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1. Uranium-series disequilibria in MORB, revisited: A systematic numerical approach to partial melting of a heterogeneous mantle

   https://doi.org/10.30909/vol.07.02.685715  

   Elkins, Lynne; Lambart, Sarah (July 2024, Volcanica)

   We present computational modeling outcomes for bilithologic (peridotite and pyroxenite) mantle melting in divergent environments, considering equilibrium and disequilibrium porous flow melting of 0–50 % pyroxenite in thermal equilibrium with peridotite, potential temperatures of 1300 and 1400 °C, upwelling rates from 1–50 cm yr−1, maximum porosities of 0.1–2.0 %, and four compositions that span pyroxenite melting behavior. Basalt-like pyroxenites (G2) uniquely produce low (226Ra/230Th) and (231Pa/235U) with high (230Th/238U), but quantities greater than ~10 % produce anomalously thick crust, restricting their global abundance. Silica-deficient pyroxenite (M7-16 and MIX1G) melts are more moderate, but require chemical re-equilibration during transport to resemble global basalts, while hybrid lithologies (KG1) produce melts similar to those of peridotites. Uranium-series disequilibria in partial melts can also be decoupled from trace elements by radioactive decay in two-dimensional regimes. The mantle must thus contain multiple types of pyroxenite on a global scale, with melts traveling by complex networks and experiencing heterogeneous extents of chemical re-equilibration. 

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2. Reynolds shear stress modeling in turbulent boundary layers subject to very strong favorable pressure gradient

   https://doi.org/https://doi.org/10.1016/j.compfluid.2020.104494  

   Saltar, German; Araya, Guillermo (January 2020, Computers fluids)

   Recent numerical predictions of turbulent boundary layers subject to very strong Favorable Pressure Gradient (FPG) with high spatial/temporal resolution, i.e. Direct Numerical Simulation (DNS), have shown a meaningful weakening of the Reynolds shear stresses with a lengthy logarithmic behavior [1,2]. In the present study, assessment of the Shear Stress Transport and Spalart-Allmaras turbulence models (hence- forth SST and SA, respectively) in Reynolds-averaged Navier-Stokes (RANS) simulations is performed. The main objective is to evaluate the ability of popular turbulence models in capturing the characteristic features present during the quasi-laminarization phenomenon in highly accelerating turbulent boundary layers. A favorable pressure gradient is prescribed by a top converging surface (sink flow) with an approximately constant acceleration parameter of K = 4 . 0 ×10 −6 . Validation of RANS results is carried out by means of a large DNS dataset [1]. Generally speaking, the SA turbulence model has demonstrated the best compromise between accuracy and quick adaptation to the turbulent inflow conditions. Turbulence models properly captured the increasing trend of the freestream and friction velocity in highly accelerated flows; however, they fail to reproduce the decreasing behavior of the skin friction coefficient, which is typical in early stages of the quasi-laminarization process. Both models have shown deficient predictions of the decreasing and logarithmic behavior of Reynolds shear stresses as well as significantly overpredicted the production of Turbulent Kinetic Energy (TKE) in turbulent boundary layers subject to very strong FPG. https://doi.org/10.1016/j.compfluid.2020.104494 

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3. Identifying the granitic composition water-saturated solidus

   Rufledt C, Thomas JB (September 2023, Xth Hutton Symposium)

   The granitic water-saturated solidus (G-WSS) is the lower temperature limit of magmatic mineral crystallization. The accepted water-saturated solidus for granitic compositions was largely determined >60 years ago1. More recent advances in experimental petrology, improved analytical techniques, and recent observations that granitic systems can remain active or spend a significant proportion of their lives at conditions below the traditional G-WSS2–5 necessitate a careful experimental investigation of the near-solidus regions of granitic systems. Natural and synthetic starting materials were melted at 10 kbar and 900°C with 48 wt% H2O to produce hydrous glasses for subsequent experiments at lower PT conditions used to locate the G-WSS. We performed crystallization experiments and melting experiments at temperatures ranging from 575 to 800°C and 1, 6, 8, and 10 kbar on 12 granitoid compositions. First, we ran a series of isothermal crystallization experiments along each isobar at progressively lower temperatures until runs completely crystallized to identify apparent solidus temperatures. Geochemical analyses of quenched glass compositions demonstrate that progressive crystallization drives all starting compositions towards silica-rich, water-saturated rhyolitic/granitic melts (e.g., ~7578 wt% SiO2). After identifying the apparent solidus temperatures at which the various compositions crystallized, we then ran series of reversal-type melting experiments. With the goal of producing rocks with hydrous equilibrium microstructures, we crystallized compositions at temperatures ~10°C below the apparent solidus identified in crystallization experiments, and then heated isobarically to conditions that produced ~20% melt during the crystallization experiments. Importantly, crystallization experiments and heating experiments at the same PT conditions produced similar proportions of melt, crystals, and vapor. A time-series of experiments 230 days at PT conditions previously identified to produce ~10% to 20% melt did not reveal any kinetic effects on melt crystallization. Experiments at 6 to 10 kbar crystallized/melted at temperatures close to the published G-WSS. However, at lower pressures where the published G-WSS is strongly curved in PT space, all compositions investigated contained melt to temperatures ~75 to 100°C below the accepted G-WSS. The similarity of crystallization temperatures for the higher-pressure experiments to previously published results, similar phase proportions in melting and crystallization experiments, and the lack of kinetic effects on crystallization collectively suggest that our lower pressure constraints on the G-WSS are accurate. The new experimental results demonstrating that the lower-pressure G-WSS is significantly lower than unanimously accepted estimates will help us to better understand the storage conditions, evolution, and potential for eruption in mid- to upper-crustal silicic magmatic systems. (1) Tuttle, O.; Bowen, N. Origin of Granite in the Light of Experimental Studies in the System NaAlSi3O8–KAlSi3O8–SiO2–H2O; Geological Society of America Memoirs; Geological Society of America, 1958; Vol. 74. https://doi.org/10.1130/MEM74. (2) Rubin, A. E.; Cooper, K. M.; Till, C. B.; Kent, A. J. R.; Costa, F.; Bose, M.; Gravley, D.; Deering, C.; Cole, J. Rapid Cooling and Cold Storage in a Silicic Magma Reservoir Recorded in Individual Crystals. Science 2017, 356 (6343), 1154–1156. https://doi.org/10.1126/science.aam8720. (3) Andersen, N. L.; Jicha, B. R.; Singer, B. S.; Hildreth, W. Incremental Heating of Bishop Tuff Sanidine Reveals Preeruptive Radiogenic Ar and Rapid Remobilization from Cold Storage. Proceedings of the National Academy of Sciences 2017, 114 (47), 12407–12412. https://doi.org/10.1073/pnas.1709581114. (4) Ackerson, M. R.; Mysen, B. O.; Tailby, N. D.; Watson, E. B. Low-Temperature Crystallization of Granites and the Implications for Crustal Magmatism. Nature 2018, 559 (7712), 94–97. https://doi.org/10.1038/s41586-018-0264-2. (5) Glazner, A. F.; Bartley, J. M.; Coleman, D. S.; Lindgren, K. Aplite Diking and Infiltration: A Differentiation Mechanism Restricted to Plutonic Rocks. Contributions to Mineralogy and Petrology 2020, 175 (4). https://doi.org/10.1007/s00410-020-01677-1. 

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4. Hyperbolic Numerical Models for Unsteady Incompressible, Surcharged Stormwater Flows

   Hodges, Ben R.; Vasconcelos, Jose G.; Sharior, Sazzad; Geller, Vitor G. (June 2022, Proceedings of the 39th IAHR World Congress)

   The transition from open-channel to surcharged flow creates problems for numerical modeling of stormwater systems. Mathematically, problems arise through a discrete shock at the boundary between the hyperbolic Saint-Venant equations and the elliptic incompressible flow equations at the surcharge transition. Physically, problems arise through trapping of air pockets, creation of bubbly flows, and cavitation in rapid emptying and filling that are difficult to correctly capture in one-dimensional (1D) models. Discussed herein are three approaches for modeling surcharged flow with hyperbolic 1D equations: (i) Preissmann Slot (PS), (ii) Two- component Pressure Approach (TPA) and (iii) Artificial Compressibility (AC). Each provides approximating terms that are controlled by model coefficients to alter the pressure wave celerity through the surcharged system. Commonly, the implementation of these models involve slowing the pressure celerity below physical values, which allows the numerical solution to dissipate the transition shock between the free surface and surcharged flows without resorting to extraordinarily small time-steps. The different methods provide different capabilities and numerical implementations that affect their behavior and suitability for different problems. https://doi.org/10.3850/IAHR-39WC2521711920221370 

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5. Multiple Element Limitation in Northern Hardwood Ecosystems (MELNHE): Net N mineralization at Hubbard Brook Experimental Forest, Bartlett Experimental Forest and Jeffers Brook, central NH USA, 2009 - 2017

   https://doi.org/10.6073/pasta/95fe44076088c6300fa861bbedc66924  

   Fisk, Melany (January 2025, Environmental Data Initiative)

   The Multiple Element Limitation in Northern Hardwood Ecosystems (MELNHE) project studies N and P acquisition and limitation through a series of nutrient manipulations in northern hardwood forests. This data set includes net N mineralization measured in Oe, Oa, and mineral soil horizons in all 13 of the MELNHE study sites. Samples are collected every several years, beginning with pretreatment (2008 and 2009) through 2017, representing 3 years of N and P fertilization. Additional detail on the MELNHE project, including a datatable of site descriptions and a pdf file with the project description and diagram of plot configuration can be found in this data package: https://portal.edirepository.org/nis/mapbrowse?scope=knb-lter-hbr&identifier=344 These data were gathered as part of the Hubbard Brook Ecosystem Study (HBES). The HBES is a collaborative effort at the Hubbard Brook Experimental Forest, which is operated and maintained by the USDA Forest Service, Northern Research Station. The following papers describe and make use of these data: Kang H, Fahey TJ, Bae K, Fisk MC, Sherman RE, Yanai RD, See C. 2016. Response of forest soil respiration to nutrient addition depends on site fertility. Biogeochemistry 127:113-124. https://doi.org/10.1007/s10533-015-0172-6. Ratliff TJ, Fisk MC. 2016. Phosphatase activity is related to N availability but not P availability across hardwood forests in the northeastern United States. Soil Biology and Biochemistry 94:61-69. https://doi.org/10.1016/j.soilbio.2015.11.009. Bae B, Fahey TJ, Yanai RD, Fisk MC. 2015. Soil nitrogen availability affects belowground carbon allocation and soil respiration in northern hardwood forests of New Hampshire. Ecosystems 18:1179-1191. https://doi.org/10.1007/s10021-015-9892-7. Fisk MC, Ratliff TJ, Goswami S, Yanai RD. 2014. Synergistic soil response to nitrogen plus phosphorus fertilization in hardwood forests. Biogeochemistry 118:195-204. https://doi.org/10.1007/s10533-013-9918-1. 

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