This work presents the fabrication of NdFeB-based magnets using a novel method that combines powder injection and 3D printing techniques. Using customized 3D-printed plastic molds, we are able to efficiently manufacture magnets with various shapes. The injected green parts maintained near-net shape geometry. A computational model was developed to validate the design of the injection mold. The volume fraction of fluid (VOF) approach in the computational model was used to understand the flow of slurry inside the mold cavity. The computational results were promising and showed a continuous flow of slurry without any air pockets. A thorough debinding of injected green parts made sure that no binder was left behind. The microstructure and properties of the injected green parts as well as the debinded parts were investigated. The proposed method would help reduce the production cost incurred in the design and manufacturing of magnets and would also increase productivity. The magnets produced from this research could serve multiple applications in the medical, electrical, automotive and aerospace industry.

We use new experiments and a theoretical analysis of the results to show that the isotopic fractionation associated with laser-heating aerodynamic levitation experiments is consistent with the velocity of flowing gas as the primary control on the fractionation. The new Fe and Mg isotope data are well explained where the gas is treated as a low-viscosity fluid that flows around the molten spheres with high Reynolds numbers and minimal drag. A relationship between the ratio of headwind velocity to thermal velocity and saturation is obtained on the basis of this analysis. The recognition that it is the ratio of flow velocity to thermal velocity that controls fractionation allows for extrapolation to other environments in which molten rock encounters gas with appreciable headwinds. In this way, in some circumstances, the degree of isotope fractionation attending evaporation is as much a velocimeter as it is a barometer.

Identifying and determining the origin of beta-cristobalite, a high-temperature silica polymorph, in natural samples is challenging as it is rarely, if ever, preserved due to polymorphic transformation to alpha-cristobalite at low temperature. Formation mechanisms for beta-cristobalite in high-silica rocks are difficult to discern, as superheating, supercooling, bulk composition, and trace element abundance all influence whether cristobalite crystallizes from melt or by devitrification. Here we report a study of alpha-cristobalite in Libyan Desert Glass (LDG), a nearly pure silica natural glass of impact origin found in western Egypt, using electron microprobe analysis (EMPA), laser ablation inductively coupled mass spectrometry (LA-ICP-MS), time-of-flight secondary ion mass spectrometry (ToF-SIMS), scanning electron microscopy (SEM), and electron backscatter diffraction (EBSD). The studied grains are mostly 250 mu m in diameter and consist of similar to 450 mu m wide cores surrounded by similar to 50 mu m wide dendritic rims. Compositional layering in LDG continues across cristobalite grains and mostly corresponds to variations in Al content. However, layering is disrupted in cores of cristobalite grains, where Al distribution records oscillatory growth zoning, whereas in rims the high Al occurs along grain boundaries. Cristobalite cores thus nucleated within layered LDG at conditions that allowed mobility of Al into crystallographically controlled growth zones, whereas rims grew when Al was less mobile. Analysis of 37 elements indicates little evidence of preferential partitioning; both LDG and cristobalite are variably depleted relative to the upper continental crust, and abundance variations correlate to layering in LDG. Orientation analysis of {112} twin systematics in cristobalite by EBSD confirms that cores were formerly single beta-cristobalite crystals. Combined with published experimental data, these results provide evidence for high-temperature (>1350 degrees C) magmatic crystallization of oscillatory zoned beta-cristobalite in LDG. Dendritic rims suggest growth across the glass transition by devitrification, driven by undercooling, with transformation to alpha-cristobalite at low temperature. This result represents the highest formation temperature estimate for naturally occurring cristobalite, which is attributed to the near pure silica composition of LDG and anomalously high temperatures generated during melting by meteorite impact processes.

The Tso Morari terrane within the Himalayan orogenic belt underwent ultrahigh-pressure (UHP) coesite-eclogite metamorphism due to northward subduction of the Indian continent under the Eurasian continent during the early Eocene. The Tso Morari UHP terrane has been intensely studied petrologically, mineralogically, and geochemically over the past several decades. However, the fluid history (e.g., phases and pressure–temperature conditions, fluid compositions and sources, and processes of fluid–rock interactions) and thermal structure during exhumation remain unresolved. To address these issues, we sampled a traverse from the center of an eclogite boudin out into the host orthogneiss. Three major fluid evolution stages (FESs) were identified and characterized using petrography, mineral and bulk-rock chemistry, and thermodynamic modeling. FES 1 constrained mineral dehydration and hydration reactions during prograde metamorphism before reaching peak pressure at 29.0 ± 0.8 kbar and 591 ± 9 °C by modeling garnet growth in the eclogites. FES 2 constrained mineral reactions in the eclogite matrix due to destabilization of internal hydrous minerals. This FES caused the formation of epidote at 22.8 ± 0.6 kbar, amphibole core domains (glaucophane) at 19.0 ± 0.4 kbar, amphibole rim domains (barroisite) at 14.5 ± 1.0 kbar, and symplectite at 9.0 ± 1.0 kbar, during isothermal decompression (600–650 °C). FES 3 caused amphibolization of eclogite at the boudin rim at 625 ± 50 °C and 9.0–14.0 kbar. Metasomatism resulted in increased K 2 O, CO 2 , and bulk-rock Fe 3+ /ΣFe in the amphibolized eclogites. Large ion lithophile elements (LILE) (e.g., K, Rb, Cs, Sr, Ba) and trace element ratios of Ba/Rb and Cs/Rb are also elevated relative to the eclogite core. The fluid most likely originated from dehydrating host orthogneiss and/or metasediments. Thermodynamic modeling also predicts that the Tso Morari complex was exhumed through a low-temperature (< 650 ± 50 °C) regime in the subduction channel.

The Tso Morari terrane within the Himalayan orogeny underwent ultrahigh-pressure (UHP) metamorphism due to northward subduction under the Eurasian continent during the early Eocene.The advancement of computational petrology and availability of relevant thermodynamic databases provide the mechanism to more precisely quantify metamorphic processes.In this study, we model the eclogite's prograde pressuretemperature (P-T) path as well as multiple fluid infiltration events during exhumation using Theriak-Domino with dataset ds62 and garnet[1] and other metabasic mineral activitycomposition relations.The effect of garnet fractionation on the rock's effective bulk composition is considered in simulating prograde garnet growth.A "fishhook" shape clockwise P-T path is obtained with a peak pressure of ~28.5 kbar at ~563 °C, followed by a peak temperature of ~613 °C at ~24.5 kbar [2].Thermodynamic modelling using P-M(H 2 O) pseudosections on Tso Morari eclogites indicates three distinct phases of fluid infiltration during exhumation.Fluid infiltration Ⅰ occurs at ~610 °C and ~23.5 kbar with ~3.1 mol % fluid expulsion due to the destabilization of lawsonite.The modelling results are consistent with petrographic observations in the eclogite: we found ~6.0 vol % epidote and ~21.0 vol % amphibole and the possible preexistence of lawsonite evidenced by its pseudomorph (as epidote and paragonite aggregates) in a garnet core and rim[3], and CNASH modelling on the epidote and its inclusion paragonite.Fluid infiltration Ⅱ occurs at ~9.2 kbar and ~608 °C with >2.6 mol % fluid infiltration at amphibolite-facies.This phase of fluid infiltration is characterized by aggressive amphibolization from the boudin core to rim.Fluid infiltration Ⅲ occurs at ~610 °C and ~8.7 kbar, caused by breakdown of phengite as predicted through modelling the symplectitic association (plagioclase, biotite, and amphibole) surrounding omphacite.In summary, this study not only illustrates the application of thermodynamic modelling in quantifying metamorphic processes, but also the need of comparison between modeling predictions and petrographic observations.

As a transition metal that is moderately volatile at high temperatures, copper shows limited isotopic fractionation in terrestrial mantle-derived rocks but significant enrichment in its heavier isotope (up to 12.5 parts per thousand for Cu-65/Cu-63) in objects that experienced volatile loss during formation, such as tektites, trinitite glasses, and lunar rocks. Previous efforts to model the Cu isotope fractionation trend from measurements of delta Cu-65 in tektites found that the trend cannot be explained by the theoretical isotope fractionation factor (alpha) for free evaporation of Cu, making it necessary to experimentally study Cu isotope fractionation under conditions similar to tektite formation. Here we present new experimental data of elemental (Na, K, Cu) and isotopic (Cu) fractionation during evaporation. Our experiments, conducted by laser-heating an aerodynamically levitated glass sphere to 1750, 2000, and 2150 degrees C, show rapid loss of Na, K, and Cu from the molten glass. In particular, > 99.99% of Cu was lost within 60 seconds. The evaporation induced loss of Cu is accompanied by progressive enrichment in its heavier isotope in the residue glass, with a maximum fractionation in delta Cu-65 of similar to 18 parts per thousand relative to the synthesized initial sample. The empirical fractionation factor (alpha) calculated from our laser levitation data is 0.9960 +/- 0.0002. Compared to similar experiments conducted for Zn, Cu appears to be significantly more volatile and show higher degrees of Cu isotope fractionation, consistent with observations in natural tektites. Comparing isotopic fractionation in a range of moderately volatile elements among laser levitation experiments, tektites, trinitites, and the bulk silicate Moon suggest that they experienced evaporation under various degrees of effective vapor saturation (similar to 74%, 93%, similar to 99%, similar to 99%), which depart significantly from free-evaporation (0%). (C) 2021 Elsevier Ltd. All rights reserved.

Earth and Space Science Open Archive Presented WorkOpen AccessYou are viewing the latest version by default [v1]Amphibolization of the Tso Morari UHP eclogites: a record of fluid infiltration at amphibolite-facies during uplift in the subduction channelAuthorsRuiguangPANiDCatherineMacrisiDCarrieMenoldSee all authors Ruiguang PANiDCorresponding AuthorIndiana University Purdue University IndianapolisiDhttps://orcid.org/0000-0003-2489-6545view email addressThe email was not providedcopy email addressCatherine MacrisiDIndiana University Purdue University IndianapolisiDhttps://orcid.org/0000-0001-6444-1524view email addressThe email was not providedcopy email addressCarrie MenoldAlbion Collegeview email addressThe email was not providedcopy email address

Introduction: Tektites are natural glasses formed from fast cooling of the molten impact plume. They are usually round, black or brown in color (sometimes green), and range from submillimeter (microtektites) to tens of centimeters (Muong-Nong type) in diameter. Tektites are roughly felsic in composition, similar to that of average continential crust, but depleted in volatiles such as water and alkalis [1]. Recent advancements in non-traditional isotope geochemistry enabled measurements of stable isotope fractionation in tektites for moderately volatile elements, some of which showed enrichment in their heavier isotopes (i.e. Cu, Zn, Sn, and Cd), consistent with evaporative loss [2,3,4,5,6]. Fundamental outstanding questions still remain, however, regarding the role of evaporation in the chemical and isotope fractionation of tektites. For example, Zn is expected to be more volatile than Cu, but higher degrees of isotope fractionation were found for d65/63Cu (up to 12.5‰, [4,5]) compared to d66/64Zn (up to 3.65‰, [3,5]). Furthermore, previous studies found it difficult to explain Zn and Cu isotope fractionation in tektites using theoretical isotope fractionation factors for free-evaporation [3,4], making it necessary to experimentally determine the isotope fractionation factors for Cu and Zn under conditions similar to tektite formation. Here we report laser levitation experiments on Cubearing silicate glasses to understand Cu evaporative loss and isotope fractionation under tektite formation in the impact plume. Our results are also combined with a similar experimental study on Zn [7], natural tektite data, and lunar rock data to achieve a general understanding of evaporative isotope fractionation of moderately volatile elements. Experimental and Analytical Methods: Vaporization experiments were performed in the High-Temperature Conical Nozzel Levitation System (also called an aerodynamic levitation laser furnace) at Indiana University – Purdue University Indianapolis (IUPUI) using a synthetic basalt glass with ~1200 ppm Cu. About 10 mg aliquots of the initial glass were fused into spheres suitable for levitation in a water-cooled oxygen-free hearth plate by defocused laser heating. The fused glass spheres, 2.30 to 2.44 mm in diameter, were then heated to 1750 – 2150 oC for 4 to 120 s while levitated in ultrahigh purity Ar, before being quenched to glass by cutting power to the laser. After each experiment, the quenched sample glass was dissolved in concentrated acids on a hot plate, and Cu was purified using a quartz glass column (0.4 cm * 7.5 cm) loaded with AG1-X8 (200 – 400 mesh) BioRad resin. The column procedure was repeated twice to ensure complete separation of Cu from matrix elements. Copper isotopic compositions were determined using the Nu Plasma II at the Carnegie Institution for Science. Analyses were conducted using the sample-standard bracketing method. The concentration of Cu in the analytical solution was between 10 to 100 ppb. Results: The experimental samples show rapid Cu loss with duration of laser heating. Copper concentrations in the samples decreased by over four orders of magnitude, from ~1200 ppm in the starting material to below 0.03 ppm within 60 s (Fig. 1a).

Thermodynamic modeling is an important technique to simulate the evolution of metamorphic rocks, particularly the poorly preserved prograde metamorphic reactions. The development of new thermodynamic modeling techniques and availability of updated thermodynamic databases and activity–composition ( a–X ) relations, call for an evaluation of best practices for modeling pressure–temperature ( P–T ) paths of metabasites. In this paper, eclogite from the Tso Morari UHP terrane, NW India, is used as a representative metabasite to directly compare the outputs (pseudosections and P–T paths) generated from recent versions of the widely used THERMOCALC and Theriak-Domino programs. We also evaluate the impact of using the most updated thermodynamic database (ds 62, Holland and Powell in J Metamorph Geol 29(3):333–383, 10.1111/j.1525-1314.2010.00923.x, 2011) relative to an older version (ds 55, Holland and Powell in J Metamorph Geol 16(3):309–343, 10.1111/j.1525-1314.1998.00140.x, 1998), and the effect of the user’s choice of mineral a–X relations while considering the effect of garnet fractionation on the rock’s effective bulk composition. The following modeling protocols were assessed: (1) TC33; THERMOCALC version 3.33 with database ds 55 and garnet a–X relations of White et al. (J Metamorph Geol 25(5):511–527, 10.1111/j.1525-1314.2007.00711.x, 2007); (2) TC47; THERMOCALC version 3.47 with database ds 62 and garnet a–X relations of White et al. (J Metamorph Geol 32(3):261–286, 10.1111/jmg.12071, 2014a); (3) TDG; Theriak-Domino with database ds 62 and garnet a–X relations of White et al. (2014a), and (4) TDW; Theriak-Domino with database ds 62 and garnet a–X relations of White et al. (2007). TC47 and TDG modeling yield a similar peak metamorphic P–T of 34 ± 1.5 kbar at 544 ± 15 °C and 551 ± 12 °C, respectively. The results are 5–8 kbar higher in pressure than that determined from TC33 modeling (26 ± 1 kbar at 565 ± 8 °C), and TDW modeling (28.5 ± 1.5 kbar at 563 ± 13 °C). Results indicate that all four modeling protocols generally provide consistent metamorphic phase relations and thermodynamic simulations regarding fractionation of the bulk composition and prograde metamorphism within uncertainty. In all model calculations, the initial bulk composition measured by XRF does not represent the effective bulk composition at the time of garnet nucleation. The choice of garnet a–X relations can affect predictions of peak pressure, regardless of program choice. This study illustrates the importance of careful consideration of which a–X relations one chooses, as well as the need for comparison between modeling predictions and evidence from the geochemistry and petrography of the rock(s) themselves.

The interaction of fluids with rock-forming minerals plays an important role in the chemical evolution of mafic and ultramafic rocks in the lower crust and upper mantle. Recent work highlights the importance of salt-rich fluids in element transport in settings such as the mantle wedge above subduction zones and high-grade granulite facies metamorphism. Forsterite (Mg2SiO4), enstatite (MgSiO3) and diopside (CaMgSi2O6) are key rock-forming minerals in these settings in the system CaO-MgO-SiO2. We determined experimentally the solubilities of diopside, enstatite and forsterite in H2O-NaCl fluids at a range of pressures and temperatures. Forsterite solubility was determined at 1 GPa, 800 and 900 °C, in pure H2O and in H2O-NaCl solutions. Forsterite dissolved congruently at nearly all conditions. Its solubility in pure H2O is low, but increases greatly with rising NaCl concentration in the fluid. Enstatite solubility was investigated in H2O-NaCl solutions at 1 GPa, 800 and 900 °C. Enstatite dissolved incongruently to yield forsterite at all conditions. Addition of excess silica led to suppression of forsterite and showed that fluids in equilibrium with enstatite with or without forsterite are strongly enriched in Si relative to Mg, though Mg solubility is significant at high salinity. Diopside solubility was determined in pure H2O at 650–900 °C and 0.7–1.5 GPa, and in H2O-NaCl solutions at 800 °C and 1 GPa, with NaCl concentrations approaching halite saturation. Diopside dissolves incongruently yielding residual forsterite at all conditions investigated. The solubility of diopside in pure H2O increases with increasing pressure, temperature and salinity. Diopside dissolution in H2O-NaCl solutions displays a dependence on fluid salinity similar to that of forsterite and wollastonite. The results of forsterite solubility experiments in H2O-NaCl solutions were used to calculate the compositions of fluid coexisting with enstatite or diopside where forsterite was present. The concentration of solutes coexisting with enstatite decreases with rising NaCl, similar to quartz. In contrast, bulk solutes coexisting with diopside increase with NaCl, similar to wollastonite and forsterite. These patterns imply complexing among rock-forming components and fluid components, that Ca-chloride species are substantially more stable than Mg-chloride species, and that hydrous Na-silicate complexes are important components of deep H2O-NaCl fluids. The results show that salt-bearing brines have substantial metasomatic power and may exert significant control on the chemical evolution of lower crustal and upper mantle mafic and ultramafic rocks.