scholarly journals Variations of Major and Minor Elements in Pt–Fe Alloy Minerals: A Review and New Observations

Minerals ◽  
2019 ◽  
Vol 9 (1) ◽  
pp. 25 ◽  
Author(s):  
Andrei Barkov ◽  
Louis Cabri
Keyword(s):  
Solid Solution ◽  
Global Scale ◽  
Source Rocks ◽  
Miscibility Gap ◽  
Layered Intrusions ◽  
Minor Elements ◽  
Fe Alloys ◽  
Compositional Variations ◽  
Lower Temperature ◽  
Compositional Series

Compositional variations of major and minor elements were examined in Pt–Fe alloys from various geological settings and types of deposits, both lode and placer occurrences. They included representatives of layered intrusions, Alaskan-Uralian-(Aldan)-type and alkaline gabbroic complexes, ophiolitic chromitites, and numerous placers from Canada, USA, Russia, and other localities worldwide. Pt–Fe alloy grains in detrital occurrences are notably larger in size, and these are considered to be the result of a special conditions during crystallization such as temperature, pressure, geochemistry or time. In addition, the number of available statistical observations is much greater for the placer occurrences, since they represent the end-product of, in some cases, the weathering of many millions of tonnes of sparsely mineralized bedrock. Typically, platinum-group elements (PGE) present in admixtures (Ir, Rh, and Pd) and minor Cu, Ni are incorporated into a compositional series (Pt, PGE)2–3(Fe, Cu, Ni) in the lode occurrences. Relative Cu enrichment in alloys poor in Pt implies crystallization from relatively fractionated melts at a lower temperature. In contrast to the lode deposits, the distribution of Ir, Rh, and Pd is fairly chaotic in placer Pt–Fe grains. There is no relationship between levels of Ir, Rh, and Pd with the ratio Σ(Pt + PGE):(Fe + Cu + Ni). The compositional series (Pt, PGE)2–3(Fe, Cu, Ni) is not as common in the placer occurrences; nevertheless, minor Cu and Ni show their maximums in members of this series in the placer grains. Global-scale datasets yield a bimodal pattern of distribution in the Pt–Fe diagram, which is likely a reflection of the miscibility gap between the ordered Pt3Fe structure (isoferroplatinum) and the disordered structure of native or ferroan platinum. In the plot Pt versus Fe, there is a linear boundary due to ideal Pt ↔ Fe substitution. Two solid solution series are based on the Ir-for-Pt and Pd-for-Pt substitutions. The incorporation of Ir is not restricted to Pt3Fe–Ir3Fe substitution (isoferroplatinum and chengdeite, plus their disordered modifications). Besides, Ir0 appears to replace Pt0 in the disordered variants of (Pt–Ir)–Fe alloys. There is a good potential for the discovery of a new species with a Pd-dominant composition, (Pd, Pt)3Fe, most likely in association with the alkaline mafic-ultramafic or gabbroic complexes, or the mafic units of layered intrusions. The “field of complicated substitutions” is recognized as a likely reflection of the crystallochemical differences of Pd and Ir, extending along the Ir-Pd axis of the Ir–Pd–Rh diagram. The inferred solid solution extends approximately along the line Ir–(Pd:Rh = 2:3). Minor Pd presumably enters the solid solution via a coupled substitution in combination with the Rh. An Ir-enrichment trend in Pt–Fe alloys typically occurs in the Alaskan-type complexes. The large size of the Pt–Fe nuggets associated with some of these complexes is considered to be related to an ultramafic-mafic pegmatite facies, whereas significant Pd-enrichment is characteristic of gabbroic source-rocks (e.g., Coldwell Complex), resulting in a markedly different trend for the Pt versus Fe (wt.%). However, based on our examination of a large dataset of Pt–Fe alloys from numerous origins, we conclude that they exhibit compositional overlaps that are too large to be useful as reliable index-minerals.

Transition alpha structure in beta-isomorphous Nb-Hf alloys

1987 ◽  
Vol 45 ◽  
pp. 232-233
Author(s):  
R.W. Carpenter ◽  
Changhai Li ◽  
David J. Smith
Keyword(s):  
Solid Solution ◽  
Solution Phase ◽  
Miscibility Gap ◽  
Large Strains ◽  
Solid Solution Phase ◽  
Two Phase ◽  
Diffuse Intensity ◽  
Metastable Form ◽  
The Matrix ◽  
Equilibrium Morphology

Binary Nb-Hf alloys exhibit a wide bcc solid solution phase field at temperatures above the Hfα→ß transition (2023K) and a two phase bcc+hcp field at lower temperatures. The β solvus exhibits a small slope above about 1500K, suggesting the possible existence of a miscibility gap. An earlier investigation showed that two morphological forms of precipitate occur during the bcc→hcp transformation. The equilibrium morphology is rod-type with axes along <113> bcc. The crystallographic habit of the rod precipitate follows the Burgers relations: {110}||{0001}, <112> || <1010>. The earlier metastable form, transition α, occurs as thin discs with {100} habit. The {100} discs induce large strains in the matrix. Selected area diffraction examination of regions ∼2 microns in diameter containing many disc precipitates showed that, a diffuse intensity distribution whose symmetry resembled the distribution of equilibrium α Bragg spots was associated with the disc precipitate.

Epitaxial Solid-Solution Films of Immiscible MgO and CaO

1994 ◽  
Vol 341 ◽  
Author(s):  
E. S. Hellman ◽  
E. H. Hartford
Keyword(s):  
Solid Solution ◽  
Molecular Beam Epitaxy ◽  
Lattice Constant ◽  
Solid Solutions ◽  
Molecular Beam ◽  
Building Blocks ◽  
Layer Growth ◽  
Growth Mode ◽  
Miscibility Gap ◽  
Layer By Layer

AbstractMetastable solid-solutions in the MgO-CaO system grow readily on MgO at 300°C by molecular beam epitaxy. We observe RHEED oscillations indicating a layer-by-layer growth mode; in-plane orientation can be described by the Matthews theory of island rotations. Although some films start to unmix at 500°C, others have been observed to be stable up to 900°C. The Mgl-xCaxO solid solutions grow despite a larger miscibility gap in this system than in any system for which epitaxial solid solutions have been grown. We describe attempts to use these materials as adjustable-lattice constant epitaxial building blocks

Non-equilibrium Ti-Fe bulk alloys with ultra-high strength and enhanced ductility

2004 ◽  
Vol 851 ◽  
Author(s):  
Dmitri V. Louzguine-Luzgin ◽  
Larissa V. Louzguina-Luzgina ◽  
Hidemi Kato ◽  
Akihisa Inoue
Keyword(s):  
Solid Solution ◽  
Supersaturated Solid Solution ◽  
High Strength ◽  
Eutectic Structure ◽  
Solution Phase ◽  
Solid Solution Phase ◽  
Mechanical Fracture ◽  
Glassy Alloys ◽  
Fe Alloys ◽  
Bulk Alloys

ABSTRACTThe high-strength and ductile hypo-, hyper- and eutectic Ti-Fe alloys were formed in the shape of the arc-melted ingots with the dimensions of about 25–40 mm in diameter and 10–15 mm in height. The structure of the samples consists of cubic Pm 3 m TiFe and BCC Im 3 m β-Ti supersaturated solid solution phase. The arc-melted hypereutectic Ti65Fe35 alloy has a dispersed structure consisting of the primary TiFe phase and submicron-size eutectic structure. This alloy exhibits excellent mechanical properties: a Young's modulus of 149 GPa, a high mechanical fracture strength of 2.2 GPa, a 0.2 % yield strength of 1.8 GPa and 6.7 % ductility. The hard round-shaped intermetallic TiFe phase and the supersaturated β-Ti solid solution result in a high strength of the Ti65Fe35 alloy which in addition has much higher ductility compared to that of the nanostructured or glassy alloys. The reasons for the high ductility of the hypereutectic alloy are discussed.

scholarly journals Rinkite–nacareniobsite-(Ce) solid solution series and hainite from the Ilímaussaq alkaline complex: occurrence and compositional variation

2014 ◽  
Vol 62 ◽  
pp. 1-15
Author(s):  
Jørn G. Rønsbo ◽  
Henning Sørensen ◽  
Encarnacion Roda-Robles ◽  
François Fontan ◽  
Pierre Monchoux
Keyword(s):  
Solid Solution ◽  
Electron Microprobe ◽  
Compositional Variation ◽  
Solid Solution Series ◽  
Alkaline Complex ◽  
Full Extension ◽  
X Ray ◽  
Solution Series ◽  
Compositional Variations ◽  
A Minor

In the Ilímaussaq alkaline complex, minerals from the rinkite–nacareniobsite-(Ce) solid solution series have been found in pulaskite pegmatite, sodalite foyaite, naujaite and naujaite pegmatite from the roof sequence, and in marginal pegmatite, kakortokite and lujavrite from the floor sequence. The electron microprobe analyses embrace almost the full extension of the solid solution series and confirm its continuity. The solid solution series shows similar compositional variations in the roof and floor sequences: Rinkite members of the series are found in the less evolved rocks in the two sequences, whereas nacareniobsite-Ce members occur in the most evolved rocks and pegmatites in the two sequences. The REE (+Y) content varies from 0.83 atoms per formula unit (apfu) in rinkite from pulaskite pegmatite to 1.31 apfu in nacareniobsite-(Ce) from naujaite pegmatite. The main substitution mechanisms in the solid solution series investigated in this work are 2Ca2+ = Na+ + REE3+ and Ti4+ + Ca2+ = Nb5+ + Na+. The increased contents of Nb5+ and REE3+ are only to a minor degree compensated through the F1– = O2– substitution. The chondrite normalised REE patterns of the minerals develop in a similar way in the two sequences, showing relative La-enrichment and Y-depletion from the less to the most evolved rocks. Hainite has not previously been found in the Ilímaussaq complex. It was here identified in a pulaskite pegmatite sample by a combination of X-ray diffraction giving the unit cell dimensions a = 9.5923(7) Å, b = 7.3505(5) Å, c = 5.7023(4) Å, α = 89.958(2)°, β = 100.260(1)°, γ = 101.100(2)°, and X-ray powder pattern and electron microprobe data giving the empirical formula (Ca1.62 Zr0.16Y 0.22) (Na0.87Ca1.11) (Ca 1.65 REE0.35)Na(Ti0.81Nb0.09Fe0.08 Zr0.02)(Si2O7)2O0.99F2.96. Based on published and the present data it is documented that minerals from the hainite-götzenite solid solution series show a compositional variation between the ideal end members (Y,REE,Zr)Na2Ca4Ti(Si2O7)2OF3 and NaCa6Ti(Si2O7)2OF3.

Solid solution decomposition and growth of precipitates in Be-Fe alloys from Mössbauer investigations

2013 ◽  
Vol 226 (1-3) ◽  
pp. 365-373 ◽  
Author(s):  
V. P. Filippov ◽  
V. P. Gladkov ◽  
S. S. Martynenko ◽  
V. I. Petrov
Keyword(s):  
Solid Solution ◽  
Solid Solution Decomposition ◽  
Fe Alloys

Structural Properties of the Cr(III)−Fe(III) (Oxy)hydroxide Compositional Series: Insights for a Nanomaterial “Solid Solution”

2010 ◽  
Vol 22 (12) ◽  
pp. 3589-3598 ◽  
Author(s):  
Yuanzhi Tang ◽  
F. Marc Michel ◽  
Lihua Zhang ◽  
Richard Harrington ◽  
John B. Parise ◽  
...  
Keyword(s):  
Solid Solution ◽  
Structural Properties ◽  
Compositional Series

Coupled substitutions in goldfieldite–tetrahedrite minerals from the Iriki mine, Japan

1991 ◽  
Vol 55 (381) ◽  
pp. 515-519 ◽  
Author(s):  
Masaaki Shimizu ◽  
Chris J. Stanley
Keyword(s):  
Solid Solution ◽  
Continuous Solid Solution ◽  
Chemical Compositions ◽  
Coupled Substitution ◽  
Compositional Variations ◽  
The Ideal

AbstractChemical compositions of goldfieldite-tetrahedrite series minerals from the Iriki mine in Japan are reported for the frst time. The compositional variations of coexisting goldfieldite [atomic proportion Te > (Sb + As + Bi)], tellurian tetrahedrite [Sb > (Te + As + Bi)], and Te-free tetrahedrite from this locality are considered alongside data from the literature. These show that the substitution of (Sb, As)3+ for Te4+ in natural goldfieldite-tetrahedrite series minerals occurs by the following two mechanisms: (i) tetrahedrite, and goldfieldite, form a continuous solid-solution according to the coupled substitution of Cu+Te4+ for (Cu,Fe,Zn)2+(Sb,As)3+, and (ii) goldfieldite, and the ideal end-member, might also form a continuous solid-solution by the coupled substitution of ☐(vacancy)Te4+ for Cu+(Sb,As)3+. According to this work, the general formulae of tellurian tetrahedrite and goldfieldite are, therefore, respectively, , with x = 0 to 2 and , with y = 0 to 2.

Effect of Gallium Oxide on Phase Assemblage in Apatite and Whitlockite Hosts for Waste Immobilization

2008 ◽  
Vol 1107 ◽  
Author(s):  
Lee. A. Gerrard ◽  
Shirley. K. Fong ◽  
Brian. L. Metcalfe ◽  
Ian. W. Donald
Keyword(s):  
Solid Solution ◽  
Gallium Oxide ◽  
Phase Assemblage ◽  
X Ray Diffraction ◽  
Apatite Phase ◽  
Complete Solid Solution ◽  
Total Phase ◽  
Simulated Waste ◽  
Lower Temperature ◽  
Gallium Phosphate

AbstractTo immobilize halide and actinide ions present in specific ILW waste a process has been developed that uses mineral phases as the host material. The mechanism of substitution of gallium into these phases will have a large effect on the phase assemblage. This will inevitably affect the total amount of halide that can be immobilized in to total phase mixture.The full simulated waste stream composition containing varying concentrations (1–40 wt.%) of gallium oxide was studied. Also nominal compositions for gallium doped fluorapatites (Ca10-1.5xGax)F2(PO4)6 (x = 0, 0.25, 0.5, 0.75, 1.0) and gallium doped whitlockites Ca9Gay(PO4)6+y (x = 0.2, 0.4, 0.6, 0.8, 1.0) were prepared at 750–1050 °C.These were studied by powder x-ray diffraction (XRD) to determine the phase assemblage and solid solution limits of gallium in the apatite and whitlockite phases. It was found that a complete solid solution was formed between whitlockite, Ca3(PO4)2, and Ca9Gay(PO4)6+y. In the nominal apatite compositions it was found that gallium did not substitute into the apatite structure but was instead partitioned over Ca9Gay(PO4)6+y, gallium phosphate, and unreacted gallium oxide. At higher temperatures gallium suppressed the formation of the apatite phase and was largely partitioned into the Ca9Gay(PO4)6+y phase whereas at lower temperature the majority was present as unreacted Ga2O3. In the full DCHP compositions it was found that gallium is likely to be partitioned over a number of phases including apatite, cationdoped whitlockite and gallium phosphate.

Deformation Mechanism of Nanocrystalline Al-Fe Alloys by Analysis from Ab-Initio Calculations

2006 ◽  
Vol 503-504 ◽  
pp. 209-214 ◽  
Author(s):  
Tokuteru Uesugi ◽  
Yorinobu Takigawa ◽  
Kenji Higashi
Keyword(s):  
Experimental Data ◽  
Solid Solution ◽  
Yield Strength ◽  
First Principles ◽  
High Strength ◽  
Misfit Strain ◽  
Solid Solution Strengthening ◽  
Solution Strengthening ◽  
Fe Alloys ◽  
Quench Method

Recently nanocrystalline Al-Fe alloys produced by a vapor quench method have been reported. These alloys are supersaturated solid solution and exhibit high strength with good ductility. It is postulated that the high strength of the Al-Fe alloys could be achieved by both the nano-grained structures and the solid solution strengthening. The contribution to the yield strength due to both the grain size strengthening and the solid solution strengthening were analyzed from the experimental data. Then the contribution to the yield strength due to the solid solution strengthening was estimated from the misfit strain calculated from the first principles in order to compare with analytical results estimated from the experimental data.

Mineral chemistry of monazite from the black sand deposits, northern Sinai, Egypt: a provenance perspective

2007 ◽  
Vol 71 (4) ◽  
pp. 389-406 ◽  
Author(s):  
Y. H. Dawood ◽  
H. H. Abd El-Naby
Keyword(s):  
Electron Microprobe ◽  
Mineral Chemistry ◽  
Eastern Desert ◽  
Source Rocks ◽  
Heavy Minerals ◽  
Large Area ◽  
Wavelength Dispersive Spectroscopy ◽  
Black Sand ◽  
Backscattered Electron ◽  
Compositional Variations

AbstractElectron microprobe analysis (EMPA) and microscopic investigations were performed on monazite grains from the black sand deposits of northern Sinai beach. Electron microprobe backscattered electron images, X-ray mapping and wavelength dispersive spectroscopy line scans showed some grains with sector zoning and others with thorite inclusions. Based on the EMPA data, the studied monazite is grouped into monazite-(Ce) and Th-rich monazite. Monazite-(Ce) is enriched in REE and P, whereas Th-rich monazite is enriched in Th, U, Ca, Y, Si and Fe. The compositional variations of monazite are governed by the substitution of REE by Th, U, Ca and Y. The monazite grains show enriched chondrite-normalized REE patterns represented mainly by LREE and only Gd from the HREE. These patterns demonstrate negative Nd and Euanomalies. The floods associated with the pluvial periods which prevailed in Egypt during the Pleistocene, were able to erode the source rocks and liberate heavy minerals including monazite. The mineral grains were transported through several wadis and tributaries to the main channel of the River Nile. At the confluence sites, these heavy minerals were mixed with Ethiopian and central African heavy mineral assemblages. The grains continued to move together downriver until being deposited in their current locations. The analytical results suggest that pegmatites and granites of the Eastern Desert are the most likely source of the monazite. However, due to the large area of the Nile watershed, other undiscovered sources are possible.

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