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Meaningful analysis of uranium‐series isotopic disequilibria in basaltic lavas relies on the use of complex forward numerical models like dynamic melting (McKenzie, 1985, https://doi.org/10.1016/0012-821x(85)90001-9) and equilibrium porous flow (Spiegelman & Elliott, 1993, https://doi.org/10.1016/0012-821x(93)90155-3). Historically, such models have either been solved analytically for simplified scenarios, such as constant melting rate or constant solid/melt trace element partitioning throughout the melting process, or have relied on incremental or numerical calculators with limited power to solve problems and/or restricted availability. The most public numerical solution to reactive porous flow, UserCalc (Spiegelman, 2000, https://doi.org/10.1029/1999gc000030) was maintained on a private institutional server for nearly two decades, but that approach has been unsustainable in light of modern security concerns. Here, we present a more long‐lasting solution to the problems of availability, model sophistication and flexibility, and long‐term access in the form of a cloud‐hosted, publicly available Jupyter notebook. Similar to UserCalc, the new notebook calculates U‐series disequilibria during time‐dependent, equilibrium partial melting in a one‐dimensional porous flow regime where mass is conserved. In addition, we also provide a new disequilibrium transport model which has the same melt transport model as UserCalc, but approximates rate‐limited diffusive exchange of nuclides between solid and melt using linear kinetics. The degree of disequilibrium during transport is controlled by a Damköhler number, allowing the full spectrum of equilibration models from complete fractional melting (Da=0) to equilibrium transport (Da=∞). Access the full executable Jupyter notebook version of this manuscript here. Key Points: Cloud‐based Jupyter notebook presents an open source, reproducible tool for modeling U‐series in basaltsEquilibrium and pure disequilibrium porous flow U‐series models with 1D conservation of massScaled porous flow model introduces incomplete equilibrium scenario with reaction rate limitations [ABSTRACT FROM AUTHOR]

Sarıhıdır travertines and associated manganese mineralization are located in an area known as the Central Anatolian Volcanic Province (CAVP). The topic of the study, the Sarıhıdır manganese mineralization, was deposited in association with fault zones in this tectonically-active region. Paragenesis of the mineralization includes pyrolusite, rhodochrosite and goethite with gangue minerals of calcite and quartz observed. Diagrams drawn using major oxide and trace elements like Fe–Mn–(Ni+Co+Cu)×10, Fe-Si×2-Mn, Co/Ni vs Cu+Co+Ni, Si/Al, Na/Mg, Fe/Ti vs. Al/(Al+Fe+Mn), Co+Ni/As+Cu+Mo+Pb+V+ Zn and FeO–MnO2–10× MgO show the mineralization found in the region is sourced in the hydrothermal field. The low total REE values and LREE>HREE ratio indicate the effect of hydrothermal solutions. Additionally, Ce, Eu and Ceanom anomalies indicate the source of the mineralization was hydrothermal with oxic-anoxic formation environment. The Y/Ho ratio is mean 30.1 which is lower compared to hydrothermal fluids. Mean values are δ13CPDB 12.24‰ and δ18OPDB 10.87‰ indicating deposition from fluids with a deep CO2 component. In conclusion, the Sarıhıdır mineralization and travertine were determined to have formed about 50–53 ka (Upper Pleistocene) based on U-series age data, as fault-controlled, hydrothermal-sourced mineralization.

To investigate whether the source of the globally occurring garnet signature in mid‐ocean ridge basalt (MORB) is "true" (imparted by melting a garnet‐bearing source) or "apparent" (produced without the involvement of garnet), we present the basalt petrogenesis model Petrogen. Petrogen is built on Kinzler and Grove (1992a, https://doi.org/10.1029/91JB02841) and Behn and Grove (2015, https://doi.org/10.1002/2015JB011885) and calculates the major element, trace element, and isotopic compositions of primary lherzolite‐saturated mantle melts and their subsequent evolution to eruption. This model is experimentally calibrated for melting in the plagioclase, spinel, and garnet fields with and without small amounts of water. Petrogen predicts that garnet‐lherzolite melting requires small mantle porosity (ϕ = ∼0.1%) and enriched (NaK# > 0.1), hot (>1400–1450°C), and damp mantle (>350–700 ppm water) sources. When garnet‐lherzolite melting does occur, the fraction of melting that takes place in the garnet field is not sufficient to impart a recognizable true garnet signature in the major and trace element composition of pooled melts except at ultraslow‐spreading rates (half rate ≤ 0.5 cm/yr). Therefore, for ambiguous garnet trace element signatures in MORB to be "true" would require that they are near‐fractional garnet‐lherzolite melts or garnet‐pyroxenite melts diluted by mixing in random proportions. While we do not test the process of random mixing, we find that near‐fractional and pooled melts of variable major and trace element mantle peridotite compositions at different mantle potential temperatures can explain the range of garnet signatures in MORB. For spinel‐peridotite melting to support garnet signatures requires mantle porosities ϕ = ∼0.1%; however, plagioclase‐peridotite melting, under specific circumstances, can explain MORB garnet signatures with ϕ = ∼1%. Key Points: The major element composition of garnet peridotite melts provides critical evidence for identifying garnet signatures in MORBsGarnet signatures in MORBs are diverse and reflect melting of compositionally and thermally variable mantle without garnetShallow melting of plagioclase peridotite can explain MORB major and trace elements and U‐series isotopes with mantle porosity ϕ ≥ 1% [ABSTRACT FROM AUTHOR]

Sarıhıdır travertines and associated manganese mineralization are located in an area known as the Central Anatolian Volcanic Province (CAVP). The topic of the study, the Sarıhıdır manganese mineralization, was deposited in association with fault zones in this tectonically-active region. Paragenesis of the mineralization includes pyrolusite, rhodochrosite and goethite with gangue minerals of calcite and quartz observed. Diagrams drawn using major oxide and trace elements like Fe–Mn–(Ni+Co+Cu)×10, Fe-Si×2-Mn, Co/Ni vs Cu+Co+Ni, Si/Al, Na/Mg, Fe/Ti vs. Al/(Al+Fe+Mn), Co+Ni/As+Cu+Mo+Pb+V+ Zn and FeO–MnO2–10× MgO show the mineralization found in the region is sourced in the hydrothermal field. The low total REE values and LREE>HREE ratio indicate the effect of hydrothermal solutions. Additionally, Ce, Eu and Ceanom anomalies indicate the source of the mineralization was hydrothermal with oxic-anoxic formation environment. The Y/Ho ratio is mean 30.1 which is lower compared to hydrothermal fluids. Mean values are δ13CPDB 12.24‰ and δ18OPDB 10.87‰ indicating deposition from fluids with a deep CO2 component. In conclusion, the Sarıhıdır mineralization and travertine were determined to have formed about 50–53 ka (Upper Pleistocene) based on U-series age data, as fault-controlled, hydrothermal-sourced mineralization. [ABSTRACT FROM AUTHOR]

In this first detailed study of zircon from Ascension Island, South Atlantic, we take a novel approach combining trace element and O isotope compositional data with double-dating (disequilibrium 238U–230Th and (U–Th)/He) to decipher timescales and dynamics of magmatic processes. The Echo Canyon (EC) sequence comprises small-volume explosive-effusive eruptions of trachyte that tapped a compositionally zoned magma system. Associated volcanic hazards may be constrained from the age of volcanism, duration of magma storage, and magma source and plumbing system character. Zircon U–Th–Pb dating of lithic lava clasts has revealed recurrent evolved volcanism at 1.34 and 0.6 Ma, and 95 ka. The (U–Th)/He zircon cooling ages indicate that most of the EC explosive-effusive sequence erupted in a brief episode at ca. 95 ka. Additionally, uniform 238U–230Th zircon crystallisation ages suggest moderately protracted magma storage with melt present at depth for at most 103–104 years before eruption. The enriched character of zircon trace element compositions, relative to MORB, in the absence of a continental crustal signature in the oxygen isotope values (δ18O range 2.67–5.63‰), suggests the presence of an enriched component in the EC magma source. Furthermore, low δ18O zircon compositions imply assimilation of high temperature hydrothermally altered country rock by the source magma. The mineral assemblage in crystal-poor pumices indicates equilibrium storage conditions: zircon saturation and Ti-in-zircon crystallisation temperatures are consistent with alkali feldspar-melt temperatures. Significantly, zircon crystals were preserved both as macrocryst inclusions and in the groundmass of EC explosive and effusive deposits. These rocks preserve evidence of magma evolution by fractional crystallisation. This process led to pre-eruptive compositional stratification, which is evidenced in the range of whole-rock major and trace element compositions and zircon Zr/Hf values. Notably, zircon crystallisation and cooling ages derived from pumice, lava, and accidental lithic lava clasts in highly explosive pyroclastic deposits, have revealed episodes of evolved magmatism that would otherwise have gone undetected. In addition, the zircon trace element and isotope compositions, in combination with the range of crystallisation ages, evidence progressively deeper tapping of less evolved magma stored in discrete lenses. Thus, a combined zircon geochronological-geochemical approach can place constraints on the ca. 0.6 Ma recurrence of past explosive-effusive pulses of millennial to decamillennial duration and their enriched magma sources. This information is relevant for assessing hazards and informing monitoring and forecasting efforts to assist in managing associated risks for small ocean island volcanoes with particularly vulnerable populations and infrastructure. [Display omitted] • U–Th–Pb dating has identified recurrent felsic volcanism (1.34 Ma, 0.6 Ma, 95 ka) at Echo Canyon. • Eruption ages of the Echo Canyon explosive-effusive deposits converge at ca. 95 ka. • Pre-eruptive zircon crystallisation occurred over ca. 103–104 from ca. 111–98.5 ka. • Zircon trace element compositions indicate melt storage in discrete, zoned, lenses. • Deposits of the most explosive phases sample lithic clasts from previous eruptions. [ABSTRACT FROM AUTHOR]

We use the uranium-series (U-Th) dating method to investigate the accuracy of a relative chronology based on laminae correlation between a pair of coeval twin stalagmites and compare their stable isotope and trace element records based on the two chronologies. U-Th dating shows that a relative chronology based on laminae correlation can be inaccurate: a hiatus in one of the stalagmites was not recognised, as well as more subtle changes in growth rates. Use of the stratigraphic correlation alone resulted in significant differences in the timing of stable isotopes and trace element peaks, with implications for their interpretation. Our results reveal the importance of a robust and direct chronology with which to interpret proxy data. Poor relative chronologies can lead to a misinterpretation of palaeoclimate data. The study reveals potential implications for speleothem records where proxy data and samples for dating were not taken in close proximity to each other and/or were correlated via laminae over distances of more than a few centimetres. [ABSTRACT FROM AUTHOR]

The Auckland volcanic field is a Quaternary monogenetic basaltic field of 50 volcanoes. Rangitoto is the most recent of these at ~500 year BP and may mark a change in the behaviour of the field as it is the largest by an order of magnitude and is unusual in that it erupted magmas of alkalic then subalkalic basaltic composition in discrete events separated by ≤50 years. Major and trace element geochemistry together with Sr-Nd and U-Th-Ra isotopes provides the basis for modelling the melting conditions that brought about the eruption of two chemically different lavas with very little spatial or temporal change. Sr-Nd isotopes suggest that the source for both eruptions is similar with a slight degree of heterogeneity. The basalts show high Th-excess compared with comparable continental volcanic fields. We show that the alkalic basalts give evidence for lower degrees of partial melting, higher amounts of residual garnet, a longer melting column and lower melting and upwelling rates compared with the subalkalic basalts. The low upwelling rates (0.1-1.5 cm/year) modelled for both magmas do not suggest a plume or major upwelling in the mantle region beneath Auckland; therefore, we suggest localised convection due to relict movement from the active subduction system situated 400 km to the southeast. A higher porosity for the initial alkalic basalt is based on Ra-excesses, suggesting movement of melt by two different porosities: the initial melt travelling in fast high porosity channels from greater depths preserving a high Th-excess and the subsequent subalkalic magma travelling from a shallower depth through lower porosity diffuse channels preserving a high Ra-excess; this creates a negative array in (Ra/Th) versus (Th/U) space previously only seen in mid ocean ridge Basalt data. This mechanism suggests the Auckland volcanic field may operate by the presence of discrete melt batches that are able to move at different depths and speeds giving the field its erratic spatial and temporal pattern of eruptions, a type of behaviour that may have implications for the evolution of other continental volcanic fields worldwide. [ABSTRACT FROM AUTHOR]

Abstract: U-series disequilibria provide important constraints on the processes and time scales of melt production, differentiation, and transport in subduction settings. Such constraints, which are essential for understanding the chemical evolution of the continental crust, are conventionally based on the assumption that the U-series disequilibria measured in mafic lavas are produced during mantle metasomatism and melting, and that intracrustal differentiation and assimilation have limited impacts. Here we show that mantle-derived U-series disequilibria in mafic lavas erupted at Volcán Llaima, Chile are significantly diminished by assimilation of plutonic rocks forming Llaima''s subvolcanic basement. This contamination process is extremely subtle in terms of “classical” indicators of crustal assimilation like Sr, Nd or Pb isotopes because it is a manifestation of assimilative recycling of the plutonic roots of the arc. This process results in variations in U-series disequilibria and incompatible trace element ratios that are significant compared to regional and global variability in arc magmas. Furthermore, it yields linear correlations between U-series excesses and incompatible trace element ratios that are generally interpreted as slab-fluid indicators and chronometers, or tracers of sediment recycling in subduction zone. Cannibalization of ancestral magmas by ascending melts warrants careful evaluation when considering the components and chemical fluxes in subduction zones. Linear arrays defined by activity ratios of U-series nuclides with different half-lives may be the most reliable indicators of assimilative recycling of ancestral intrusive magmas. [Copyright &y& Elsevier]

Abstract: Recent studies document the synchronous nature of shifts in North Atlantic regional climate, the intensity of the East Asian monsoon, and productivity and precipitation in the Cariaco Basin during the last glacial and deglacial period. Yet questions remain as to what climate mechanisms influenced continental regions far removed from the North Atlantic and beyond the direct influence of the inter-tropical convergence zone. Here, we present U-series calibrated stable isotopic and trace element time series for a speleothem from Moaning Cave on the western slope of the central Sierra Nevada, California that documents changes in precipitation that are approximately coeval with Greenland temperature changes for the period 16.5 to 8.8ka. From 16.5 to 10.6ka, the Moaning Cave stalagmite proxies record drier and possibly warmer conditions, signified by elevated δ 18O, δ 13C, [Mg], [Sr], and [Ba] and more radiogenic 87Sr/86Sr, during Northern Hemisphere warm periods (Bølling, early and late Allerød) and wetter and possibly colder conditions during Northern Hemisphere cool periods (Older Dryas, Inter-Allerød Cold Period, and Younger Dryas). Moaning Cave stable isotope records indicate that wet conditions persisted in this area well beyond 11.5ka, suggesting the effects of the Younger Dryas event may have been longer lived in the western Sierra Nevada than in Greenland. However, a shifting drip center and corresponding change in seepage water routing may have influenced the trace element records between 10.6 and 9.6ka. Linkages between northern high-latitude climate and precipitation in the Sierra Nevada suggested here could indicate that, under conditions of continued global warming, this drought-prone region may experience a reduction in Pacific-sourced moisture. [Copyright &y& Elsevier]

Abstract: Trace element and U-series isotope analyses are presented for a suite of recent (<10 ka) basalts from the axial portion of the Kenya rift. Samples from throughout the rift have LREE-enriched patterns with HREE >10×chondrite and the LREE between 60 and 200×chondrite. REE fractionation is consistent with melting a garnet lherzolite source region with between 2% and 6% modal garnet. Other trace element ratios are distinct from OIB, notably Zr/Hf which ranges from 43 to 48, whilst at a given Zr content the Zr/Hf ratio is significantly greater than that found in OIB. (238U/232Th) range from 0.362 to 1.036, (230Th/232Th) from 0.503 to 1.109, with (230Th/238U) ranging from 0.783 to 2.966. All but two samples are in 230Th excess or in secular equilibrium. Samples with elevated (238U/232Th), also have Rb/Cs>120, but unexceptional 208Pb⁎/206Pb⁎ and hence κ Pb values. These samples have experienced U and Cs loss and are excluded from further consideration. Of the unaltered samples, all have (238U/232Th) generally lower than OIB, with maximum values of <0.8, and some <0.6. The maximum (230Th/238U) is 1.39, similar to OIB. Although none of the basalts has a primary composition, (230Th/238U) does not vary systematically with indices of fractionation, and comparison with evolved rocks from Kenya indicates that 238U–230Th disequilibrium in the basalts is not the product of fractionation and crustal residence, but a product of melt generation. The maximum (230Th/238U) that can be generated by batch melting, assuming a source mineralogy consistent with the REE variation is 1.05 and so the variation in (230Th/238U) is attributed to more complex models of melt generation and/or transport. Both dynamic melting and equilibrium porous flow suggest mantle upwelling rates of ≤2 cm year−1. It is suggested that the Kenya basalts represent melts derived from lithospheric mantle that has been thermally reactivated by and incorporated into the underlying (East African) mantle plume. [Copyright &y& Elsevier]