Metal Segregation Research Articles

Ruthenium isotopic fractionation in primitive achondrites: Clues to the early stages of planetesimal melting

Primitive achondrites derive from the residual mantle of incompletely differentiated planetesimals, from which partial silicate and metallic melts were extracted. As such, primitive achondrites are uniquely useful to examine the early stages of planetesimal melting and differentiation. To better understand this early melting and melt segregation as well as the nature of the melts involved, we obtained mass-dependent Ru isotopic compositions of 17 primitive achondrites, including winonaites, acapulcoite-lodranites, ureilites, brachinites, and two ungrouped samples. Most primitive achondrites with subchondritic Ru concentrations are characterized by heavy Ru isotopic compositions relative to chondrites, likely reflecting the extraction of isotopically light partial metallic melts. While the segregation of early-formed partial Fe-Ni-S melts likely had no effect on the Ru isotope compositions, the subsequent extraction of S-free partial metallic melts at higher temperatures provides a viable mechanism for producing the observed Ru isotopic fractionation and fractionated highly siderophile element ratios among primitive achondrites. Together, these observations indicate that differentiation of primitive achondrite parent bodies involved the segregation of distinct partial metallic melts over a range of temperatures, and that these melts ultimately formed a partial core with fractionated and light Ru isotopic composition. This contrasts with the unfractionated Ru isotope signatures previously estimated for bulk iron meteorite cores, which therefore indicates quantitative metal segregation during core formation in the iron meteorite parent bodies. The less efficient metal segregation in primitive achondrite parent bodies most likely reflects lower initial amounts of heat-producing 26Al due to later accretion or impact disruption of the parent bodies during differentiation.

Mapping surface segregation of single-atom Pt dispersed in M surfaces (M = Cu, Ag, Au, Ni, Pd, Co, Rh and Ir) under hydrogen pressure at various temperatures

Single-atom alloys (SAAs) are emerging materials containing isolated metal atoms dispersed on host metal surfaces, exhibiting unique reactivity compared with the corresponding monometallic counterparts. However, the stability of the isolated atoms in the host metal has hardly been studied, although, metal segregation has been commonly observed in bimetallic nanoparticles under reaction conditions. In this work we focus on single-atom Pt anchored on various metallic support surfaces. Density Functional Theory (DFT) calculations coupled with environmental segregation energy analysis are performed to map the segregation trends of 22 different Pt-SAA surfaces under various hydrogen conditions. The results show the high stability of single-atom Pt in Ni, Co, Rh and Ir host metallic surfaces while no stability is predicted on Au and Ag surfaces. For Pd and Cu host supports, the single-atom Pt is found to be stable on specific surface facets and within definite temperature and pressure conditions. This work brings an important understanding of SAA systems through the prediction of surface atomic ordering changes under operating conditions which related to the reactivity will ultimately allow the design of more efficient catalysts.

Shear-coupled grain boundary migration in bicrystal Ni with metallic dopant segregation

The shear-coupled grain boundary (GB) migration in bicrystal Ni with metallic dopant segregation was investigated by the molecular dynamics simulations. Different from the approximately linear relation of the GB migration of pure bicrystal Ni with the nominal shear strain, the curve of doped bicrystal Ni can be divided into three stages. The threshold strain, saturated strain, and saturated GB migration displacement can be used to characterize them. They are considerably affected by the Cr concentration in GB, temperature, and dopant type. The higher the dopant concentration is or the lower the temperature is, the greater the resistance to GB migration is. Cu dopant induces the greatest resistance, Cr and Fe dopants have great effect on the GB migration, but Co has almost no influence. All these hindering effects can be explained from the variation of the number of pinning points induced by the dopant atoms in GB.

Toward a global conceptual model for metal enrichment in felsic, mafic-ultramafic, and alkaline-carbonatitic magmas

The formation of intrusion-related metal ore deposits commences with a combination of sequential metal and melt interactions in the magma reservoir: (i) metal diffusion within the melt; (ii) melt motion; (iii) metal partitioning between silicate melts and a magmatic immiscible phase (MIP, including immiscible melts and/or immiscible vapor phases, and crystalized solids; (iv) metal advection in the melt; (v) chemical interactions between the MIP and the mush; and (vi) finally metal deposition. Occasionally, these processes may also develop simultaneously, and lead to formation of multiple depositional centers. During those events, the presence of the MIP seems preponderant and a prerequisite to metal segregation and transport with the interactive mush. Based on forward and inverse modeling, novel diffusion-partitioning-advection models are proposed to account for economic metal enrichment (three to five orders of magnitude relative to initial concentrations in parental melts). For felsic to intermediate magmas, metals (Cu, Mo, W, Sn) are enriched in a saline aqueous phase by diffusion and metal partitioning. Progressive stagnation of melt motion enhances metal diffusion according to the tortuosity of a developing mush and destabilization of plagioclases. The metal-rich liquids separate from the magma reservoir by advection and transfer the metals to the country rocks. For mafic/ultramafic magmas, the MIP is a dense, sulfide melt, which preferentially sequesters metals (Ni, Cu, platinum group elements). The sulfide droplets interact with olivine to scavenge more Ni before they sink toward the bottom of the magma chamber due to negative buoyance. The down-going flow may even become turbulent according to the melt viscosity, leading to disperse and chaotic ore. In peralkaline magmas, CO2-rich carbonatitic melts are the MIPs formed by segregation of CO2-poor feldspathoid syenite melts, and attracting rare earth elements. Those are selectively partitioned by fenitization. In all the three different types of magmatic system, metals diffuse from viscous evolved parental melts toward a MIP, which is responsible for metal partitioning, segregation and transports. This global conceptual model for metal enrichment focuses on the competition between metal diffusion within the melt, melt viscosity and metal partitioning between the parental melt and MIP. However, a second stage of metal enrichment occurs during interaction of the already enriched melt and the mush. Such conceptual model is a first order model that could suggests newer ideas to ore formation.

Highly Stable Transition Metal Alloy Catalysts Wrapped with C-Dots for Hydrogen Evolution Reaction in Acidic Solution

This work reports a large-scale and low-cost synthesis of highly effective, durable, and cheap NiCoPt/C-dot catalysts for hydrogen evolution reaction (HER). Simultaneous co-reduction of the metal precursors and carbon dots (C-dots) was confirmed by TEM, XPS, and Raman techniques. The SEM result clearly indicates that C-dots act as a structure-directing agent assisting to generate 3D nanosponge complex structure, which has an abundance of the electrochemically active sites. Synthesis procedure yields NiCoPt/C-dot nanoporous alloy wrapped with graphene, where the synergetic effect of the metal alloy constituents with outer graphene dots stimulates the electrochemical catalytic activity. Graphene dots additionally act as a protective layer. The optimization of the alloy composition along with lowering Pt loading (down to 0.04mM) for the highest catalytic activity for HER yields Ni48Co48Pt4/C-dot nanohybrid. XPS analysis revealed the nanohybrid surface is enriched up to 86.7 at% of Pt, suggesting that the surface composition of an alloy is controlled by the tendency of Pt metal segregation towards the surface. Such surface electronic structure led to the superior catalytic activity of Ni48Co48Pt4/C-dot, which generates an overpotential of only 45.54 mV at a current density of 10 mAcm-2 in acidic solution. The highest catalytic activity correlates well with the lowest charge transfer resistance in conjunction with the highest ECSA value of 57.51 cm2 of the nanohybrid. The synthesized nanocomposite showed good stability retaining 94% of current density after 21 hours of operation. The catalytic activity and durability of developed nanocomposite catalyst are comparable to those of the commercial Pt/C. The aforementioned advantages allow stating that 3D Ni48Co48Pt4/C-dot nanosponge is a low-cost, durable, and efficient electrocatalyst for hydrogen evolution. The developed nanohybrid may be considered as an upcoming alternative catalyst for hydrogen gas production. Figure 1

Segregation of Refractory Metals at Grain Boundaries in High-Temperature Alloys

Segregation of Refractory Metals at Grain Boundaries in High-Temperature Alloys

Coke formation during high-temperature CO2 electrolysis over AFeO3 (A = La/Sr) cathode: Effect of A-site metal segregation

In this study, strontium-doped lanthanum ferrite perovskite oxides (LSF) with different A-site occupancies were used as cathode catalysts for CO2 electrolysis at 800 °C. XRD, EXAFS, XPS, FTIR, and temperature-programmed desorption were used to characterize the properties of the material. Fe K-edge EXAFS indicated that oxygen vacancy concentration and oxidation states of Fe atoms increased with concomitant improvement of electronic and ionic conductivities with a decrease in the A-site occupancy. XPS spectra revealed that Sr atoms segregated on the surface of A-site excess LSF92 to a greater degree than that on the A-site deficient LSF72. These segregated A-site metal oxides, especially SrO, are alkaline in nature and hence strongly bind to acidic CO2 forming stable SrCO3, which consequently facilitates carbon formation. This study highlights the effect of A-site stoichiometric modulation on carbon formation during electrolysis of CO2, which is crucial for improving the long- term performance of an SOEC.

Three-Dimensional Atomic Structure of Grain Boundaries Resolved by Atomic-Resolution Electron Tomography

Summary Grain boundaries (GBs) determine the properties of polycrystals, and tailoring the GB structure offers a promising method for the discovery and engineering of new materials. However, GB structures are far from well understood because of their structural complexity and limitations of conventional projection imaging methods. Here, we decipher three-dimensional atomic structure and crystallography of GBs in nanometals using atomic-resolution electron tomography. Unlike conventional descriptions, whereby they are either straight or curved planar planes with one-dimensional translational symmetry, we show that the high-angle GBs completely lose translational symmetry due to undulated curvature related to configurations of structural units. Moreover, we directly visualize kinks and jogs at the single-atom scale in dislocation-type GBs and investigate their mobilities. Our findings bring new insights to the conventional wisdom of GBs and show the importance of developing methods to include the non-planar nature of GBs to statistically evaluate the behavior of GBs in modeling studies.

Speciation, contamination, ecological and human health risks assessment of heavy metals in soils dumped with municipal solid wastes

The main aim of this work is to assess the extent of soil contamination, potential ecological and health risks associated with the disposal of municipal solid waste (MSW) near a Ramsar site in Assam, India. Soil samples were collected and analysed for three heavy metals (HMs), namely, chromium (Cr), manganese (Mn) and zinc (Zn). The sources of HMs and their pollution levels were evaluated using different indices. The results demonstrated that Cr contamination was high near the metal scrap segregations unit within the dumping site, otherwise, the ecological risks associated with Zn and Mn were found to be low. The speciation of Cr and Zn were associated with the Fe–Mn oxide bound (F4) fraction, accounting 44.23% and 30.68%, respectively, whereas Mn (52.55%) was associated with the exchangeable fraction (F2). The fate and origin of HMs were assessed using mobility and enrichment factors and 16 out of the 20 sampling sites fell under the category of heavily polluted category for Cr, while others which were nearby the metal segregation units fell under the strongly to extremely polluted category. In few sites, significant enrichment was observed for Zn and minimal to moderate enrichment for Mn, respectively. Health risk assessment results indicated that Cr posed higher threat to human health through ingestion.

Core‒rim structure, bi-solubility and a hierarchical phase relationship in hot-pressed ZrB2‒SiC‒MC ceramics (M=Nb, Hf, Ta, W)

Core‒rim structures were identified as a common feature in hot-pressed ZrB2‒SiC‒MC ceramics (M = Nb, Hf, Ta and W) by a combination of X-ray diffraction, scanning and transmission electron microscopies. Quantitative analyses associate them with the bi-solubility of M in ZrB2 phase, in which transition of solubility across the core/rim boundary is abrupted, signifying their creation via dissolution‒reprecipitation process facilitated by transient liquid-phase. The cores were retained from starting powder after surface melting and the rims were grown from the liquid-phase to incorporate more solutes, leaving the residual liquid to turn into ZrC phase with higher solubility of M. We propose g-point scheme in the ZrB2‒MB2 diagrams to combine the bi-solubility and the core‒rim structures into an intra-phase relationship created by sintering, leading further to a hierarchical phase relationship. The temperature dependence of flexural strength in the ZrB2‒SiC‒MC ceramics varies with MC additions, which can be respectively strengthened by the strain energy created in the core‒rim structures and metal segregation to grain boundaries.

Features of basaltic melt-hydrogen interaction at hydrogen pressure 10–100 MPa and temperature 1100–1250 °C

New experimental data on interaction of basaltic melt with hydrogen at high temperature (1100–1250 °C) and hydrogen pressure (10–100 MPa) have been obtained to gain insight into the possible role of hydrogen in the processes occurring in basaltic melts in the earth's crust under reducing conditions (f(O2) = 10−13–10−15). The experiments were carried out in a unique in house built internally heated pressure vessel (IHPV). This apparatus is equipped with an internal device, which allows long-term experiments under hydrogen pressure at high temperatures without losing hydrogen. Two types of experiments were carried out: 1 - kinetic experiments with isobaric quenching, 2 - crystallization experiments with subsequent isobaric quenching. It was found that, despite the high reducing potential of the H2 - basaltic melt system, the hydrogen oxidation reactions and the Fe oxides reduction in the melt are not complete. Initially homogeneous basaltic melts become heterogeneous. H2O is formed in the fluid phase (initially consisted of pure hydrogen); H2O (0.34–0.9 wt%) also dissolves in the basaltic melts, and small metal blobs with an emulsion-like texture are formed in the melts at temperature significantly lower than the melting temperature of the metal phase (Fe). The texture and dimensions of the metal segregations resemble those reported from natural magmatic rocks. Some new features of the crystallization process of basaltic melt under very reducing conditions are also discussed. The assemblage of subliquidus minerals (olivine + clinopyroxene + plagioclase) formed in the crystallization experiment at T = 1100 °C, P(H2) = 10 MPa with run duration 2 h, and their chemical compositions match closely those described in natural lavas (e.g. Kamchatka volcanoes). This result can be considered as an experimental confirmation of the participation of hydrogen in the magmatic process, which also corroborates with the composition of volcanic gases.

Automation of Metal, Dry and Wet Waste Materials Segregation using Microcontroller in Scrap Industry

Automation of Metal, Dry and Wet Waste Materials Segregation using Microcontroller in Scrap Industry

Measurable surface d charge of Pd as a descriptor for the selective hydrogenation activity of quinoline

AbstractAuPd nanoalloys with tunable Pd concentrations have been synthesized and used as model catalysts. They have been directly imaged by high-angle annular dark-field scanning transmission electron microscopy and investigated by thorough analyses of their extended X-ray absorption fine structure, X-ray absorption near-edge structure, X-ray diffraction and X-ray photoelectron spectroscopy measurements. The bimetallic nanoparticles are embedded in a carbonaceous matrix and have almost an identical structure at the atomic level and the same electronic properties as AuPd bulk alloys with the same compositions. The d-electron increase at surface Pd sites is determined by the Pd concentration of the alloy. Similarly, their activation entropy and catalytic activity for the hydrogenation of quinoline is related to the Pd concentration, with Au50Pd50 the most active of the alloys investigated. An almost 11 times higher activity was achieved compared to a pure Pd catalyst. The experimentally measurable surface d charge at the Pd sites in the AuPd was found to linearly correlate with the activation entropy and catalytic activity for the hydrogenation of quinoline. The alloy structure is stable, showing negligible metal segregation, dissolution-redeposition and aggregation during the hydrogenation process which involves strong adsorption.

High-quality LiNi0.8Co0.15Al0.05O2 cathode with excellent structural stability: Suppressed structural degradation and pore defects generation

Although LiNi0.8Co0.15Al0.05O2 (NCA) cathode materials have been widely used for electric vehicles, the poor cycle performance still limits the further application. In this work, high-quality NCA with desired stoichiometric ratio and few structural defects is prepared by using N-methyl-2-pyrrolidone (NMP)- and urea-based solvothermal reaction. The as-prepared NCA exhibits high capacity (203 mAh g−1 at 0.1 C), excellent rate capability (117 mAh g−1 at 10 C, attributed to enhanced exposure of {010} planes), and good cycle performance (74.4% capacity retention at 300th cycle). Compared with NCA prepared by NaOH, NCA prepared by NMP and urea shows superior ability in suppressing structural degradation of R3‾m phase-to-Fd3‾m/Fm3‾m phase transformation, transition metal segregation, and pore defects generation after prolonged cycling, which can be used for ultrafast and long-lifespan lithium storage.

Microstructure Investigations of Powders and Additive Manufactured Parts

This paper presents an advanced microstructural analysis of the AlSiMg, Ti64, and N700 powders used for additive manufacturing. The internal microstructure of the regular and irregular powder grains were characterized down to atomic resolution by using scanning electron microscopy and high resolution scanning transmission electron microscopy.The accretionary forms on top of the irregular AlSiMg powder grains exhibit a slightly coarse microstructure with a network of eutectic Si consisting of nano-crystallites, suggesting a slower cooling than the grain itself that contain a predominately amorphous Si network.A nm thin amorphous C layer on the surface of some Ti64 plasma atomized powder grains promoted the attachment of satellites and growth of envelopes. In case of gas atomized N700 powder grains, we identified thin oxide and carbon amorphous layers as well as metal segregations at the interface between the grain body and the accretionary forms.

Examining the compositions of impactors striking the Moon using Apollo impact melt coats and anorthositic regolith breccia meteorites

Impactors striking the Moon since the formation of its crust have left an indelible imprint on the lunar surface, in the guise of craters and associated impact rocks. The lunar crust has low intrinsic abundances of the highly siderophile elements (HSE: Re, Os, Ir, Ru, Pt, Rh, Pd, Au), at greater than 3000 times lower than in chondrite meteorites. Consequently, during impact, bolides with chondritic or differentiated iron-rich compositions should impart elevated HSE signatures to the lunar crust. Here we examine glassy lunar impact melt coats (IMC) from the outside rims of Apollo 16 cataclastic anorthosites (60015, 65325) and breccias (65035), as well as both fragments and powders of Antarctic anorthositic regolith breccia (ARB) meteorites (Miller Range 090034/36/70/75 and MacAlpine Hills 88105) for their petrography, mineral chemistry and bulk-rock compositions. The HSE concentrations for IMC range from ∼0.001 to 0.1 × CI chondrite, with measured 187Os/188Os between 0.1189 and 0.1366. Anorthositic regolith breccia meteorites, which have components with 2.6–4.1 Ga ages, have similar HSE concentrations to IMC, but typically have lower 187Os/188Os (0.1164–0.1284). These latter Os ratios are generally less radiogenic than those measured in ∼3.8–3.9 Ga Apollo impact melt breccias. The Apollo 16 IMC are not well-dated, but their KREEPy trace-element signatures and associated ages of 3.7 to 3.8 Ga for Apollo 16 glasses might imply, at least in part, an origin from the Imbrium or Serenitatis basin-forming impacts. Within the IMC, metal-schreibersite-troilite assemblages record significant inter-element HSE fractionation which is also reflected in bulk HSE patterns for both IMC and ARB meteorites. Variations in relative and absolute HSE compositions directly reflect the control of metal and sulfide segregation within and between impact melt and breccia lithologies. Collectively, IMC and ARB meteorites exhibit approximately 50% of the variation in Ru/Ir and 187Os/188Os observed in lunar impact melt breccias. These results imply that significant variations in inter-element compositions can occur during impact brecciation and melting and so some impact melt rock HSE compositions may not record the compositions of impactors that struck the Moon with fidelity. Nonetheless, the generally low 187Re/188Os of lunar impact melt rocks means that osmium isotope ratios provide evidence for impact composition, and a change from ordinary to carbonaceous-like impactors either with time – or location – striking the Moon.

Effects of Micro-Alloying Elements on Microstructure, Element Distribution and Mechanical Properties in Gray Irons

This paper elucidates the effects of micro-alloying (Cr, Mo, rare earth and Ag) on the microstructure, element distribution and mechanical properties including Brinell hardness and tensile strength in cast gray irons. Experimental results show that the morphology of main graphite transforms from type C to type A and is refined obviously in the modified gray iron after micro-alloying. The pearlite content is also reduced, and the pearlite interlamellar spacing is smaller in the modified gray iron. The distribution and segregation of micro-alloying elements have determined the change of microstructure. More Cr and Mo atoms are tended to dissolve in pearlite and are likely to replace Fe atoms to form M3P in final solidified phosphorus eutectic regions. Meanwhile, segregation of rare earth metals toward boundaries should be considered into roles in refining graphite and pearlite interlamellar spacing. No obvious enrichment of Ag is found in matrix or at grain boundaries from experimental EPMA results. Multiple micro-alloying in gray irons improves the hardness and tensile strength at room temperature and at 700 °C by modifying the microstructure as well. Finer graphite and smaller pearlite interlamellar spacing results in better hardness, tensile strength and elongation in modified gray irons.

Energetics of CO2 and H2O adsorption on alkaline earth metal doped TiO2.

The process of CO2 and H2O adsorption on the surface of nano-oxide semiconductors is important in the overall performance of artificial photosynthesis and other applications. In this study, we explored the thermodynamics of CO2 and H2O adsorption on TiO2 as a function of surface chemistry. We applied gas adsorption calorimetry to investigate the energetics of adsorption of those molecules on the surface of anatase nanoparticles. In an attempt to increase TiO2 surface affinity to CO2 and H2O, TiO2 was doped with alkaline earth metals (MgO, CaO, SrO, and BaO) by manipulating the chemical synthesis. Adsorption studies using diffuse reflectance infrared spectroscopy at different temperatures indicate that due to the segregation of alkaline earth metals on the surface of TiO2 nanoparticles, both CO2 and subsequent H2O adsorption amounts could be increased. CO2 adsorbs in two different manners, forming carbonates which can be removed at temperatures lower than 700 °C, and a more stable linear adsorption that remains even at 700 °C. Additionally to the surface energetic effects, doping also increased specific surface area, resulting in further improvement in net gas adsorption.

Copper Minerals at Vesuvius Volcano (Southern Italy): A Mineralogical Review

This work is part of a project focused on the Somma–Vesuvius volcano and aimed at identifying Cu minerals related to mineralizing processes associated with magmatic activity in an active magmatic-hydrothermal system. A mineralogical survey was carried out on a set of samples represented by sublimates and fumarolic products from the collection of the Mineralogical Museum of the University of Naples Federico II (Italy). These samples are mainly related to most recent eruptive episodes of Vesuvius activity, from 1631 onward. Copper-bearing minerals were characterized, as well as associated minerals, by X-ray diffraction (XRD) scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS). An investigation on the structural complexity of Cu-mineral assemblages with different temperature formations was also carried out using the TOPOS software package. The main copper phases are sulfates, followed by vanadates, hydroxyhalides, oxides, carbonates, silicates and finally, phosphates. New mineral occurrences for Vesuvius, both Cu-bearing and Cu-free, are described. Nevertheless, the fumarolic/alteration minerals at Vesuvius cannot be considered of economic relevance as a copper reservoir, this type of mineralizations are significant for copper crystal chemistry and for the knowledge of the mineralogical variants. The obtained datasets can be of interest for the knowledge of volcanic byproducts of copper ore deposits (i.e., porphyry copper systems) and of (base) metal segregation processes.

Modeling ore generation in a magmatic context

Magmatic ore deposit models are constructed from a set of measurables (e.g., ore grade, fluid composition, structure) from which important parameters (temperature, pressure, chemistry) can be estimated and possible genetic processes can be constrained. Such models include direct, inverse or iterative problems. Direct problems separately consider an Eulerian and a Lagrangian formulation. In the first case, an analytical approach describes the bulk system from an external frame, whereas the Lagrangian approach provides a description from a discrete element attached to the system. Conversely, inverse problems mostly rely on a system of equations or differential equations. Their solution requires a matrix inversion, using statistical criteria to bracket errors. Subsequently, an iterative approach is adopted, commencing with an initial bulk model that is successively refined to fit the observations. The direct problem always results in a unique solution, though the formulation is highly overdetermined. Such unique solution highly depends on the input parameters, and multiple solutions vary with the initial imposed conditions. Conversely, the inverse problem is underdetermined by construction. Accordingly, it provides a set of solutions, generally identified and separated by statistical tests, as exemplified by the least squares approximation. Both methods intrinsically ignore feedback loops. Iterative methods are weak in quantifying the results. Based on the insights gained from this review, we developed a new integrative model for porphyry deposits that relies on the magmatic segregation of metals through a fluid sparging process. A formulation under the direct problem basically considers the enrichment factor for groups of metals (e.g., Cu, Mo, Au). A Lagrangian approach using a lattice Boltzmann model examines metal diffusion from the melt toward an immiscible phase, commonly a salty aqueous fluid. Metals first diffuse in the melt, the motion of which slows down when the mush development reduces the porosity, thus tapping the mobile fluid phase. Gas bubbles turn to tubes. They offer more mobility and allow the progression of the fluid phase, leading to metal advection, followed by metal precipitation. The quantitative results are poorly constrained owing to the large uncertainties on the input parameters but the metal enrichment factor fits observations from crustal abundance to ore grade levels. Nevertheless, the results aid in designing an inverse approach linking metal enrichment to metal partitioning, diffusion and viscous melt motion. From this approach, a simple diagram can be deduced using a logarithmic scale to smooth the parametric uncertainties. The diagram serves to illustrate the link between the above parameters and metal enrichment, also explaining differences in ore grade for different metals-magma pairs.