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  • Elsevier  (5,804,786)
  • Public Library of Science  (275,023)
  • Periodicals Archive Online (PAO)  (190,459)
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  • 1
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    Alkalinity and elemental cycles in present and past ocean: Insight from geochemical modeling and alkali and alkaline earth metal isotopes (2024)
    Elsevier
    Details
    Publication Date: 2024-06-19
    Description: This chapter provides an overview of near-surface geochemical processes operating on Earth, with special emphasis placed on (i) marine weathering such as alteration and dissolution of silicates, carbonates and terrigenous riverine particles in the ocean, complemented by (ii) reverse weathering reactions leading to marine authigenic clay formation, and the impact of these phenomena on ocean alkalinity budget and the chemical and isotope composition of seawater. Model simulations of the above processes provide estimates of the global marine fluxes of major cations (Na+, K+, Mg2+, Ca2+) and alkalinity in the ocean induced by silicate weathering and dissolution of terrigenous material in seawater. Additional constraints on silicate vs. carbonate weathering, oceanic/coastal CaCO3 cycling, and paleo-seawater reconstructions are provided via the stable and radiogenic isotope systems of alkali and alkaline earth metals (Li, K, Mg, Ca, and Sr isotopes) that are discussed within the context of marine and reverse weathering in the present and past ocean. Key points • Impact of weathering processes on marine elemental cycles and the ocean alkalinity budget. • Alteration and dissolution of silicate minerals and riverine particles in the ocean quantified via thermodynamic equilibrium (PHREEQC) calculations, in seawater and top sediment settings. • Estimates of global ocean fluxes of dissolved cations (Na+ , K+ , Mg 2+ , Ca2+ ) and alkalinity induced by alteration and dissolution of terrigenous material in seawater and marine sediments. • Principles and mechanisms of isotope variability in nature (mass-dependent and radiogenic isotope effects) observed for alkali and alkaline earth metals. • Silicate vs. carbonate weathering and coastal carbon/carbonate cycling constrained via stable and radiogenic Ca and Sr, and Li isotopes. • Oceanic processes, marine carbonate chemistry (alkalinization vs. acidification), and paleo-seawater reconstructions constrained via d44 Ca, d88 Sr, d26 Mg proxies and numerical (MATLAB) modeling. • Emerging metal isotope proxies (d41 K) for silicate and reverse weathering in the ocean.
    Type: Book chapter , NonPeerReviewed , info:eu-repo/semantics/bookPart
    Format: text
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  • 2
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    A remnant root of a Neoproterozoic island arc in the Northern Eastern Desert of Egypt: Evidence from the whole-rock and amphibole chemistry of the Gattar gabbro (2024)
    Elsevier
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    Publication Date: 2024-06-19
    Type: Article , PeerReviewed
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  • 3
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    Terrestrial vegetation and lake aquatic community diversity under climate change during the mid–late Holocene in the Altai Mountains (2023)
    Elsevier
    In:  EPIC3Palaeogeography Palaeoclimatology Palaeoecology, Elsevier, 623, pp. 111623-111623, ISSN: 0031-0182
    Details
    Publication Date: 2024-06-18
    Description: Using pollen analysis and metabarcoding of plant sedimentary ancient DNA (sedaDNa), we infer the floristic diversity in the vicinity of Lake Balyktukel, Ulagan Plateau, the Altai Mountains, over the last 7 kyr. The SedaDNA method identified 200% more taxa than found by morphological pollen analysis. In particular, it revealed that the dominant tree for the last 7 kyr was Larix rather than Pinus, which was less frequent in the vicinity of Lake Balyktukel. About 7 ka, larch forest mixed with dwarf birch was widespread on the Ulagan Plateau. The period between 5.3 and 3.4 kyr BP was characterized by the maximal spread of larch forest with an understorey cover of Vaccinium vitis-idaea. Pollen-based annual precipitation reconstruction indicates the most humid phase was between 6.95 and 4.3 ka, and generally coincides with maximal phytodiversity. The most bioproductive period of the lake was from 7 to 6 ka. After that, the trophicity of the lake decreased until 4.5 ka. The appearance of Hippuris vulgaris and increase in Ranunculus subgen. Batrachium at about 5.3–5 ka may indicate the extension of shallow-water ecotopes. Between 3.7 and 3.5 ka, the cyanobacterium Anabaena – an indicator of increased organic matter and algal blooms – was widespread. A planktic thermophilic cladoceran Bosmina longirostris appeared after 1.8 ka and colonized the lake, suggesting an increase in lake trophicity. The last 100 years have been characterized by dramatic changes in the cladoceran community reflecting significant warming of climate.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 4
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    The contribution of mesh opening angle to the drag of netting panels (2024)
    Elsevier
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    Publication Date: 2024-06-18
    Description: Highlights • a high-fidelity RANS CFD method is used to simulate the flow through netting panels. • The influence of netting solidity, twine diameter, mesh opening angle and incident angle is examined. • Mesh opening angle, solidity and angle of incidence greatly influence the hydrodynamic force coefficients and efficiency. To ensure the economic and environmental sustainability of the fisheries and aquaculture industries, it is necessary to address issues related to fuel consumption, environmental degradation, and fish welfare. Hence, we need a thorough understanding of the filtration efficiency and the hydrodynamic forces acting on towed fishing gears and netting structures. Here we apply a Reynolds-averaged Navier-Stokes (RANS) CFD method to model the flow through netting panels, where we vary the operational and design parameters of flow speed, netting solidity, twine diameter, mesh opening angle and the incidence angle of the flow to the panel. Thus, we create a simulated data set which we analyze to provide a fundamental understanding of the functional relationships for the pressure drop and tangential drag coefficients, and the flow deflection in terms of these parameters. We pay particular attention to the effect of mesh opening angle, a parameter that has not received much attention in the literature. We demonstrate that it has a large influence on the drag and lift coefficients and consequently on the hydrodynamic efficiency of netting panels. These results will be particularly useful for reducing the hydrodynamic forces on netting structures and improving the fuel efficiency of towed fishing gear operations.
    Type: Article , PeerReviewed
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  • 5
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    The geochemical riddle of “low-salinity gypsum” deposits (2022)
    Elsevier
    Details
    Publication Date: 2024-06-18
    Description: Gypsum makes up about one fifth of giant salt deposits formed by evaporation of seawater throughout Earth’s history. Although thermodynamic calculations and precipitation experiments predict that gypsum precipitates when the salinity of evaporating seawater attains about 110 g kg-1, gypsum deposits of the Mediterranean Salt Giant often bear the geochemical signature of precipitation from less saline water masses. Addressing this geochemical riddle is important because marine gypsum deposition and continental gypsum erosion affect the global carbon cycle. We investigated gypsum deposits formed in the marginal basins of the Mediterranean Sea during the Messinian Salinity Crisis (about 6 million years ago). These often bear low-salinity fluid inclusions and isotopically light crystallization water, confirming previous published reports that the Mediterranean Salt Giant harbors low-salinity gypsum deposits. A geochemical model constrained by fluid inclusion salinity and isotope (87Sr/86Sr, δ34SSO4, δ18OH2O, δDH2O) measurements excludes that Ca2+- and SO42--enriched continental runoff alone provides the trigger for gypsum precipitation at low salinity. We propose that, concurrent with the prevalent evaporative conditions and with Ca2+- and SO42--bearing runoff, the biogeochemical sulfur cycle is capable of producing a spatially-restricted and temporally-transient increase of Ca2+ and SO42- within benthic microbial mats, creating local chemical conditions conductive to gypsum precipitation. This hypothesis is supported by the presence of dense packages of fossils of colorless sulfur bacteria within gypsum in several Mediterranean marginal basins, together with independent geochemical and petrographic evidence for an active biogeochemical sulfur cycle in the same basins. Should this scenario be confirmed, it would expand the range of environments that promote marine gypsum deposition; it would also imply that an additional, biological coupling between the calcium, sulfur and carbon cycles exists.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
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  • 6
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    Seismic evidence for possible entrainment of rising plumes by subducting slab induced flow in three subduction zones surrounding the Caribbean Plate (2024)
    Elsevier
    Details
    Publication Date: 2024-06-18
    Description: The dynamic processes associated with subducting tectonic plates and rising plumes of hot material are typically treated separately in dynamical models and seismological studies. However, various types of observations and related models indicate these processes overlap spatially. Here we use precursors to PP and SS reflecting off mantle transition zone discontinuities to map deflections of these discontinuities near three subduction zones surrounding the Caribbean Plate: 1) Lesser Antilles, 2) Middle America and 3) northern South American subduction zones. In all three regions slow seismic anomalies are present behind the sinking slab within the transition zone in tomographic images. Using array methods, we identify precursors and verify their in-plane propagation for MW ≥ 5.8 events occurring between the years 2000 and 2020 by generating a large number of source receiver combinations with reflection points in the area, including crossing ray paths. The measured time lag between PP/SS arrivals and their corresponding precursors on robust stacks are used to measure the depth of the mantle transition zone discontinuities. In all three areas we find evidence for upward deflection of the 660 discontinuity behind the sinking slab, consistent with the presence of hot plume material (average temperature anomalies of 180 to 620 K), while there is not a corresponding downward deflection of the 410 km discontinuity. One interpretation of these disparate observations is suggested based on comparison to existing models of mantle convection and subduction: plume material rising across 660 km discontinuity could be entrained by lateral flow in the transition zone induced by the nearby sinking slab, and thus delaying the rise of hot material across the 410 km discontinuity.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
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  • 7
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    Why are oceanic arc basalts Ca-rich and Ni-poor? Insights from olivine-hosted melt inclusions from Kibblewhite Volcano in the Kermadec arc (2024)
    Elsevier
    Details
    Publication Date: 2024-06-18
    Description: Highlights • Ankaramites are Ca-rich and Ni-poor porphyritic basalts that are common in oceanic arcs. • Melt inclusions from Kibblewhite Volcano show similar compositions to ankaramites. • Ankaramite is a primary magma component in oceanic arcs. • Interaction between melt and mantle can produce ankaramitic melts. • Harzburgite formed by melt-mantle interactions is the source of high-Mg andesites. Abstract Ankaramites, which are clinopyroxene-rich basalts with primitive whole-rock compositions (Mg# 〉65), are common in oceanic arcs and are characterized by high whole-rock CaO/Al2O3 (〉1.0) ratios and olivine crystals with anomalously low nickel contents (〈0.2 wt% NiO). These geochemical characteristics cannot be explained by the melting of ordinary mantle peridotite. However, their origin is critical for understanding the formation of primary magmas in oceanic arcs. Here, we investigated olivine-hosted melt inclusions (MIs) from ankaramites and magnesian andesites of the Kibblewhite Volcano in the Kermadec arc. The MIs from the ankaramites have similar major and trace element characteristics to the host rocks, indicating that the ankaramites did not result from an accumulation of mafic minerals but rather represent the primary magma in the Kibblewhite Volcano. The MIs from the magnesian andesites were hosted in forsteritic olivine xenocrysts with a wide range of NiO contents (Fo90–92; 0.13–0.39 wt% NiO) and have similar major element compositions to the ankaramites but exhibit a wide range of CaO/Al2O3 (0.85–1.54). The trace element characteristics of the MIs from the magnesian andesites do not match those of the host rocks, indicating that they are not primary melts of the magnesian andesites but primitive basaltic melts generated before the magnesian andesites formed. Interestingly, the CaO/Al2O3 ratio of MIs from the magnesian andesites was negatively correlated with the NiO content of their host olivines. This correlation suggests that the composition of the primary basaltic magmas of the Kibblewhite Volcano changed continuously from peridotite-derived to ankaramitic. This correlation could not be explained by grain-scale process, crustal anatexis, or contribution of slab-derived carbonate-rich fluids. Instead, we propose that this correlation can be explained by the interaction of the ascending primary basaltic melts with the lithospheric mantle. During melt-mantle interaction, the assimilation of clinopyroxene and fractionation of olivine and orthopyroxene caused the CaO/Al2O3 ratio to increase in the melt and the Ni content to decrease. Furthermore, because the magnesian andesites have low CaO/Al2O3 ratios and could be derived from a clinopyroxene-poor mantle lithology, the interaction between the melt and mantle may also be closely related to the origin of the magnesian andesites at Kibblewhite Volcano. This interpretation provides a new perspective on the origin of the oceanic arc ankaramites and why primary andesitic and basaltic magmas coexist in the Kibblewhite Volcano.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
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  • 8
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    Modeling the crystallization conditions of clinopyroxene crystals erupted during February–April 2021 lava fountains at Mt. Etna: Implications for the dynamic transfer of magmas (2024)
    Elsevier
    Details
    Publication Date: 2024-06-17
    Description: In the period February–April 2021, seventeen energetic hours-long episodes of intense lava fountaining occurred at Mt. Etna, producing lava flows and ash plumes followed by heavy fallout. Clinopyroxene mesocrysts from these paroxysms show complex sector and concentric zoning patterns, with juxtaposition of Si-Mg-rich (Al-Ti-poor) and Si-Mg-poor (Al-Ti-rich) crystal layers. Clinopyroxene-based equilibrium thermobarometry and hygrometry define an overall crystallization path in the range of ~170–480 MPa, ~1060–1110 °C, and ~ 1.2–2.7 wt% H2O, with a main magma storage region estimated at depths of ~11–15 km. From this perspective, we observe that 2021 lava fountains were fed by hotter magmas of deeper origin with respect to those feeding 2011–2012 paroxysms. Zoning patterns of 2021 clinopyroxene mesocrysts formed in a vertically-extended plumbing system upon the effect of mixing phenomena and crystal recycling caused by recurrent inputs of fresh magmas into interconnected mushy reservoirs. Kinetic growth modeling constrains the formation of 2021 clinopyroxene mesocrysts over timescales of ~30–90 h and small degrees of undercooling ≤28 °C. Fesingle bondMg diffusion chronometry confirms that the time elapsed between the formation of clinopyroxene rim and magma eruption is utterly related to growth kinetics caused by pre-eruptive dynamic transfer of magma at crustal depths. Kinetic effects are exacerbated for clinopyroxene microlites/microcrysts forming at the syn-eruptive stage, when magma decompression, degassing, and cooling become more effective in the last 1.5 km below the vent of Mt. Etna. Kinetic growth modeling reveals that eruption dynamics within the conduit promote an exceptionally rapid disequilibrium growth of clinopyroxene microlites/microcrysts in only ~0.4–3.3 min upon large degrees of undercooling 〉60 °C. The resulting ascent velocity of 2021 magmas within the conduit is ~8–63 m/s, a factor of ~3 higher than the less energetic 2011–2012 paroxysms.
    Description: Published
    Description: 106710
    Description: OSV1: Verso la previsione dei fenomeni vulcanici pericolosi
    Description: OSV2: Complessità dei processi vulcanici: approcci multidisciplinari e multiparametrici
    Description: JCR Journal
    Keywords: Magma dynamics at Mt. Etna ; Clinopyroxene zoning patterns ; P-T-H2O magma crystallization histories ; Magma ascent velocities ; petrology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 9
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    The efficacy of high frequency petrological investigation at open-conduit volcanoes: The case of May 11 2019 explosions at southwestern and northeastern craters of Stromboli (2024)
    Elsevier
    Details
    Publication Date: 2024-06-17
    Description: Petrological studies of active volcanoes typically focus on eruptive phenomena occurring over long timescales of the order of days to years, aiming at identifying major changes in the physico-chemical state of magma during ascent towards the surface. Exceptionally, we present results from an integrated petrological and statistical approach based on the compilation of ∼5300 major and trace element data for glass and crystals, in combination with volcanological data on eruptive events occurred over timescales of minutes at Stromboli volcano (Sicily). On May 11, 2019, we had the rare opportunity to collect individual fresh fallout ash products from eighteen mostly consecutive explosions, erupted in a 2-h time span and, at the same time, to acquire continuous high frequency (50 Hz) infrared thermal data of the same explosions. Through video analysis, we observe that explosions were more frequent and ash-dominated at the southwestern crater area (SCA, 8–10 events/h) than at the northeastern crater area (NCA, 3–5 events/h), where coarser material was ejected. The statistical analysis of glass and plagioclase compositions reveals differences in the products erupted from the two crater areas. SCA explosions tapped less differentiated magmas (Mg#∼42–46, ∼257–365 LaN, ∼0.7–0.9 Eu/Eu*) in equilibrium with more anorthitic plagioclase cores (An∼72–88), whereas NCA area explosions are more differentiated (Mg#∼40–44, ∼286–387 LaN, ∼0.6–0.8 Eu/Eu*) and in equilibrium with less anorthitic plagioclase cores (An∼68–82). Thermometric calculations based on major and trace element clinopyroxene-plagioclase-melt equilibrium modeling highlight that the SCA explosions were statistically fed by hotter magmas in comparison to NCA explosions. Plagioclase-based diffusion modeling also indicates longer timescales for the dynamic ascent of NCA magmas, leading to preferential groundmass crystallization at the conduit walls and transition from sideromelane to tachylite groundmass textures. The final emerging picture is that in May 2019, concurrent normal eruptions from different crater areas at Stromboli were heralds of compositionally and thermally diverse magmas rising at different rates within the uppermost branched part of the conduit region. High frequency petrological investigations aided by statistical treatment of data have the potential to constrain dynamic conduit processes related to transient, explosive eruptions in persistently active volcanoes, thereby offering new insights on the interplay between magma dynamics, ascent timescales, and eruptive behavior.
    Description: Published
    Description: 107255
    Description: OSV1: Verso la previsione dei fenomeni vulcanici pericolosi
    Description: OSV2: Complessità dei processi vulcanici: approcci multidisciplinari e multiparametrici
    Description: JCR Journal
    Keywords: High-temporal resolution petrology ; Stromboli volcano ; Thermobarometry ; Eruptive timescales ; Plumbing, conduit and eruptive dynamics ; Petrology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 10
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    Effect of undercooling on clinopyroxene crystallization in a high K basalt: Implications for magma dynamics at Stromboli volcano (2024)
    Elsevier
    Details
    Publication Date: 2024-06-17
    Description: We present undercooling (∆T) experiments aimed at investigating the effect of growth kinetics on the textural and compositional evolution of clinopyroxene crystals growing from a high-K basalt erupted during the 2003 paroxysm of Stromboli volcano (Italy). The experiments were performed at P = 350 MPa, T = 1050–1210 °C, H2Omelt = 0–3 wt%, and fO2 = Ni-NiO + 1.5 buffer. An initial stage of supersaturation was imposed to the melt under nominally anhydrous (∆Tanh = 10–150 °C) and hydrous (∆Thyd = 25–125 °C) conditions. Afterwards, this supersaturation state was mitigated by melt relaxation phenomena over an annealing time of 24 h. Results show that plagioclase is the liquidus mineral phase of the high-K basalt at ∆Tanh = 10 °C and dominates the phase assemblage as the degree of undercooling increases. Conversely, clinopyroxene and spinel co-saturate the melt at ∆Thyd = 25 °C, followed by the subordinate formation of plagioclase. At ∆Tanh/hyd ≤ 50 °C, the textural maturation of clinopyroxene produces polyhedral crystals with {−111} (hourglass) and {hk0} (prism) sectors typical of a layer-by-layer growth mechanism governed by an interface-controlled crystallization regime. At ∆Tanh/hyd ≥ 75 °C, the attainment of dendritic and skeletal morphologies testifies to the establishment of diffusion-limited reactions at the crystal-melt interface. 3D reconstructions of synchrotron radiation X-ray microtomographic data reveal a composite growth history for clinopyroxene crystals obtained at ∆Tanh/hyd ≥ 95 °C. The early stage of melt supersaturation produces rosette-like structures composed of dendritic branches of clinopyroxene radiating from a common spinel grain, which acts as surface for heterogeneous nucleation. As diffusive relaxation phenomena progress over the annealing time, the elongate dendrites that constitute the inner crystal domain are partially infilled by the melt and develop skeletal overgrowths in the outer domain. With the increasing degree of undercooling, TAl and M1Ti cations are progressively incorporated in the lattice site of clinopyroxene at the expense of TSi and M1Mg cations. Because of the effect of H2Omelt on the liquidus depression and melt depolymerization, crystals obtained at ∆Thyd are also more enriched in TAl and M1Ti and depleted in TSi and M1Mg than those growing at ∆Tanh. The emerging picture is that the morphological and geochemical evolution of clinopyroxene is mutually controlled by the combined effects of melt supersaturation and relaxation phenomena. A new empirical relationship based on the cation exchange reactions in the lattice site of clinopyroxene is finally proposed to estimate the degree of undercooling governing the crystallization of augitic phenocrysts erupted during normal and violent explosions at Stromboli.
    Description: Published
    Description: 107327
    Description: OSV2: Complessità dei processi vulcanici: approcci multidisciplinari e multiparametrici
    Description: JCR Journal
    Keywords: Clinopyroxene ; Undercooling ; Hourglass ; Crystallization ; Microtomography ; Stromboli ; Experimental Petrology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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