LAFLAMMEITE, Pd3Pb2S2, A NEW PLATINUM-GROUP MINERAL SPECIES FROM THE PENIKAT LAYERED COMPLEX, FINLAND

Barkov, Andrei Y.; Martin, Robert F.; Halkoaho, Tapio; Criddle, Alan J.

doi:10.2113/gscanmin.40.2.671

Cited by 16 publications

(3 citation statements)

References 8 publications

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“…The "field of complicated substitutions, FCC" (Figure 14b) may likely be a reflection of the crystallochemical differences existing between Pd and Ir, which, at least under normal crystallization conditions, seem to avoid each other, and they do not participate in mutual substitution schemes in all of the PGM species presently known. Only minor substitutions are known, e.g.,~1 wt.% Ir in laflammeite Pd 3 Pb 2 S 2 [47].…”

Section: Discussionmentioning

confidence: 99%

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

Barkov

Cabri²

2019

Minerals

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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.

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Section: Discussionmentioning

confidence: 99%

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

Barkov

Cabri²

2019

Minerals

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“…the Fe-dominant thiospinel, and laflammeite (cf. Barkov et al , 2000, 2002, 2004). In these systems, the PGE-rich pentlandite or ferhodsite series formed from small volumes of fractionated Fe–Ni–Cu sulfide melts considerably enriched in the PGE.…”

Section: Concluding Commentsmentioning

confidence: 97%

Platinum-group minerals from Seyba, Eastern Sayans, Russia, and substitutions in the PGE-rich pentlandite and ferhodsite series

Barkov

Shvedov

et al. 2019

MinMag

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Chromitite zones associated with ultramafic units of the Lysanskiy layered complex of dunite–peridotite–gabbro composition could well represent the primary source for the placers bearing platinum-group minerals (PGM) of the entire drainage of the River Sisim and its tributaries, the rivers Ko and Seyba, eastern Sayans. Alluvial gold present in the placers of River Seyba, as elsewhere in the Sisim Placer Zone, reflects mineralisation during a recent period of tectonic activity. We focus on the PGM in the Seyba suite, and in particular on the attributes of pentlandite enriched in platinum-group-elements (PGE) and the compositionally similar and recently defined ferhodsite, which were trapped in host grains of Os–Ir–Ru alloy. Both minerals formed from small volumes of fractionated Fe–Ni–Cu melt considerably enriched in the PGE. In the Seyba suite, as in several others, the amounts of PGE in ferhodsite exceeds that in pentlandite, which results in a greater proportion of vacancies than in pentlandite.

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“…Similarly, the substitution of Pb (under Ni) allows the realization of Pd 3 Pb 2 Se 2 with unchanged crystal structure [39], and superconductivity under pressure [40]. Moreover, Pd 3 Pb 2 S 2 with shandite structure was reported [41], as well as laflammeitethe "new" mineral Pd 3 Pb 2 S 2 , with C2/m symmetry was reported [42]. Theoretical study suggests that Pt 3 Pb 2 Ch 2 (Ch = S, Se) should be Dirac semi-metals with higher-order Fermi arcs [43].…”

Section: Introductionmentioning

confidence: 99%

$T_{3}$Pb$_{2}Ch_{2}$ ($T$=Pd,Pt and $Ch$=S,Se) with transition metal kagome net: Dynamical properties, phonon nodal line, phonon surface states, and chiral phonons

Basak¹,

Kobiałka²,

Ptok³

2023

Preprint

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Shandite with Ni3Pb2S2 chemical formula and R 3m symmetry, contains the kagome sublattice formed by the transition metal atoms. Recent experimental results confirmed the possibility of successfully synthesizing Pd3Pb2Ch2 (Ch=S,Se) with the same structure. In this paper, we theoretically investigate the dynamical properties of such compounds. Furthermore, we study the possibility of realizing Pt3Pb2Ch2 with the shandite structure. We show that the Pd3Pb2Ch2 and Pt3Pb2S2 are stable with R 3m symmetry. In the case of Pt3Pb2S2, there is a soft mode, which is the source of the structural phase transition from R 3m to R 3c symmetry, related to the distortion within the kagome sublattice. We discuss realized phonon nodal lines in the bulk phonon dispersions in upper frequency modes. We show that the shandite structure can host the phonon surface states, with strong dependence by the surface kind. Additionally, chiral phonons with circular motion of the Pb atoms around the equilibrium position are realized.

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LAFLAMMEITE, Pd3Pb2S2, A NEW PLATINUM-GROUP MINERAL SPECIES FROM THE PENIKAT LAYERED COMPLEX, FINLAND

Cited by 16 publications

References 8 publications

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

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

Platinum-group minerals from Seyba, Eastern Sayans, Russia, and substitutions in the PGE-rich pentlandite and ferhodsite series

$T_{3}$Pb$_{2}Ch_{2}$ ($T$=Pd,Pt and $Ch$=S,Se) with transition metal kagome net: Dynamical properties, phonon nodal line, phonon surface states, and chiral phonons

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