Occurrence of rare Ru-Fe-Os-Ir-oxide and associated Platinum-group minerals (PGM) in the chromitite of Mugla ophiolite, SW-Turkey

Uysal, İbrahi̇m; Zaccarini, Federica; Sadıklar, M. Burhan; Bernhardt, Heinz-Jürgen; Bigi, Simona; Garuti, Giorgio

doi:10.1127/0077-7757/2009/0131

Cited by 30 publications

(29 citation statements)

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“…Despite the numerous reported occurrences of Ru-Os-Ir-Fe and O mineral phases (Zaccarini et al 2005, Proenza et al 2007, 2008, Tsoupas & Economou-Eliopoulos 2007, Uysal et al 2009, 2012, Kapsiotis et al 2011, they were never investigated with X-ray methods. As a consequence, it was never possible to establish if they represent new oxide minerals.…”

Section: Discussionmentioning

confidence: 96%

“…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: 95%

“…The first report of Ru-Os-Ir-Fe and O mineral phases was by from podiform chromitites of the Vourinos ophiolite complex, Greece. Later, several podiform chromitites associated with different ophiolites worldwide, namely Othrys, Pindos, and Veria (Greece), Loma Peguera (Dominican Republic), Tehuitzingo (Mexico), Ray-Iz (Polar Urals), Mugla and Islahiye (Turkey), and the Nurali lherzolite-gabbro complex (Southern Urals) (Tsoupas & Economou-Eliopoulos 2007, Zaccarini et al 2005, Proenza et al 2007, 2008, Uysal et al 2009, 2012, Kapsiotis et al 2011, were shown to contain PGM compounds with similar composition. Despite the numerous reported occurrences and oxygen-bearing compositions, it was impossible to establish whether these phases were fine intergrowths of a Ru-rich alloy with Fe-oxides/hydroxides or true oxides of PGE, mainly because their small size (<30 μm) prevented any X-ray investigation.…”

Section: Introductionmentioning

confidence: 96%

See 2 more Smart Citations

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: 96%

Section: Introductionmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 96%

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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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“…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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“…Radial-fibrous internal textures of secondary PGM derived from the in situ alteration of magmatic laurite at low temperatures were reported from ophiolite-related chromitite samples from Greece [26], and similar secondary grains were also described by [27] from Turkish ophiolites. The latter authors demonstrated that dark zones in BSE images contain significant contents of Si and Mg (up to 9 and 10 at %, respectively), which accounted for sub-microscopic particles of chlorite or serpentine.…”

Section: Discussionmentioning

confidence: 69%

Fibrous Platinum-Group Minerals in “Floating Chromitites” from the Loma Larga Ni-Laterite Deposit, Dominican Republic

et al. 2016

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This contribution reports on the observation of enigmatic fibrous platinum-group minerals (PGM) found within a chromitite body included in limonite ("floating chromitite") from Ni-laterites in the Dominican Republic. Fibrous PGM have a Ru-Os-Ir-Fe dominated composition and are characterized by fibrous textures explained by grain-forming fibers which are significantly longer (1-5 µm) than they are wide (~100 nm). Back-scattered electron (BSE) images suggest that these nanofibers are platinum-group elements (PGE)-bearing and form <5 µm thick layers of bundles which are oriented orthogonal to grains' surfaces. Trace amounts of Si are most likely associated with PGE-bearing nanofibers. One characteristic fibrous PGM was studied in detail: XRD analyses point to ruthenian hexaferrum. However, the unpolished fibrous PGM shows numerous complex textures on its surface which are suggestive for neoformation processes: (i) features suggesting growth of PGE-bearing nanofibers; (ii) occurrence of PGM nanoparticles within film material (biofilm?) associated with PGE-bearing nanofibers; (iii) a Si-rich and crater-like texture hosting PGM nanoparticles and an Ir-rich accumulation of irregular shape; (iv) complex PGM nanoparticles with ragged morphologies, resembling sponge spicules and (v) oval forms (<1 µm in diameter) with included PGM nanoparticles, similar to those observed in experiments with PGE-reducing bacteria. Fibrous PGM found in the limonite may have formed due to supergene (bio-)weathering of fibrous Mg-silicates which were incorporated into desulphurized laurite during stages of serpentinization.

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Occurrence of rare Ru-Fe-Os-Ir-oxide and associated Platinum-group minerals (PGM) in the chromitite of Mugla ophiolite, SW-Turkey

Cited by 30 publications

References 0 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

Fibrous Platinum-Group Minerals in “Floating Chromitites” from the Loma Larga Ni-Laterite Deposit, Dominican Republic

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