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Combined U-Pb and Lu-Hf isotope analyses of zircons from 16 tonalite-trondjemite-granodiorite (TTG) gneiss and granite samples from Swaziland reveal that the oldest rocks of the Ancient Gneiss Complex in southern Africa formed by reworking of Early Archaean or perhaps Late Hadean crust at 3.66 Ga, and that new crust was extracted from a depleted mantle source during Palaeoarchaean events between 3.54 and 3.32 Ga. This interpretation is supported by εHft of -1.6±2.0 obtained from 3.66 Ga TTG gneisses, corresponding to hafnium model ages between 3.77±0.18 Ga, for a presumed Hadean-Early Archaean chondritic mantle, and 4.08±0.18 Ga, for a presumed Hadean depleted mantle reservoir, with the first model age being the most likely in the light of recent data from worldwide sources. Furthermore, it is reflected by superchondritic εHft up to +2.2±2.0 for TTGs formed at 3.54, 3.45 and 3.32 Ga. The new datasets additionally show that the Palaeoarchaean crust formed between 3.54 and 3.32 Ga was intensely reworked afterwards, without significant addition of depleted mantle derived material, during orogenic and intracratonic melting processes at 3.23, 3.1 and 2.7 Ga. This is well reflected by an array of decreasing εHft from +2.2 to -7.2 between 3.3 and 2.7 Ga, which can be forced by 176Lu/177Hf of 0.0113, which is similar to that of present-day average continental crust, and might result from lower crust zircon fractionation during Archaean crust reworking.

The Třebíč 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 εNd337  ≤ 7.6). Upon their passage through the Moldanubian upper plate, ultrapotassic primary magmas mixed with felsic anatectic melts (87Sr/86Sr337 < 0.710; εNd337  > – 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.

Dating of extensive alluvial fan surfaces and fluvial features in the hyperarid core of the Atacama Desert, Chile, using cosmogenic nuclides provides unrivalled insights about the onset and variability of aridity. The predominantly hyperarid conditions help to preserve the traces of episodic climatic and/or slow tectonic change. Utilizing single clast exposure dating with cosmogenic 10 Be and 21 Ne, we determine the termination of episodes of enhanced fluvial erosion and deposition occurring at ~19, ~14, ~9.5 Ma; large scale fluvial modification of the landscape had ceased by ~2–3 Ma. The presence of clasts that record pre-Miocene exposure ages (~28 Ma and ~34 Ma) require stagnant landscape development during the Oligocene. Our data implies an early onset of (hyper-) aridity in the core region of the Atacama Desert, interrupted by wetter but probably still arid periods. The apparent conflict with interpretation that favour a later onset of (hyper-) aridity can be reconciled when the climatic gradients within the Atacama Desert are considered.

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 δ¹ 8 O (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 δ¹ 8 O (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. Ancient rocks from northwest Scotland show that early continental crust formed in water-rich environments. The data suggest that primordial water was already present in the lower crust and was recycled from altered surface rocks into deeper crustal levels.

Acesta excavata (Fabricius, 1779) is a slow growing bivalve from the Limidae family and is often found associated with cold-water coral reefs along the European continental margin. Here we present the compositional variability of frequently used proxy elemental ratios (Mg/Ca, Sr/Ca, Na/Ca) measured by laser-ablation mass spectrometry (LA-ICP-MS) and compare it to in-situ recorded instrumental seawater parameters such as temperature and salinity. Shell Mg/Ca measured in the fibrous calcitic shell section was overall not correlated with seawater temperature or salinity; however, some samples show significant correlations with temperature with a sensitivity that was found to be unusually high in comparison to other marine organisms. Mg/Ca and Sr/Ca measured in the fibrous calcitic shell section display significant negative correlations with the linear extension rate of the shell, which indicates strong vital effects in these bivalves. Multiple linear regression analysis indicates that up to 79% of elemental variability is explicable with temperature and salinity as independent predictor values. Yet, the overall results clearly show that the application of Element/Ca (E/Ca) ratios in these bivalves to reconstruct past changes in temperature and salinity is likely to be complicated due to strong vital effects and the effects of organic material embedded in the shell. Therefore, we suggest to apply additional techniques, such as clumped isotopes, in order to exactly determine and quantify the underlying vital effects and possibly account for these. We found differences in the chemical composition between the two calcitic shell layers that are possibly explainable through differences of the crystal morphology. Sr/Ca ratios also appear to be partly controlled by the amount of magnesium, because the small magnesium ions bend the crystal lattice which increases the space for strontium incorporation. Oxidative cleaning with H 2 O 2 did not significantly change the Mg/Ca and Sr/Ca composition of the shell. Na/Ca ratios decreased after the oxidative cleaning, which is most likely a leaching effect and not caused by the removal of organic matter.

Combined U-Pb and Hf isotope analyses of detrital zircons from the Fig Tree and Moodies Groups of the Barberton Greenstone Belt, South Africa, yield similar Hf isotope compositions and age populations, thus pointing to a similar provenance. Zircon populations of Fig Tree Group greywacke and Moodies Group quartzarenite are both dominated by age clusters at 3.53, 3.47, and 3.28 Ga, and a minor cluster at 3.36 Ga. The Moodies quartzarenite sample additionally contains a younger age population at 3.23-3.19 Ga. Hafnium isotope data indicate that the source area of both sediments was affected by new crust formation from depleted mantle sources at 3.53, 3.47, and perhaps at 3.36 Ga (εHft between -1.7 and +4.5), accompanied by partial reworking of an Eoarchaean crustal component as old as 3.75-3.95 Ga. In contrast, crustal reworking was the predominant process between 3.28 and 3.22 Ga (εHft between -6.0 and +0.9), probably related to subduction and collision of terranes along the Inyoka Fault system. The zircon U-Pb and Hf isotope datasets favour a southern provenance for the Fig Tree and Moodies sediments, comprising granitoids in the vicinity of the southern Barberton Greenstone Belt and in Swaziland. This finding is in contrast to the sedimentary record of the Moodies Group, which mostly suggests a northern and along-strike provenance. This discrepancy may be due to reworking of sediments during extensive syn- and postorogenic strike-slip faulting and high uplift or subsidence between 3.26 and 3.19 Ga.

Reconstructing hydrological conditions of past warm periods, such as the Eocene ‘hot house’ provides empirical data to compare to state of the art climate models. However, reconstructing these changes in deep time is challenging, for example, given the complex interplay between evapotranspiration, precipitation and runoff. As a proxy for past changes in these hydrological systems, the dynamics of fresh water input into marginal seas can be used to identify the spatiotemporal distribution of riverine runoff. Elemental barium (Ba) and radiogenic strontium ( 87 Sr) are, depending on the amount of runoff and the background geology of the catchment area, typically enriched in river waters in comparison to seawater and can thus be utilized to determine changes in riverine fresh water discharge. Here, we use barium to calcium ratios (Ba/Ca) and radiogenic strontium isotopes ( 87 Sr/ 86 Sr) measured in fossil bivalve shells to reconstruct patterns of fresh water input into the paleo North Sea during the early to middle Eocene. Our reconstruction shows the potential of Ba/Ca and 87 Sr/ 86 Sr to serve as proxies for riverine runoff and highlights the spatiotemporal complexity of Eocene hydrological conditions in western Europe. In particular, our results enable changes in riverine input along geological to perennial time scales for different coastal regions to be determined, revealing a steady influx of fresh water, but with distinct spatiotemporal differences.

The accessories perovskite, pyrochlore, zirconolite, calzirtite and melanite from carbonatites and carbonate-rich foidites from the Kaiserstuhl are variously suited for the in situ determination of their U–Pb ages and Sr, Nd- and Hf-isotope ratios by LA-ICP-MS. The 143Nd/144Nd ratios may be determined precisely in all five phases, the 176Hf/177Hf ratios only in calzirtite and the 87Sr/86Sr ratios in perovskites and pyrochlores. The carbonatites and carbonate-rich foidites belong to one of the three magmatic groups that Schleicher et al. (1990) distinguished in the Kaiserstuhl on the basis of their Sr, Nd and Pb isotope ratios. Tephrites, phonolites and essexites (nepheline monzogabbros) form the second and limburgites (nepheline basanites) and olivine nephelinites the third. Our 87Sr/86Sr isotope data from the accessories overlap with the carbonatite and olivine nephelinite fields defined by Schleicher et al. (1990) but exhibit a much narrower range. These and the εNd and εHf values plot along the mantle array in the field of oceanic island basalts relatively close to mid-ocean ridge basalts. Previously reported K–Ar, Ar–Ar and fission track ages for the Kaiserstuhl lie between 16.2 and 17.8 Ma. They stem entirely from the geologically older tephrites, phonolites and essexites. No ages existed so far for the geologically younger carbonatites and carbonate-rich foidites except for one apatite fission track age (15.8 Ma). We obtained precise U–Pb ages for zirconolites and calzirtites of 15.66, respectively 15.5 Ma (± 0.1 2σ) and for pyrochlores of 15.35 ± 0.24 Ma. Only the perovskites from the Badberg soevite yielded a U–P concordia age of 14.56 ± 0.86 Ma while the perovskites from bergalites (haüyne melilitites) only gave 206Pb/238U and 208Pb/232Th ages of 15.26 ± 0.21, respectively, 15.28 ± 0.48 Ma. The main Kaiserstuhl rock types were emplaced over a time span of 1.6 Ma almost 1 million years before the carbonatites and carbonate-rich foidites. These were emplaced within only 0.32 Ma.

In this contribution we report the first systematic study of zircon U‐Pb geochronology and δ18O‐εHf(t) isotope geochemistry from 10 islands of the hot‐spot related Galapagos Archipelago. The data extracted from the zircons allow them to be grouped into three types: (a) young zircons (0–∼4 Ma) with εHf(t) (∼5–13) and δ18O (∼4–7) isotopic mantle signature with crystallization ages dating the islands, (b) zircons with εHf(t) (∼5–13) and δ18O (∼5–7) isotopic mantle signature (∼4–164 Ma) which are interpreted to date the time of plume activity below the islands (∼164 Ma is the minimum time of impingement of the plume below the lithosphere), and (c) very old zircons (∼213–3,000 Ma) with mostly continental (but also juvenile) εHf(t) (∼−28–8) and δ18O (∼5–11) isotopic values documenting potential contamination from a number of sources. The first two types with similar isotopic mantle signature define what we call the Galápagos Plume Array (GPA). Given lithospheric plate motion, this result implies that GPA zircon predating the Galápagos lithosphere (i.e., >14–164 Ma) formed and were stored at sublithospheric depths for extended periods of time. In order to explain these observations, we performed 2D and 3D thermo‐mechanical numerical experiments of plume‐lithosphere interaction which show that dynamic plume activity gives rise to complex asthenospheric flow patterns and results in distinct long‐lasting mantle domains beneath a moving lithosphere. This demonstrates that it is physically plausible that old plume‐derived zircons survive at asthenospheric depths below ocean islands. Key Points Our data define the Galápagos Plume Array defined by mantle εHf(t) and δ18O values in the range ∼0–164 Ma This finding allows dating back plume activity to, at least, early Middle Jurassic (∼164 Ma) Numerical experiments confirm it is plausible that old Plume‐derived zircons survive in the asthenosphere for extended periods of time

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.