Bulk Liquid for the Skaergaard Intrusion and Its PGE-Au Mineralization: Composition, Correlation, Liquid Line of Descent, and Timing of Sulphide Saturation and Silicate–Silicate Immiscibility

2019 ◽  
Vol 60 (10) ◽  
pp. 1853-1880 ◽  
Author(s):  
Troels F D Nielsen ◽  
C Kent Brooks ◽  
Jakob K Keiding
Keyword(s):  
Precious Metal ◽  
Bulk Composition ◽  
Precious Metals ◽  
Bulk Liquid ◽  
Skaergaard Intrusion ◽  
Liquid Line ◽  
Multi Stage ◽  
Silicate Liquids ◽  
Crystallization Zone ◽  
Liquid Line Of Descent

Abstract Preferred and modelled bulk composition of the Skaergaard intrusion are compared to coeval basaltic compositions in East Greenland and found to relate to the second evolved cycle of Geikie Plateau Formation lavas and coeval Skaergaard-like dikes in major and trace element (Mg# ∼45, Ce/Nb ∼2·5, (Dy/Yb)N ∼1·35), and precious metal composition (Pd/Pt ∼3, Au/Pt ∼2) as well as in age (∼56 Ma). Successful comparisons of precious metal compositions only occur with Skaergaard models based on mass balance. The bulk liquid of the intrusion evolved along the liquid line of descent to immiscibility between Si- and Fe-rich silicate liquids after ∼90% of crystallization (F = ∼0·10) in agreement with experimental constraints. Immiscibility led to accumulation and fractionation of the Fe-rich silicate melt in the mushy floor of the intrusion and continued accumulation of granophyre component in the remaining bulk liquid. The composition of plagioclase in the precious metal mineralized gabbro and modelling of Pd/Pt and Au/Pt in first formed droplets of sulphide melt suggest that sulphide saturation was reached in interstitial melts in crystal mushes in the floor and roof and in bulk liquid with a composition equivalent to that of the bulk liquid at lower UZa times and after crystallization of 82–85% of the bulk liquid (F = 0·19–0·16). Prior to sulphide saturation in UZa type melt, the precious metals ratios of the bulk liquid were controlled by the loss of Pt relative to Pd and Au in agreement with the low empirical and experimental solubility of Pt of ∼9ppb compared to a much higher value for Pd and Au. The relative timing between sulphide saturation (F = ∼0·18) and immiscibility between silicate melts (F = ∼0·10) and modelled precious metal ratios underpin the proposed multi-stage model for the mineralization, advocating initial accumulation in the mushy floor of the magma chamber controlled by sulphide saturation in mush melts rather than bulk melt, followed by redistribution of precious metals in a macro-rhythmic succession of gabbroic layers of the upward migrating crystallization zone.

scholarly journals Genesis of Precious Metal Mineralization in Intrusions of Ultramafic, Alkaline Rocks and Carbonatites in the North of the Siberian Platform

Minerals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 354
Author(s):  
Anatoly M. Sazonov ◽  
Aleksei E. Romanovsky ◽  
Igor F. Gertner ◽  
Elena A. Zvyagina ◽  
Tatyana S. Krasnova ◽  
...  
Keyword(s):  
High Temperature ◽  
Siberian Platform ◽  
Precious Metal ◽  
Native Gold ◽  
Precious Metals ◽  
Ore Formation ◽  
Central Type ◽  
Alkaline Rocks ◽  
The North ◽  
Pge Mineralization

The gold and platinum-group elements (PGE) mineralization of the Guli and Kresty intrusions was formed in the process of polyphase magmatism of the central type during the Permian and Triassic age. It is suggested that native osmium and iridium crystal nuclei were formed in the mantle at earlier high-temperature events of magma generation of the mantle substratum in the interval of 765–545 Ma and were brought by meimechite melts to the area of development of magmatic bodies. The pulsating magmatism of the later phases assisted in particle enlargement. Native gold was crystallized at a temperature of 415–200 °C at the hydrothermal-metasomatic stages of the meimechite, melilite, foidolite and carbonatite magmatism. The association of minerals of precious metals with oily, resinous and asphaltene bitumen testifies to the genetic relation of the mineralization to carbonaceous metasomatism. Identifying the carbonaceous gold and platinoid ore formation associated genetically with the parental formation of ultramafic, alkaline rocks and carbonatites is suggested.

scholarly journals A Liquid Line of Descent of the Jotunite (Hypersthene Monzodiorite) Suite

1998 ◽  
Vol 39 (3) ◽  
pp. 439-468 ◽  
Author(s):  
J. Vander Auwera ◽  
J. Longhi ◽  
J.-C. Duchesne
Keyword(s):  
Liquid Line ◽  
Liquid Line Of Descent

New route for synthesis of Synroc-like ceramic using non-selective sorbent LHT-9

MRS Advances ◽  
2018 ◽  
Vol 3 (20) ◽  
pp. 1111-1116 ◽  
Author(s):  
B.Yu. Zubekhina ◽  
B.E. Burakov ◽  
Yu.Yu. Petrov ◽  
S.N. Britvin ◽  
V.F. Mararitsa ◽  
...  
Keyword(s):  
Radioactive Waste ◽  
Chemical Durability ◽  
Bulk Liquid ◽  
Distilled Water ◽  
Selective Sorbent ◽  
Ceramic Synthesis ◽  
Multi Stage ◽  
High Level ◽  
Radionuclide Incorporation ◽  
Titanate Ceramic

ABSTRACT:Immobilization of bulk liquid high level radioactive waste (HLW) in Synroc ceramic is well-known reliable way for final isolation of dangerous long-lived radionuclides from biosphere. The alternative method of Synroc-like ceramic synthesis has been proposed. Radionuclide incorporation into crystalline titanate host-phases can be provided as a result of direct radionuclide sorption from liquid HLW using non-selective sorbent – layered hydrazinium titanate (LHT-9). Such an approach allows excluding expensive multi-stage procedure of precursor preparation. The precipitate obtained after sorption can be easily transformed into Synroc-like ceramic by cold pressing followed with sintering in air at 1000-1200°C. The highly radioactive samples of titanate ceramic loaded with real HLW have been synthesized and preliminary studied at KRI hot-cell facility. Chemical durability of this sample has been studied using static leach test in distilled water at 90°C and the leach rates for 154Eu, 241Am, 244Cm were (in g·m-2·day-1) from 2·10-4 to 5·10-3. Normalised 137Cs mass loss was 0.3 g·m-2 for 110 days at the same conditions.

Variant Offset-Type Platinum Group Element Reef Mineralization in Basal Olivine Cumulates of the Kapalagulu Intrusion, Western Tanzania

2021 ◽  
Author(s):  
M. D. Prendergast
Keyword(s):  
Precious Metal ◽  
Platinum Group Element ◽  
Early Stage ◽  
Precious Metals ◽  
Parental Magma ◽  
Group Element ◽  
Metal Enrichment ◽  
Reef Development ◽  
Platinum Group ◽  
Olivine Cumulates

Abstract The Kapalagulu intrusion in eastern Tanzania hosts a major, 420-m-thick, stratiform/stratabound platinum group element (PGE)-bearing sulfide zone—the Lubalisi reef—within a prominent, chromititiferous, harzburgite unit close to its stratigraphic base. Several features of the vertical base and precious metal distributions (in a composite stratigraphic section based upon two deep exploration drill holes) display similarities to those of offset-type PGE reefs that formed under the overall control of Rayleigh fractionation: (1) composite layering (at several scales) defined by systematic vertical variations of sulfide and precious metal contents and intermetallic ratios, indicating repeated cycles of PGE enrichment and depletion in the order Pd-Pt-Au-Cu, and (2) in the lower part of the reef, stratigraphic offsets of the precious metal peaks below peak sulfide (Cu) content. The form and geochemistry of the reef are consistent with overturns of basal liquid layers within a liquid layering system (i.e., stable density-driven stratification of a magma chamber), plus at least two minor inputs of parental magma during which the resident magma was recharged with sulfur and metals, and the effective depletion of precious metals in the magma midway through reef development. The Lubalisi reef differs from classic offset-type PGE reefs, however, principally because individual Pd, Pt, and Au enrichment peaks are coincident, not offset. The reef is set apart from other offset-type PGE reefs in three additional ways: (1) its association with olivine cumulates that crystallized soon after initial magma emplacement and well below the first appearance of cumulus pyroxene or plagioclase (implying attainment of sulfide saturation and precious metal enrichment without prolonged concentration of sulfur and chalcophile metals by normal magma cooling and differentiation), (2) the probable role of chromite crystallization in not only triggering sulfide segregation during reef formation but also facilitating precious metal enrichment in the early stages of reef development, and (3) its great width. The early stage of fractionation may also help explain the coincident precious metal peaks through its effect on apparent precious metal partition coefficients.

scholarly journals Editorial: Special Issue Catalysis by Precious Metals, Past and Future

Catalysts ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 247
Author(s):  
Svetlana Ivanova ◽  
Marcela Martínez Tejada
Keyword(s):  
Precious Metal ◽  
Precious Metals ◽  
Special Issue ◽  
Metal Catalysis ◽  
Editorial Special Issue ◽  
Precious Metal Catalysis

Precious metal catalysis is often synonymous with diversity and versatility [...]

The distribution of trace precious metals in minerals and mineral products

1992 ◽  
Vol 56 (384) ◽  
pp. 289-308 ◽  
Author(s):  
Louis J. Cabri
Keyword(s):  
Electron Microprobe ◽  
Analytical Methods ◽  
Precious Metal ◽  
Precious Metals ◽  
Analytical Techniques ◽  
Environmental Concerns ◽  
Ion Microprobe ◽  
Future Directions ◽  
Specific Analysis ◽  
Process Mineralogy

AbstractData on the distribution of the precious metals (Au, Ag and the platinum=group elements Ru, Rh, Pd, Os, Ir, Pt) are rapidly accumulating as a consequence of the application of microbeam analytical techniques such as the electron microprobe, the proton microprobe, and the ion microprobe. The new data obtained with these techniques build on knowledge accumulated over the last 140 years using bulk analytical methods (e.g. spectrographic). The nature of the occurrence, the concentrations, and the variation in amount s of precious metals in minerals and mineral products are reviewed with comments as to the significance of the results with respect to industrial and environmental concerns. Future directions in mineral-specific analysis of trace precious-metal concentrations and applications outside of process mineralogy are discussed.

scholarly journals Equilibrium crystallization of massif-type anorthosite residual melts: a case study from the 1.64 Ga Ahvenisto complex, Southeastern Finland

2020 ◽  
Vol 175 (9) ◽  
Author(s):  
Riikka Fred ◽  
Aku Heinonen ◽  
Jussi S. Heinonen
Keyword(s):  
Magma Chambers ◽  
Equilibrium Crystallization ◽  
Liquid Line ◽  
Rock Types ◽  
Residual Magma ◽  
Icp Ms ◽  
Mineral Assemblages ◽  
Residual Melt ◽  
Liquid Line Of Descent

Abstract Fe–Ti–P-rich mafic to intermediate rocks (monzodiorites and oxide–apatite–gabbronorites, OAGNs) are found as small intrusions in most AMCG (anorthosite–magnerite–charnokite–granite) suites. The origin of the monzodioritic rocks is still debated, but in many studies, they are presumed to represent residual liquid compositions after fractionation of anorthositic cumulates. In the 1.64 Ga Ahvenisto complex, SE Finland, monzodioritic rocks occur as minor dike-like lenses closely associated with anorthositic rocks. We report new field, petrographic, and geochemical (XRF, ICP-MS, EMPA) data complemented with crystallization modeling (rhyolite-MELTS, MAGFRAC) for the monzodioritic rocks, apatite–oxide–gabbronorite, and olivine-bearing anorthositic rocks of the Ahvenisto complex. The presented evidence suggest that the monzodioritic rocks closely represent melt compositions while the apatite–oxide–gabbronorite and olivine-bearing anorthositic rocks are cumulates. The monzodioritic rocks seem to form a liquid line of descent (LLD) from primitive olivine monzodiorites to more evolved monzodiorites. Petrological modeling suggests that the interpreted LLD closely corresponds to a residual melt trend left after fractional crystallization (FC) and formation of the cumulate anorthositic rocks and minor apatite–oxide–gabbronorite in shallow magma chambers. Consequent equilibrium crystallization (EC) of separate monzodioritic residual magma batches can produce the observed mineral assemblages and the low Mg numbers measured from olivine (Fo25–45) and pyroxenes (En48–63, Mg#cpx 60–69). The monzodioritic rocks and apatite–oxide–gabbronorites show similar petrological and geochemical characteristics to corresponding rock types in other AMCG suites, and the model described in this study could be applicable to them as well.

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