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The first generations of stars left their chemical fingerprints on metal-poor stars in the Milky Way and its surrounding dwarf galaxies. While instantaneous and homogeneous enrichment implies that groups of conatal stars should have the same element abundances, small amplitudes of abundance scatter are seen at fixed [Fe/H]. Measurements of intrinsic abundance scatter have been made with small high-resolution spectroscopic data sets where measurement uncertainty is small compared to this scatter. In this work, we present a method to use mid-resolution survey data, which have larger errors, to make this measurement. Using APOGEE Data Release 17, we calculate the intrinsic scatter of Al, O, Mg, Si, Ti, Ni, and Mn relative to Fe for 333 metal-poor stars across six classical dwarf galaxies around the Milky Way, and 1604 stars across 19 globular clusters (GCs). We calibrate the reported abundance errors in bins of signal-to-noise ratio and [Fe/H] using a high-fidelity halo data set. Applying these calibrated errors to the APOGEE data, we find small amplitudes of average intrinsic abundance scatter in dwarf galaxies ranging from 0.03 to 0.09 dex, with a median value of 0.047 dex. For the GCs, we find intrinsic scatters ranging from 0.01 to 0.11 dex, with particularly high scatter for Al and O. Our measurements of intrinsic abundance scatter place important upper bounds, which are limited by our calibration, on the intrinsic scatter in these systems, as well as constraints on their underlying star formation history and mixing that we can look to simulations to interpret. [ABSTRACT FROM AUTHOR]

The first results of 147Sm‒143Nd and Rb‒Sr ID-TIMS isotopic–geochronological results of a comparative study of 12 samples of volcanic rocks of the Bashkirian Meganticlinorium, which were previously dated by zircons from these samples using the U‒Pb SHRIMP-II method showing the predominance of the Paleozoic ages among three stratigraphic levels with Riphean magmatic events in the South Urals, are presented. New 147Sm‒143Nd and Rb‒Sr ID-TIMS isotopic data showed that the volcanic rocks evolved as a result of crustal–mantle interaction. The Nd model ages (TDM) (2302–2540 Ma) of volcanic rocks of the Taratash Anticlinorium represent the ages of the protolith characterized by εNd(t) values from –17.4 to –20.5. The TDM value (2033 Ma) of the Paleozoic volcanic rocks of the Yamantau Anticlinorium indicates a younger (Paleoproterozoic) substrate. The minimum Nd model ages (TDM = 1160–1233 Ma) are determined for the volcanic rocks, which are spatially related to metabasalts of the Igonin magmatic event (707‒732 Ma) in the Tirlyan Syncline. The smallest εNd(t) values (–3.2, –0.9, –0.7) indicating a decrease in the amount of a crustal component relative to the mantle material are determined for the Paleozoic metabasalts in the Tirlyan Syncline in the eastern wing of the Bashkirian Meganticlinorium, which is probably related to the activation of plume processes in the eastern part of the orogen. The Rb‒Sr and 147Sm‒143Nd ID-TIMS isotopic systematics of the studied volcanic rocks expands our understanding of mantle–crustal interactions within three stratigraphic levels with Riphean magmatic events of the South Urals. [ABSTRACT FROM AUTHOR]

Comet 81P/Wild 2 is a ∼4.5 km-sized primordial object that almost has not been modified by internal heating by 26Al decay. Its nucleus could have been formed by hierarchical agglomeration or gravitational collapse of pebble swarms concentrated by streaming instability. To shed light on the cometesimal formation mechanism from laboratory sample analysis, we reexamined the 26Al–26Mg isotope systematics of the plagioclase-bearing fragment, Pyxie (from Wild 2 track 81), with significantly improved analytical precision. The revised upper limit of the initial (26Al/27Al)0 of Pyxie is ≤1.5 × 10−6, 2 times smaller than those estimated from other Wild 2 fragments. Assuming homogenous distribution of 26Al in the early solar system, the minimum crystallization age of Pyxie is estimated to be >3.6 Ma after calcium–aluminum-rich inclusions. Additional petrologic examination demonstrated that it is a chondrule fragment formed in disk environments enriched in moderately volatile elements comparable to the Si-rich rim of CR chondrules before accreting by comet Wild 2. The late accretion of the Wild 2 nucleus with most silicates likely from a common source are not favored by the hierarchical agglomeration model that considers early and continuous accretion. Instead, the results are more in line with comet formation by gentle gravitational collapse of pebbles when the 26Al abundance is extremely low (26Al/27Al ≤ 1.5 × 10−6) before gas dispersal. [ABSTRACT FROM AUTHOR]

To date, the most complete paleolake‐level reconstructions for the late Pleistocene water bodies that once occupied the Dead Sea depression have been based on the combination of dating of lake sediments and terrestrial materials. However, despite these major accomplishments, there is still limited spatial control regarding the water levels, suggesting some degree of uncertainty concerning the magnitude and rate of lake‐level changes. Here, we re‐examine the late Pleistocene lake‐level changes in the Dead Sea during the transition from paleolake Lisan to the present‐day Dead Sea. We rely on systematic dating of fossil stromatolites including 84 radiocarbon and 15 U‐series ages, stable‐isotope measurements, paleobiology, high‐resolution topography, and numerical modeling to assess lake‐level changes. Our results indicate that the highstand of paleolake Lisan was of shorter duration and the transition between Lake Lisan and the Dead Sea occurred at least 5 Kyrs earlier than previously indicated. By refining the timeline and accuracy of lake‐level positions during the transition paleolake Lisan—Dead Sea, our study offers new insights into the regional and local paleo‐climatic conditions during the last glacial period in this region. Plain Language Summary: Index points, reflecting the unique position of the water levels in space and time, have been broadly used in marine realms to reconstruct past sea‐level changes. Here we study lake‐level variations using index points based on geomorphic and biological markers collected along the western and eastern coasts of the Dead Sea. Previous studies indicate that during the last glacial period (20–30 ka), the Dead Sea depression was filled by paleolake Lisan, which lasted 10 Kyrs. As it dried, dozens of paleo‐shorelines remained etched in the landscape. Lake level index points estimated from 99 radiometric ages in these paleo‐shorelines suggest that Lisan's highstand was shorter and the transition to the Dead Sea occurred 5 Kyrs earlier than previously thought. These novel results suggest an initial and wet period followed by drier conditions, altering the regional paleo‐climatic narrative during the last glacial period. Key Points: Lake paleo‐shorelines and fossil stromatolites are used to reconstruct lake‐level changes during the transition paleolake Lisan‐Dead SeaFossil stromatolites were dated using radiocarbon and U‐series applying temporal and vertical correctionsThe transition between paleolake Lisan and the Dead Sea occurred ∼5 Kyrs earlier than estimated by previous reconstructions [ABSTRACT FROM AUTHOR]

Disentangling inputs of aeolian dust, ice-rafted debris (IRD), and eroded continental detritus delivered by ocean currents to marine sediments provide important insights into Earth System processes and climate. This study uses Sr-Nd-Pb isotope ratios of the continent-derived (lithogenic) fraction in deep-sea core TN057-6 from the subantarctic Southern Ocean southwest of Africa over the past 150,000 y to identify source regions and quantify their relative contributions and fluxes utilizing a mixing model set in a Bayesian framework. The data are compared with proxies from parallel core Ocean Drilling Program Site 1090 and newly presented data from potential South America aeolian dust source areas (PSAs), allowing for an integrated investigation into atmospheric, oceanic, and cryospheric dynamics. PSA inputs varied on glacial/interglacial timescales, with southern South American sources dominating up to 88% of the lithogenic fraction (mainly Patagonia, which provided up to 68%) during cold periods, while southern African sources were more important during interglacials. During the warmer Marine Isotope Stage (MIS) 3 of the last glacial period, lithogenic fluxes were twice that of colder MIS2 and MIS4 at times, and showed unique isotope ratios best explained by Antarctic-derived IRD, likely from the Weddell Sea. The IRD intrusions contributed up to 41% at times and followed Antarctic millennial warming events that raised temperatures, causing instability of icesheet margins. High IRD was synchronous with increased bioavailable iron, nutrient utilization, high biological productivity, and decreased atmospheric CO2. Overall, TN057-6 sediments record systematic Southern Hemisphere climate shifts and cryospheric changes that impacted biogeochemical cycling on both glacial/interglacial and subglacial timescales. [ABSTRACT FROM AUTHOR]

The Skagerrak basin represents the main sink area for fine-grained sediment in the North Sea region and constitutes a natural deposition center for sediments that are supplied from the Atlantic, the Baltic Sea and the surrounding continental margins and coasts. However, the exact sources and their proportional contributions to the North Sea sediments and to the Skagerrak deposits are not well understood. To trace the predominant sources of the sediment and to gain a better understanding of the sedimentary processes in the North Sea and the Skagerrak basin, radiogenic Sr, Nd, and Hf isotope signatures and clay mineral compositions of the detrital clay fraction of surface sediment samples from the North Sea, the Scandinavian margins and the Baltic Sea were measured. The results indicate that the major source for Skagerrak clay-size sediments is the northern North Sea but Scandinavia as well as the southern North Sea including the southern England coast also contribute material. Seabed and coastal erosion in the northern North Sea are enhanced by the inflowing Atlantic Currents, which provide the Skagerrak with high amounts of clay size sediments. In contrast, the southern North Sea, the Baltic Sea and mid-European rivers such as Weser, Elbe and Ems are only minor contributors. As Skagerrak deposits are dominated by clay sized material (up to 60%), the reconstructed sediment processes in this study deviate from findings in previous sediment budget studies, which were based on both clay and silt fraction and indicated predominant influences from the southern North Sea. These results highlight that coastal and seabed erosion in the North Sea is a previously underestimated source of fine-grained sediments for depocenters in the entire North Sea. With regard to climate change, the global sea-level rise will likely enhance erosional processes and can therefore significantly influence the sediment budget of the entire North Sea. [ABSTRACT FROM AUTHOR]

The regional impact of abrupt glacial climate variability remains poorly constrained for arid southwestern Asia, particularly winter dynamics during Marine Isotope Stage 3, due to limited paleoarchives in the Middle East. Here, we present continuous speleothem records of δ18O and δ13C with robust chronologies for southwestern and central Iran, spanning ∼50–30 ka. Stable‐isotope signals in the two stalagmites are generally uncorrelated and do not exhibit a consistent response to Greenland stadials or interstadials; however, both show a positive δ18O excursion that coincides with Heinrich event 4. We explore the potential mechanisms for intermittent coupling of speleothem δ18O across Iran through isotope‐enabled atmospheric modeling outputs, from which we utilize the spatial δ18O gradient as a proxy for wintertime westerly versus southerly jet strength. Our results suggest that during Heinrich event 4 and several Greenland stadials, stronger westerly winds enhanced Mediterranean moisture contributions to both sites and reduced aridity in southern Iran. Plain Language Summary: Stalagmites are useful archives to reconstruct the climate of the past. In order to shed light on the past climate of western Asia and the response of this region to the rapid climate changes, here we present two stalagmites from central and southwestern Iran that span 50,000 to 30,000 yrs ago. Our findings suggest that during extreme cold events, the moisture originates mostly from the west, whereas out of these extraordinarily cold periods moisture comes mostly from the south. Key Points: Continuous high‐resolution speleothem record of climatic change in southwestern and central Iran between 50 and 30 kaDecoupled responses of stable‐isotope gradients in central and southern Iran to glacial climate variability, except during Heinrich event 4Decreased impact of southerly moisture sources and reinforced westerlies during extreme cold events [ABSTRACT FROM AUTHOR]

This study uses a multiproxy approach including the first use of 187Os/188Os, %C37:4 biomarkers, carbonate content, sedimentological grain size, geochemical X‐ray fluorescence and microfossil benthic foraminifera species combined with radiocarbon dating, measured on six cores from across the Skagerrak, in order to study the Lateglacial to Middle Holocene history of the area. A new chronostratigraphic framework is developed based on the appearance of specific benthic foraminifera species along with changes in carbonate/X‐ray fluorescence and grain size data. This allowed the correlation of cores based on a series of radiocarbon dated tie points. Analysing the cores together reveals several events recorded in the Skagerrak including: (i) an increased freshwater input (bracketed between 13.3 and 11.3 cal. ka BP) signified by radiogenic 187Os/188Os values, high %C37:4 values and an increase in sand content; (ii) the Glomma drainage event, signified by a sudden appearance of Valvulineria as well as higher %C37:4; and (iii) the opening of the Danish Straits and English Channel leading to the development of modern‐day conditions and circulation patterns in the Skagerrak, signified by the appearance of Hyalinea balthica and a fall in %C37:4. [ABSTRACT FROM AUTHOR]

While basaltic volcanism is dominant during rifting and continental breakup, felsic magmatism may be a significant component of some rift margins. During International Ocean Discovery Program (IODP) Expedition 396 on the continental margin of Norway, a graphite‐garnet‐cordierite bearing dacitic unit (the Mimir dacite) was recovered in two holes within early Eocene sediments on Mimir High (Site U1570), a marginal high on the Vøring Transform Margin. Here, we present a comprehensive textural, petrological, and geochemical study of the Mimir dacite in order to assess its origin and discuss the geodynamic implications. The major mineral phases (garnet, cordierite, quartz, plagioclase, alkali feldspar) are hosted in a fresh rhyolitic, vesicular, glassy matrix that is locally mingled with sediments. The major element chemistry of garnet and cordierite, the presence of zircon inclusions with inherited cores, and thermobarometric calculations all support an upper crustal metapelitic origin. While most magma‐rich margin models favor crustal anatexis in the lower crust, thermobarometric calculations performed here show that the Mimir dacite was produced at upper‐crustal depths (<5 kbar, 18 km depth) and high temperature (750–800°C) with up to 3 wt% water content. In situ U‐Pb analyses on zircon inclusions give a magmatic crystallization age of 54.6 ± 1.1 Ma, consistent with emplacement that post‐dates the Paleocene‐Eocene Thermal Maximum. Our results suggest that the opening of the Northeast Atlantic was associated with a phase of low‐pressure, high‐temperature crustal anatexis preceding the main phase of magmatism. Plain Language Summary: Fifty‐six million years ago, the continents were beginning the final phase of their journey to their modern‐day locations. This included the rifting and formation of the Northeast Atlantic Ocean, known in particular for producing considerable magmatism during continental break‐up. In summer 2021, Expedition 396 of the International Ocean Discovery Program drilled the oceanic floor off the coast of present‐day Norway to collect volcanic and sedimentary rocks deposited at this time. Their main goal was to investigate the cause of the excess magmatism and its potential implications for the global climate. While sampling sediments on the expedition, an unexpected volcanic unit, a glassy garnet‐cordierite dacite, was recovered. To determine its origin, we combined multiple methods (petrography, stratigraphy, thermodynamic calculations, petrochronology, in situ compositional analyses) and showed that the unit is a product of melting of in the continental crust at shallow depth during the rifting process and likely later emplaced in shallow water. Our results demonstrate that the rifting process in the Northeast Atlantic included a long and intense period of continental crustal thinning. This research provides evidence needed to reconstruct the evolution of the Northeast Atlantic Ocean. Key Points: A dacitic unit was recovered in early Eocene sediments on the Vøring margin during International Ocean Discovery Program Expedition 396The Mimir dacite was formed by upper crustal anatexis at 54.6 ± 1.1 Ma, shortly after the Paleocene‐Eocene Thermal MaximumThe dacite is evidence for a break‐up phase associated with significant continental lithospheric extension [ABSTRACT FROM AUTHOR]

Sedimentary provenance is a powerful tool for reconstructing convergent margin evolution. However, single mineral approaches, like detrital zircon, have struggled to track sediment input from mafic and metamorphic sources. Detrital rutile complements detrital zircon datasets by offering a path forward in sedimentary provenance reconstructions where metamorphic terranes are potential source regions. However, U–Pb geochronology in rutile can be difficult due to low uranium concentrations and incorporation of common Pb, and multiple workflows are currently in use. Here, we investigate U–Pb and trace element data reduction, processing, and common Pb correction workflows using new detrital rutile U–Pb geochronology and trace element geochemistry results from the Late Cretaceous to Eocene Central Sakarya and Sarıcakaya basins in Anatolia. A significant number of analyses were rejected (54 %) due to signal intensity limitations, namely low U, low Pb, anomalous signal, and inclusions. We identify this as a universal limitation of large- n detrital rutile studies and recommend the systematic reporting of the amount of discarded analysis and the processes for rejection in all studies using detrital rutile U–Pb geochronology. Additionally, we show that (1) the 208 Pb and 207 Pb common Pb reduction schemes produce similar age distributions and can be used interchangeably, while (2) the Stacey–Kramers distance is a suitable metric for quantifying U–Pb discordance, but a discordance filter is not recommended. (3) Instead, filtering U–Pb data by a power law function based on the corrected date uncertainty is appropriate. (4) The exclusion of low uranium concentration rutile biases date distributions and favors pelitic-derived, higher Zr-in-rutile temperature, and higher U–Pb concordance grains. (5) Paired U–Pb and trace elements can be used to evaluate potential bias in U–Pb data rejection, which reveals that data rejection does not bias the provenance interpretations. Finally, (6) The signature of sediment recycling can be identified through U–Pb dates and Zr-in-rutile temperatures. To better navigate the complexity of detrital rutile datasets and to facilitate the standardization of data reporting approaches, we provide open-access code as Jupyter notebooks for data processing and analysis steps, including common Pb corrections, uncertainty filters, discordance calculations, and trace element analysis. [ABSTRACT FROM AUTHOR]

Paleoceanographic interpretations of Plio-Pleistocene climate variability over the past 5 million years rely on the evaluation of event timing of proxy changes in sparse records across multiple ocean basins. In turn, orbital-scale chronostratigraphic controls for these records are often built from stratigraphic alignment of benthic foraminiferal stable oxygen isotope (δ18 O) records to a preferred dated target stack or composite. This chronostratigraphic age model approach yields age model uncertainties associated with alignment method, target selection, the assumption that the undated record and target experienced synchronous changes in benthic foraminiferal δ18 O values, and the assumption that any possible stratigraphic discontinuities within the undated record have been appropriately identified. However, these age model uncertainties and their impact on paleoceanographic interpretations are seldom reported or discussed. Here, we investigate and discuss these uncertainties for conventional manual and automated tuning techniques based on benthic foraminiferal δ18 O records and evaluate their impact on sedimentary age models over the past 3.5 Myr using three sedimentary benthic foraminiferal δ18 O records as case studies. In one case study, we present a new benthic foraminiferal δ18 O record for International Ocean Discovery Program (IODP) Site U1541 (54°13 ′ S, 125°25 ′ W), recently recovered from the South Pacific on IODP Expedition 383. The other two case studies examine published benthic foraminiferal δ18 O records of Ocean Drilling Program (ODP) Site 1090 and the ODP Site 980/981 composite. Our analysis suggests average age uncertainties of 3 to 5 kyr associated with manually derived versus automated alignment, 1 to 3 kyr associated with automated probabilistic alignment itself, and 2 to 6 kyr associated with the choice of tuning target. Age uncertainties are higher near stratigraphic segment ends and where local benthic foraminiferal δ18 O stratigraphy differs from the tuning target. We conclude with recommendations for community best practices for the development and characterization of age uncertainty of sediment core chronostratigraphies based on benthic foraminiferal δ18 O records. [ABSTRACT FROM AUTHOR]

The Younger Dryas stadial was characterised by a rapid shift towards cold-climate conditions in the North Atlantic realm during the last deglaciation. While some climate parameters including atmospheric temperature and glacier extent are widely studied, empirical constraints on permafrost temperature and snow thickness are limited. To address this, we present a regional dataset of cryogenic cave carbonates (CCCs) from three caves in Great Britain that formed at temperatures between - 2 and 0 °C. Our CCC record indicates that these permafrost temperatures persisted for most of the Younger Dryas. By combining ground temperatures with surface temperatures from high-resolution ground-truthed model simulations, we demonstrate that ground temperatures were approximately 6.6 ± 2.3 °C warmer than the mean annual air temperature. Our results suggest that the observed temperature offset between permafrost and the atmosphere can be explained by an average snow thickness between 0.2 and 0.9 m , which persisted for 233 ± 54 d per year. By identifying modern analogues from climate reanalysis data, we demonstrate that the inferred temperature and snow cover characteristics for the British Isles during the Younger Dryas are best explained by extreme temperature seasonality, comparable to continental parts of today's Arctic Archipelago. Such a climate for the British Isles necessitates a winter sea ice margin at approximately 45° N in the North Atlantic Ocean. [ABSTRACT FROM AUTHOR]

The 8.2 ka event has been extensively investigated as a remarkable single event but rarely considered as a part of multi-centennial climatic evolution. Here, we present absolutely dated speleothem multi-proxy records spanning 9.0–7.9 ka from Beijing in North China, near the northern limit of the East Asian summer monsoon (EASM) and thus sensitive to climate change, to provide evidence of the intensified multi-decadal climatic oscillations since 8.52 ka. Three extreme excursions characterized by inter-decadal consecutive δ18 O excursions exceeding ±1σ are identified from 8.52 ka in our speleothem record. The earlier two are characterized by enriched 18 O at ∼8.50 and 8.20 ka, respectively, suggesting a prolonged arid event, which is supported by the positive trend in δ13 C values, increased trace element ratios, and lower growth rate. Following the 8.2 ka event, an excessive rebound immediately emerges in our δ18 O and trace element records but moderate in the δ13 C, probably suggesting pluvial conditions and nonlinear response of the local ecosystem. Following two similar severe droughts at 8.50 and 8.20 ka, the different behavior of δ13 C suggests the recovering degree of resilient ecosystem responding to different rebounded rainfall intensity. A comparison with other high-resolution records suggests that the two droughts–one pluvial pattern between 8.52 and 8.0 ka is of global significance instead of being a regional phenomenon, and is causally linked to the slowdown and acceleration of the Atlantic Meridional Overturning Circulation that was further dominated by the freshwater injections in the North Atlantic. [ABSTRACT FROM AUTHOR]

The Eocene–Oligocene transition (EOT, ca. 40–33 Ma) marks a transformation from a largely ice-free to an icehouse climate mode that is well recorded by oxygen-stable isotopes and sea surface temperature proxies. Opening of the Southern Ocean gateways and decline in atmospheric carbon dioxide levels have been considered as factors in this global environmental transformation and the growth of ice sheets in Antarctica during the Cenozoic. A more comprehensive understanding is still needed of the interplay between forcing versus response, the correlation among environmental changes, and the involved feedback mechanisms. In this study, we investigate the spatio-temporal variation in export productivity using biogenic Ba (bio- Ba) from Ocean Drilling Program (ODP) sites in the Southern Ocean, focusing on possible mechanisms that controlled them as well as the correlation of export productivity changes to changes in the global carbon cycle. We document two high export productivity events in the Southern Ocean during the late Eocene (ca. 37 and 33.5 Ma) that correlate to proposed gateway-driven changes in regional circulation and to changes in global atmospheric pCO2 levels. Our findings suggest that paleoceanographic changes following Southern Ocean gateway openings, along with more variable increases in circulation driven by episodic Antarctic ice sheet expansion, enhanced export production in the Southern Ocean from the late Eocene through early Oligocene. These factors may have played a role in episodic atmospheric carbon dioxide reduction, contributing to Antarctic glaciation during the Eocene–Oligocene transition. [ABSTRACT FROM AUTHOR]

The Multiple-Diffusion Domain (MDD) model empirically describes the diffusive behavior of noble gases in some terrestrial materials and has been commonly used to interpret 40Ar/39Ar stepwise degassing observations in K-feldspar. When applied in this manner, the MDD model can be used to test crustal exhumation scenarios by identifying the permissible thermal paths a rock sample could have undergone over geological time, assuming the diffusive properties of Ar within the mineral are accurately understood. More generally, the MDD model provides a framework for quantifying the temperature-dependent diffusivity of noble gasses in minerals. However, constraining MDD parameters that successfully predict the results of step-heating diffusion experiments is a complex task and the assumptions made by existing numerical methods used to quantify model parameters can bias the absolute temperatures permitted by thermal modeling. For example, the most commonly used method (Lovera et al., 1997) assumes that no domains lose more than 60 % of their gas during early heating steps. This assumption is unverifiable, and we show that Lovera et al.'s (1997) procedure may bias predicted temperatures towards lower values when it is violated. To address this potential bias and to provide greater accessibility to the MDD model, we present a new, open-source method for constraining MDD parameters from stepwise degassing experimental results, called the "MDD Tool Kit." This software optimizes all MDD parameters simultaneously and removes any need for user-defined Ea or regression-fitting choices used by other tools. In doing so, this new method eliminates assumptions about the domain size distribution. To test the validity of our thermal predictions, we then use the MDD Tool Kit to interpret the 40Ar/39Ar results of Wong et al. (2023) from the Grayback Fault, AZ, USA. Although the resulting thermal histories are consistently ~ 60–75 °C higher than those found by Wong et al. 2023), they agree with independent observations from apatite fission track, zircon fission track, and (U-Th)/He (Howard and Foster, 1996). [ABSTRACT FROM AUTHOR]

Composition and age of unserpentinized harzburgites found as boudins and relict bodies in the Voikar–Synya massif in the olivine–antigorite fields have been studied. Rock and mineral structure and composition, as well as REE distribution and Sm–Nd absolute dating (≈2330 Ma) make it possible to consider these unserpentinized harzburgites as mantle fragments and the earliest ultramafic rocks of the Voikar–Synya massif. Silicates of these harzburgites are characterized by higher chromium which turns into chrome spinellide in different subsequent processes. Based on the data obtained, the resources of chromium mobilized during the transformation of primary ultramafic rocks have been evaluated. [ABSTRACT FROM AUTHOR]

Calcium, aluminum-rich inclusions (CAIs) are the oldest solids dated that formed in the solar system. Most CAIs in unmetamorphosed chondritic meteorites (chondrites; petrologic type ≤3.0) have uniform solar-like 16O-rich compositions (Δ17O ∼ −24‰) and a high initial 26Al/27Al ratio [(26Al/27Al)0] of ∼(4–5) × 10−5, consistent with their origin in a gas of approximately solar composition during a brief (<0.3 Ma) epoch at the earliest stage of our solar system. The nature of O-isotope heterogeneity in CAIs (Δ17O range from ∼−24 up to ∼+5‰) from weakly metamorphosed chondrites (petrologic type >3.0) remains an open issue. This heterogeneity could have recorded fluctuations of O-isotope composition of nebular gas in the CAI-forming region and/or postcrystallization O-isotope exchange of CAI minerals with aqueous fluids on the chondrite parent asteroids. To obtain insights into possible processes resulting in this heterogeneity, we investigated the mineralogy, rare-earth element abundances, and O- and Mg-isotope compositions of a CAI from the CO3.1 chondrite Dar al Gani 083. This concentrically zoned inclusion has a Zn-hercynite core surrounded by layers of (from core to edge) grossite, spinel, melilite, and Al-diopside. The various phases have heterogeneous Δ17O (from core to edge): −2.2 ± 0.6‰, −0.9 ± 2.1‰, −13.7 ± 2.1‰, −2.6 ± 2.3‰, and −22.6 ± 2.1‰, respectively. Magnesium-isotope compositions of grossite, spinel, melilite, and Al-diopside define an undisturbed internal Al–Mg isochron with (26Al/27Al)0 of (2.60 ± 0.29) × 10−6. We conclude that the variations in Δ17O of spinel and diopside recorded fluctuations in O-isotope composition of nebular gas in the CAI-forming region prior to injection and/or homogenization of 26Al at the canonical level. The 16O depletion of grossite and melilite resulted from O-isotope exchange with asteroidal fluid, which did not disturb Al–Mg isotope systematics of the CAI primary minerals. [ABSTRACT FROM AUTHOR]

The elemental abundances between strontium and silver (Z = 38–47) observed in the atmospheres of very metal-poor stars in the Galaxy may contain the fingerprint of the weak r -process and ν p -process occurring in early core-collapse supernovae explosions. In this work, we combine various astrophysical conditions based on a steady-state model to cover the richness of the supernova ejecta in terms of entropy, expansion timescale, and electron fraction. The calculated abundances based on different combinations of conditions are compared with stellar observations, with the aim of constraining supernova ejecta conditions. We find that some conditions of the neutrino-driven outflows consistently reproduce the observed abundances of our sample. In addition, from the successful combinations, the neutron-rich trajectories better reproduce the observed abundances of Sr–Zr (Z = 38–40), while the proton-rich ones, Mo–Pd (Z = 42–47). [ABSTRACT FROM AUTHOR]

Asian dust delivers highly reactive iron (FeHR) to the Pacific Ocean, affecting marine biogeochemical cycles and Earth's climate. Tracing the source of dust deposited in the Pacific is vital for assessing global nutrient cycles but poses challenges. This work applies the (234U/238U) activity ratio to determine the pre‐deposition time and provenance of dust in North Pacific Ocean sediments (Ocean Drilling Program site 1209B). Results indicate a consistent dust pre‐deposition time (134 ± 10 ka) over the past 300,000 years, except during Marine Isotope Stage 7 when volcanic ash input shortened it to 31 ± 19 ka. Comparing the dust pre‐deposition times to those of the potential source deserts, we identify the dust transported to the North Pacific Ocean was primarily from the Taklamakan Desert, which contains higher FeHR content than other deserts. This finding enhances our understanding of soluble Fe supplied to the oceans, especially in dust circulation models. Plain Language Summary: Unraveling the provenance of aeolian dust deposited in the oceans is critical for understanding marine biogeochemical cycles, past climate changes, and dust transport mechanisms. Here we measured the (234U/238U) activity ratio of marine sediments in the North Pacific Ocean to understand the source and pre‐deposition time of dust deposited in the Pacific. The source of dust in the Pacific has remained debated because of the non‐unique geochemical signatures of possible source regions and the complexity introduced by the volcanic ash. The (234U/238U) of the dust fraction in marine sediments informs the source‐to‐sink transport time for dust particles, providing a new source tracer. We compared the (234U/238U)‐derived pre‐deposition time, Nd isotopes, grain size, magnetic susceptibility and aeolian dust flux of the North Pacific marine sediments to those of potential dust source regions, and identify the Taklamakan Desert as a major source delivering dust to the North Pacific. Our work highlights the (234U/238U) and associated particle pre‐deposition time as a promising tool for tracing sources of dust in marine sediments, holding profound implications for our understanding of global dust‐nutrient cycles. Key Points: Uranium isotope‐based pre‐deposition time serves as a novel tool to trace the provenance of Asian dust transported to the North Pacific OceanDust pre‐deposition time at site 1209B remains relativity stable (134 ± 10 ka), but decreases during MIS 7 due to volcanic ash inputTaklimakan Desert is the major source of dust delivered to the North Pacific Ocean, supplying dust with highly reactive iron [ABSTRACT FROM AUTHOR]

High‐resolution records from past interglacial climates help constrain future responses to global warming, yet are rare. Here, we produce seasonally resolved climate records from subarctic‐Canada using micron‐scale measurements of oxygen isotopes (δ18O) in speleothems with apparent annual growth bands from three interglacial periods—Marine Isotope Stages (MIS) 11, 9, and 5e. We find 3‰ lower δ18O values during MIS 11 than MIS 5e, despite MIS 11 likely being warmer. We explore controls on high‐latitude speleothem δ18O and suggest low MIS 11 δ18O values reflect greater contribution of cold‐season precipitation to dripwater from longer annual ground thaw durations. Other potential influences include changes in precipitation source and/or increased fraction of cold‐season precipitation from diminished sea ice in MIS 11. Our study highlights the potential for high‐latitude speleothems to yield detailed isotopic records of Northern Hemisphere interglacial climates beyond the reach of Greenland ice cores and offers a framework for interpreting them. Plain Language Summary: Few climate records pre‐dating the last ice age exist from high‐latitude North America, which inhibits our understanding of how regions with permafrost responded to past warming and how they might change in the future. Here, we help fill this data gap by using six speleothems (cave mineral deposits) from a cave in the Northwest Territories, Canada to produce climate records that span thousands of years during former warm periods of Earth's history. We find that speleothems that grew during an exceptionally warm super‐interglacial period 400,000 years ago have 3‰ lower oxygen isotope (δ18O) values compared to those that grew during a likely cooler interglacial 125,000 years ago. We explore potential explanations for the difference in δ18O across interglacials, and suggest that lower δ18O values during warmer periods reflect greater infiltration of cool‐season precipitation with longer annual ground thaw durations. This study highlights the importance of high‐latitude speleothems to provide detailed climate records beyond the range available from Greenland ice cores. Key Points: Long high‐latitude terrestrial climate records are rare in the Northern HemisphereHigh‐latitude speleothems can provide ultra‐high‐resolution climate records beyond the reach of Greenland ice coresMean oxygen isotopes of Arctic and subarctic speleothems likely are controlled by annual ground thaw durations [ABSTRACT FROM AUTHOR]

Chronological records of elemental concentrations in fish otoliths are a widely used tool to infer the environmental conditions experienced by individual fish. To interpret elemental signals within the otolith, it is important to understand how both external and internal factors impact ion uptake, transport and incorporation. In this study, we have combined chronological records from otoliths and archival data storage tags to quantify the influence of internal (sex, size, age, growth) and external (temperature, depth, salinity) conditions on otolith elemental chemistry of cod (Gadus morhua) in natural settings of the Baltic Sea. This study focused on elements primarily under physiological control: Phosphorus (P), magnesium (Mg) and zinc (Zn); and elements under environmental control: Strontium (Sr), barium (Ba) and manganese (Mn). Based on known spatial and temporal patterns in environmental conditions and fish size, growth, and maturity, we posed a series of hypotheses of expected otolith element patterns. Partial effects of internal and external drivers on element concentration were analyzed using a Linear Mixed Model approach with random variables (fish and year). Predicted effects of otolith concentrations of all elements under physiological control (P, Mg, Zn) showed similar trends, with distinct seasonal patterns (lowest concentration in late spring, highest concentrations in winter), and a positive correlation with water temperature, in addition to higher Zn and lower P in spawning individuals. Predicted effects of otolith concentrations of elements expected to be predominantly under environmental control showed the predicted geographic and depth-related trends based on ambient salinity (Ba) and coastal hypoxia (Mn). However, contrary to expectation, Sr was unrelated to salinity. Predicted otolith Ba, Sr and Mn concentrations also exhibited pronounced seasonal patterns that were out of phase with each other but appeared to be partly explained by spawning/feeding migrations. While performing laboratory validation studies for adult fish is typically not possible, these results highlight the importance of assessing local water chemistry and freshwater endmembers in one's study system before otolith elemental chemistry can be reliably used to reconstruct fish habitat use and environmental histories. [ABSTRACT FROM AUTHOR]

Surface heat flow is a geophysical variable that is affected by a complex combination of various heat generation and transport processes. The processes act on different lengths scales, from tens of meters to hundreds of kilometers. In general, it is not possible to resolve all processes due to a lack of data or modeling resources, and hence the heat flow data within a region is subject to residual fluctuations. We introduce the REgional HEAT-Flow Uncertainty and aNomaly Quantification (REHEATFUNQ) model, version 2.0.1. At its core, REHEATFUNQ uses a stochastic model for heat flow within a region, considering the aggregate heat flow to be generated by a gamma-distributed random variable. Based on this assumption, REHEATFUNQ uses Bayesian inference to (i) quantify the regional aggregate heat flow distribution (RAHFD) and (ii) estimate the strength of a given heat flow anomaly, for instance as generated by a tectonically active fault. The inference uses a prior distribution conjugate to the gamma distribution for the RAHFDs, and we compute parameters for a uninformed prior distribution from the global heat flow database by. Through the Bayesian inference, our model is the first of its kind to consistently account for the variability in regional heat flow in the inference of spatial signals in heat flow data. Interpretation of these spatial signals and in particular their interpretation in terms of fault characteristics (particularly fault strength) form a long-standing debate within the geophysical community. We describe the components of REHEATFUNQ and perform a series of goodness-of-fit tests and synthetic resilience analyses of the model. While our analysis reveals to some degree a misfit of our idealized empirical model with real-world heat flow, it simultaneously confirms the robustness of REHEATFUNQ to these model simplifications. We conclude with an application of REHEATFUNQ to the San Andreas fault in California. Our analysis finds heat flow data in the Mojave section to be sufficient for an analysis and concludes that stochastic variability can allow for a surprisingly large fault-generated heat flow anomaly to be compatible with the data. This indicates that heat flow alone may not be a suitable quantity to address fault strength of the San Andreas fault. [ABSTRACT FROM AUTHOR]

While the mission's primary goal was focused on exoplanet detection and characterization, Kepler made and continues to make extraordinary advances in stellar physics. Stellar rotation and magnetic activity are no exceptions. Kepler allowed for these properties to be determined for tens of thousands of stars from the main sequence up to the red giant branch. From photometry, this can be achieved by investigating the brightness fluctuations due to active regions, which cause surface inhomogeneities, or through asteroseismology as oscillation modes are sensitive to rotation and magnetic fields. This review summarizes the rotation and magnetic activity properties of the single main-sequence solar-like stars within the Kepler field. We contextualize the Kepler sample by comparing it to known transitions in the stellar rotation and magnetic-activity evolution, such as the convergence to the rotation sequence (from the saturated to the unsaturated regime of magnetic activity) and the Vaughan-Preston gap. While reviewing the publicly available data, we also uncover one interesting finding related to the intermediate-rotation gap seen in Kepler and other surveys. We find evidence for this rotation gap in previous ground-based data for the X-ray luminosity. Understanding the complex evolution and interplay between rotation and magnetic activity in solar-like stars is crucial, as it sheds light on fundamental processes governing stellar evolution, including the evolution of our own Sun. [ABSTRACT FROM AUTHOR]

Provenance records from sediments deposited offshore of the West Antarctic Ice Sheet (WAIS) can help identify past major ice retreat, thus constraining ice‐sheet models projecting future sea‐level rise. Interpretations from such records are, however, hampered by the ice obscuring Antarctica's geology. Here, we explore central West Antarctica's subglacial geology using basal debris from within the Byrd ice core, drilled to the bed in 1968. Sand grain microtextures and a high kaolinite content (∼38–42%) reveal the debris consists predominantly of eroded sedimentary detritus, likely deposited initially in a warm, pre‐Oligocene, subaerial environment. Detrital hornblende 40Ar/39Ar ages suggest proximal late Cenozoic subglacial volcanism. The debris has a distinct provenance signature, with: common Permian‐Early Jurassic mineral grains; absent early Ross Orogeny grains; a high kaolinite content; and high 143Nd/144Nd and low 87Sr/86Sr ratios. Detecting this "fingerprint" in Antarctic sedimentary records could imply major WAIS retreat, revealing the WAIS's sensitivity to future warming. Plain Language Summary: Ice loss from the West Antarctic Ice Sheet (WAIS) could potentially raise global sea level by up to 4 m over the coming decades to centuries. However, projections of sea‐level contributions from the WAIS are highly uncertain. Understanding when the WAIS was smaller in warm times in the Earth's more recent history would reduce these uncertainties, but direct evidence for the most recent large‐scale WAIS retreat is lacking. Tracing the source of sediments deposited offshore will help detect WAIS retreat because, under a smaller WAIS, there would be more erosion of presently ice‐covered areas in central West Antarctica. However, the subglacial geology of central West Antarctica is poorly known, making it difficult to identify a WAIS retreat signal in sedimentary records. Here, we present new results from debris in the Byrd ice core, drilled in the center of the WAIS to its base in 1968. The mineralogical, geochemical and age compositions of the debris provide a distinct geological "fingerprint" that should be identifiable in sedimentary records. This fingerprint can be searched for in existing and upcoming Antarctic drill core records, which will ultimately help constrain the environmental conditions that would lead to future WAIS retreat and the resulting sea‐level rise. Key Points: Debris from the base of the Byrd ice core comprises predominantly of sedimentary strata weathered before the onset of Antarctic glaciation40Ar/39Ar dated hornblende grains support evidence for recent subglacial volcanismByrd geochemical data reveal the provenance signature expected in marine sediments following major West Antarctic Ice Sheet retreat [ABSTRACT FROM AUTHOR]

The hydrocarbon seepage chronology during deglaciation across the formerly glaciated Barents Sea was established using uranium-thorium (U-Th) dating of seep carbonates. Seep carbonates were sampled with remotely operated vehicles (ROV) from the seafloor at three active hydrocarbon seeps (water depth 156-383 m), located in the north-west (Storfjordrenna), north-central (Storbanken High), and south-west (Loppa High) Barents Sea. Overall, the U-Th dates range from 13.5 to 1.2 thousand years (ka) before present, indicating episodic seep carbonate formation since the late Pleistocene throughout the Holocene. The new U-Th dates indicate protracted post-glacial gas seepage, congruent with previously published seep carbonate ages from the south-west Barents Sea. Gas hydrate dissociation and associated seep carbonate formation occurred at Storfjordrenna between ≈6 and 1.2 ka, and around 13.5 and 6 ka at Storbanken. Early and late Holocene seep carbonate ages from Loppa High support post-glacial seismic activity as potential seepage trigger mechanism. [ABSTRACT FROM AUTHOR]

Between 14.5 and 5 ka, the Sahara was vegetated owing to a wet climate during the African humid period. However, the climatic factors sustaining the "green Sahara" are still a matter of debate. Particularly the role of winter precipitation is poorly understood. Using the stable hydrogen isotopic composition (δ D, where D stands for deuterium) of high molecular weight (HMW) n -alkanoic acids in a marine sediment core from the eastern Mediterranean, we provide a continuous record for winter precipitation in the Nile river delta spanning the past 18 kyr. Pairing the data with δ D records from HMW n -alkanes from the same core, we show that HMW n -alkanoic acids constantly derived from the delta, while the HMW n -alkanes also received significant contributions from the headwaters between ∼ 15–1 ka when fluvial runoff enhanced. This enables us to reconstruct the evolution of Mediterranean (winter) and monsoonal (summer) rainfall in the Nile river watershed in parallel. In the delta, the Heinrich stadial 1 (HS1) evolved in two phases, with a dry episode between ∼ 17.5–16.0 ka, followed by wet conditions between ∼ 16–14.5 ka. Winter rainfall enhanced substantially between 11–6 ka, lagging behind the intensification of the summer monsoon by ca. 3 kyr. Heavy winter rainfall resulted from a southern position of the Atlantic storm track combined with elevated sea surface temperatures in the eastern Mediterranean, reinforcing local cyclogenesis. We show that during the green Sahara, monsoon precipitation and Mediterranean winter rainfall were both enhanced and infer that the winter rainfall zone extended southwards, delivering moisture to the Sahara. Our findings corroborate recent hypotheses suggesting that winter rains that extended southward were a crucial addition to the northward displacement of the summer monsoon in helping to sustain a green Sahara. [ABSTRACT FROM AUTHOR]

Reconstructing of past hydroclimates at regional scales during the Common Era (CE) is necessary to place the current warming in the context of natural climate variability. Here we present a composite record of oxygen isotope variations during last 2500 years based on eight stalagmites from four caves in the central Pyrenees (NE Spain) dominated by temperature variations, with the amount of precipitation playing a minor role. The dataset is compared with other Iberian reconstructions that show a high degree of internal coherence with respect to variability at the centennial scale. The Roman Period (RP) (especially 0–200 CE), the Medieval Climate Anomaly (MCA), and part of the Little Ice Age (LIA) represent the warmest periods, while the coldest decades occurred during the Dark Ages (DA) and most of the LIA intervals (e.g., 520–550 CE and 1800–1850 CE). Importantly, the LIA cooling or the MCA warming were not continuous or uniform and exhibited high decadal variability. The Industrial Era (IE) shows an overall warming trend although with marked cycles and partial stabilization during the last 2 decades (1990–2010). The strong coherence between the speleothem data, European temperature reconstructions and global tree-ring data informs about the regional representativeness of this new record as Pyrenean past climate variations. Solar variability, likely through its impact on the North Atlantic Oscillation, and major volcanic eruptions appear to be the two main drivers of climate in southwestern Europe during the past 2.5 millennia. [ABSTRACT FROM AUTHOR]

The latitudinal position of the Intertropical Convergence Zone (ITCZ) reflects the energy imbalance between the hemispheres. Southward displacements of the ITCZ during the Last Glacial Maximum (LGM; 19–26.5 ka) and Heinrich Stadial 1 (HS1; 14.6–17.5 ka), are widely accepted, but their magnitude is controversial. Geochemistry of detrital fractions in down‐core sediments collected from 6°N to equator along the 131.5°W transect reveal a distinct shift in εNd, La/Yb, and La–Sc–Th composition from predominantly northern hemisphere‐sourced to mixed northern and southern hemisphere‐sourced signal at 3°N–4°N during the LGM and 3°N–6°N during HS1. These contrasting provenance signals point to the past ITCZ functioning as a dust barrier. Given that a comparable geochemical demarcation currently occurs at 6°N–7°N, our data suggest that the ITCZ migrated southward by ∼3° during the LGM and ∼1°–3° during HS1 relative to its modern position in the central Pacific. Plain Language Summary: The tropical rainbelt, called the Intertropical Convergence Zone (ITCZ), plays a major role in the Earth's climate system. It encircles the equatorial region slightly biased to the northern hemisphere in latitude. Wind‐blown dust deposited on the deep‐sea floor to the north and south of this belt have distinct composition because heavy rainfall prevents the dust from passing through. We collected sediments at regular intervals in a north‐south direction in the equatorial central Pacific (0°–6°N, 131.5° W), and analyzed the chemical composition of dust deposited during two cold intervals, the Last Glacial Maximum (LGM; 19–26.5 ka) and Heinrich Stadial 1 (HS1; 14.6–17.5 ka). The results show that the latitudinal boundary where the dust chemistry diverges was ∼3° south during the LGM and ∼1°–3° south during HS1 relative to today, which provides an estimate of the past movement of the ITCZ. Key Points: The mean ITCZ position can be traced geochemically with hemispheric shift in dust provenance along a meridional transectThe hemispheric shift in dust provenance occurred ∼3° and ∼1°–3° farther south than today during the LGM and HS1, respectivelyIn the central Pacific, the ITCZ responded with a similar or greater southward displacement during the LGM compared to HS1 [ABSTRACT FROM AUTHOR]

High-resolution sea-level data and high-precision dating of corals in the northern South China Sea (SCS) during the Holocene provide a reference and historical background for current and future sea-level changes and a basis for scientific assessment of the evolutionary trend of coral reefs in the SCS. Although sporadic studies have been performed around Hainan Island in the northern SCS, the reconstructed sea level presents different values or is controversial because the indicative meaning of the sea-level indicators were neither quantified nor uniform criteria. Here, we determined the quantitative relationship between modern living coral and sea level by measuring the top surfaces of 27 live Porites corals from the inner reef flat along the east coast of Hainan Island and assessed the accuracy of results obtained using coral as sea-level indicators. Additionally, three in situ fossil Porites corals were analyzed based on elevation measurements, digital X-ray radiography, and U-Th dating. The survey results showed that the indicative meanings for the modern live Porites corals is (146.09 ± 8.35) cm below the mean tide level (MTL). It suggested that their upward growth limit is constrained by the sea level, and the lowest low water is the highest level of survival for the modern live Porites corals. Based on the newly defined indicative meanings, 6 new sea-level index points (SLIPs) were obtained and 19 published SLIPs were recalculated. Those SLIPs indicated a relative sea level fluctuation between (227.7 ± 9.8) cm to (154.88 ± 9.8) cm MTL between (5 393 ± 25) cal a BP and (3 390 ± 12) cal a BP, providing evidences of the Mid-Holocene sea-level highstand in the northern SCS. Besides that, our analysis demonstrated that different sea-level histories may be produced based on different indicative meanings or criteria. The dataset of 276 coral U-Th ages indicates that coral reef development in the northern SCS comprised the initial development, boom growth, decline, and flourishing development again. A comparison with regional records indicated that synergistic effects of climatic and environmental factors were involved in the development of coral reefs in the northern SCS. Thus, the cessation of coral reef development during the Holocene in the northern SCS was probably associated with the dry and cold climate in South China, as reflected in the synchronous weakening of the ENSO and East Asian summer monsoon induced by the reduction of the 65°N summer insolation, which forced the migration of the Intertropical Convergence Zone. [ABSTRACT FROM AUTHOR]

Isotopic and elemental signatures in arc magmas bear similarities to marine sediments from the forearc. Partial melts of subducted sediments were previously invoked as the predominant carrier of material between the slab and mantle wedge, whereas aqueous fluids were deemed too inefficient at mobilizing trace elements to account for arc magma compositions. However, trace element solubility in aqueous fluids may be significantly affected by the formation of chloride complexes. We introduced NaCl into the sediment‐H2O system, and re‐investigated trace element partitioning between aqueous fluids and metasediments in a series of piston cylinder experiments at 2.5–4.5 GPa and 600–700°C. The diamond trap method was employed to separate the fluids, which were analyzed in the frozen state. Trace element compositions of fluids and all solid phases were obtained by LA‐ICP‐MS. We combined our data with published literature to demonstrate that saline fluids and sediment melts have a comparable efficiency in extracting incompatible elements from subducted sediments, producing similar element fractionation during mobile phase expulsion. Accessory phases such as allanite may only be stable in particularly Rare Earth Elements‐enriched lithologies. The Sr, Pb and Nd isotopic signatures of arc magma suggest that the mantle wedge is infiltrated by mobile phases derived from both the sediment and basalt sections of the subducted oceanic crust. Up to several percent of either sediment‐derived saline fluid or melt can account for the isotopic and elemental compositions of most arc magma. Geochemical similarities between arc magma and forearc sediments are not necessarily evidence of slab melting. Plain Language Summary: Comparing the compositions of arc magmas to marine sediments from the forearc shows that terrigenous material is subducted at convergent margins, and recycled back to the Earth's surface. It was previously thought that only partial melting of the slab could mobilize a sufficient amount of trace elements to explain the similarities between arc magma and forearc sediments. In this study, we show that both sediment melts and saline sediment‐derived aqueous fluids have a comparable efficiency in extracting trace elements from the slab. Geochemical similarities between arc magma and forearc sediments do not immediately imply slab melting. Key Points: Saline aqueous fluids and silicate melts are similarly efficient in extracting incompatible trace elements from subducted metasedimentsMiniscule amounts of sediment‐derived aqueous fluids may transfer the Pb isotopic signature from sediments to arc magmasThe presence of an elemental or isotopic "sediment fingerprint" in arc magmas does not necessarily imply sediment melting [ABSTRACT FROM AUTHOR]

Phosphorites of the Georgina Basin (northern Australia) are an established economic source of phosphate and have recently been recognized to be a potential source of rare earth elements (REE). Previous bulk‐rock geochemistry work focused on the eastern margin of the basin revealed that phosphorites from the southern region have significantly higher (up to 0.5%) REE contents than equivalent prospects further to the north. In this study, we examine the origin of REE enrichment in the Georgina Basin phosphorites using an integrated geochemical, petrographic, mineralogical, and isotopic (Sm‐Nd and Sr) approach. The trace element geochemistry of primary phosphate minerals is consistent with a seawater origin for the REEs in phosphorites, with minimal input from the underlying basement rocks. Variations in total REE concentrations are controlled largely by the seawater composition, depositional environment, and the texture of the phosphorite (grainstone vs. mudstone phosphorite). Grainstone phosphorite yields on average higher concentrations of REEs compared to the mudstone phosphorite, likely due to the higher surface‐to‐mass ratio of the grainstone phosphorite resulting in the uptake of higher concentrations of REEs during coastal reworking. The formation of the low‐REE northern and central deposits took place during early transgression in oxidized, shallow supratidal to subtidal platformal environments. During the subsequent main transgressive event, fault‐controlled topography in the southern domain allowed phosphogenesis along basement highs to be facilitated along a redox boundary, where more saline and REE‐rich deep anoxic bottom waters, along with Fe‐cycling and bacterial mediation played a major role in the enrichment of REEs in the southern phosphorites. Key Points: The origin of rare earth element (REE) enrichment in phosphorites of the Georgina Basin in northern Australia, was determined using an integrated geochemical, mineralogical, and isotopic approachThe enrichment of REEs in phosphorites is controlled by the texture and the depositional environment at the time of phosphorite formationVarying levels of REE enrichment occurred at different stages of marine transgression [ABSTRACT FROM AUTHOR]

Understanding the geochemical behavior of the Mo isotopes in estuarine systems is essential for determining the isotopic composition of riverine inputs to the ocean and for assessing the historical oxidation state of Earth's ancient oceans. However, the extent and mechanisms of Mo isotope fractionation during estuarine processes are not yet fully understood. This study systematically investigated the seasonal and spatial variations in aqueous and particulate δ98Mo values within the Pearl River Estuary (PRE). Our research found that aqueous δ98Moaque. values in both summer and winter deviated significantly from the theoretical mixing line for the PRE. Based on the geochemical characteristics of the water column, particulate matter, and pore water in the PRE, we first propose that diagenesis release from sediments is the predominant factor resulting in lower than anticipated aqueous δ98Moaque. values. Given the prevalence of suboxic and anoxic sediments in estuarine and coastal areas, such diagenetic release may substantially decrease the global riverine influx of aqueous Mo isotopes to the ocean. Additionally, particulate δ98MoSPM values exhibit an increasing trend (from 0.02 to 1.62‰) with increasing salinity in both seasons, suggesting that the terrestrial input particulate δ98MoSPM value would be heavier than the mean value for UCC. We hypothesize that the adsorption and desorption processes involving Fe (hydro) oxides predominantly influence this trend. This study advances our understanding of the mechanisms of aqueous and particulate Mo isotopic fractionation in estuarine systems and would be helpful in constraining Mo isotopic compositions of rivers and oceans. Plain Language Summary: The reliability of using Mo isotopes to trace historical shifts in global ocean redox depends heavily on precise constraints of the Mo isotopic composition of riverine inputs to the ocean. Estuaries, serving as dynamic interfaces between terrestrial and marine environments, can substantially alter the Mo isotopic composition of riverine inputs to the ocean. To more accurately constrain the Mo isotopic composition of riverine inputs to the ocean, understanding the extent and mechanisms of Mo isotope fractionation during estuarine processes is crucial. Addressing this knowledge gap, our study investigates the seasonal and spatial variations in δ98Mo values of aqueous and particulate Mo in the Pearl River Estuary (PRE), China. Our findings reveal that aqueous δ98Moaque. values are markedly lower than the theoretical mixing‐line values in both summer and winter seasons, whereas particulate δ98MoSPM values demonstrate a distinct increasing trend from the upper to lower reaches of the PRE. This suggests that estuaries can profoundly modify the Mo isotopic composition of riverine inputs to the ocean. In conclusion, we propose that the reductive release from sediments likely explains the lower aqueous δ98Moaque. values, while the adsorption and desorption of Fe (hydro) oxides primarily drive the observed increase in particulate δ98MoSPM values. Key Points: Aqueous δ98Mo values in different seasons were substantially lower than theoretical mixing‐line values in the Pearl River Estuary (PRE)Reductive release from sediments is responsible for the aqueous δ98Mo values being lower than theoretical levelsFe (hydro) oxides are the dominant factors controlling the increasing trend in the particulate δ98Mo values with salinity [ABSTRACT FROM AUTHOR]

Phosphorites can record oceanic conditions during their deposition, but the faithful retention of primary information in Paleoproterozoic deposits can be mitigated by post‐depositional processes. Here, we examine a peritidal phosphorite within a microbialite reef complex in the 2.4–2.2 Ga Turee Creek Group in Western Australia to assess the environmental information retained. Field mapping and petrography distinguishes between authigenic and locally transported phosphorite fragments, each of which contains unique information regarding the deposit. Elemental mapping and laser‐ablation analyses differentiate the impact of depositional versus early diagenetic versus metamorphic processes within these fragments. Samples within a near‐shore pebble conglomerate have mixed riverine‐oceanic signals and lack cerium anomalies, consistent with the depositional environment. Clasts from off‐shore peloidal grainstone beds retain "hat‐shaped" patterns with small negative cerium anomalies, reflective of transport and redeposition within potentially oxic seawater. U‐Pb isotopic dates range from ∼1.8 to 2.3 Ga and are generally uncorrelated with rare earth element and yttrium data. The youngest date (∼1.8 Ga) is associated with recrystallized apatite, with concave down, middle rare earth element enriched patterns. A potential depositional age, ∼2.3 Ga, is associated with massive apatite in a chert‐rich clast that has rare earth element patterns reflective of riverine‐oceanic signals. Overall, the peritidal system in the reef was dynamic, with potentially oxic seawater that had a strong riverine influence. Local recycling and reworking, early diagenesis, and later orogenic events impacted the preserved geochemical signals and together show that spatially resolved geochronological and geochemical data are ideal for interpreting ancient phosphorites. Plain Language Summary: Understanding our ancient rock record is challenging because very few rocks are preserved from early Earth. Phosphorites are sedimentary deposits that are useful environmental archives because apatites can preserve primary chemical information. Here, we examined a shallow water phosphorite deposit from a reef complex in the c. 2.4–2.2 Ga Turee Creek Group to see what information is preserved. Knowing what the environment was like at this time will provide important insights into life at the time of the Great Oxidation Event. The phosphorite here contains a variety of textures of apatite, representative of different environmental and secondary processes, so we used spatially resolved techniques to study the different textures. Our data show that more chemically pristine apatite textures record a potentially oxic, mixed riverine‐oceanic signal, while others are more representative of transport and early diagenesis or metamorphism. Overall, we show that deep‐time phosphorites are useful archives for environmental information and that life at this time may have encountered oxygenated water in the very shallow oceans. Key Points: Spatially resolved data differentiate depositional and secondary information from a peritidal phosphorite in a Paleoproterozoic microbialite reef complexApatite rare earth element data indicate a mixed riverine‐oceanic, potentially oxic signal for the depositional environmentApatite U‐Pb data show a prospective depositional/early diagenetic age (∼2.3 Ga) alongside ages coincident with regional orogenic events at ∼2.1 and ∼1.8 Ga [ABSTRACT FROM AUTHOR]

Modern Fe‐Si oxyhydroxide deposits occur in global marine hydrothermal vent sites. Despite their role as biogenic substrates and potential ore resources, much remains unknown about their formation processes. Here, we apply analyses of major and trace elements as well as Sr‐Nd‐Pb‐Fe isotopes combined with 238U‐230Th dating to Fe‐Si oxyhydroxides obtained from several hydrothermal fields along the Southwest Indian Ridge. These mineralized oxyhydroxides primarily consist of poorly crystalline two‐line ferrihydrite and amorphous opal‐A, with lesser amounts of nontronite and birnessite. The ubiquitous and characteristic Fe‐rich ultrastructures in the oxyhydroxides directly indicate microbial activity. The 238U‐230Th dating constrains their crystallization ages from ca. 11,873 to 384 years old. The seawater‐like 87Sr/86Sr and varying 143Nd/144Nd ratios underline a high proportion of seawater mixed with hydrothermal fluids. The radiogenic Pb isotopic patterns suggest a primary derivation of Pb leached from substrate basalts and to a lesser extent Pb from seawater. Stable iron isotopic compositions for different oxyhydroxides display a remarkable range between −1.47 and 0.82‰, which were interpreted as reflecting the fractionation processes during the formation of the deposits under evolving depositional redox conditions. The partial oxidation of Fe(II) and the subsurface removal of isotopically heavy Fe oxyhydroxides are suggested to play a vital role in shifting the Fe isotopic signature toward more negative values. Given that these Fe‐Si oxyhydroxide deposits exhibit features similar to certain ancient iron formations (IFs), Fe isotope systematics of these deposits may hold significant potential for fingerprinting the biological Fe oxidation processes that drove IF deposition on early Earth. Plain Language Summary: This study introduces a comprehensive examination of Fe‐Si oxyhydroxide deposits in marine hydrothermal vent sites along the Southwest Indian Ridge. Applying innovative techniques of major and trace element and Sr‐Nd‐Pb‐Fe isotope analysis combined with 238U‐230Th dating, the investigation uncovers new insights into the composition, age, and origin of microbial Fe‐Si oxyhydroxide ultrastructures. Notably, these deposits are found to be primarily composed of ferrihydrite and amorphous opal‐A, with ages ranging from ca. 11,873 to 384 years old. Our study provides evidence for their low‐temperature hydrothermal origin, with geochemical characteristics highlighting rare earth element patterns and radiogenic Sr‐Nd‐Pb isotopic compositions. Of particular significance is the discovery of a wide range of stable iron isotopic compositions, shedding new light on the depositional redox conditions. Our data, in concert with previous studies, reveal similarities between biogenic Fe‐Si oxyhydroxide deposits and ancient iron formations (IFs). This link indicates the potential use of Fe isotope systematics in tracing Fe oxidation processes and the biosignatures that may have shaped IF deposition on early Earth. These novel findings contribute fresh perspectives to the understanding of low‐temperature hydrothermal deposit geochemistry and the search for geological biosignatures. Key Points: We present a comprehensive Sr‐Nd‐Pb‐Fe isotope investigation of modern Fe‐Si oxyhydroxide deposits in marine hydrothermal vent sitesSr‐Nd‐Pb isotope variations in Fe‐Si oxyhydroxides were produced by varying degrees of seawater mixing with diffuse hydrothermal fluidsFe isotope systematics of Fe‐Si oxyhydroxides can provide key information for Fe oxidation processes during the formation of the deposits [ABSTRACT FROM AUTHOR]

The Sorskoe (Sorsk, Sora) porphyry Cu–Mo deposit is located in the Kuznetsk Alatau, in the northwest of the Altai-Sayan folded region. Commercial Cu–Mo mineralization is closely associated with small porphyry intrusions (stocks, dikes) localized in the Uibat pluton. The magmatites of the pluton and small intrusions are composed of rocks of the gabbroid, monzonitoid, and granite/leucogranite associations. The rock associations of the pluton and small porphyry intrusions are similar in mineral composition, type of metallogenic specialization, petrogeochemical and isotopiс characteristics. The gabbroic and monzonitic rocks were probably generated by fractionation of the mafic magma and assimilation of lower crustal material. The geochemical characteristics indicate the absence of a genetic relationship between basic/intermediate rocks and the granite/leucogranite association. The rocks of the granite/leucogranite association were probably derived from the silicic magma generated by partial melting of the juvenile lower mafic crust due to the heat released from the mafic magma. U-Pb geochronological data indicate a time gap between the completion of pluton formation (∼478 Ma) and emplacement of small porphyry intrusions (from ∼467 to ∼457 Ma). Age differences between pluton and small intrusions suggest they are not coeval and were probably sourced from independent upper-middle crust magma chambers, which were formed by ascending melts derived from a deep large long-lived magma reservoir. The rocks of the Uibat pluton represent the remnant of the earlier solidified and eroded magma chamber. Periodic episodes of magma supply from a late shallow magma chamber resulted in the formation of small porphyry intrusions. Together these observations suggest that the magmatites of the pluton and small intrusions are not comagmatic. Their magmas may have been derived from a common deep-seated source, but possibly evolved independently, that is, they do not represent a single magma lineage, as often noted for porphyry Cu–Mo deposits. Changing tectonic environment before the emplacement of small intrusions triggered porphyry magma ascent, fluid saturation and exsolution and provided favorable conditions for large-scale mineralization. [ABSTRACT FROM AUTHOR]

We report rhenium–osmium (Re–Os) isotope data and age information for bornite, chalcocite, and chalcopyrite from the Spar Lake and Rock Creek copper–silver (Cu–Ag) sediment-hosted deposits in the Spar Lake district, Mesoproterozoic Belt–Purcell Basin, Montana, USA. The Re–Os geochronometers in chalcocite and chalcopyrite do not record plausible mineralization ages at the Spar Lake deposit, which is currently interpreted to have formed at ca. 1410 million years ago (Ma) from prior work. However, a Re–Os isochron date of bornite (253.2 ± 26.9 Ma, n = 6) at Rock Creek with an extremely high initial 187Os/188Os ratio of 19.1 ± 0.2 can be interpreted as resetting of Re–Os in bornite that originally recorded a Mesoproterozoic timing of Cu–Ag mineralization in the Spar Lake district. The new Re–Os age of bornite at Permian–Triassic boundary time is compatible with a resetting at the time of building of the Sonoma Foreland Basin that resulted from the loading of an accretionary prism (i.e., Golconda Allochthon) onto the North American Plate. Our ca. 253 Ma bornite age does not constrain whether Cu was introduced to Spar Lake at this time or simply redistributed, but our findings open the possibility that Cu–Ag mineralization in the Spar Lake district might have taken place not only in the Mesoproterozoic, but also in addition, at Permian–Triassic boundary time. Indeed, numerous Cu–Ag, vanadium–uranium (V–U) sandstone-hosted and black shale-hosted deposits of assumed Permian to Triassic age are documented in the Midcontinent copper belt from western Texas to southern Idaho, including (1) Cu–Ag sediment-hosted deposits in western Colorado, southeastern Utah, and northern Arizona and (2) the Montpelier and Lake Alice sandstone-hosted Cu–Ag deposits in southeastern Idaho and western Wyoming, respectively. [ABSTRACT FROM AUTHOR]

The January 2022 eruption of the Hunga Tonga-Hunga Ha'apai (HTHH) volcano discharged 2,900 teragrams of ejecta, most of which was deposited in the South Pacific Ocean. Here we investigate its impact on the biogeochemistry of the South Pacific Gyre (SPG) using samples collected during the GEOTRACES cruise GP21 in February-April 2022. Surface water neodymium isotopes and rare earth element compositions showed a marked volcanic impact in the western SPG, potentially extending to the eastern region. Increasing trace metal concentrations in surface waters and chlorophyll-a inventories in euphotic layers between the eastern and western SPG further suggest that the volcanic eruption supplied (micro)nutrients potentially stimulating a biological response. We estimate that the HTHH eruption released up to 0.16 kt of neodymium and 32 kt of iron into the SPG, which is comparable to the annual global dust-borne Nd flux and the annual dust-borne Fe flux to the entire SPG, respectively., (© 2024. The Author(s).)

We investigated the geochemistry of gas, pore fluid, and methane-derived authigenic carbonate (MDAC) from four sites in the southern Ulleung Basin, South Korea. In contrast to Sites 16GH-P1 and 16GH-P5, Sites 16GH-P3, and 16GH-P4 are characterized by acoustic chimney structures associated with gas flux. The composition of gas and isotopic signatures of methane (CH4) (C1/C2+ > 300, Ψ13CCH4 < -60‰, ΨDCH4 = -190‰) indicate microbial source CH4 at all sites. The upward migration of CH4 can affect the chemical and isotopic properties of pore fluid and gas-related byproducts (e.g., gas hydrate (GH) and MDAC) within the shallow sediments including the current sulfate-methane transition (SMT) (< 5 meters below seafloor). Although no GH was found, elevated Clconcentrations (maximum = 609 mM) with low dD and d18O values in Site 16GH-P4 pore fluids delineate the influence of massive GH formation in deeper sediment. In contrast, relatively constant Cl-, ΨD, and Ψ18O values in fluids from Sites 16GH-P1, 16GH-P3, and 16GH-P5 indicate a predominant origin from seawater. Pore fluids also exhibit higher concentrations of H4SiO4, B, Mg2+, and K+, along with increasing alkalinity compared to seawater. These observations suggest that marine silicate weathering alters fluid chemistry within the sediment, affecting element and carbon cycles. High alkalinity (up to 60 mM) and Mg2+/Ca2+ ratios (> 6) alongside decreasing Ca2+ and Sr2+ concentrations imply carbonate precipitation. MDACs with diverse morphologies, mainly composed of aragonite and magnesian calcite, and characterized by low carbon isotopic values (Ψ13CMDAC < -31.3‰), were found at Sites 16GH-P3 and 16GH-P4. Interestingly, d13CMDAC values at Site 16GH-P3 are clearly differentiated above and below the current SMT. High d13CMDAC values above the SMT (> -34.3‰) suggest the combined influence of seawater and CH4 migrating upward on MDAC precipitation, whereas low Ψ13CMDAC values below it (< -41.6‰) indicate a predominant impact of CH4 on MDAC formation. Additionally, the vertical variation of d18OMDAC values at Site 16GH-P4, compared to the theoretical values, reflects an association with GH dissociation and formation. Our findings improve the understanding of fluid, gas, and MDAC geochemistry in continental margin cold seeps, providing insights into global carbon and element cycles. [ABSTRACT FROM AUTHOR]

The South China Sea (SCS) is the largest marginal sea in the western Pacific, fed by large Asian rivers, characterized by substantial volumes of sediment derived from surrounding Asian continents and islands. This study utilizes the rare earth elements (REEs), Sr isotopes (87Sr/86Sr), and Nd isotopes (ƐNd) in detritus fractions of MD05-2901 sediments in northwestern SCS, to evaluate the relative contribution among the Mekong River, the Red River, the Pearl River, and rivers in SW Taiwan over the last 32 ka. This deep-sea core is located off the coast of central Vietnam, an upwelling region with only minor continental inputs, and this study is important for a better understanding of the main sources of terrigenous material and their temporal variations in the region. In addition, potential particle exchange is examined using the same proxies in the Fe-Mn oxyhydroxide fractions. The obtained records are systematically compared with the available climatic archives in the region. The REEs in the Fe-Mn oxyhydroxides support the argument of water mass signature separation in bulk sediments by chemical leaching procedures. These 87Sr/86Sr in the Fe-Mn oxyhydroxides phase fall in a range between 0.709262 and 0.709313, deviating significantly from the modern seawater. ƐNd values vary >3Ɛ, being more radiogenic in the Fe-Mn oxyhydroxides, where the lowest value occurred in the Bølling/Allerød (B/A) and higher values occurred during the Younger Dryas (YD). The latter implies increased contribution of loess dusts or Taiwanese rivers under dry/cold climatic conditions, compared with the situation in modern times. The Red River and the Mekong River together may have contributed >60% during the Last Glacial Maximum (LGM) and YD. In contrast, the Pearl River components have increased sharply to ~60% during the warm B/A. These results demonstrate that the MD05-2901 sediments sensitively record changes in weathering intensity on land and transport pathways in the coastal regions in the Holocene. [ABSTRACT FROM AUTHOR]

The stellar evolution and chemical make-up of the Universe are determined by nuclear reactions occurring in a wide variety of stellar sites. Precise determinations of the cross sections of these reactions are crucial for the calculation of reaction rates and for the development of stellar evolution models. The Laboratory for Underground Nuclear Astrophysics (LUNA) collaboration has been at the forefront of the direct measurement of nuclear reactions at the low energies of astrophysical interest for the last 35 years. The many significant results achieved at LUNA have been made possible due to the low background conditions uniquely available thanks to its location deep underground at the Laboratori Nazionali del Gran Sasso. Another key aspect of these successes is due to the experience of the LUNA collaboration in the production and characterization of a variety of solid targets used in reaction measurements. In this review, the main production techniques of solid targets are described, as well as the common methods adopted for target degradation monitoring. We also present the results of recent measurements using these targets and the future plans of the LUNA collaboration for measurements using solid targets at the LUNA400 kV and the new Ion Beam Facility (IBF) 3.5 MV are also presented. [ABSTRACT FROM AUTHOR]

The presence of a late Quaternary ice sheet/ice shelf over the East Siberian Sea has been proposed in several papers. Here, we further document its duration/resilience based on the sedimentary, bulk mineralogical, and geochemical (organic matter content and its stable isotopic composition, U‐Th series) properties of a core raised from the southernmost Mendeleev Ridge. The chronostratigraphy of the studied core was mainly built from the 230Th excess (230Thxs) distribution and decay downcore. At the core‐top, peaking 230Thxs values during the early MIS 3 and mid‐MIS 1 encompassing an MIS 2 hiatus were observed. As documented in several papers, these peaks suggest seasonally open ice conditions over proximal continental shelves. Below, the interval spanning MIS 4 and possibly MIS 5d records major ice‐rafting events illustrated by overall high coarse‐fraction contents. Underlying MIS 5e, down to MIS 11, the sediment depicts relatively low sand (1.7±2.5 dw%), high clay (33.5±4.7 dw%), and very low organic carbon (0.10±0.06 dw%) contents, and low δ13Corg values (−24.3±0.9‰). This section is interpreted as recording fine sediment transport by deep currents and/or meltwater plumes below a resilient ice cover, only interrupted by a few short‐duration events. These events include (i) detrital carbonate pulses assigned to deglacial events along the NW Laurentide Ice Sheet margin (Termination (T) III), and (ii) intervals with some planktonic foraminifer occurrences, likely relating to their advection from open areas of the Arctic Ocean (MIS 5e, 9 and 11). All Terminations, but TII and the early MIS 3, show peaking Mn/Al values linked to the submergence of Arctic shelves under a rising sea level. We conclude that the resilient ice cover, likely an ice shelf, has been present over the southern Mendeleev Ridge during most of the interval after the Mid‐Pleistocene Transition and was favoured by the low summer insolation of the MIS 14 to 10 interval. [ABSTRACT FROM AUTHOR]

Vesteris Seamount is a large Quaternary intraplate submarine volcano in the SW Greenland Sea, about 1,000 km NE of Iceland and 300 km NW of the Mohn's spreading ridge, whose mode of formation remains unsolved. We present geochemical data for new samples dredged from the Vesteris edifice, including major, trace elements and Sr‐Nd‐Pb‐Hf isotopes. The isotopic characteristics of the alkaline lavas, covering the basanite/tephrite to benmoreite range, indicate the involvement of depleted and enriched mantle components. The source is dominated by the depleted mantle (85%–90%) and a deep enriched component possibly supplied by the Iceland Plume (IP) (10%–15%). Additional source enrichment was due to recycled crust and sub‐continental lithospheric mantle, as suggested by Hf isotopes (0.283147 ± 0.000005) measured for the first time in Vesteris lavas and by a decoupling in Pb isotopes evidenced by relatively low‐radiogenic 207Pb/204Pb (15.510) and high‐radiogenic 208Pb/204Pb (38.554) with respect to the Northern Hemisphere Reference Line. We interpret the geochemical results using existing knowledge about the regional lithospheric and upper mantle structure. Our findings suggest that a deep (ca. 420–320 km) mantle anomaly, with seismological characteristics of the Iceland mantle plume, extends from East Greenland to the north of Jan Mayen Fracture Zone. The regional lithospheric thinning toward the Greenland Basin enabled the melting events that produced the Vesteris seamount. This lateral NNE‐directed flow lobe of the Iceland plume may have carved and transferred enriched components from the continental lithospheric margin of Greenland north of Scoresby Sund toward the Vesteris source. Plain Language Summary: This study investigates the formation of Vesteris Seamount, the largest submarine volcano in the Greenland Sea, situated north of Iceland and the Jan Mayen Fracture Zone and east of the Greenland continental margin. Given the isolated position of Vesteris, it is challenging to define its formation mechanisms and the mantle source. This study presents geochemical data by analyzing samples dredged from Vesteris' flanks. A deep mantle component, similar to the Iceland plume, seems to contribute to the mantle source of Vesteris magmas and the regional depleted asthenosphere. However, our results also suggest a contribution of an enriched component. This could be the sub‐continental mantle lithosphere (SCLM) and a crustal component. These components could have been transported from the Northeastern Greenland Margin, North of Scoresby Sund, along with the mantle flow. Subsurface seismic tomography images indicate an NNE‐directed flow lobe from the mantle plume under Iceland. We suggest that this setting played an important role in the seamount formation and explain the isotope signatures of SCLM‐like and crustal components by deep mantle carving of the western Greenland margin. Key Points: New volcanic rock samples are dredged from Vesteris Seamount in the SW Greenland SeaSample analysis shows geochemical evidence of deep mantle component and continental crust remobilizationMelting underneath Vesteris was enhanced by steep lithospheric thickness change that allowed channeling of the Iceland plume branch [ABSTRACT FROM AUTHOR]

On the southern edge of the Amazonian Craton, the Mirassol d'Oeste and Guia formations constitute the cap carbonate of the Araras Group. Petrography, X-ray diffraction, and quantification of terrigenous material allowed the identification of detrital grains (e.g., mica, quartz, and feldspar) in different proportions and diagenetic features. The sequential leaching of carbonates along a section of the upper portion of the Guia Formation yielded 87Sr/86Sr ratios increasing from 0.7070 to 0.7077, which is considered the primary Sr isotopic signature of seawater. The increasing continental influx of dissolved Sr from freshwater accounts for the increase in 87Sr/86Sr along the section. Such abrupt change toward more radiogenic values is also observed in carbonate layers soon after the Marinoan glaciation, elsewhere in the world. The same samples provided Nd-TDM model ages (1.84-2.54 Ga) comparable with those of the continental crust of the Paleoproterozoic provinces of the Amazonian Craton, which forms the basement of the Araras Group. The εNd(635Ma) values between -4.7 and -11.1, probably indicate the presence of Nd from the suspended material transported by continental waters to the ocean where the carbonates precipitated. The random variations of Nd-TDM ages and εNd(635Ma) values suggest important and rapid variations in the continental contribution to the post-Marinoan oceans. [ABSTRACT FROM AUTHOR]

Geochemical, geochronological (U–Pb zircons, ID-TIMS) and isotope-geochemical (Sm–Nd) studies of the rocks of the Bambukoy volcano-plutonic association, which form the Zhanok-Bambukoy volcano-tectonic structure within the Anamakit–Muya terrane on the northern flank of the Barguzin–Vitim superterrane of the East Transbaikalian segment of the Central Asian orogenic belt. The association includes volcanic rocks of the Zhanok Suite (dacites and rhyolites mainly), as well as leucocratic and biotite granites of the Bambukoy Complex that cut through them. The granites of this complex host the Mokhovoe tin deposit, which is attributed to the tin-porphyry formation. Subvolcanic rocks of the Zhanok Suite are considered as ore-bearing. The geochemical features of the volcanic rocks of the Zhanok Suite and the granites of the Bambukoy complex bring them closer to S-type granites, and belonging to a single tin-bearing Bambukoy volcanic-plutonic association. The formation of this association is determined by the age interval 834 ± 23–818 ± 7 Ma. The isotopic data point to a source of parental magmas from the rocks of the Bambukoy volcano-plutonic association, formed as a result of mixing of the material of two crustal sources, the mature Early Precambrian and the juvenile Early Baikal. The geochemical data also point to an exclusively crustal source of the rocks of this association. Thus, the Bambukoy tin-bearing volcano-plutonic association was formed in the Neoproterozoic time (Tonian), most likely under lithospheric extension conditions due to a source with a complex and long crustal prehistory. [ABSTRACT FROM AUTHOR]

Climatic and associated hydrological changes controlled the transport processes and composition of the sediments in the central Red Sea during the last ca. 200 kyr. Three different source areas for mineral dust are identified. The dominant source is located in the eastern Sahara (Sudan and southernmost Egypt). We identify its imprint on Red Sea sediments by high smectite and Ti contents, low 87 Sr / 86 Sr, and high εNd. The availability of deflatable sediments was controlled by the intensity of tropical rainfall and vegetation cover over North Africa linked to the African monsoon. Intense dust input to the Red Sea occurred during arid phases, and low input occurred during humid phases. A second, less significant source indicated by palygorskite input is probably located on the eastern Arabian Peninsula and/or Mesopotamia, while the presence of kaolinite suggests an additional minor dust source in northern Egypt. Our grain size data reflect episodes of fluvial sediment discharge to the central Red Sea and document the variable strength in response to all of the precession-paced insolation maxima during our study interval including both those that were strong enough to trigger sapropel formation in the eastern Mediterranean Sea and those that were not. The African humid period most strongly expressed in our Red Sea record was the one during the Eemian last interglacial at ca. 125 ka (when the Baraka River was far more active than today), followed by those at 198, 108, 84, and 6 ka. [ABSTRACT FROM AUTHOR]

Chemical and isotopic indicators were used to recognize the origin of hydrothermal groundwater, to assess the mineralization processes and groundwater quality, to identify the source of solutes and the likely mixing with cold, and elucidate the fluid geothermometry in the Jérid field of Southern Tunisia. The results show that the geothermal groundwater is neutral to slightly alkaline. They are characterized by SO 4 -Cl-Na-Ca water type. The dissolution of evaporates and pyrite-bearing rocks is the dominant mineralization process. The groundwater quality index indicates that the majority of samples are very hard and belong to poor to unsuitable for drinking classes. Applications and calculations of hydrogeochemical parameters, including SAR, %Na, PI, Kr, and MAR, showed that the majority of samples are unsuitable for agricultural practices. The human health risk was assessed based on hazard quotient and total hazard index through ingestion and dermal contact with iron-rich groundwater. The consumption of CI groundwaters does not present non-carcinogenic risk to adults and children. The δ 18 O and δ 2 H signatures indicate that the geothermal groundwater was recharged by ocean precipitation during cold and wet paleoclimatic periods. The slight enrichment of oxygen-18 and deuterium contents suggests a limited mixing effect between geothermal water and cold groundwater within the same aquifer. This mixing effect is confirmed by the Na-K-Mg and the chloride-enthalpy diagrams. The K-Mg and SiO 2 geothermometers provided fairly reliable reservoir temperature values, ranging between 69.6 and 99 °C. Calculated geothermal potential values, varying between 469 and 16987 kWth, which allow several applications such as domestic and agricultural heating., (© 2024. The Author(s), under exclusive licence to Springer Nature Switzerland AG.)

The climate response of tropical Southeast Asia to abrupt climate change originating from high northern latitudes remains poorly understood. Here, marine sediments recovered from the Northwest Borneo Trough are analyzed to trace variations in terrigenous material composition associated with sea level and palaeoflood activities over the past 40 ka. We describe for the first time the influence of sea level change on terrigenous deposition from a tropical island with small mountainous rivers surrounded by narrow continental shelves and the coupling between North Atlantic dynamics and climate feedbacks in tropical Southeast Asia during the Dansgaard‐Oeschger stadials. This study demonstrates that climate oscillations occurring at high northern latitudes can be transmitted to tropical Southeast Asia through the functions of sea level, the East Asian winter monsoon and the Intertropical Convergence Zone. Such information is fundamental to correctly assessing future sea level rise and flood risks in tropical Southeast Asia. Plain Language Summary: Sea level rise and extreme climate events are two global climate issues currently faced by humanity under the background of global warming. However, the climate feedbacks in tropical Southeast Asia remain unknown, although portions of this region are now densely populated. Here, a gravity core retrieved from the Northwest (NW) Borneo Trough is employed to reveal variations in terrigenous material composition and their controlling factors over the past 40 ka. We found that the terrigenous sediments delivered to the NW Borneo Trough are primarily sourced from NW Borneo, and their deposition is mainly controlled by sea level change and flooding. Further in‐depth analysis reveals that northern high‐latitude cooling could cause floods in NW Borneo both in the modern and during the past by influencing the East Asian winter monsoon (EAWM) and/or the Intertropical Convergence Zone (ITCZ). Furthermore, our new records suggest that a stronger EAWM during cold stadials could have transported high levels of northerly moisture to NW Borneo, resulting in relatively higher speleothem δ18O values in NW Borneo. In short, abrupt climate changes in the high‐latitude Northern Hemisphere can be transmitted to tropical Southeast Asia through the functions of sea level, the EAWM and the ITCZ. Key Points: Sea level change and flooding are the main controlling factors for terrigenous deposition from tropical Southeast AsiaNorthern high‐latitude cooling could lead to the outbreak of floods in Northwest Borneo via atmospheric teleconnectionClimate oscillations occurring at high northern latitudes can be transmitted to tropical Southeast Asia [ABSTRACT FROM AUTHOR]

Paleoceanographic interpretations of Plio-Pleistocene climate variability over the past 5 million years rely on the evaluation of event timing of proxy changes in sparse records across multiple ocean basins. In turn, orbital-scale chronostratigraphic controls for these records are often built from stratigraphic alignment of benthic foraminiferal stable oxygen isotope (δ18O) records to a preferred dated target stack or composite. This chronostratigraphic age model approach yields age model uncertainties associated with alignment method, target selection, the assumption that the undated record and target experienced synchronous changes in benthic foraminiferal δ18O values, and the assumption that any possible stratigraphic discontinuities within the undated record have been appropriately identified. However, these age model uncertainties and their impact on paleoceanographic interpretations are seldom reported or discussed. Here, we investigate and discuss these uncertainties for conventional manual and automated tuning techniques based on benthic foraminiferal δ18O records and evaluate their impact on sedimentary age models over the past 3.5 Myr using three sedimentary benthic foraminiferal δ18O records as case studies. In one case study, we present a new benthic foraminiferal δ18O record for International Ocean Discovery Program (IODP) Site U1541 (54°13'S, 125°25'W), recently recovered from the South Pacific on IODP Expedition 383. The other two case studies examine published benthic foraminiferal δ18O records of Ocean Drilling Program (ODP) Site 1090 and the ODP Site 980/981 composite. Our analysis suggests average age uncertainties of 3 to 5 kyr, 1 to 3 kyr, and 2 to 6 kyr associated with the use of manual over automated alignment methods, automated probabilistic alignment itself, and the choice of tuning target, respectively. Age uncertainties are higher near stratigraphic segment ends and where local benthic foraminiferal δ18O stratigraphy differs from the tuning target. We conclude with recommendations for community best practices for the development and characterization of age uncertainty of sediment core chronostratigraphies based on benthic foraminiferal δ18O records. [ABSTRACT FROM AUTHOR]

This paper presents the data on the structure and composition of a concentric-zonal komatiite pillow from the Ruvinvaar Formation of the Neo-Archean Kostomuksha greenstone structure of the Fennoscandian Shield. The features of the zonal pillow structure include a narrow range of variations in concentrations of rare-earth elements (REEs), similar REE patterns of dacite and andesite from the pillow core and komatiite and komatiitic basalt from the outer part, and higher REE contents of andesite relative to dacite. These features of REE distribution indicate liquation differentiation of basic melts. According to the Sm–Nd isotopic systematics of rocks of the komatiite matrix and dacite, their isochron age is 2874 ± 35 Ma (εNd = +1.5). Our data indicate an older (than was previously considered) age of the Kontok Group of the Kostomuksha greenschist structure. [ABSTRACT FROM AUTHOR]