Resources Of Platinum-group Elements Research Articles

Occurrence of Native Platinum and PGE-bearing Pyrite in the Porphyry-Skarn-Epithermal Ore Complex at Recsk, Hungary

In this short report we present the first detection of a platinum group element (PGE) mineral and Cu-bearing native platinum in a hydrothermal breccia pipe in the intermediate sulfidation mineralization of the Recsk ore complex in Hungary. Trace element analyses of pyrite provide further insights into the enrichment of PGE in the mineralized complex.The occurrence of native platinum is associated with one of the highest observed Pt contents in pyrite, as well as with other ore minerals such as Sn- and Pt-bearing native copper, pure native copper, and Ag-bearing tenorite. Crocoite and vanadinite were identified by SEM-EDS as secondary minerals possibly from the same paragenesis. Our new results suggest that the Recsk complex might contain economic PGE resources.

CRYPTIC VARIATION OF CHROMITE CHEMISTRY, PLATINUM GROUP ELEMENT AND PLATINUM GROUP MINERAL DISTRIBUTION IN THE UG-2 CHROMITITE: AN EXAMPLE FROM THE KAREE MINE, WESTERN BUSHVELD COMPLEX, SOUTH AFRICA

The UG-2 chromitite of the Bushveld Complex in South Africa contains the world’s largest resources of platinum group elements (PGEs). However, only limited work has been conducted on the fine-scale chemical variation of chromite, and the distribution of PGEs and platinum group minerals (PGMs) within the UG-2. In the present study, one drill core (155 cm long) covering the sequence of the UG-2 chromitite at the Karee mine in the western Bushveld Complex was studied in detail. Geochemically, Pt correlates well with Pd, but not with Ni, Cu, and S, and Pt and Pd show high concentrations at the bottom and in the center of the main UG-2 layer. The mineral chemistry of chromite is characterized by distinct cryptic variation, leading to the division of the UG-2 sequence into 10 distinct sublayers. From bottom to top (with exception of the basal sublayer), each sublayer is defined by an upward decrease of Mg# combined with increases of Cr# and TiO2. It is proposed that these trends reflect magmatic differentiation of individual chromitite entities, which coalesced to form a massive chromitite seam. Sulfides (pentlandite, chalcopyrite) interstitial to chromite grains are rare, and associated PGM grains are mainly Pt-Fe alloy, laurite, and cooperite-braggite. The PGEs are bimodally distributed in the UG-2. Platinum and the IPGE (Os, Ir, Ru) are dominantly present as discrete PGMs, whereas large proportions of Pd and Rh are hosted in the crystal lattice of pentlandite. Palladium and rhodium contents of pentlandite reach a maxima of 2.2 wt % Pd and 3.0 wt % Rh. The present data suggest that a succession of chromitite sublayers formed due to magmatic differentiation and segregated sequentially on top of each other, finally forming a massive chromitite seam. Contemporaneously with chromite segregation, PGE-rich magmatic sulfides segregated with chromite grains, but large proportions of these sulfides were subsequently removed mainly by reaction of sulfide with chromite, thereby upgrading the PGE contents of the remaining sulfides. Upon cooling, the PGE-bearing sulfide droplets recrystallized, leading to a bimodal distribution of the PGEs in the UG-2. The bulk of the Pd and Rh is hosted in pentlandite, whereas Pt and the IPGEs, apparently incompatible in the remaining sulfides, formed a distinct suite of discrete PGMs.

Key trends in the resource sustainability of platinum group elements

Platinum group elements (PGEs) are increasingly used in a variety of environmentally-related technologies, such as chemical process catalysts, catalytic converters for vehicle exhaust control, hydrogen fuel cells, electronic components, and a variety of specialty medical uses, amongst others — almost all of which have strong expected growth to meet environmental and technological challenges this century. Economic geologists have been arguing on the case of abundant geologic resources of PGEs for some time while others still raise concerns about long-term supply — yet there remains no detailed analysis of formally reported mineral resources and key trends in the PGEs sector. This paper presents such a detailed review of the PGEs sector, including detailed mine production statistics and mineral resources by principal ore types, providing an authoritative case study on the resource sustainability for a group of elements which are uniquely concentrated in a select few regions of the earth. The methodology, compiled data sets and trends provide strong assurance on the contribution that PGEs can make to the key sustainability and technology challenges of the 21st century such as energy and pollution control.

Quantitative mineral resource assessment of undiscovered PGE resources in Finland

Most of the known platinum group element (PGE) resources in Finland are in contact-type and reef-type deposits in 2.45 Ga mafic–ultramafic layered intrusions. These intrusions are also estimated to contain the majority of possibly existing, yet undiscovered PGE resources in Finland. The undiscovered Pt, Pd, Au, Ni, and Cu resources in contact-type and reef-type deposits were estimated down to 1000 m depth using a three-part quantitative assessment method. This included the delineation of 19 contact-type and 24 reef-type permissive tracts, the formulation of a grade-tonnage model for the contact-type deposits and a separate model for each reef-type tract, estimation of the number of undiscovered deposits for each permissive tract, and Monte Carlo simulation to estimate the frequency distributions of metal tonnages in the undiscovered deposits. The expected number of undiscovered contact-type deposits is 29 and that of reef-type deposits is 23. At the 50% probability level, the total undiscovered PGE resources of Finland are estimated to be at least 5600 t Pt, 12,000 t Pd, 430 t Au, 4.2 Mt Ni, and 5.7 Mt Cu. At the 90% probability level, the corresponding tonnages are 720 t Pt, 1700 t Pd, 59 t Au, 0.87 Mt Ni, and 0.91 Mt Cu. More than 80% of the Pt + Pd in the undiscovered resources are estimated to be in reef-type deposits. The known PGE resources in Finland are 259 t Pt + Pd in six contact-type deposits, plus 69 t Pt + Pd in the atypical Kevitsa deposit. These figures indicate that the presently known deposits account for approximately 2% of the total assessed PGE resources in Finland. They suggest that significant potential exists for the discovery of additional PGE resources in the country.

PRECISE AGE OF THE PLATINIFEROUS MERENSKY REEF, BUSHVELD COMPLEX, SOUTH AFRICA, BY THE U-Pb ZIRCON CHEMICAL ABRASION ID-TIMS TECHNIQUE

The Bushveld Complex, South Africa, is the world’s largest layered intrusion and host to the majority of the known resources of platinum group elements, chromium, and vanadium. Despite intensive study, determining the precise crystallization age of the Bushveld Complex has proven to be difficult. In this study, zircon and rutile were identified in thin section and separated from a sample of pegmatitic feldspathic orthopyroxenite from the PGE-rich Merensky reef, West mine (Townlands shaft), Rustenburg section. Low U (21–105 ppm) zircon occurs with interstitial biotite and is locally in direct contact with sulfide. Rutile occurs mainly as inclusions within or overgrowths on chromite, especially in the chromitite stringers that bound the reef, and also as acicular grains with biotite. A U-Pb crystallization age of 2054.4 ± 1.3 Ma was determined from single-crystal chemical abrasion ID-TIMS U-Pb dating of zircon, and multigrain fractions of rutile yielded a U-Pb cooling age of 2055.0 ± 3.9 Ma. Integration of the Merensky reef crystallization age with existing U-Pb age determinations for intrusions that pre- and postdate emplacement and crystallization of the layered rocks of the Bushveld Complex indicate that magmatism occurred at ca. 2054 Ma and is contemporaneous with related magmatic activity across the northern Kaapvaal craton of South Africa and Botswana.

Trace Element and Platinum Group Element Distributions and the Genesis of the Merensky Reef, Western Bushveld Complex, South Africa

The Merensky Reef of the Bushveld Complex is one of the world’s largest resources of platinum group elements (PGE); however, mechanisms for its formation remain poorly understood, and many contradictory theories have been proposed. We present precise compositional data [major elements, trace elements, and platinum group elements (PGE)] for 370 samples from four borehole core sections of the Merensky Reef in one area of the western Bushveld Complex. Trace element patterns (incompatible elements and rare earth elements) exhibit systematic variations, including small-scale cyclic changes indicative of the presence of cumulus crystals and intercumulus liquid derived from different magmas. Ratios of highly incompatible elements for the different sections are intermediate to those of the proposed parental magmas (Critical Zone and Main Zone types) that gave rise to the Bushveld Complex. Mingling, but not complete mixing of different magmas is suggested to have occurred during the formation of the Merensky Reef. The trace element patterns are indicative of transient associations between distinct magma layers. The porosity of the cumulates is shown to affect significantly the distribution of sulphides and PGE. A genetic link is made between the thickness of the Merensky pyroxenite, the total PGE and sulphide content, petrological and textural features, and the trace element signatures in the sections studied. The rare earth elements reveal the important role of plagioclase in the formation of the Merensky pyroxenite, and the distribution of sulphide.

Platinum-group element resources in podiform chromitites from California and Oregon

Rock samples from about 280 podiform chromite deposits in California and Oregon were analyzed for Pt, Pd, Rh, and Ir by fire assay-atomic absorption and spectrographic techniques to estimate by-product platinum-group element potential of chromite mining. These deposits include ophiolites from the Sierra Nevada, Klamath Mountains, Coast Ranges, and the Canyon Mountain Complex; the deposits vary from Paleozoic to Mesozoic age and vary in size, shape, texture, and degree of metamorphism. The maximum platinum-group element contents (in ppm) measured for chromitites are: Pt, 2.53; Pd, 0.2; Rh, 0.14; Ru, 4.93; and Ir, 2.93.Correlations between Pt and Rh (0.60), Rh and Ir (0.64), Rh and Ru (0.71), and Ir and Ru (0.85) are significant at the 1 percent level. Relatively small but significant differences in platinum-group element content exist between geologic terranes. Chromite production from California and Oregon amounts to about 692,000 metric tons (1914-1985); the mean contained platinum-group element amounts in troy ounces are: Pt, 850; Pd, 100; Rh, 260; Ru, 4200; and Ir, 1,700, using estimated Previous investigators have suggested that relatively few samples can represent the platinum-group element content of a podiform chromite deposit; therefore, these analyses are assumed to approximate grades. Total world resources of platinum-group elements in podiform chromite deposits are estimated in troy ounces to be: Pt, 210,000; Pd, 25,000; Rh, 64,000; Ru, 1,000,000; and Ir, 420,000.