Composition and Mineralogy of Pge-Rich Chromitites in the Nurali Lherzolite Gabbro Complex, Southern Urals, Russia

Zaccarini, Federica; Pushkarev, E. V.; Ферштатер, Г. Б.; Garuti, Giorgio

doi:10.2113/gscanmin.42.2.545

Cited by 53 publications

(56 citation statements)

References 26 publications

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“…According to the genetic models proposed , Tsoupas & Economou-Eliopoulos 2007, Proenza et al 2007, Uysal et al 2009), the grains formed at low temperature by in situ alteration of a pre-existing laurite-erlichmanite mineral. This assumption is supported by (1) the fact that the composition of the studied grains in terms of Ru-Os-Ir overlaps the field of lauriteerlichmanite, and (2) by the finding of several grains composed of a core of laurite rimmed by the O-bearing material in the Nurali chromitite (Zaccarini et al 2004). This observation confirms the idea that the lauriteerlichmanite grains lost their S, which was then replaced by Fe and O during alteration processes at low temperature , Tsoupas & Economou-Eliopoulos 2007, Proenza et al 2007, Uysal et al 2009).…”

Section: Discussionmentioning

confidence: 76%

“…Therefore, they are grouped among the socalled noble metals. However, it has been suggested (Cabri et al 1981, Olivo & Gauthier 1995, Nixon et al 1990, Legendre & Augé 1993, Jedwab & Cassedanne 1998, Barkov et al 1999, 2012, McDonald et al 1999, Weiser & Bachmann 1999, Tolstykh et al 2000, Oberthür et al 2003, Cabral et al 2004, Jedwab 2004, Zaccarini et al 2004, Melcher et al 2005, Shcheka et al 2005, Tsoupas & Economou-Eliopoulos 2007, Proenza et al 2007, 2008, Uysal et al 2009, 2012, Kapsiotis et al 2011, Tuisku 2012) that under the appropriate physical-chemical conditions in the natural environment, PGE may form PGE-bearing oxides and hydrated oxides, thus implying that they do not always behave as noble elements. These PGE oxide compounds, if they exist, are rare in nature and most have been reported from alluvial placers.…”

Section: Introductionmentioning

confidence: 99%

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Ruthenium and Magnetite Intergrowths From the Loma Peguera Chromitite, Dominican Republic, and Relevance to the Debate Over the Existence of Platinum-Group Element Oxides and Hydroxides

Zaccarini

Bindi

Garuti

et al. 2014

The Canadian Mineralogist

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Two small grains, about 50 × 60 × 70 μm in size, occurring in the chromitite associated with the altered harzburgite of Loma Peguera (Dominican Republic) have been investigated by electron microprobe analyses, X-ray computed tomography, and X-ray diffraction. Electron microprobe data indicate the grains to be composed of Ru, Os, Ir, Fe, and O. The obtained composition is similar to those reported from podiform chromitites worldwide and often reported as evidence for the existence of PGE-bearing oxide minerals. X-ray computed tomography and X-ray diffraction data, provided for the first time in this study, reveal that the Loma Peguera grains consist of a fine intergrown of ruthenium and magnetite not detectable at the scale of the electron microprobe. We believe that the investigated grains were originally laurite, ideally (Ru,Os)S 2 , crystallized during the magmatic stage. During alteration processes at low temperature, the mineral lost its original S, which transformed the laurite to ruthenium. The newly formed ruthenium was probably porous and, during the final stage of the alteration process, oxidizing fluids enriched in Fe filled the cavities leading to the subsequent crystallization of magnetite.

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Section: Discussionmentioning

confidence: 76%

Section: Introductionmentioning

confidence: 99%

Ruthenium and Magnetite Intergrowths From the Loma Peguera Chromitite, Dominican Republic, and Relevance to the Debate Over the Existence of Platinum-Group Element Oxides and Hydroxides

Zaccarini

Bindi

Garuti

et al. 2014

The Canadian Mineralogist

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“…Its composition suggests that the Sulawesi laurites, even the crystals found in contact with secondary silicates, were not affected by post-magmatic alteration, as observed in laurites associated with other ophiolitic chromitites [12,14,[57][58][59][60][61][62][63][64][65]. During the alteration processes, laurite released S that was replaced by Fe and O to form a fine intergrowth of native ruthenium and magnetite [61] or it has lost part of the Os and Ir to form Ru-rich laurite [14].…”

Section: Origin Of the Pgm In The Sulawesi Chromititesmentioning

confidence: 99%

Chromite Composition and Accessory Minerals in Chromitites from Sulawesi, Indonesia: Their Genetic Significance

2016

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Several chromite deposits located in the in the South and Southeast Arms of Sulawesi, Indonesia, have been investigated by electron microprobe. According to the variation of the Cr# = Cr/(Cr + Fe 3+ ), the chromite composition varies from Cr-rich to Al-rich. Small platinum-group minerals (PGM), 1-10 µm in size, occur in the chromitites. The most abundant PGM is laurite, which has been found included in fresh chromite or in contact with chlorite along cracks in the chromite. Laurite forms polygonal crystals, and it occurs as a single phase or in association with amphibole, chlorite, Co-pentlandite and apatite. Small blebs of irarsite (less than 2 µm across) have been found associated with grains of awaruite and Co-pentlandite in the chlorite gangue of the chromitites. Grains of olivine, occurring in the silicate matrix or included in fresh chromite, have been analyzed. They show a composition typical of mantle-hosted olivine. The bimodal composition and the slight enrichment in TiO 2 observed in some chromitites suggest a vertical zonation due to the fractionation of a single batch magma with an initial boninitic composition during its ascent, in a supra-subduction zone. This observation implies the accumulation of Cr-rich chromitites at deep mantle levels and the formation of the Al-rich chromitites close or above the Moho-transition zone. All of the laurites are considered to be magmatic in origin, i.e., entrapped as solid phases during the crystallization of chromite at temperature of around 1200˝C and a sulfur fugacity below the sulfur saturation. Irarsite possibly represents a low temperature, less than 400˝C, exsolution product.

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“…The other examples of species of "high-temperature" PGM include alloys of refractory elements, such as an Os-Ir alloy, or laurite-erlichmanite (RuS 2 -OsS 2 ). The latter is commonly considered to be one of the first PGM to crystallize, and its composition may even reflect the Ru:Os ratio of the primitive mantle (Zaccarini et al 2004). On the other hand, in fluid-rich systems, these and other species of PGM could have crystallized at a lower temperature, corresponding to a postmagmatic-hydrothermal stage, e.g., cooperite was observed as a product of low-temperature hydrothermal synthesis (Plyusnina et al 2000), and laurite of hydrothermal origin was described from the Imandra layered complex, Russia (Barkov & Fleet 2004).…”

Section: Implications Based On the Inclusions In Placer Grains Of Pt-mentioning

confidence: 99%

Platinum-Group Minerals From a Placer Deposit in Burwash Creek, Kluane Area, Yukon Territory, Canada

Fedortchouk¹,

LeBarge²,

Barkov³

et al. 2010

The Canadian Mineralogist

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Five placer grains of Pt-Fe alloy, ca. 0.5 to 2 mm, roundish in shape, and hitherto unconfirmed from this locality, were recovered from a placer deposit in Burwash Creek, Kluane area, Yukon. Our results of multiple electron-microprobe analyses (EMP) display the presence of elevated levels of Pd (0.49-5.84, mean 2.38 wt.%), Rh (1.05-1.94, mean 1.50 wt.%), Ir (<0.2 to 6.91, mean 1.33 wt.%), and Cu (0.17-1.19, mean 0.62 wt.%) in these alloy grains; a compositional series is observed, in which values of SPGE/(Fe + Cu + Ni) vary from 3.0 to 5.7. Concentrations of Ru are invariably low (<0.03 to 0.11 wt.%) in this series. These grains of Pt-Fe alloy host micro-inclusions of various species of platinum-group minerals, PGM, diopside Mg 37.5-48.0 Fe 4.9-16.8 , mg# = 100Mg/(Mg + Fe 2+ ) in the range 69.0-90.7], plagioclase (Ab 57.5-60 An 35.1-39.9 Or 2.6-4.8 ), and sodic-calcic amphiboles (0.6 and 1.1 Na apfu), some of which are rich in Cl (0.72 and 1.17 wt.%, or 0.17 and 0.36 Cl apfu, respectively). The analyzed inclusions of PGM are members of the bowieite Rh 2 S 3 -kashinite Ir 2 S 3 solid-solution series, miassite (Rh,Pt,Pd) 17 S 15 , cooperite PtS, isoferroplatinum Pt 3 Fe (or Fe-rich platinum), vasilite (Pd,Cu,Pt) 16 S 7 , keithconnite Pd 20 Te 7 , an unusual Pt-Pd-Ni-Cu alloy (i.e., Pd-rich platinum: Pt 47.7-52.8 Pd 29.3-37.9 Ni 6.3-8.0 Cu 6.1-7.5 ), and a sulfotelluride of Pd, Pd 11 Te 2 S 2 (?), which may represent a new isomertieite-type compound. The trace-element composition of the silicate melt inclusions determined using laser-ablation ICP-MS shows a notable enrichment in large-ion lithophile elements. We infer that the reported association of PGM and the trace-element composition of silicate melt inclusions observed at Burwash Creek probably correspond to an Alaskan-Uralian-type mineralization; considered less likely is a relation with a Triassic ultramafic-mafic complex (sill-like) of so-called Kluane-type, also developed in the placer area.

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Composition and Mineralogy of Pge-Rich Chromitites in the Nurali Lherzolite Gabbro Complex, Southern Urals, Russia

Cited by 53 publications

References 26 publications

Ruthenium and Magnetite Intergrowths From the Loma Peguera Chromitite, Dominican Republic, and Relevance to the Debate Over the Existence of Platinum-Group Element Oxides and Hydroxides

Ruthenium and Magnetite Intergrowths From the Loma Peguera Chromitite, Dominican Republic, and Relevance to the Debate Over the Existence of Platinum-Group Element Oxides and Hydroxides

Chromite Composition and Accessory Minerals in Chromitites from Sulawesi, Indonesia: Their Genetic Significance

Platinum-Group Minerals From a Placer Deposit in Burwash Creek, Kluane Area, Yukon Territory, Canada

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