the overlying Mesozoic cover, governing the transport and trapping of mineral resources.