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The Morelos district, located in the center of the Guerrero gold belt, Guerrero State, southern Mexico, has been the site of several recent gold ± copper skarn discoveries (total of ~8.5 Moz Au) associated with Upper Cretaceous-Paleocene granodiorite intrusions. The Limon, Guajes, and Media Luna skarn deposits developed along the contact of the El Limon granodiorite and the sedimentary host rocks. Native gold is associated with retrograde alteration of garnet-pyroxene skarn and is accompanied by native bismuth as well as telluride and sulfide minerals. The Media Luna deposit is characterized by a distinct magnesium-rich skarn mineralogy and contains an average of ~1 wt % Cu, in addition to gold and silver. This distinguishes it from the other gold-only skarn deposits in the Guerrero gold belt. This observation suggests that skarns in the Guerrero gold belt, which replaced magnesium-rich sedimentary protoliths, may host significant copper resources in addition to gold. Uranium-lead laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) zircon ages of the El Limon granodiorite range from 66.86 ± 0.40 to 65.88 ± 0.79 Ma. Preskarn molybdenite-quartz veins cut through the El Limon granodiorite and yield Re-Os molybdenite ages between 66.63 ± 0.22 and 65.55 ± 0.25 Ma. A series of pre-, syn-, and postskarn porphyritic dikes intruded the El Limon granodiorite, having zircon ages ranging from 65.9 ± 1.1 to 64.68 ± 0.38 Ma. The timing of skarn formation at Limon and Media Luna was constrained to 64.6 ± 1.2 to 63.2 ± 1.0 Ma, applying U-Pb LA-ICP-MS to garnet. The ubiquitous presence of garnet in skarn deposits and the time- and cost-efficiency of in situ geochronology are striking advantages of this method to constrain the timing of mineralization.

The area northeast of Sudbury, Ontario, is well known for hosting one of the largest unexplained geophysical anomalies in the Canadian Shield, the Temagami Anomaly. In search of a geological explanation for this anomaly, low-grade metamorphic ultrabasic dykes have been discovered in the overlying Huronian Supergroup sedimentary rocks, both in outcrop and in a deep drill core. Here, we report on the first geochemical and geochronological data obtained on these dykes and compare these data with known magmatic units in and around the 1850 Ma impact-generated Sudbury Igneous Complex (SIC). The NW-striking dykes, which cut across sedimentary rocks of the ca. 2.3 Ga Cobalt Group, and which are, in turn, crosscut by pseudotachylitic breccia, are characterized by distinctively high concentrations of Ti, P, Nb, and Zr, highly fractionated rare earth element patterns (La/YbN 7.6–15.5), and a lack of crustal contamination (Nb/Th > 10). Such features are typical of modern ocean island basalts but very different from Palaeoproterozoic rocks previously documented in the wider region. Multigrain U–Pb laser ablation inductively coupled plasma mass spectrometry analyses performed on magmatic titanite and apatite with high Th/U ratios yielded 1876.0 ± 8.7 and 1880.9 ± 8.3 Ma, respectively, which we interpret as the intrusion age of the dykes. This interpretation is supported by similar whole-rock Sm-Nd model ages of 1890–2000 Ma (initial εNd +2.5). This magmatic event in the footwall of the SIC shortly before the impact was coeval with, and likely genetically related to, the 1.88–1.87 Ga Circum-Superior Large Igneous Province.

Petrographic observations and in situ U–Pb ages of melilitites, foidites, basanites, phonolites, and trachytes from the southern part of the Central European Volcanic Province (CEVP) and related plutonic inclusions therein reveal two distinct age groups separated by a gap of ~ 20 Myr. A late Cretaceous to early Eocene group (~ 73–47 Ma; Taunus, Lower Main plain, Odenwald and Kraichgau area, Bonndorfer Graben and Freiburger Bucht area, Vosges and Pfälzerwald) is characterized by nephelinites and basanites mostly devoid of melilite and perovskite, and by rare haüynites, and trachytes. In contrast, a late Oligocene to late Miocene group (~ 27–9 Ma; Lorraine, southern Upper Rhine Graben, Urach, Hegau area) is dominated by melilitites, melilite-bearing nephelinites (both carrying perovskite), and phonolites. Both magmatic episodes are related to domal topographic uplift, erosion, and formation of major angular unconformities in the Upper Rhine Graben, suggesting an association with dynamic topography interrupted by phases of subsidence (or abatements of uplift). The investigated rocks in the southern CEVP (south of a line Eifel–Vogelsberg–Rhön–Heldburg), except for the Kaiserstuhl volcanic complex, mostly comprise small and isolated occurrences or monogenetic volcanic fields, whereas the northern CEVP is dominated by large volcanic complexes and dyke swarms, which are mostly SiO2-saturated to weakly SiO2-undersaturated. In the northern CEVP, evidence of spatially varying but recurrent volcanic activity exists since the Eocene, lacking the distinct 20 Myr gap as documented from the southern CEVP. While the temporal and spatial distribution of volcanism are a result of the Cretaceous to Miocene tectonic evolution in Central Europe, further studies are needed to explain the petrographic differences between the two age groups in the south.

Metarodingites are metasomatized mafic dykes that are embedded within serpentinized mantle rocks and commonly contain garmet. Garnet in this rock type has the potential to preserve compositional and chronological information of the entire metamorphic-metasomatic evolution, from the ocean floor to deep subduction. In this study, we investigate the chemical and chronological record of garnet from chloritized metarodingites and garnet veins, from the Zermatt-Saas unit (Unter Theodulgletscher unit and Pfulwe pass). Compositional major and trace element maps reveal that a first generation of Ti-rich garnet is consumed during chloritization, while a second generation of Ti-poor garnet grows in textural equilibrium with chlorite and titanite. In both metarodingite and garnet vein, garnet rim displays an enrichment in Cr, suggesting that late garnet records the infiltration of fluids equilibrated with serpentinites. Fluids liberated from dehydrating serpentinites infiltrate the metarodingite leading to the first garnet generation dissolution, chloritization and titanite crystallization. To validate this hypothesis, we performed LA-ICPMS U-Pb dating of garnet, titanite and zircon. U-Pb dating of garnet core and rim, returned overlapping ages between ca. 44 and 46 Ma, which coincide with previous estimation of peak metamorphic conditions. Titanite from the metarodingite samples yields an age of ca. 45 Ma, which indicates that fluid release and chloritization occurred indeed at peak conditions. Garnet veins cutting across the foliation of the metarodingite and associated titanite are instead resolvably younger and yield ages of ca. 38-39 Ma and ca. 36 Ma, respectively. Zircon in chloritized mafic dykes from Pfulwe pass consists of a Jurassic magmatic core and a metamorphic rim of ca. 47 Ma, confirming that the major fluid-release event and related metasomatism occurred between 45-47 Ma. Rutile yields a younger age of ca. 34 Ma, probably linked to re-setting during exhumation. In conclusion, we show how garnet from metarodingites preserves the metamorphic-metasomatic history and can be used to gather information on (de)hydration reactions during subduction. The consistency of our multi-mineral geochronological data further indicates that petrochronology of garnet from metarodingites is a robust way to track in time metasomatic events in the subducted oceanic lithosphere.

Garnet xenocrysts from kimberlites provide unique insights into the composition, structure and evolution of the subcontinental lithospheric mantle (SCLM). For example, different metasomatic events in the SCLM are reflected in compositional differences between garnet xenocrysts. As mantle metasomatism largely controls the physical and chemical properties of the SCLM, it exerts first order control over the genesis of kimberlitic magmas and diamond formation. However, dating mantle lithologies and processes is complicated by high ambient temperatures that allow the equilibration of most isotopic systems up to the time of kimberlite eruption. As a consequence, the temporal connection between metasomatic events in the mantle and kimberlite genesis is commonly ambiguous.In this study, we applied LA-ICPMS U-Pb dating to 43 harzburgitic, lherzolithic and megacrystic garnet xenocrysts from the ~376 Ma diamondiferous V. Grib kimberlite, Russia, in order to investigate the link between different types of mantle metasomatism and kimberlite genesis.Our results indicate that, with two possible exceptions, only harzburgitic garnet overlaps in age with the kimberlite eruption, whereas lherzolitic and megacrystic garnet crystals are ~20 to 130 million years older. Furthermore, garnet U-Pb ages and Ni-in-garnet temperatures of ~820 to 1200 °C do not correlate. This, and the high closure temperature of U-Pb in garnet (≥900 °C) suggests that the garnet U-Pb ages indeed reflect metasomatic events in the SCLM. However, the U-Pb ages could also reflect cooling ages. In this case, the metasomatic events recorded in the garnet crystals must still have occurred up to ~130 million years prior to the eruption of the V. Grib kimberlite.These findings have far-reaching implications for the genesis of (diamondiferous) kimberlites, as they clearly show that the time lag between metasomatic events in the SCLM, as recorded in kimberlitic garnet xenocrysts, and kimberlite eruption may extend to tens of millions of years.

Understanding the disruption of a tectonic nappe that experiences a subduction-related pressure temperature (P-T) loop is challenging. Thrust imbrications may disrupt single nappes during its subduction and/or exhumation which can be revealed by detailed petrological and geochronological work. Garnet commonly forms during subduction. It most likely hosts early prograde, peak high-pressure (HP) and subsequent metamorphic mineral inclusions making such assemblages a useful tool for detailed petrological and geochronological investigations. Multiple approaches were used to determine the detailed P-T loop of the Cycladic Blueschist Unit passive margin sequence (Greece) such as Zr-in-rutile thermometry coupled with quartz-in-garnet elastic barometry, average P-T and phase equilibrium thermodynamic modeling. U-Pb garnet and zircon geochronology age data were in addition determined to complement already existing age data.The results of this approach reveal that the passive margin sequence in Thera (Santorini), Ios and Naxos was subducted as a coherent continental fragment at a subduction rate of ~2.1 km/My and a heating rate of ~12 °C/My. Prograde and peak HP metamorphism occurs at c. 50 and c. 40 Ma respectively. Along Thera, Ios and Naxos, prograde and peak P-T condition increase from sub-blueschist to upper blueschist facies metamorphism. Subsequently, the sequence was disrupted by one or several thrust faults during its exhumation. The passive margin sequence of Naxos was thrust onto the Ios sequence during the Oligocene at c. 30 Ma. This imbrication is revealed by different exhumation rates of ~6 km/My for the passive margin sequence of Naxos and of ~3 km/My for the one of Ios. The passive margin sequence of Thera, Ios and the upper part of Naxos was exhumed to upper crustal levels, whereas the lower part of the Naxos passive margin sequence was exhumed to the lower crust leading to thermal relaxation of 9–96°C following tectonic accretion. This indicates that thermal relaxation following tectonic accretion in the Cyclades controlled the thermal evolution of the evolving Cycladic orogen during a tectonically quiet period before lithospheric extension.

The Saharo-Arabian desert is part of the largest near-continuous chain of drylands stretching from north-western Africa to the northern China. This harsh and often hyper-arid belt acts as a transition zone separating major biogeographic realms, including the Palearctic, Afrotropics and Indomalayan. This aridity is thought responsible for the creation of unique geographic endemism between Africa and Eurasia. However, there are no direct hydroclimate records from the Arabian hyper-arid interior before the mid-Pleistocene, leaving the terrestrial hydroclimate and the role of Arabia as a biogeographic crossroads or barrier largely unknown.We use desert speleothems preserved from the northern Arabian interior to identify past humid phases over the last 8 million years. These are particularly useful terrestrial climate archives as they act as underground rain gauges, requiring a minimum of ~300 mm a-1 precipitation, pedogenesis and vegetation cover to form. Moreover, they can be accurately and precisely dated and are subsequently a valuable tool in identifying past large-scale hydrological and vegetation changes in ancient drylands. Our data reveal evidence of multiple ‘windows of opportunity’ of climate amelioration, allowing biogeographic exchange and dispersals to occur across the Arabian hyper-arid zone. Further, the novel analyses of the isotopic composition (d18O and d2H) of speleothem fluid inclusion waters, representing ‘fossil rainwater’, reveal the diminishing influence of tropical rain-belt precipitation in Arabia across Earth’s transition from a largely ‘ice-free’ northern hemisphere to an ‘ice-age’ world. The extent of Arabian aridity may thus be important in controlling biogeographic dispersals through the Arabian corridor, becoming increasingly less favourable through time. This is supported by fossil evidence which suggest that exchange between biogeographic regions across the Old World Savannah Biome were favoured in the Late Miocene, but became increasingly latitudinally fragmented from the Pliocene onwards. These results have significant implications for understanding the drivers of dryland aridity in non-polar deserts globally.

Aim: Using geochemical proxies to record changes in environmental conditions during the Ediacaran-Cambrian timeMethods: Thin section petrography combined with high-resolution analyses of trace elements and U-Pb, Sr, B and Li isotopes by LA-ICPMS (single and multi-collector)Problem: Identification of pristine early diagenetic carbonate phases and their distinction from late diagenetic and altered carbonates. In this study, we use high spatial resolution multi-element and isotope analyses to identify pristine carbonate phases in samples from recent drill cores from Namibia, drilled by International Continental Scientific Drilling Program project GRIND-ECT. GRIND-ECT aims to capture, in drill core, the Ediacaran-Cambrian transition in key successions worldwide.The method applied allows for relatively high sample throughput (>200) and precise detection of heterogeneous altered domains. Exclusion criteria are the presence or increased concentration of various trace elements (Al, Rb, LREE ...), heterogeneity of the 87Sr/86Sr isotope ratio, a lack of discernible populations in U/Pb isotope space, resulting in non-correlated scattering, and too young U-Pb dates.To date, about 10-15% of the samples analyzed yielded a U-Pb date consistent with depositional age or an early post-depositional age. Geochronologic control of ancient sedimentary sequences is critical for evaluating cause and effect and rates of change in ancient environments. However, precision of LA-ICPMS ages (ca. 1-2%, e.g., 6-11 Ma) is insufficient to resolve changes in the Ediacaran-Cambrian oceans on timescales relevant for biological and environmental change. Therefore, the ages of these pre-characterized samples need to be refined using high-precision methods (Cantine et al., EGU 2023).Analyses of Li and B isotopes are in progress on the pre-characterized, potentially pristine carbonate areas. We expect to see a change in the Li, B and Sr isotope records through Ediacaran-Cambrian time hopefully with significant anomalies. The correlation of the three isotope systems would be a confirmation for us that we are targeting pristine, early diagenetic carbonates.

Establishing geochronological controls on ancient sedimentary successions is critical for evaluating cause and effect, as well as rates of change, in ancient environments. Towards this goal, U-Pb dating of carbonate phases by in situ LA-ICP-MS offers a rapid and reasonably precise method for evaluating not only depositional ages but also the ages of post-depositional processes affecting carbonate rock. However, this technique is still in its first decade of application to carbonate rocks. Determining the best practices for applying this technique and evaluating the meaning, reliability, and robustness of the data it produces remain areas of interest. In this study, we present the first results from U-Pb dating and geochemical characterization of samples from recent drillcores from Namibia, drilled by International Continental Scientific Drilling Program project GRIND-ECT. GRIND-ECT aims to capture, in drillcore, the Ediacaran-Cambrian transition in key successions worldwide. The Namibian portion of GRIND-ECT targets the Nama Group of southern Namibia, well-known for its abundant fossils and detailed geochemical and geochronological records from outcrop, with the goal of elucidating changes in the Earth system during the diversification of early animals. With both abundant interbedded ashes amenable to U-Pb zircon dating and abundant carbonate, these drillcores offer a natural experiment for comparing results from LA-ICP-MS carbonate dating and other geochronological techniques. Our results show that a significant fraction of samples yield geologically meaningful ages when dated using LA-ICP-MS. These ages are consistent with depositional or early post-depositional ages. Microbially-influenced facies are often the most successful. Theses ages can be further refined using higher-precision techniques. Efforts to date vein calcites, which are often very low in U, have not yet yielded robust ages. Integration of Sr and trace and rare earth element data indicate the promise and the limitations of using these proxies as tests for “datability.”

One the world’s largest geothermal reservoirs, “The Geysers” in the California Coast Ranges, is underlain by a composite granitic pluton at shallow depth (~1–3 km, based on geothermal well penetration). Published U-Pb zircon geochronology indicates that this Geysers Plutonic Complex (GPC) intruded between c. 1.8 and 1.1 Ma in three major pulses: the oldest formed a cap of orthopyroxene-biotite microgranite porphyry, followed by orthopyroxene-biotite granite and hornblende-biotite-orthopyroxene granodiorite dominating at deeper levels. Lavas and minor pyroclastic deposits of the overlying Cobb Mountain Volcanic Center erupted between c. 1.2–1.0 Ma. The Geysers-Cobb Mountain plutonic-volcanic association shares common magmatic origins rooted in asthenospheric upwelling into a migrating slab window, where lower-crustal hybridization of mantle-derived magmas was followed by upper-crustal intrusion and differentiation. When and how shallow intrusions or eruptions were fed from this common source, however, remains unclear. This can be reconstructed from crystal-scale analysis of trace elements, oxygen and hafnium isotopes in zircon that can uniquely track magmatic processes in an evolving, long-lived magma system.GPC microgranite zircons display strongly negative Eu anomalies, high levels of incompatible trace elements, and near-solidus Ti-in-zircon temperatures (~670 °C for aTiO2 = 0.55 and aSiO2 = 1). This is distinct from zircons from GPC granite and granodiorite that have moderately negative Eu anomalies, inconspicuous trace element enrichments, and variable Ti-in-zircon temperatures (~850–700 °C). Unlike trace elements, O and Hf isotopes in zircon are indistinguishable between GPC microgranite porphyry and the main population of granite-granodiorite zircons (δ18O = +4.76 to +9.18; εHf = +1.4 to +10.7). There is, however, a subgroup of zircon in GPC granite and granodiorite with elevated δ18O (~8.05) and lower εHf (~4.4) indicating that some late-stage melts experienced higher degrees of assimilation compared to the other magma types. Zircons from Cobb Mountain lavas are similar to those from the GPC granite and granodiorite, but distinct from the granophyre.We set up a thermal model for zircon crystallization to satisfy the following observations: (1) evolved magma from which zircon crystallized was continuously present between c. 2.1 and 1.1 Ma, and (2) crystal recycling from the GPC microporphyry stage in subsequent intrusive or eruptive pulses was negligible. A magma reservoir at ~7 km depth which incrementally grew in three stages matches requirements imposed by zircon ages and compositions: (1) initial magma accumulation at low recharge fluxes starting at 2.1 Ma (0.1 km3/ka), (2) a brief flare-up at 1.6 Ma (4 km3/ka for 50 ka), (3) a return to low recharge fluxes (0.1 km3/ka) between 1.3 and 1.1 Ma. The total injected magma volume amounts to ~300 km3, three times the volume of the GPC as constrained by geothermal wells. According to this model, magma accumulation was long-lived, thus capable of sustaining protracted geothermal activity, but the main igneous growth occurred almost instantaneously. One implication is that accumulation of large volumes of magma can be rapid, and may require special circumstances that are only realized ephemerally despite overall long-lived magmatic activity.

The novel technique of U-Pb dating of garnet allows us to date rocks that were previously impossible to put into a temporal context, either because of the absence of traditional geochronometers such as zircon, monazite, and rutile or because of isotopic disequilibrium, e.g. Lu-Hf or Sm-Nd. The possibility to exclusively date garnet crystals can give us important information to understand the geological evolution of a particular region.In this contribution, we present data from a garnet-quartz vein from the Cabo Ortegal complex, NW Iberian Massif. In the vein, andraditic garnet is associated with chlorite and serpentine in fissures, which cut the foliation of the surrounding lithologies. Field evidence thus indicates that vein formation postdates the formation of the regional foliation (ca. 390 Ma). However, until now, it is unknown, if vein formation is related to thrusting and fluid circulation during the uplift of the area (350-330 Ma) or as the consequence of igneous intrusions (ca. 300 Ma). Vein garnet was analysed in two analytical sessions. The analyses yielded unanchored lower intercept ages of 253.5 ± 7.6 Ma (MSWD = 1.1, n = 62/64) and 252.2 ± 9.5 Ma (MSWD = 1.33, n = 40/40). Those results are much younger than the basement rocks and structures in the Cabo Ortegal complex. The obtained ages coincide with the Permo-Triassic rifting widely documented from other geological domains of the Iberian Peninsula, but has never before been recognised in the Allochthonous Complexes of NW Iberian massif. The study of these types of samples may therefore provide clues to the geological history of the Cabo Ortegal Complex, which may not be available from other techniques and lithologies.

Reduced landward moisture transport due to the cold upwelled surface waters of the Humboldt Current System (HCS) is one of the primary triggers of hyperarid conditions in the Atacama Desert. Marine sediments exposed along the coastline of northern Chile provide a unique archive of land-ocean coupling between coastal upwelling related HCS and paleoclimate in the Atacama Desert during the Neogene. Here we aim to establish a refined stratigraphic framework for the emplacement of diatom-rich deposits of the Bahía Inglesa Formation at Quebrada Tiburón (27°S).The marine sediments exposed at Quebrada Tiburón lie transgressively above the pre-Cenozoic basement. A c. 9m-thick succession of laminated diatomaceous muds is intercalated with sandy deposits. Benthic foraminiferal assemblages and test morphology reveal a shift from trochospiral and planospiral (predominantly epifaunal) to serial (infaunal) morphotypes between sands and diatomaceous muds, respectively. Together with plankton assemblages dominated by diatoms and Globigerina bulloides, the diatomaceous muds reflect a highly productive coastal upwelling regime and low oxic, eutrophic conditions at the seafloor. However, occasional layers of bioturbation within the diatomaceous succession also imply phases of relaxed upwelling conditions. The new stratigraphic framework will thus allow the assessment of Neogene upwelling behavior and variability off Chile on orbital time scales.Preliminary results based on calcareous nannoplankton, diatoms and planktonic foraminifera indicate a stratigraphic range from the upper Miocene (Messinian) to the lower Pliocene for the diatomaceous muds. Evidence from the δ18O of the benthic foraminifera Uvigerina peregrina further ties the upper part of the succession to an uppermost Zanclean age < 3.9 Ma. In a next step, the stratigraphic framework will be further improved by new data from magnetostratigraphy, Sr isotopes, and tephrochronology.This study contributes to CRC 1211 “Earth-Evolution at the dry limit”, funded by the Deutsche Forschungsgemeinschaft (DFG).

The recent discovery of Ediacaran ophiolites in the SW Iberian Massif has made it possible to pinpoint the evolution of the Cadomian basement of Europe. The Calzadilla and Merida ophiolites (gabbroic protoliths dated at c. 600 and 594 Ma, respectively) have geochemical characteristics typical of supra-subduction zone ophiolites. They are interpreted as originating during the initial opening of a fore-arc basin with boninitic magmatism (Calzadilla), followed by the formation of a back-arc basin with arc-tholeiites (Merida). Widening of the back-arc leads to the rifting and drifting of a section of the active continental margin (Cadomia). These oceanic domains initiated a rapid contraction, culminating in the collision of Cadomia with Gondwana (c. 590-540 Ma). The application of a PANALESIS model to this paleogeographic setting confirms the plausibility of Cadomian rifting and the likely opening of broad oceanic domains. It also confirms the final collision of Cadomia with Gondwana, although the synthetic and regional data disagree in the precise chronology of the convergence and collision of Cadomia with the West Africa Craton. This work shows that the evolution of the Cadomian basement is much more complex than traditionally considered.

Knowledge of pressure-temperature-time (P-T-t) evolution of Archean high-grade (deep crustal) metamorphic rocks is important for deciphering the nature of Archean tectonic processes. However, exposures of such rocks are limited in the present rock record. Here, we study a suite of high-grade, mafic rocks that are present along a crustal-scale shear zone (called the Mercara Shear Zone) between two Archean terrains of India, the Coorg block and the Dharwar Craton. Given that the Mercara Shear Zone is dated to be Mesoarchean, these shear zone rocks are well suited to elucidate Archean orogenic processes. Petrological investigation shows that these mafic rocks are characterized by a granulitic assemblage of orthopyroxene, clinopyroxene, plagioclase, quartz, amphibole ± garnet, and with accessory phases such as apatite, ilmenite, magnetite and rutile in some cases. We distinguish the investigated rocks into low-Mg and high-Mg varieties based on their whole rock composition as well as their mode of occurrence in the field and mineral chemistry. This difference in the bulk composition led to different reaction histories – for example, the low-Mg mafic granulites underwent partial melting while high-Mg granulites were less fertile. Combining these observations with the results of geothermobarometry, phase equilibria modelling, geochronology (U-Pb in zircon and Lu-Hf garnet geochronology) and diffusion modeling, we have reconstructed a multi-stage P-T-t history for these rocks. The first phase (Stage 1) is represented by granulite-grade metamorphism at ~750 – 900 °C and 8 – 13 kbar during ~3100 Ma (with uncertainties permitting a timing as recent as ~2700 Ma), after which they resided at T < 500 °C, likely at lower crustal levels (Stage 2). Subsequently, these rocks were reheated to a T of 700 – 750 °C at 7 – 10 kbar at ~2400 Ma (Stage 3) and then again cooled down to ~500 – 600 °C at 6 – 8 kbar (Stage 4). Application of diffusion chronometry shows that: (1) the cooling rates of these granulites at high temperatures (> 600 °C) varied in the range of 25 – 50 °C/Ma, and (2) the rocks resided for a long duration (~500 million years) at the Stage 2 metamorphic conditions i.e., at T < 500 °C. We infer that such a protracted, high-T metamorphic history involving at least two heating pulses, and the relatively slow cooling rates on the order of 10’s °C/Ma are consistent with the operation of peel-back styled orogenesis (an embryonic form of plate tectonics) on an early hotter Earth (Mesoarchean to Palaeoproterozoic). Moreover, the controls of bulk rock compositions on reaction histories provide a mechanism for intracrustal differentiation and generating Mg-rich, refractory material that may have eventually formed the lower continental crust over a protracted and pulsed thermal evolution spanning several hundred million years.

The dinosaur–bird transition involved several anatomical, biomechanical, and physiological modifications of the theropod bauplan. Non-avian maniraptoran theropods, such as Troodon , are key to better understand changes in thermophysiology and reproduction occurring during this transition. Here, we applied dual clumped isotope (Δ 47 and Δ 48 ) thermometry, a technique that resolves mineralization temperature and other nonthermal information recorded in carbonates, to eggshells from Troodon , modern reptiles, and modern birds. Troodon eggshells show variable temperatures, namely 42 and 29 ± 2 °C, supporting the hypothesis of an endothermic thermophysiology with a heterothermic strategy for this extinct taxon. Dual clumped isotope data also reveal physiological differences in the reproductive systems between Troodon , reptiles, and birds. Troodon and modern reptiles mineralize their eggshells indistinguishable from dual clumped isotope equilibrium, while birds precipitate eggshells characterized by a positive disequilibrium offset in Δ 48 . Analyses of inorganic calcites suggest that the observed disequilibrium pattern in birds is linked to an amorphous calcium carbonate (ACC) precursor, a carbonate phase known to accelerate eggshell formation in birds. Lack of disequilibrium patterns in reptile and Troodon eggshells implies these vertebrates had not acquired the fast, ACC-based eggshell calcification process characteristic of birds. Observation that Troodon retained a slow reptile-like calcification suggests that it possessed two functional ovaries and was limited in the number of eggs it could produce; thus its large clutches would have been laid by several females. Dual clumped isotope analysis of eggshells of extinct vertebrates sheds light on physiological information otherwise inaccessible in the fossil record.

The Levant Basin in the Eastern Mediterranean contains a ~3 km-thick, predominantly siliciclastic section of Oligocene-Miocene age, which hosts large hydrocarbon reservoirs (“Tamar Sands Play”). A fundamental question raised with respect to this siliciclastic section concerns its origin and the sedimentary pathways into the deep basin. Here we present an advanced provenance study, including detrital zircon U-Pb-Hf and heavy mineral assemblage investigations, of Oligocene-Miocene siliciclastic sediments retrieved from four boreholes across the Levant Basin. Our investigations reveal a preponderance of Neoproterozoic and older Precambrian zircons with mostly negative εHf values. This U-Pb-Hf pattern indicates that the studied sediments were mainly reworked from Paleozoic-Mesozoic sandstones of Afro-Arabia with variable derivation from the juvenile basement of the Arabian-Nubian Shield. Comparison of the detrital signal in various stratigraphic levels of the Levant Basin shows that Early Oligocene and Early Miocene sand intervals are typified by a large proportion of pre-900 Ma zircons (ca. 50%), by a relatively small proportion of Neoproterozoic zircons with positive εHf values (ca. 25%), and by abundant detrital apatite peloids in the heavy mineral fraction. Resembling Miocene clastic sequences preserved in Israel, these characteristics are taken by us to indicate a dominant provenance in the Arabian side of the Red Sea Rift. On the other hand, Late Oligocene-lowest Early Miocene and Middle-Late Miocene intervals are typified by a mild proportion of pre-900 Ma zircon (ca. 35%) and by a larger proportion of Neoproterozoic zircons with positive εHf values (ca. 35%), they also contain scarce Mesozoic-Cenozoic zircons. These similarities to the Nile Delta sediments are taken by us to indicate a dominant provenance in NE Africa. Overall, our findings suggest that the Levant Basin was fed by varying proportions of sediments derived both from Arabia via the Levant continental margin and from NE Africa via the Nile Delta. While Early Oligocene and Early Miocene sediments, including the main section of the “Tamar Sands”, were chiefly derived from Arabian sources, Late Oligocene-lowest Early Miocene and Middle-Late Miocene sediments mainly sourced from NE Africa. The mere absence of Paleozoic and Mesozoic-aged detrital zircons, abundant in the Eurasian side of the Eastern Mediterranean, suggests that sand sourcing in the overriding plate of the Arabian-Eurasian collision belt did not reach the Levant Basin.

Extensive morphological and age studies on more than 4600 detrital zircon grains recovered from modern sands of Namibia reveal complex mechanisms of sediment transport. These data are further supplemented by a zircon age database containing more than 100,000 single grain analyses from the entire southern Africa and allow for hypothesising of a large Southern Namibian Sediment Vortex located between the Damara Orogen and the Orange River in southern Namibia. The results of this study also allow assuming a modified model of the Orange River sand highway, whose origin is likely located further south than previously expected. Moreover, studied samples from other parts of Namibia give first insights into sediment movements towards the interior of the continent and highlight the potential impact of very little spatial variations of erosion rates. Finally, this study points out the huge potential of detrital zircon morphology and large geo-databases as an easy-to-use additional tool for provenance analysis.

The timing of vertical motions adjacent to the Dead Sea Transform plate boundary is not yet firmly established. We utilize laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) U-Pb geochronology of carbonate cave deposits (speleothems) to constrain paleo-groundwater levels along the western margin of the Dead Sea Transform and provide a proxy for the timing of large-scale incision and tectonic uplift. Phreatic speleothems can form in caves that are located slightly below the groundwater level. Tectonic uplift and/or base level subsidence can trigger incision of canyons and induce a drop in the groundwater table. This can cause dewatering of the caves, cessation of the deposition of phreatic speleothems, and initiation of growth of vadose speleothems. The transition between deposition of phreatic and vadose speleothems can therefore reflect tectonic or erosive events. We obtained 102 U-Pb ages from 32 speleothems collected from three cave complexes across a 150-km-long, north-to-south transect. These ages indicate that phreatic deposition began between 14.68 ± 1.33 and 11.34 ± 1.62 and ended by 6.21 ± 0.59 Ma. Later, vadose speleothems grew intermittently until the Quaternary. These results suggest an abrupt drop in the water table starting at ca. 6 Ma with no re-submergence of the caves. We interpret this to indicate river incision of ~150–200 m that was driven by uplift and folding of the western margin of the Dead Sea Transform and by inland morpho-tectonic, base-level subsidence in the Dead Sea area. The observed timing corresponds with a change in the Euler pole of the plates motion along the Dead Sea Transform. The growth period of phreatic speleothems suggests groundwater level stability and limited vertical tectonic motions between 14 Ma and 6 Ma.

The detrital zircon grains from two catchments in the East Eifel Volcanic Field consist of crystals sourced from proximal deposits of Quaternary trachytic–phonolitic volcanic centres, Hocheifel Paleogene trachytic rocks and the Paleozoic basement. The outcrop patterns indicate the derivation of a significant detrital zircon population from deposits of the c. 13 ka Lower and Upper Laacher See Tephra. Intercalated Middle Laacher See Tephra, consisting of valley-filling ignimbrites, by contrast, is a minor zircon source despite thick ignimbrite deposits in one of the catchments. This reflects zircon undersaturation in the hotter and less evolved phonolite tapped from deeper parts of the magma reservoir as the eruption unfolded, as well as fewer antecrysts recycled from the plutonic carapace. A previously unrecognized zircon age population of c. 63 ka, mostly derived from Lower Laacher See Tephra, marks the onset of the presence of evolved magma at the top of the reservoir. Correlative Hf and O isotopic analysis reveals significant crustal interactions during phonolite differentiation in a shallow reservoir, with the assimilation of cogenetic, but hydrothermally modified, plutonic margins. Raman spectra indicate that magmatically heated crustal zircon xenocrysts are absent. Detrital zircon can thus provide more integrated insights into the evolution of Quaternary magma systems than the punctuated sampling of volcanic or cogenetic plutonic rocks. Supplementary material: Data tables presenting U–Th, U–Pb, O–Hf and Raman geochronology results are available at https://doi.org/10.6084/m9.figshare.c.6123823

The volatile transfer in subduction zones and the role of sulfate as a vector for the mobilization of oxidized components from down-going slabs remain hotly debated issues. Orogenic spinel and garnet peridotite lenses from the Ulten Zone (Eastern Alps, Italy), exhumed as part of felsic metamorphic terranes in continental collision zones, bear witness to mass transfer processes in these pivotal environments. In this study, we carried out a multi-method investigation of mantle sulfides coexisting with four generations of carbonates, indicating coupled sulfur and carbon mobility throughout the peridotites’ metamorphic evolution as part of the Variscan subduction architecture. Detailed petrography, bulk rock measurements, in situ chemical and geochemical analyses of sulfides as well as Sr isotope analyses of associated clinopyroxene and amphibole are combined with the aim to constrain the origin, nature and effect of multiple C-O-H-S-bearing fluids and melts the peridotites interacted with. The first, pre-peak, metasomatic pulse (Stage 1) is represented by an H2S-CO2-bearing melt from the subduction-modified hot mantle wedge, which formed a pyroxenite layer hosting matrix pentlandite with δ34S of +2.77‰. Matrix carbonates occasionally occur in the coarse-grained peridotite under eclogite-facies conditions (Stage 2), with heavier δ34S (up to +3.43‰), radiogenic Sr (87Sr/86Srclinopyroxene > 0.7052) and elevated Pb abundances. These are ascribed to interaction with isotopically heavy melts carrying recycled crustal component, permissive of, but not requiring, involvement of oxidized S species. Conversely, isotopically lighter matrix pentlandite (δ34S = −1.62 to +0.67‰), and radiogenic Sr in amphibole (87Sr/86Sr = 0.7056) and associated dolomite (published data) from fine-grained garnet-amphibole peridotites may point to involvement of H2S-CO2-bearing crustal fluids, which variably equilibrated with the mantle before interacting with the peridotites. The post-peak Stage 3 marks the entrapment of peridotites into a tectonic melange. Here, kelyphitization of garnet is catalyzed by further ingress of a S-bearing fluid (δ34S = −0.38‰), while carbonate veining with occasional sulfides bear witness to channelized fluid flow. Sulfide and amphibole grains in retrogressed spinel peridotites reveal the highest contents of fluid-mobile elements (As, Sb) and 87Sr/86Sramphibole up to 0.7074, suggesting late interactions with isotopically heavy crustal fluids at high fluid-rock ratios. Textural observations indicate that, during Stage 4, serpentinization of peridotites at low ƒS2 played an active role not only in CO2 release by conversion of dolomite to calcite + brucite intergrowths, but also in local removal of 32S during the final exhumation stage. Late channelized sulfur remobilization is evidenced by the serpentine + magnetite (±millerite ± calcite) vein carrying > 300 ppm S. Overall, the relatively narrow range of sulfur isotope composition (δ34S = −1.62 to +3.76‰) is indicative of limited interaction with isotopically heavy crustal liquids, and points to a subordinate role of subduction-derived sulfate throughout the extended fluid(melt)/rock evolution of the Ulten Zone peridotites, first in the mantle wedge and then as part of a tectonic melange.

This study integrates field structural data, petrographic and geochemical (δ18O, δ13C, Δ47, 87Sr/86Sr, and elemental composition) analyses and U–Pb dating of calcite veins cutting the Bóixols-Sant Corneli anticline (Southern Pyrenees) in order to date and to investigate the spatio-temporal relationships between fluid flow and fold evolution. This E-W trending anticline grew from Late Cretaceous to Paleocene at the front of the Bóixols thrust sheet deforming pre-growth and growth sedimentary sequences. U–Pb dating reveals Late Cretaceous to late Miocene deformation ages, which agree with the age of growth strata deposition and the sequence of deformation interpreted from field and microstructural data. Dates coeval (71.2 ± 6.4 to 56.9 ± 1.4 Ma) and postdating (55.5 ± 1.2 to 27.4 ± 0.9 Ma) Upper Cretaceous to Paleocene growth strata are interpreted to record: (i) the growth of the Bóixols-Sant Corneli anticline during the Bóixols thrust emplacement, and (ii) the tightening of the anticline during the southern tectonic transport of the South-Central Pyrenean Unit. Other ages (20.8 ± 1.2 to 9.0 ± 4.6 Ma) postdate the folding event and have been associated with the collapse of the Bóixols-Sant Corneli anticline. The geochemistry of calcite veins indicates that the fluid flow behavior varied across the Bóixols-Sant Corneli anticline through its growth, showing a compartmentalized fluid system. In the hinge of the anticline and in the upper Santonian to middle Campanian syn-orogenic sequence along the footwall of the Bóixols thrust, the similar petrographic and geochemical features between all calcite cements and host rocks point towards a locally-derived or well-equilibrated fluid system. Contrarily, along large faults such as the Bóixols thrust, and in the anticline limbs, the geochemistry of vein cements indicates a different scenario. Cements in large faults yielded the lightest δ18O values, from −8 to −14 ‰VPDB, and variable enrichment in δ13C, 87Sr/86Sr, elemental composition and δ18Ofluid. This is interpreted as the migration of fluids, through fault zones, that evolved from distinct fluid origins. Cements in the fold limbs exhibit δ18O and δ13C between −8 and −6 ‰VPDB and between −10 and + 2 ‰VPDB, respectively, the lowest Sr contents and the lowest precipitation temperatures, suggesting that the anticline limbs recorded the infiltration and evolution of meteoric waters. The paleohydrological system in the Bóixols-Sant Corneli anticline was restricted to the Bóixols thrust sheet. The Upper Triassic evaporitic basal detachment likely acted as a lower fluid barrier, preventing the input of fluids from deeper parts of the Pyrenean crustal thrust system. This study provides a well-constrained absolute timing of fracturing and fluid flow during basin inversion and folding evolution and highlights the suitability of U–Pb geochronology to refine the age of fractures and veins and their sequential evolution in orogenic belts., This research was carried out within the framework of the DGICYT Spanish project PGC2018-093903- B-C22 (Ministerio de Ciencia, Innovaci´on y Universidades/Agencia Estatal de Investigación/10.13039/501100011033/Fondo Europeo de Desarrollo Regional, Uni´on Europea), the Grup Consolidat de Recerca “Geologia Sediment`aria” (2017-SGR-824) and the Grup Consolidat de Recerca “Modelitzaci´o Geodin`amica de la Litosfera” (2017SGR-847). This work was also partially funded by ALORBE project (PIE–CSIC–202030E310). The PhD research of DML is supported by the FPI2016 (BES-2016-077214) Spanish program from MINECO. DC acknowledges the Spanish Ministry of Science and Innovation for the “Juan de la Cierva Formaci´on” fellowship FJC2020-043488-I AEI/ 10.113039/501100011033. We thank Luis Fernando Martínez for helping in the fieldwork during his master’s degree at the Universitat de Barcelona. Carbon and oxygen isotopic analyses were carried out at the Centre Científics i Tecnol`ogics of the Universitat de Barcelona. Strontium analyses were performed at the CAI de Geocronología y Geoquímica Isot´opica of the Universidad Complutense de Madrid. The elemental composition was analyzed at the geochemistry facility labGEOTOP of Geosciences Barcelona (GEO3BCN–CSIC). U–Pb analyses were performed at the Frankfurt Isotope and Element Research Center (FIERCE) from the Goethe-University Frankfurt (Germany).

The global development and modern distribution of arid zones in subtropical regions (drylands) are likely associated with the global cooling marking the dawn of the Quaternary (~2.6 Ma). This coincides with global shifts in ocean circulation patterns, the intensification of the Walker-Hadley circulation, declining atmospheric CO2, the initiation of glacial–interglacial cycles and the intensification of Northern Hemisphere glaciation, the combination of which has led to the current global distribution of non-polar deserts at ~30° latitude. Although modern drylands represent Earth’s largest terrestrial biome, covering ~46% of global land surfaces and supporting a global population of ~3 billion people, it is currently unclear how drylands will change under future climate change scenarios. Speleothems, preserved in arid-zone caves, are particularly useful terrestrial climate archives as they act as underground rain gauges, which require a minimum of ~300 mm a-1 precipitation, pedogenesis and vegetation cover to form. Moreover, they can be accurately and precisely dated and are subsequently a valuable tool in identifying past large-scale hydrological and vegetation changes in ancient drylands. Here, we present new data from speleothems during past ‘warm periods’ from the Arabian hyper-arid zone. We apply a novel technique of extracting speleothem fluid inclusions waters to reconstruct the isotopic composition (d18O and d2H) of ‘fossil rainwater’ preserved in the speleothem fabric pristinely over millions of years. Speleothem evidence suggests that during the last 7 million years, the Sahara-Arabian desert experienced numerous intermittent humid phases, typically occurring with periods of low global ice-volume and warmer global temperatures. We further explore tropical push-pull mechanisms driving heating of the deep tropics and subsequent expansion of the tropical zone and synchronicity of humid phases regionally. These results have significant implications for understanding the drivers of dryland aridity in non-polar deserts globally.

[Paleogeographic reconstruction of the Levant area in the Early Miocene (15–20 Ma) highlighting the main sediment routing systems into the deep Levant Basin and their detrital zircon and rutile U‐Pb age spectra and a non metric multi‐dimensional scaling map (MDS) of detrital zircon U‐Pb ages of studied Israeli Miocene samples and Miocene Nile Delta samples. ASG, Azrqa Sirhan Graben; DST, Dead Sea Transform. , Abstract Isolated, Miocene continental basins scattered over Israel and Jordan represent the remnants of a continental‐wide fluvial system, which originated in Arabia and transported siliciclastic sediments westward to the deep Levant Basin. These basins define two geographically separated sedimentary provinces. The detrital zircon age spectra in both provinces are dominated by Neoproterozoic U‐Pb ages (550–1,000 Ma), resembling those of Paleozoic‐Mesozoic sandstones exposed along the uplifted Red Sea Rift flank. However, while the southern province exhibits two prominent peaks at ~600 and ~1,000 Ma, similar to those seen in Cambrian‐Ordovician sandstones in southern Israel and Jordan, the northern province shows an additional significant age peak at ~800 Ma and its overall spectrum resembles that of Devonian sandstones in northern Saudi Arabia. These variations distinguish the two Miocene clastic outliers as pertaining to two separate, NW‐directed transport systems delivering siliciclastic sediments from Arabia towards the deep Levant Basin. The detrital zircon U‐Pb‐Hf signal of the Israeli Miocene clastic units differs from that of the River Nile, particularly in the lack of Cenozoic‐Mesozoic‐aged zircons in the former. This allows us to distinguish the properties of the fluvial system that existed in Arabia, on the eastern side of the Red Sea, from that of the River Nile that drained its western flanks. While it is commonly accepted that the (proto‐)Nile River played a key role in the Levant Basin fill, the eastern fluvial system that prevailed on the Arabian side may have been also important.]

Due to their relatively high Hf contents (i.e., several hundreds to thousands of ppm), columbite-group minerals (CGMs) are suitable for Lu–Hf isotope analysis, which can provide new insights into the source of such minerals in combination with the U–Pb age of rare-metal deposits. However, few studies have reported Lu–Hf isotope data for CGMs. Tantalum is a major element in CGMs (12–48 wt% Ta2O5) and has a significant effect on measurements of Hf isotopes using MC-ICP-MS. This effect was first evaluated in this study by analysis of mixed Hf–Ta standard solutions with different Ta/Hf ratios and LA-MC-ICP-MS analysis of various CGMs. This analytical artifact reflects serious tailing of the large 181Ta signal onto the 180Hf and 179Hf masses during analysis. Therefore, in order to obtain accurate Hf isotope data for CGMs by MC-ICP-MS, we present an improved chemical separation procedure for Hf from Ta, and also a novel analytical protocol for LA-MC-ICP-MS analysis of CGMs. Accurate in situ176Hf/177Hf ratios for CGMs can be obtained by normalization to 178Hf/177Hf = 1.4672, rather than 179Hf/177Hf = 0.7325, using the exponential law. This approach was validated by solution and laser ablation MC-ICP-MS analysis of four CGM samples from China and Africa. The Lu–Hf isotopic composition of CGMs provides a new geochemical tracer for rare-metal deposits.

The Menderes Massif in Turkey represents one of the largest metamorphic core complexes in the world. It is regarded as a section of lower continental crust exhumed along low-angle detachment faults in the Late Miocene during a period of extension that affected the entire Aegean province. Syn-extensional magmatic activity within the Menderes metamorphic core complex is predominantly felsic forming several plutons, whereas mantle-derived magmatism has not been known so far. Here, we present a detailed study of the petrology and geochemistry of previously unreported mafic to intermediate lamprophyres within the Menderes Massif and assess their role in the geodynamic evolution of the core complex. The Menderes lamprophyres are mostly kersantites, with 49–60 wt % SiO2, 3.2–8.4 wt % MgO, 100–360 ppm Cr, 32–132 ppm Ni and Mg# of 37–50. Positive Pb and negative Ti–Nb–Ta anomalies suggest a clear orogenic affinity. Isotopes of Sr and Pb are relatively radiogenic (87Sr/86Sr = 0.70609–0.71076; 206Pb/204Pb = 18.88–19.03, 207Pb/204Pb > 15.71), while Nd is unradiogenic (εNd = −1.4 to −3.2). Most phenocrysts are sharply zoned with a primitive core (Mg# 77–85, up to 0.95 wt % Cr2O3 in clinopyroxene; Mg# 72–76 in amphibole) and a more evolved rim (Mg# 68–74

Final fragmentation of Rodinia occurred during the Ediacaran Period as Amazonia, Baltica and Laurentia drifted apart to form the Iapetus Ocean. Accompanying rift-related mafic dyke swarms of the Central Iapetus Magmatic Province (CIMP) were emplaced between 0.62 and 0.55 Ga, which are preserved in Laurentia and Baltica, whereas no coeval mafic rocks are known from Amazonia. First evidence for the CIMP extending into Oaxaquia (Rodinia-type basement of Mexico) was reported as tholeiitic dykes that intruded the Novillo gneiss, NE Mexico, at 619 ± 9 Ma. In Chiapas, SE Mexico, amphibolite dykes that are chemically similar to the Novillo dykes intruded anorthosite and gneiss. In this paper, a new dating approach to obtain mafic dyke intrusion ages is presented by targeting contact metamorphic zircon with the U Pb method, employing Secondary Ion Mass Spectrometry. Zircon that crystallized in anorthosite at intrusive contacts to mafic dykes and at temperatures exceeding 700 °C (Ti-in-zircon thermometry) yields ages between 615 ± 7 Ma and 608 ± 12 Ma, reflecting the time of dyke intrusion. Zircon chemical and isotopic (Hf, O) characteristics suggest a diachronous sequence of metamorphic processes involving Zr release from Fe Ti oxides, breakdown and recrystallization of other phases, and fluid-mitigated reactions during Ordovician metamorphism. Zircon δ18O values of granulites from Oaxaquia range from +6.2‰ to +9.8‰, whereas Tonian (~0.92 Ga) metamorphic zircon from SE Chiapas yielded low δ18O values from +2.0‰ to +2.8‰ that are explained by the reactivation of major tectonic boundaries during Tonian gravitational collapse. The observations increase the known extent of the CIMP in Mexico, suggesting that a Neoproterozoic superplume was still active during the Early Ediacaran producing a Large Igneous Province that extended over Amazonia, Baltica and Laurentia. The results further suggest that Oaxaquia at the northern edge of Amazonia formed the conjugate margin of Baltica during rifting.

The Cenozoic Kalahari Basin covers large parts of southern Africa. A continuous 400 m core was obtained in northern Namibia and analyzed in detail. Here, we present sedimentological, geochemical, mineralogical, granulometric, and hydraulic data, which were used to derive the sedimentation history and the Cenozoic paleoclimate and paleogeography of SW Africa. The first absolute ages for the Kalahari Basin were obtained by dating of calcretes, which showed that the core covers almost the entire Cenozoic. Two megafans could be distinguished. The older, buried Olukonda Megafan stems from a mafic source rock, potentially the Kunene Intrusive Complex, and was deposited by a paleo–Kunene River towards the southeast and east, under a semiarid climate. The younger Cubango Megafan (Andoni Formation) has a completely different provenance, namely felsic metamorphic and granitoid rocks, transported from the north by the Cubango River. The capture of the Kunene towards the Atlantic during the Eocene resulted in this change in provenance. Despite the distinct differences between the formations, the temporal hiatus between them must have been short. The results are a showcase of the potential of megafans for hosting major deep freshwater aquifers.

Detrital U-Pb zircon age dating and grain morphometrics were used for provenance and maximum deposition age determination for the Lower Permian Dwyka and Middle to Upper Permian Ecca groups of sout...

The Třebic Pluton (TP) comprises plutonic rocks of the ‘durbachite series’, i.e., ultrapotassic biotite–amphibole quartz melasyenites–melagranites with conspicuous K-feldspar phenocrysts and abundant mafic enclaves. The TP with its satellite bodies intruded the eastern Moldanubian Zone (orogenic root of the Variscan Bohemian Massif) at c. 338 Ma. Overall, the entire TP durbachite series (SiO2 = 52–67 wt%) remains highly magnesian, reduced, and (except when strongly contaminated) metaluminous. The durbachitic rocks are markedly enriched in lithophile elements (esp. Cs, Rb, Th, U, K and Pb) and LREE; in contrast, the contents of high-field strength elements (Nb, Ta, and Ti) and Sr are much lower, resulting in conspicuous negative anomalies in Primitive mantle-normalized multielement plots. The proposed petrogenetic model requires re-enrichment of the depleted, harzburgitic lithospheric mantle by deeply subducted crustal material of the Saxothuringian lower plate, directly and/or via (U)HP melt/fluid. This process produced phlogopite-rich metasomes (phlogopite harzburgites and/or glimmerites). The metasomes re-melted soon thereafter by a short thermal pulse caused by slab break-off or decompression melting of rising diapirs of the relatively light metasomatized mantle, yielding primary ultrapotassic melts (87Sr/86Sr337 > 0.712 and $$\varepsilon_{{{\text{Nd}}}}^{337}$$ ≤ 7.6). Upon their passage through the Moldanubian upper plate, ultrapotassic primary magmas mixed with felsic anatectic melts (87Sr/86Sr337 – 6.5). K-feldspar-driven fractional crystallization ± accumulation represented only a late modifying influence. The occurrence of such ultrapotassic enriched/crustally contaminated mantle-derived magmatism complicates any conventional mass-balance assessments of relative roles of crustal recycling vs. growth in hot collisional orogens, e.g., Variscides or Himalayas.