Genesis and mechanisms of metal enrichment in the Baimazhai Ni-Cu-(PGE) deposit, Ailaoshan Orogenic Belt, SW China

2021 ◽  
Vol 59 (6) ◽  
pp. 1543-1570
Author(s):  
Yiguan Lu ◽  
C. Michael Lesher ◽  
Liqiang Yang ◽  
Matthew I. Leybourne ◽  
Wenyan He
Keyword(s):  
Platinum Group Element ◽  
Crustal Contamination ◽  
Platinum Group Elements ◽  
Group Element ◽  
Orogenic Belt ◽  
Large Igneous Province ◽  
Type I ◽  
Monosulfide Solid Solution ◽  
Platinum Group ◽  
Host Rocks

ABSTRACT The ∼259 Ma Baimazhai Ni-Cu-(platinum-group element) deposit is located in the Ailaoshan-Red River fault zone on the southwest margin of the Yangtze Plate in the Jinping area of southeastern Yunnan Province. The intrusion is lenticular (∼530 m long × 190 m wide × 24–64 m thick) and concentrically zoned (margin to core) from gabbro through pyroxenite to peridotite. It contains ∼50 kt of Ni-Cu-(platinum-group element) mineralization, concentrically zoned (margin to core) from disseminated through net-textured to massive sulfides with an average grade of 1.03 wt.% Ni, 0.81 wt.% Cu, and 0.02∼0.69 ppm Pd+Pt. The sulfide assemblage comprises pyrrhotite, chalcopyrite, and pentlandite, with lesser magnetite, violarite, galena, and cobaltite. The mineralization is enriched in Ni-Cu-Co relative to the platinum-group elements and the host rocks are enriched in highly incompatible lithophile elements relative to moderately incompatible lithophile elements with high Th/Yb and intermediate Nb/Yb ratios. These host rocks, and those at most other Ni-Cu-platinum-group element deposits in the Emeishan Large Igneous Province, have high γOs and intermediate εNd values, indicating that they crystallized from a magma derived from a subduction-modified pyroxenite mantle source and modified by crustal contamination. The initial concentrations of metals in the primary magma are estimated to have been on the order of 200 ppm Ni and 100 ppm Cu, but only 0.4 ppb Pd, 0.2 ppb Pt, 0.005 ppb Rh, 0.02 ppb Ru, and 0.01 ppb Ir. The δ34S values of ores and separated sulfides range from 5.8‰ to 8.6‰, between the ∼10‰ value of sulfides in the metasedimentary country rocks and the 0 ± 0.5‰ value expected for magmas derived from MORB-type mantle, or the –2.5 ± 0.3‰ value expected for subduction-modified mantle, consistent with equilibration at magma:sulfide mass ratios (R factors) of 100–1000. Variations in Ir100 and Pd100 (metals in 100% sulfide) are consistent with 40–60% fractional crystallization of monosulfide solid solution to form Ni-Co-intermediate platinum-group element (Ru, Os, Ir)-rich massive ores and Cu-palladium/platinum-group elements (Pt, Pd, Rh)-Au-rich residual sulfide liquids. This process is also recorded by magnetite: Type I (early magmatic), type II (late magmatic), and type III (secondary) magnetites exhibit progressively lower Cr-Ti-V concentrations. The platinum-group element contents in base-metal minerals are low, and only pentlandite, violarite, and cobaltite contain detectable concentrations of Pd, Rh, and Ru. There is abundant textural evidence for metamorphic-hydrothermal alteration of sulfides in the Baimazhai intrusion, with secondary violarite, chalcopyrite, and pentlandite being enriched (Ag, Sb, Au, Pb) or depleted (Sn) in more mobile chalcophile elements. The different tectonic and petrogenetic settings of the Baimazhai and other deposits in China highlight the potential of Ni-Cu-platinum-group element deposits to occur in subduction or post-subduction settings and demonstrate that the key controls are magma flux and access to crustal S. Exploration potential remains for the Ailaoshan orogenic belt to host additional magmatic Ni-Cu deposits.

Genesis of the Jinbaoshan PGE-(Cu)-(Ni) deposit: Distribution of chalcophile elements and platinum-group minerals

2021 ◽  
Vol 59 (6) ◽  
pp. 1511-1542
Author(s):  
Yiguan Lu ◽  
C. Michael Lesher ◽  
Liqiang Yang ◽  
Matthew I. Leybourne ◽  
Wenyan He ◽  
...  
Keyword(s):  
Solid Solution ◽  
Platinum Group Element ◽  
Platinum Group Elements ◽  
Group Element ◽  
Monosulfide Solid Solution ◽  
Platinum Group Minerals ◽  
Pd Alloy ◽  
Platinum Group ◽  
Lower Temperature ◽  
Subduction System

ABSTRACT The Jinbaoshan platinum group element-(Cu)-(Ni) deposit in southwest China is a sulfide-poor magmatic platinum-group element deposit that experienced multiple phases of post-magmatic modification. The sulfide assemblages of most magmatic Ni-Cu-platinum-group element deposits in China and elsewhere in the world are dominated by pentlandite-pyrrhotite-chalcopyrite with lesser magnetite and minor platinum-group minerals. However, Jinbaoshan is characterized by (1) hypogene violarite-pyrite 1-millerite-chalcopyrite and (2) supergene violarite-(polydymite)-pyrite 2-chalcopyrite assemblages. The platinum-group minerals are small (0.5–10 μm diameter) and include moncheite Pt(Te,Bi)2, mertieite-I Pd11(Sb,As)4, the atokite Pd3Sn – rustenburgite Pt3Sn solid solution, irarsite IrAsS, and sperrylite PtAs2 hosted mainly by violarite, silicates (primarily serpentine), and millerite. The platinum-group minerals occur in two sulfide assemblages: (1) mertieite-I-dominant (with irarsite, palladium, and Pd-alloy) in the hypogene assemblage and (2) moncheite-dominant (with irarsite, sperrylite, and atokite) in the supergene assemblage. Palladium and intermediate platinum-group elements (Os, Ir, Ru) are concentrated mainly in violarite, polydymite, and pyrite 2. Platinum is seldom hosted by base metal sulfides and occurs mainly as discrete platinum-group minerals, such as moncheite, sperrylite, and merenskyite. Violarite and polydymite in the Jinbaoshan deposit contain more Pb-Ag than pentlandite and pyrrhotite in the Great Dyke and Lac des Iles deposit. The formation of the sulfide assemblages in Jinbaoshan can be interpreted to have occurred in three stages: (1) a magmatic Fe-Ni-Cu sulfide melt crystallized Fe-Ni monosulfide and Cu-rich intermediate solid solutions, which inverted to a primary pyrrhotite-pentlandite-chalcopyrite-magnetite assemblage; (2) an early-secondary hypogene voilarite-millterite-pyrite 1-chalcopyrite assemblage formed by interaction with a lower-temperature magmatic-hydrothermal deuteric fluid; and (3) a late-secondary supergene violarite-polydymite-pyrite 2-chalcopyrite assemblage formed during weathering. Late-magmatic-hydrothermal fluids enriched the mineralization in Pb-Ag-Cd-Zn, which are incompatible in monosulfide solid solution, added Co-Pt into violarite, and expelled Pd to the margins of hypogene violarite and millerite, which caused Pd depletion in the hypogene violarite and the formation of mertieite-I. Supergene violarite inherited Pd and intermediate platinum-group elements from primary pentlandite. Thus, the unusual sulfide assemblages in the Jinbaoshan platinum-group element-(Cu)-(Ni) deposit results from multiple overprinted post-magmatic processes, but they did not significantly change the chalcophile element contents of the mineralization, which is interpreted to have formed at high magma:sulfide ratios (R factors) through interaction of crustally derived sulfide and a hybrid picritic-ferropicritic magma derived from subduction-metasomatized pyroxenitic mantle during impingement of the Emeishan plume on the Paleo-Tethyan oceanic subduction system.

Progress in Platinum Group Element (PGE) in Black Shale Series

2013 ◽  
Vol 353-356 ◽  
pp. 1183-1186 ◽  
Author(s):  
Jun Liu ◽  
Ying Chen ◽  
Zhen Xiu Liao ◽  
Yong Zhan ◽  
You Fei Guan
Keyword(s):  
Mineral Resource ◽  
Fluid Inclusion ◽  
Black Shale ◽  
Precious Metal ◽  
Platinum Group Element ◽  
Platinum Group Elements ◽  
Group Element ◽  
Metal Elements ◽  
Platinum Group

The black shale enriched in various precious metal elements and platinum group elements. And the PGE deposit in black shale series is a new promising mineral resource. Comprehensive research on the geology, geochemistry, petrology, mineralogy, fluid inclusion and geochronology of the PGE in black shale series has been carried out and made a series of achievements. This paper summarized the advances in PGE in black shale series and pointed out the controversial views about the source of the PGE.

Nano- and Micrometer-Sized PGM in Ni-Cu-Fe Sulfides from an Olivine Megacryst in the Udachnaya Pipe, Yakutia, Russia

2021 ◽  
Vol 59 (6) ◽  
pp. 1755-1773
Author(s):  
José María González-Jiménez ◽  
Irina Tretiakova ◽  
Marco Fiorentini ◽  
Vladimir Malkovets ◽  
Laure Martin ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Field Emission ◽  
Platinum Group Element ◽  
Group Element ◽  
Monosulfide Solid Solution ◽  
Mineral Particles ◽  
Transmission Electron ◽  
Sulfide Melt ◽  
Platinum Group

ABSTRACT This paper focuses on a nanoscale study of nano- and micrometer-size Os-rich mineral particles hosted in a Ni-Fe-Cu sulfide globule found in an olivine megacryst from the Udachnaya pipe (Yakutia, Russia). These platinum-group element mineral particles and their host sulfide matrices were investigated using a combination of techniques, including field emission gun electron probe microanalyzer, field emission scanning electron microscopy, and focused ion beam and high-resolution transmission electron microscopy. The sulfide globule is of mantle origin, as it is hosted in primitive olivine (Fo90–93), very likely derived from the crystallization of Ni-Fe-Cu sulfide melt droplets segregated by liquid immiscibility from a basaltic melt in a volume of depleted subcontinental lithospheric mantle. Microscopic observations by means of field emission scanning electron microscopy and single-spot analysis and mapping by field emission gun electron probe microanalyzer reveal that the sulfide globule comprises a core of pyrrhotite with flame-like exsolutions (usually <10 μm thickness) of pentlandite, which is irregularly surrounded by a rim of granular pentlandite and chalcopyrite. Elemental mapping by energy dispersive spectroscopy (acquired using the high-resolution transmission electron microscopy) of the pyrrhotite (+ pentlandite) core reveals that pentlandite exsolution in pyrrhotite is still observable at the nanoscale as fringes of 100 to 500 nm thicknesses. The sulfide matrices of pyrrhotite, pentlandite, and chalcopyrite contain abundant nano- and micrometer-size platinum group element mineral particles. A careful inspection of eight of these platinum group element particles under focused ion beam and high-resolution transmission electron microscopy showed that they are crystalline erlichmanite (OsS2) with well-developed crystal faces that are distinctively oriented relative to their sulfide host matrices. We propose that the core of the Ni-Fe-Cu sulfide globule studied here was derived from a precursor monosulfide solid solution originally crystallized from a sulfide melt at >1100 °C, which later decomposed into pyrrhotite and the pentlandite flame-like exsolutions upon cooling at <600 °C. Once solidified, the solid monosulfide solid solution reacted with non-equilibrium Cu-and Ni-rich sulfide melt(s), giving rise to the granular pentlandite in equilibrium with chalcopyrite now forming the rim of the sulfide globule. Meanwhile, nano- to micron-sized crystals of erlichmanite crystallized directly from or slightly before monosulfide solid solution from the sulfide melt. Thus, Os, and to a lesser extent Ir and Ru, were physically partitioned by preferential uptake via early formation of nanoparticles at high temperature instead of low-temperature exsolution from solid Ni-Fe-Cu sulfides. The new data provided in this paper highlight the necessity of studying platinum group element mineral particles in Ni-Fe-Cu sulfides using analytical techniques that can image nanoscale textural features in order to better understand the mechanisms of platinum group element fractionation in magmatic systems. These processes may play a crucial role in controlling the background geochemical budgets for siderophile and chalcophile elements in a wide range of mantle-derived magmas.

Diversity of platinum-group element mineralization styles in the North Atlantic Igneous Province: new evidence from Rum, UK

2003 ◽  
Vol 140 (5) ◽  
pp. 499-512 ◽  
Author(s):  
M. R. POWER ◽  
D. PIRRIE ◽  
J. C. Ø. ANDERSEN
Keyword(s):  
North Atlantic ◽  
Platinum Group Element ◽  
Platinum Group Elements ◽  
Group Element ◽  
The North ◽  
Igneous Province ◽  
Two Generations ◽  
Platinum Group ◽  
New Evidence ◽  
North Atlantic Igneous Province

Two generations of sulphide-hosted platinum-group element mineralization occur in the West Sgaorishal ultramafic plug, Rum. Disseminated Cu and Ni sulphides around the margin of the plug host a restricted platinum-group mineral assemblage that is dominated by Pd bismutho-tellurides and sperrylite (PtAs2) with subordinate electrum (AuAg), froodite (PdBi2) and unidentified Pt–Bi–Te phases. Later sulphide-rich dykes cross-cut the plug and host an assemblage dominated by Pd bismutho-tellurides, sperrylite and locally very abundant paolovite (Pd2Sn). Whole rock combined platinum-group element+Au concentrations are proportional to the sulphide abundance with slightly elevated values in disseminated sulphide lithologies (>400 ppb) and very high values (>2000 ppb) in the sulphide-rich dykes. Both generations have relatively flat chondrite-normalized plots indicating a primitive magmatic source. Negative δ34S values (−9.2 to −18.3 ‰) indicate that the disseminated mineralization is due to contamination probably derived from Jurassic sedimentary rocks leading to sulphur saturation and collection of platinum-group elements. The sulphide-rich dykes must have entrained a platinum-group element-rich sulphide liquid collected from a much larger volume of magma. The presence of platinum-group elements and sulphide-rich dykes with δ34S values between −10.8 and −15.0 ‰ indicates that parts of the Rum Layered Suite became sulphur saturated through magmatic contamination. It appears likely that platinum-group element mineralization styles within the southern North Atlantic Igneous Province are diverse and may be present in a wider variety of mineralogical associations than previously recognized.

Platinum Group Element Enrichment of Natural Quenched Sulfide Solid Solutions, the Norilsk 1 Deposit, Russia

2020 ◽  
Vol 115 (6) ◽  
pp. 1343-1361
Author(s):  
Valeriya D. Brovchenko ◽  
Sergey F. Sluzhenikin ◽  
Elena V. Kovalchuk ◽  
Sofia V. Kovrigina ◽  
Vera D. Abramova ◽  
...  
Keyword(s):  
Solid Solution ◽  
High Temperature ◽  
Solid Solutions ◽  
Platinum Group Element ◽  
Group Element ◽  
Temperature Fields ◽  
Chemical Compositions ◽  
Monosulfide Solid Solution ◽  
Icp Ms ◽  
Platinum Group

Abstract The deepest terminations of the Mount Rudnaya subvertical massive sulfide offshoots of the Norilsk 1 orebody are composed of exceptionally fine grained sulfides that are believed to be natural quenched sulfide solid solutions. Copper-rich intermediate solid solution (ISS) and Fe-rich monosulfide solid solution (MSS) form an equigranular and lamellar matrix hosting MSS- and ISS-dominant globules. The nonstoichiometric chemical compositions of the solid solutions plot within their high-temperature fields known from experiments. MSS contains 19 to 35 wt % Ni, 0.09 to 0.45 wt % Co, and up to 0.6 wt % Cu and is heterogeneously enriched in Rh (up to 32 ppm), Ir (up to 0.6 ppm), Pt (up to 65 ppm), and Pd (up to 168 ppm). ISS occurs as the lamellar intergrowths of the chalcopyrite (Ccpss) and cubanite (Cubss) solid solutions, which bear up to 4.74 wt % Ni and 0.2 wt % Co and are heterogeneously enriched in Zn, Ag, and In. The assemblage of platinum group minerals (PGMs) is hosted mostly in the ISS and is dominated by Pt-Fe alloys and minerals of the rustenburgite-atokite series, like the set of PGMs at the Norilsk 1 deposit. Similar Pt-Pd-Sn compounds in the laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) spectra of profiles through MSS and ISS are interpreted to be trapped microinclusions. The pentlandite contains up to 0.13 wt % Pt, up to 4.62 wt % Pd, <0.53 wt % Co, and <0.4 wt % Cu according to electron microprobe analysis. LA-ICP-MS data and mapping show that Pd content in the pentlandite increases toward contacts with ISS and decreases toward contacts with MSS, supporting a reaction origin of pentlandite. The wide variations of the concentrations of major and trace elements in the solid solutions, as well as the coexistence of Pd-poor (a few ppm Pd) and Pd-rich (over 4.62 wt % Pd) pentlandite within a single sample, seem to characterize the different generations of the MSS to MSS-ISS globules, antecrysts, and phenocrysts with the distinct histories of enrichment due to exchange with fractionated Cu-platinum group element-rich residue. The directional distribution of Pd of high-temperature primary magmatic origin is preserved due to rapid quenching of the sulfides from ~650°C.

Platinum-group element sulpharsenides and Pd bismuthotellurides in the metamorphosed Ni-Cu deposit at Las Aguilas (Province of San Luis, Argentina)

1997 ◽  
Vol 61 (409) ◽  
pp. 861-877 ◽  
Author(s):  
Fernando Gervilla ◽  
Alejandro Sáncnez-Anguita ◽  
Rogelio D. Acevedo ◽  
Purificación Fenoll Hach-Ali ◽  
Andres Paniagua
Keyword(s):  
Platinum Group Element ◽  
Shear Zones ◽  
Group Element ◽  
Monosulfide Solid Solution ◽  
Crustal Rocks ◽  
Grade Metamorphism ◽  
San Luis ◽  
Sulphide Ore ◽  
High Grade Metamorphism ◽  
Platinum Group

AbstractThe Las Aguilas Ni-Cu-PGE deposit is associated with a sequence of basic-ultrabasic rocks made up of dunite, harzurgite, norite and amphibolite. These igneous (partially metamorphosed) rocks, and their host granulites, gneisses and migmatites of probable Precambrian age, are highly folded. The sulphide ore, consisting of pyrrhotite, pentlandite and chalcopyrite, occurs in the cores of both antiform and synform structures, within dunite, harzburgite and mainly along shear zones in bronzitite, replacing small mylonitic subgrains. The platinum-group mineral assemblage is dominated by Pd bismuthotellurides (Pt-free merenskyite, palladian bismuthian melonite and michenerite), with minor sperrylite, and PGE-sulpharsenides. The latter often occur as single, zoned crystals frequently showing cores of irarsite; outside these are concentric zones of cobaltian hollingworthite, rhodian nickelian cobaltite and Fe-rich nickelian cobaltite.Mineralogical, textural and chemical evidence indicate that the sperrylite and platinum-group element sulpharsenides were formed during a primary magmatic event associated with the fractionation of a basaltic melt, which was contaminated by the assimilation of metamorphic crustal rocks. PGE sulpharsenides crystallized from As-bearing, residual magmatic liquids that collected PGE and segregated after the crystallization of the monosulfide solid solution. During high-grade metamorphism, sulpharsenides were remobilized as solid crystals in the liquated sulfides suffering partial dissolution and fracturing. On the other hand, there is no evidence of a primary concentration of Pd-bismuthotelluride minerals, and their present spatial distribution is only the consequence of their formation under high- to medium-grade metamorphism, down to temperatures of below 500°C. Pd bismuthotellurides crystallize even in fractures of sulpharsenides, attached to the boundaries of highly dissolved sulpharsenide crystals, and intergrown with molybdenite.

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