Ppm Pd Research Articles

The role of hydrothermal processes and the formation of the J-M reef and associated rocks of olivine-bearing zone I of the Stillwater Complex, Montana

AbstractSeveral lines of evidence, including hydrous melt inclusions and unusually Cl-rich apatite, have been used to suggest that the reappearance of olivine and PGE-sulfide of the J-M Reef in the Stillwater Complex, Montana, is due to fluid infiltration and hydration melting. This study builds upon the hydration melting model using the programs MELTS and PELE with Stillwater bulk rock compositions for the original protolith. Cl-bearing phases are not modeled by MELTS and thus simple oxide mixtures of either a pure H2O or a H2O + Na2O “faux brine” are added to norite, gabbronorite, and melanorite protoliths at 1050 °C at 2 kbar pressure, conditions for which the nominally “dry” protolith is > 95% solid. Incongruent hydration melting results in up to 37% olivine produced in the melanorite. The olivine Fo content is a function of the partial melt retained on cooling, and ranges between 76 and 86, overlapping the natural range of olivine compositions observed in the rocks. Modeling with the PELE program, which includes a silicate liquid Cl component, sulfur species, and a more complex C-O–H-S fluid, suggests that, for CO2-rich fluids, fluid metal concentrations on the order of 25 ppm Pt, 75 ppm Pd, 0.03 wt.% Cu, and 0.20 wt.% Ni at a fluid/rock mass ratio of ~ 0.25 are needed to account for the observed ore grades. Sulfide and ore metals are readily remobilized for more H2O-rich fluids, consistent with heterogeneous distribution of sulfide and regionally variable ore grades.

Fertility Indicators for Porphyry-Cu-Au+Pd±Pt Deposits: Evidence from Skouries, Chalkidiki Peninsula, Greece, and Comparison with Worldwide Mineralizations

The research interest for many authors has been focused on the origin, recovery, and exploration of critical metals, including platinum-group elements (PGEs), with the aim of finding new potential sources. Many giant porphyry Cu deposits are well known around the Pacific Rim, in the Balkan–Carpathian system, Himalayas, China, and Malaysia. However, only certain porphyry Cu-Au deposits are characterized by the presence of significant Pd and Pt contents (up to 20 ppm). This contribution provides new analytical data on porphyry-Cu-Au±Pd±Pt deposits from the Chalkidiki Peninsula and an overview of the existing geochemical characteristics of selected porphyry-Cu deposits worldwide in order to define significant differences between PGE-fertile and PGE-poor porphyry-Cu intrusions. The larger Mg, Cr, Ni, Co, and Re contents and smaller LILE elements (Ba and Sr) in fertile porphyry-Cu-Au-(PGE) reflect the larger contribution from the mantle to the parent magmas. In contrast, the smaller Mg, Cr, Ni, Co, and Re contents and larger Ba and Sr in PGE-poor porphyry-Cu-Mo deposits from the Chalkidiki Peninsula (Vathi, Pontokerasia, and Gerakario) and Russia–Mongolia suggest the presence of parent magmas with a more crustal contribution. Although there is an overlap in the plots of those elements, probably due to the evolution of the ore-forming system, consideration of the maximum contents of Mg, Cr, Ni, and Co is proposed. Magnetite which separated from the mineralized Skouries porphyry of Greece showed small negative Eu anomalies (Eu/Eu* ≥ 0.55), reflecting a relatively high oxidation state during the cooling of the ore-forming system. The relatively high, up to 6 ppm (Pd+Pt), and low Cr content towards the transition from the porphyry to epithermal environment, coupled with the occurrence of Pd, Te, and Se minerals (merenskyite, clausthalite), and tetrahedrite–tennantite in fertile porphyry Cu deposits (Elatsite deposit, Bulgaria), reflect a highly fractionated ore-forming system. Thus, in addition to the crustal and mantle recycling, metasomatism, high oxidation state, and abundant magmatic water, other factors required for the origin of fertile porphyry-Cu deposits are the critical degree of mantle melting to release Pt and Pd in the ore-forming fluids and the degree of fractionation, as reflected in the mineral chemistry and geochemical data.

Behavior of Platinum-Group Elements during Hydrous Metamorphism: Constraints from Awaruite (Ni3Fe) Mineralization

Abstract Natural Fe-Ni alloys are common in meteorites and, presumably, the Earth’s core, where they host significant platinum-group elements (PGE). However, little is known on PGE concentrations in hydrothermal or metamorphic Fe-Ni alloys (i.e., awaruite Ni3Fe) from terrestrial rocks. In this work, we examine the geochemistry of awaruite and related minerals from several placer deposits sourced from the suprasubduction ophiolitic (Kamchatsky Mys, Karaginsky Island, and Mamet) and Ural-Alaskan (Galmoenan) complexes of Kamchatka and the Koryak Highlands (Far East Russia) in order to assess the abundance of PGE in awaruite and constrain their mobility under metamorphic and hydrothermal conditions. Studied awaruite from ophiolitic and Ural-Alaskan type complexes formed via desulfurization of pentlandite during serpentinization. Three groups of platinum-group minerals (PGMs) are associated with awaruite from Kamchatsky Mys: (1) Pt-Fe alloys such as ferronickelplatinum (Pt2FeNi) or unnamed Ni2FePt alloys; (2) Os-Ir-Ru alloys of various composition; (3) Pd-Sb minerals which form together with serpentine during hydrothermal alteration. Despite the abundance of PGM inclusions, no significant PGE concentrations were measured in awaruite from the Kamchatsky Mys, Karaginsky Island, or Mamet ophiolites. In contrast, pentlandite relicts in awaruite from placers related to the Galmoenan Ural-Alaskan type complex contain exceptionally high, previously unreported, Os (up to 540 ppm). Awaruite that forms on behalf of this pentlandite does not show any significant Os enrichment. Rare Galmoenan awaruite analyses yield up to 3 ppm Pd. The new data are not in complete accordance with previous studies that reported relatively high (up to first 10 ppm) PGE content in awaruite. We attribute this to low PGE concentration in precursor sulfides and preferential partitioning of PGE into discrete secondary PGM within awaruite. Nevertheless, abundant inclusions of secondary PGM in awaruite provide evidence of PGE mobility during metamorphic and hydrothermal alteration of ultramafic rocks.

ZnFexAl2-xO4 spinel supported PdZnβ bifunctional catalyst for methanol steam reforming

PdZnβ alloy catalysts, long regarded as a very promising copper replacement, not only possess copper-like reactivity, but also have superior thermal and chemical stability as well as non-pyrophoric nature that copper catalysts lack. In this contribution, we successfully synthesized the ZnFexAl2-xO4 (x = 0.05–0.2) spinel support, i.e., by replacing Al with a small amount of Fe in ZnAl2O4 spinel. The synthesized support, featuring a high surface area and superior stability, enabled the PdZnβ alloy formation at extremely low Pd loadings (e.g., 1000 ppm Pd), which shows high reactivity and CO2 selectivity toward methanol steam reforming (MSR) reaction. Moreover, it has the unique advantage of constructing bi-functional sites with a specific interfacial structure like PdZn/Fe2O3, the latter of which can effectively enhance water dissociation. Thanks to the synergetic effect, the 0.1 wt% Pd/ZnFe0.1Al1.9O4 catalyst exhibits a much higher ATOF value during the MSR reaction than the 0.1 wt% Pd/ZnAl2O4 counterpart, demonstrating excellent atomic utilization efficiency of noble metal and great potential in the practical application.

Behavior of palladium during fractionation of sulfide liquid: New constraints from the Kalatongke Cu-Ni sulfide-bearing intrusion in the central Asian orogenic belt, NW China

The distribution of platinum-group elements (PGE; Os, Ir, Ru, Rh, Pt, and Pd) in base metal sulfides (BMS) of magmatic Ni-Cu-(PGE) sulfide deposits has been extensively studied. However, the origin of Pd in pentlandite and the role of Te, As, Bi, Sb, and Se (TABS) in collecting PGE during fractionation of sulfide liquid have not yet been well constrained. Representative massive sulfide ores of the Kalatongke Cu-Ni sulfide-bearing mafic intrusion in the central Asian orogenic belt (CAOB) were selected to identify platinum-group minerals (PGM) using a scanning electron microscope (SEM) and to investigate the distribution of PGE and TABS in the BMS using in situ laser-ablation inductively coupled-plasma mass spectrometry (LA-ICP-MS). The results show that concentrations of Os, Ir, Ru, Rh, and Pt in the BMS are all below or close to the detection limits and only pentlandite contains 0.1 to 3.6 ppm Pd. Three generations of pentlandite are recognized in the massive sulfide ores; i.e., coarse-grained, granular pentlandite that crystallized earlier from monosulfide solid solution (MSS) prior to crystallization of pyrrhotite, loop-textured pentlandite around pyrrhotite that crystallized after pyrrhotite, and pentlandite that crystallized from evolved Fe-rich MSS and is associated with fine-grained myrmekitic magnetite. Granular pentlandite contains higher Pd (1.4 to 3.6 ppm) than that of loop-textured pentlandite (0.8 to 1.7 ppm Pd) and pentlandite associated with myrmekitic magnetite (0.1 to 0.5 ppm Pd). Given that Pd is incompatible to MSS during fractionation of sulfide liquid and is preferentially concentrated to residual sulfide liquid, we propose that the distribution of Pd in pentlandite may be attributed to rapid diffusion of Pd from the residual sulfide liquid into MSS/pentlandite on cooling and that Pd concentrations in the three generations were likely controlled by their crystallization sequence from MSS. In addition, LA-ICP-MS elemental mapping for BMS shows that TABS are not preferentially concentrated in chalcopyrite and euhedral Ni-merenskyite [(Pd,Pt)(Te,Bi)2] grains are mainly enclosed within pyrrhotite (n = 187) rather than chalcopyrite (n = 19). The random distribution of Ni-merenskyite in the BMS is supportive of an idea that Pt and a portion of Pd were likely stabilized by the presence of Te and Bi ligands in sulfide liquid and Te-Bi-Pd-Pt associations were then randomly distributed in MSS and intermediate solid solution (ISS) during fractionation of sulfide liquid. This study shows that the formation of TABS-bearing PGM in the massive sulfide ores of the Kalatongke intrusion was not controlled by fractionation of sulfide liquid, providing a new case that the behavior of PGE is mainly controlled by TABS rather than their partitioning coefficients in sulfide liquid.

Supported-Pd catalyzed carbonylative synthesis of phthalimides and isoindolinones using Oxalic acid as in situ CO surrogate with 2-iodobenzamides and 2-iodobenzylanilines in ppm-level catalyst loading

Polystyrene supported palladium (Pd@PS) nanoparticles (NPs) catalyzed intramolecular aminocarbonylation of 2-iodobenzamides and 2-iodobenzylanilines using bench stable Oxalic acid as in situ CO source for the synthesis of phthalimides and isoindolin-1-one is described. Low catalyst loadings (0.2 mol%, 2000 ppm Pd) with appreciable recyclability up to six cycles, external base free, Oxalic acid as inexpensive and safer in situ C1 source and vast substrate scope are some remarkable features of the present protocol. Furthermore, we scale up the present reaction up to 1.5 gram.

The Geochemical and Textural Transition between the Reef Package and its Hanging Wall, Stillwater Complex, Montana, USA

Abstract The highest grade Pd-Pt deposit on Earth, the J-M Reef, is hosted in coarse-grained to pegmatoidal cumulates called the Reef Package. Decades of mine development of the J-M Reef have revealed that a distinct discontinuity in rock fabric marks the top of the rock unit that hosts economic-grade sulfide mineralization. Mine geologists refer to this discontinuity as the hanging wall contact. This contact is the top of the Reef Package and is always locatable—either by the change in rock fabric or by distinctive hanging wall textures of silicate minerals—even when the reef sulfide mineralization is absent. This rather subtle textural feature is used reliably by mine geologists to follow the Reef during exploration and mine development. Although some high tenor sulfides (>1000 ppm Pd in 100% sulfide) are found sporadically in the hanging wall cumulates, these accumulations are too small to be economically viable. We present quantitative rock fabric data for four Reef Package and hanging wall intersections collected by electron back-scattered diffraction (EBSD). Plagioclase fabrics in the hanging wall are characterized by low variance in grain sizes and a strong point maximum concentration of (010) and a perpendicular girdle distribution of [100] consistent with an axial B-type fabric. These fabrics are indicative of either compaction of the crystal mush or crystal settling of nucleated crystals, the bulk magma in a chamber. Conversely, the fabrics of the Reef Package show higher variance grain in size distributions and weak to undeveloped preferred orientation of plagioclase crystals that did not undergo significant alignment or textural equilibration of plagioclase grains. The absence of foliation in the Reef Package stands in contrast both to hanging wall fabrics and to other reported EBSD datasets of plagioclase crystals orientations from the Bushveld Complex, the Skaergaard Intrusion, and the Rum Intrusion. Furthermore, plagioclase crystal size distributions for the Reef Package show flatter slopes and convex profiles with fewer crystals at small size fractions indicating the dissolution of small crystals during partial melting and textural coarsening (i.e. Ostwald ripening) and crystal growth. Crystal growth was favored over the nucleation of new crystals during prolonged interaction with a hot infiltrating melt into the resident mush resulting in the coarse-grained textures of the Reef Package cumulates. The hanging wall contact represents a boundary between partially remelted crystal mush of the Reef Package, where sulfide mineralization formed and accumulated, and an overlying essentially barren cumulate pile. The hanging wall cumulates formed following the cessation of footwall erosion and the resumption of crystal accumulation by normal magma chamber processes.

ZnAl2O4 Spinel-Supported PdZnβ Catalyst with Parts per Million Pd for Methanol Steam Reforming

PdZnβ alloy catalysts have Cu-like properties for a wide range of industrially important reactions, such as methanol synthesis, water–gas shift, and methanol steam reforming, but overcome the major disadvantages inherited by Cu such as sintering and pyrophoric nature. However, high Pd loadings (e.g., >5.0 wt %) are typically required for the synthesis of the PdZnβ alloy, preventing its practical consideration as the replacement of Cu catalysts. Here, we report the synthesis of ZnAl2O4-supported PdZnβ alloy catalysts at extremely low Pd loadings (e.g., 1000 ppm Pd). In particular, a cuboctahedral ZnAl2O4 spinel support with exclusively polar facets provides a strong interaction between Pd and Zn, leading to PdZnβ alloy formation even at low Pd loadings. A 0.1 wt % Pd/ZnAl2O4 catalyst is shown to exhibit superior CO2 selectivity (97%) in the methanol steam reforming reaction, confirming the Cu-like catalytic properties of the PdZnβ alloy even at 1000 ppm Pd. The top-layer Zn species on the exposed polar facets of zinc spinel were found to play a critical role in the preferential formation of the PdZnβ alloy. The advances toward the PdZnβ alloy catalysts with extremely low Pd loadings bring the PdZn alloy catalysts one step closer to a wide range of applications.

Genesis and mechanisms of metal enrichment in the Baimazhai Ni-Cu-(PGE) deposit, Ailaoshan Orogenic Belt, SW China

ABSTRACT The ∼259 Ma Baimazhai Ni-Cu-(platinum-group element) deposit is located in the Ailaoshan-Red River fault zone on the southwest margin of the Yangtze Plate in the Jinping area of southeastern Yunnan Province. The intrusion is lenticular (∼530 m long × 190 m wide × 24–64 m thick) and concentrically zoned (margin to core) from gabbro through pyroxenite to peridotite. It contains ∼50 kt of Ni-Cu-(platinum-group element) mineralization, concentrically zoned (margin to core) from disseminated through net-textured to massive sulfides with an average grade of 1.03 wt.% Ni, 0.81 wt.% Cu, and 0.02∼0.69 ppm Pd+Pt. The sulfide assemblage comprises pyrrhotite, chalcopyrite, and pentlandite, with lesser magnetite, violarite, galena, and cobaltite. The mineralization is enriched in Ni-Cu-Co relative to the platinum-group elements and the host rocks are enriched in highly incompatible lithophile elements relative to moderately incompatible lithophile elements with high Th/Yb and intermediate Nb/Yb ratios. These host rocks, and those at most other Ni-Cu-platinum-group element deposits in the Emeishan Large Igneous Province, have high γOs and intermediate εNd values, indicating that they crystallized from a magma derived from a subduction-modified pyroxenite mantle source and modified by crustal contamination. The initial concentrations of metals in the primary magma are estimated to have been on the order of 200 ppm Ni and 100 ppm Cu, but only 0.4 ppb Pd, 0.2 ppb Pt, 0.005 ppb Rh, 0.02 ppb Ru, and 0.01 ppb Ir. The δ34S values of ores and separated sulfides range from 5.8‰ to 8.6‰, between the ∼10‰ value of sulfides in the metasedimentary country rocks and the 0 ± 0.5‰ value expected for magmas derived from MORB-type mantle, or the –2.5 ± 0.3‰ value expected for subduction-modified mantle, consistent with equilibration at magma:sulfide mass ratios (R factors) of 100–1000. Variations in Ir100 and Pd100 (metals in 100% sulfide) are consistent with 40–60% fractional crystallization of monosulfide solid solution to form Ni-Co-intermediate platinum-group element (Ru, Os, Ir)-rich massive ores and Cu-palladium/platinum-group elements (Pt, Pd, Rh)-Au-rich residual sulfide liquids. This process is also recorded by magnetite: Type I (early magmatic), type II (late magmatic), and type III (secondary) magnetites exhibit progressively lower Cr-Ti-V concentrations. The platinum-group element contents in base-metal minerals are low, and only pentlandite, violarite, and cobaltite contain detectable concentrations of Pd, Rh, and Ru. There is abundant textural evidence for metamorphic-hydrothermal alteration of sulfides in the Baimazhai intrusion, with secondary violarite, chalcopyrite, and pentlandite being enriched (Ag, Sb, Au, Pb) or depleted (Sn) in more mobile chalcophile elements. The different tectonic and petrogenetic settings of the Baimazhai and other deposits in China highlight the potential of Ni-Cu-platinum-group element deposits to occur in subduction or post-subduction settings and demonstrate that the key controls are magma flux and access to crustal S. Exploration potential remains for the Ailaoshan orogenic belt to host additional magmatic Ni-Cu deposits.

Effective Pd(II) carriers for classical extraction and pseudo-emulsion system

This work aims to study the performance of three new extracting agents: N-decyloxy-1-(pyridin-3-yl)methaneimine (D-3MI), N-decyloxy-1-(pyridin-3-yl)ethaneimine (D-3EI) and N- decyloxy-1-(pyridin-4-yl)ethaneimine (D-4EI), in the solvent extraction of palladium. For this purpose, the effect of several parameters on the extraction of Pd(II) from hydrochloric acid medium was examined. The stripping of Pd(II), the stability of the extractant in multiple extraction/stripping cycles and the separation of Pd(II)/Pt(IV) were also investigated. After the classical solvent extraction studies, the Pseudo-Emulsion based Hollow Fibre Strip Dispersion (PEHFSD) technique was used for the recovery of Pd(II). The kinetics of permeation was found to be strongly dependent on the extractant concentration, the stripping of Pd(II) with thiourea being quite slower than its removal from the feed phase. The recovery of Pd(II) with the PEHFSD technique was also checked, using a commercial extractant, the amine Alamine 308, for comparison. The results obtained show that the ethaneimine D-3EI has the highest potential for extracting and stripping Pd(II) among the reagents tested. The use of 0.03 M D-3EI in toluene, as the membrane phase, allowed to remove practically all the metal content from the aqueous phase (100 ppm Pd, 1.5 M HCl) with relatively fast kinetics and led to a Pd(II) recovery above 90% for moderate permeation times.

Environmentally friendly Pd(II) recovery from spent automotive catalysts using resins impregnated with a pincer-type extractant

Extractant-impregnated resins have potential for recovering platinum group metals selectively and efficiently. Herein, 1,3-bis(2-(octylthio)propan-2-yl)benzene (1), a pincer-type extractant, was impregnated in Amberlite XAD-7 resin (1-EIR), and the batch Pd(II) sorption conditions, including impregnated amount, shaking time, Pd(II) concentration, HCl concentration, and Pd(II) desorption reagents, were optimized. The maximum Pd(II) sorption capacity of 1-EIR was 49 mg g−1 after 24 h in a 700 ppm Pd(II) solution. Over 20 adsorption–desorption cycles, 1-EIR showed good reusability, with a sorption percentage (S%) of > 92%. However, not all Pd(II) was desorbed from 1-EIR. Complete Pd(II) collection was achieved by combining desorption with flaking of the Pd–extractant complex from Pd(II)-loaded 1-EIR by Soxhlet extraction, as ~ 13 mg g−1 remained after the 20th adsorption–desorption cycle by absorptiometric method. The sorption mechanism was elucidated based on the Langmuir isotherm model, thermodynamic parameters, and sorption kinetics. Pd(II) sorption by 1-EIR was spontaneous and endothermic, and the sorption kinetics followed a pseudo-second-order model. Notably, 1-EIR also exhibited high selectivity for Pd(II) from a simulated mixed metal solution and a spent automotive catalyst leachate (S% = 98% and > 99%, respectively). Thus, this extractant-impregnated system is promising for selective Pd(II) recovery from spent automotive catalysts and other secondary resources.

Platinum Group Element Enrichment of Natural Quenched Sulfide Solid Solutions, the Norilsk 1 Deposit, Russia

Abstract The deepest terminations of the Mount Rudnaya subvertical massive sulfide offshoots of the Norilsk 1 orebody are composed of exceptionally fine grained sulfides that are believed to be natural quenched sulfide solid solutions. Copper-rich intermediate solid solution (ISS) and Fe-rich monosulfide solid solution (MSS) form an equigranular and lamellar matrix hosting MSS- and ISS-dominant globules. The nonstoichiometric chemical compositions of the solid solutions plot within their high-temperature fields known from experiments. MSS contains 19 to 35 wt % Ni, 0.09 to 0.45 wt % Co, and up to 0.6 wt % Cu and is heterogeneously enriched in Rh (up to 32 ppm), Ir (up to 0.6 ppm), Pt (up to 65 ppm), and Pd (up to 168 ppm). ISS occurs as the lamellar intergrowths of the chalcopyrite (Ccpss) and cubanite (Cubss) solid solutions, which bear up to 4.74 wt % Ni and 0.2 wt % Co and are heterogeneously enriched in Zn, Ag, and In. The assemblage of platinum group minerals (PGMs) is hosted mostly in the ISS and is dominated by Pt-Fe alloys and minerals of the rustenburgite-atokite series, like the set of PGMs at the Norilsk 1 deposit. Similar Pt-Pd-Sn compounds in the laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) spectra of profiles through MSS and ISS are interpreted to be trapped microinclusions. The pentlandite contains up to 0.13 wt % Pt, up to 4.62 wt % Pd, <0.53 wt % Co, and <0.4 wt % Cu according to electron microprobe analysis. LA-ICP-MS data and mapping show that Pd content in the pentlandite increases toward contacts with ISS and decreases toward contacts with MSS, supporting a reaction origin of pentlandite. The wide variations of the concentrations of major and trace elements in the solid solutions, as well as the coexistence of Pd-poor (a few ppm Pd) and Pd-rich (over 4.62 wt % Pd) pentlandite within a single sample, seem to characterize the different generations of the MSS to MSS-ISS globules, antecrysts, and phenocrysts with the distinct histories of enrichment due to exchange with fractionated Cu-platinum group element-rich residue. The directional distribution of Pd of high-temperature primary magmatic origin is preserved due to rapid quenching of the sulfides from ~650°C.

Modified cellulose with tunable surface hydrophilicity/hydrophobicity as a novel catalyst support for selective reduction of nitrobenzene

Cellulose with tailorable hydrophilicity/hydrophobicity were synthesized by grafting F-containing groups and utilized as supports for palladium nanoparticles. The obtained catalysts were applied in the synthesis of N-phenylhydroxylamine from controllable reduction of nitrobenzene. Unexpectedly high conversion and selectivity could be achieved with 25 ppm Pd catalyst at room temperature in water. The precise modification of the catalyst surface is crucial to realize this targeted transformation. Further investigation indicated that modified cellulose with a more hydrophobic surface would favour the adsorption of nitrobenzene over N-phenylhydroxylamine thus prevent full hydrogenation to aniline.

Low-Sulfide Platinum–Palladium Deposits of the Paleoproterozoic Fedorova–Pana Layered Complex, Kola Region, Russia

Several deposits of low-sulfide Pt–Pd ores have been discovered in recent decades in the Paleoproterozoic Fedorova–Pana Layered Complex located in the Kola Region (Murmansk Oblast) of Russia. The deposits are divided into two types: reef-style, associated with the layered central portions of intrusions, and contact-style, localized in the lower parts of intrusions near the contact with the Archean basement. The Kievey and the North Kamennik deposits represent the first ore type and are confined to the North PGE Reef located 600–800 m above the base of the West Pana Intrusion. The reef is associated with a horizon of cyclically interlayered orthopyroxenite, gabbronorite and anorthosite. The average contents of Au, Pt and Pd in the Kievey ore are 0.15, 0.53 and 3.32 ppm, respectively. The North Kamennik deposit has similar contents of noble metals. The Fedorova Tundra deposit belongs to the second ore type and has been explored in two sites in the lower part of the Fedorova intrusion. Mineralization is mainly associated mainly with taxitic or varied-textured gabbronorites, forming a matrix of intrusive breccia with fragments of barren orthopyroxenite. The ores contain an average of 0.08 ppm Au, 0.29 ppm Pt and 1.20 ppm Pd. In terms of PGE resources, the Fedorova Tundra is the largest deposit in Europe, hosting more than 300 tons of noble metals.

Palladium Nanoparticles Anchored on Thiol Functionalized Xylose Hydrochar Microspheres: An Efficient Heterogeneous Catalyst for Suzuki Cross-Coupling Reactions

Novel thiol functionalized xylose hydrochar microspheres supported palladium nanoparticles (C–SH–Pd) were synthesized by gentle heating of palladium (II) acetate and thiol functionalized xylose hydrochar (C–SH) in ethanol. The as-prepared C–SH–Pd exhibited high catalytic activity towards Suzuki reactions with a yield of high up to 100%. Moreover, it could be reused for at least five times without heavily loss of the catalytic activity. The amount of palladium entrapped on C-SH microspheres was measured by AAS and found to be 1.42 mmol/g. Leaching studies showed that the filtrate contained less than 0.2 ppm Pd. Due to the superior catalytic performance and stability of the C–SH–Pd catalyst, it can be exploited in other cross coupling reactions in the long run.

Platinum, Pd, Mo, Au and Re deportment in hyper-enriched black shale Ni-Zn-Mo-PGE mineralization, Peel River, Yukon, Canada

Middle Devonian Ni-Mo-Zn-Pt-Pd-Au-Re hyper-enriched black shales (HEBS) from Peel River in north Yukon have high abundances of platinum group elements (PGE; ca. 500 ppb), Au (40–130 ppb) and Re (8–55 ppm). Mineralization occurs in up to three thin (0.5–10 cm thick) layers that include the regionally extensive HEBS at the Road River Group-Canol Formation stratigraphic contact (e.g., correlative with the Nick Ni-Mo-Zn-PGE-Au-Re prospect, northwestern Yukon); two other previously undocumented HEBS layers stratigraphic layers underlie the upper layer. Although the three different layers have minor textural differences, they display marked mineralogical and geochemical similarities to each other. Millerite is the predominant Ni sulfide, and it postdates several textural varieties of pyrite.A longstanding, unresolved question regarding this mineralization in Yukon is the mineralogical host of PGE, Mo, Au and Re. We analyzed the sulfide mineral assemblages using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). LA-ICP-MS analyses reveal that pyrite within all of the layers is the principal host of PGE, Re, Au and Mo, and that paragenetically late pyrite (spatially associated with millerite) contains the highest abundances, with up to 4 ppm Pd, 8 ppm Pt, 500 ppm Re, 1.5 ppm Au and 7000 ppm Mo. Rare, late pyrite-marcasite veins in the upper HEBS layer cross-cut all previous generations of sulfides and also postdate quartz cement. The late sulfide veins are devoid of Mo-Pd-Re-Pt-Au, indicating that mineralization coincided with early to late diagenesis and predates lithification. The high abundances of these elements in diagenetic varieties of pyrite suggests that hyper-enrichment occurred near the seafloor, and that this suite of elements was likely derived from ambient seawater.

Sonogashira Couplings Catalyzed by Fe Nanoparticles Containing ppm Levels of Reusable Pd, under Mild Aqueous Micellar Conditions

Nanoparticles derived from FeCl3 containing the ligand XPhos and only 500 ppm Pd effect Sonogashira couplings in water between rt and 45 °C. The entire aqueous reaction medium can be easily recycled using an “in-flask” extraction. Several tandem processes in one pot are illustrated, including a sequence involving five steps (10 reactions) in good overall yield.

Sustainableppm level palladium-catalyzed aminations in nanoreactors under mild, aqueous conditions.

A 1 : 1 Pd : ligand complex, [t-BuXPhos(Pd-π-cinnamyl)]OTf, has been identified as a highly robust pre-catalyst for amination reactions leading to diarylamines, where loadings of metal are typically at 1000 ppm Pd, run in water at temperatures between rt and 45 °C. The protocol is exceptionally simple, is readily scaled, and compares very favorably vs. traditional amination conditions. It has also been shown to successfully lead to key intermediates associated with several physiologically active compounds.

Catalyst shuttling enabled by a thermoresponsive polymeric ligand: facilitating efficient cross-couplings with continuously recyclable ppm levels of palladium.

A polymeric monophosphine ligand WePhos has been synthesized and complexed with palladium(ii) acetate [Pd(OAc)2] to generate a thermoresponsive pre-catalyst that can shuttle between water and organic phases, with the change being regulated by temperature. The structure of the polymeric ligand was confirmed with matrix-assisted laser desorption/ionization-time-of-flight (MALDI-TOF) mass spectrometry and size-exclusion chromatography (SEC) analysis, as well as nuclear magnetic resonance (NMR) measurements. This polymeric metal complex enables highly efficient Pd-catalyzed cross-couplings and tandem reactions using 50 to 500 ppm palladium, and this can facilitate reactions that are tolerant to a broad spectrum of (hetero)aryl substrates and functional groups, as demonstrated with 73 examples with up to 99% isolated yields. Notably, 97% Pd remained in the aqueous phase after 10 runs of catalyst recycling experiments, as determined via inductively coupled plasma-atomic emission spectrometry (ICP-AES) measurements, indicating highly efficient catalyst transfer. Furthermore, a continuous catalyst recycling approach has been successfully developed based on flow chemistry in combination with the catalyst shuttling behavior, allowing Suzuki-Miyaura couplings to be conducted at gram-scales with as little as 10 ppm Pd loading. Given the significance of transition-metal catalyzed cross-coupling and increasing interest in sustainable chemistry, this work is an important step towards the development of a responsive catalyst, in addition to having high activity, by tuning the structures of the ligands using polymer science.

Igneous architecture and implications for diverse Cu-PGE mineralization styles in a conduit system: an example from the Area 41 Cu-PGE occurrence, Coldwell Complex, Canada

The Area 41 copper-platinum-group element (PGE) occurrence was discovered in 2006 at the northwestern margin of the Coldwell Complex. The discovery was significant because of the sizable mineralized intersections, including 1.4 ppm Pd + Pt and 0.32% Cu over 43 m. Since then, exploration along the northern margin has resulted in the discovery of several other Cu-PGE zones with similar grades and host rocks. Field relationships, drill-core logging, petrography, and lithogeochemistry indicate that the rocks formed from several extrusive and intrusive events related to at least three magmatic series that are from oldest to youngest: Metabasalt, the Layered Series, and the Marathon Series. Three types of Cu-PGE mineralization are hosted within separate intrusions of the Marathon Series. Type 1 is hosted by coarse-grained subophitic gabbro and exhibits high Cu/Pd (> 100,000) and low PGE grades, formed at R-factors of 105) and low S/Se ratios (800–2000) that suggest S loss. Three-dimensional modeling of the occurrence shows a north-south, keel-shaped trough at the western end of mineralization and a systematic spatial variation in the proportions of various Marathon Series units, including pegmatitic subophitic gabbro, breccia units, apatitic clinopyroxenite, and oxide melatroctolite, that correlate with decreasing thickness of mineralization, eastward and away from the trough. These observations suggest that multiple intrusions were emplaced along a feeder channel, some of which flowed laterally outwards to form sills. Taken together, these characteristics are consistent with a conduit model for deposit formation and are thus important vectors for exploration.