The development of platinum-group minerals in laterites

Bowles, John F. W.

doi:10.2113/gsecongeo.81.5.1278

Cited by 138 publications

(107 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Where conditions were compatible with the stability field of palladium, native palladium would have formed from the Pd-O phase (cf. stability diagrams of Bowles 1986, Wood et al 1989, Olivo & Gammons 1996. On the other hand, the presence of some mercury in the Pd-O-bearing phase may also suggest involvement of a low-temperature hydrothermal fluid.…”

Section: Native Palladiummentioning

confidence: 99%

PALLADIUM AND PLATINUM MINERALS FROM THE SERRA PELADA Au-Pd-Pt DEPOSIT, CARAJAS MINERAL PROVINCE, NORTHERN BRAZIL

Cabral

Lehmann

Kwitko-Ribeiro

et al. 2002

The Canadian Mineralogist

View full text Add to dashboard Cite

The Serra Pelada garimpo (1980)(1981)(1982)(1983)(1984) was the site of the most spectacular gold rush in recent history, but the mineralogy of the bonanza-style mineralization has not so far been documented in detail. Rediscovery of an early drill-core, recovered in 1982 from the near-surface lateritic portion of the garimpo area, has provided coarse-grained gold aggregates for this study. The centimeter-long aggregates of gold occur in powdery, earthy material. They exhibit a delicate arborescent fabric and are coated by goethite. Four compositional types of gold are recognized: palladian gold with an atomic ratio Au:Pd of 7:1 ("Au 7 Pd"), Hgbearing palladian gold (Au-Pd-Hg), Pd-bearing gold with up to 3 wt.% Pd (Pd-poor gold) and pure gold. A number of platinumgroup minerals (PGM) are included in, or attached to the surface of, palladian gold: "guanglinite", Sb-bearing "guanglinite", atheneite and isomertieite, including the noteworthy presence of Se-bearing PGM (Pd-Pt-Se, Pd-Se, Pd-Hg-Se and Pd-Bi-Se phases, and sudovikovite and palladseite). They define an As-Sb-Hg-Se mineral assemblage typical of hydrothermal vein-type deposits formed at relatively low temperatures. Native palladium, characteristically situated in the goethite coating, is intimately associated with a Pd-O phase. The remarkable occurrence of native platinum associated with Pd-bearing gold, PGM (compositionally close to mertieite-II and isomertieite) and berzelianite from a nearby prospect (Elefante prospect) is also recorded.

show abstract

Section: Native Palladiummentioning

confidence: 99%

PALLADIUM AND PLATINUM MINERALS FROM THE SERRA PELADA Au-Pd-Pt DEPOSIT, CARAJAS MINERAL PROVINCE, NORTHERN BRAZIL

Cabral

Lehmann

Kwitko-Ribeiro

et al. 2002

The Canadian Mineralogist

View full text Add to dashboard Cite

show abstract

“…One of the questions refers to secondary growth of platinum-group minerals (PGM) in laterites (e.g., Bowles 1986Bowles , 1995. The neoformation of PGM in the supergene environment has been advocated by some authors, whereas others have concluded that the PGM in placer deposits are of magmatic origin [vide Wood (2002) for a comprehensive list of references].…”

Section: Introductionmentioning

confidence: 99%

On the Rosettes of "Native Palladium" From Minas Gerais, Brazil: Evidence From Gongo Soco

Cabral¹,

Kwitko-Ribeiro²

2004

The Canadian Mineralogist

View full text Add to dashboard Cite

Minute rosette-like crystals (~1 m) were found on the surface of a gold nugget from Gongo Soco, an iron ore deposit in Minas Gerais, Brazil. The rosettes consist essentially of palladium with some oxygen. The presence of oxygen and the occurrence of many of the rosettes on a coating of iron oxyhydroxide suggest that the rosettes crystallized from a Pd-O precursor that precipitated from aqueous solution, probably in the supergene environment, on the pre-existing gold nugget.Keywords: rosettes, oxygen-bearing palladium, gold nugget, Gongo Soco, Minas Gerais, Brazil. SOMMAIREDe très petits cristaux (~1 m) en rosettes ont été déposés sur la surface d'une pépite d'or trouvée à Gongo Soco, gisement de fer à Minas Gerais, au Brésil. Ces rosettes contiennent essentiellement du palladium avec de l'oxygène. D'après la présence d'oxygène et la déposition de plusieurs de ces rosettes sur une couche d'oxyhydroxyde de fer, nous croyons que ces rosettes ont cristallisé à partir d'un précurseur de Pd-O déposé d'un solution aqueuse sur la pépite pré-existante, probablement dans un milieu supergène.(Traduit par la Rédaction)

show abstract

“…This difference has created debate concerning whether supergene processes could be responsible for the observed mineralogical differences. It has been suggested [5][6][7] that some of the PGM from the host rocks were altered during weathering and the platinum-group elements (PGE) products transported in solution to a regime of changed Eh and pH where growth of a new PGM suite occurred. Others consider this to be a "scientifically untenable hypothesis" [8].…”

Section: Introductionmentioning

confidence: 99%

“…There is textural evidence in the alluvial PGM, however, that is consistent with low-temperature growth and re-solution and re-growth. Aware of the abundant organic material and microbial fauna beneath the tropical rain forest cover of the intrusion and the ease with which the PGE react with organic materials [9,10], some studies [11][12][13] have examined the possible role of humic and fulvic acid in taking the PGE into solution at 25 • C. It is clearly possible for the PGE to enter solution under these conditions within a short time frame. Importantly, recent work has shown the ability of bacteria to play a part in the growth of PGM [14,15].…”

Section: Introductionmentioning

confidence: 99%

“…In all cases, the alkane distribution consists of the nC 27 , nC 29 , nC 31 alkanes to the virtual exclusion of lighter alkanes, especially those lighter than nC 22 . The lighter alkanes (nC 12 to nC 19 ) are indicative of derivation from algae in marine or lacustrine environments. This summary includes recent studies that correspond with the established view of this subject [24][25][26][27].…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

C14–22 n-Alkanes in Soil from the Freetown Layered Intrusion, Sierra Leone: Products of Pt Catalytic Breakdown of Natural Longer Chain n-Alkanes?

Bowles

Giże³

2018

Minerals

View full text Add to dashboard Cite

Abstract:Soil above a platinum-group element (PGE)-bearing horizon within the Freetown Layered Intrusion, Sierra Leone, contains anomalous concentrations of n-alkanes (C n H 2n+2 ) in the range C 14 to C 22 not readily attributable to an algal or lacustrine origin. Longer chain n-alkanes (C 23 to C 31 ) in the soil were derived from the breakdown of leaf litter beneath the closed canopy humid tropical forest. Spontaneous breakdown of the longer chain n-alkanes to form C 14-22 n-alkanes without biogenic or abiogenic catalysts is unlikely as the n-alkanes are stable. In the Freetown soil, the catalytic properties of the PGE (Pt in particular) may lower the temperature at which oxidation of the longer chain n-alkanes can occur. Reaction between these n-alkanes and Pt species, such as Pt 2+ (H 2 O) 2 (OH) 2 and Pt 4+ (H 2 O) 2 (OH) 4 can bend and twist the alkanes, and significantly lower the Heat of Formation. Microbial catalysis is a possibility. Since a direct organic geochemical source of the lighter n-alkanes has not yet been identified, this paper explores the theoretical potential for abiogenic Pt species catalysis as a mechanism of breakdown of the longer n-alkanes to form C 14-22 alkanes. This novel mechanism could offer additional evidence for the presence of the PGE in solution, as predicted by soil geochemistry.

show abstract

The development of platinum-group minerals in laterites

Cited by 138 publications

References 0 publications

PALLADIUM AND PLATINUM MINERALS FROM THE SERRA PELADA Au-Pd-Pt DEPOSIT, CARAJAS MINERAL PROVINCE, NORTHERN BRAZIL

PALLADIUM AND PLATINUM MINERALS FROM THE SERRA PELADA Au-Pd-Pt DEPOSIT, CARAJAS MINERAL PROVINCE, NORTHERN BRAZIL

On the Rosettes of "Native Palladium" From Minas Gerais, Brazil: Evidence From Gongo Soco

C14–22 n-Alkanes in Soil from the Freetown Layered Intrusion, Sierra Leone: Products of Pt Catalytic Breakdown of Natural Longer Chain n-Alkanes?

Contact Info

Product

Resources

About