Platinum-group minerals and tetraauricupride in ophiolitic rocks of Skyros island, Greece

Tarkian, M.; Economou-Eliopoulos, Maria; Eliopoulos, Demetrios G.

doi:10.1007/bf01165297

Cited by 37 publications

(29 citation statements)

References 14 publications

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“…This is similar to Skyros and Rhodope complexes [38,39] strongly indicating that f S2 was sufficiently high from the beginning of the magmatic evolution of the west Othrys chromitites. Most likely, f S2 was raised above the Os-OsS 2 buffer, as it is deduced by the appearance of erlichmanite.…”

Section: Petrogenetic Implicationssupporting

confidence: 59%

Investigation of Platinum-Group Minerals (PGM) from Othrys Chromitites (Greece) Using Superpanning Concentrates

et al. 2016

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Platinum-group minerals were concentrated using superpanning from two composite chromitite samples, which were collected from two old mines within the Othrys ophiolite. This method allows for the recovery of a broad spectrum of these rare and fine-grained minerals, and helps to better identify them and interpret their origin. Major differences between the east and west Othrys ophiolites were determined, probably as a result of their different origin and evolution. Primary Os-, Ir-, and Ru-bearing platinum-group minerals (IPGM)-alloys and the Rh-, Pt-and Pd-bearing platinum-group minerals (PPGM) occur only in the east Othrys chromitite, indicating an evolution from initially low f S2 conditions at shallower mantle levels with the subsequent implication of a S-saturated ascending fluid. In contrast, the absence of primary IPGM-alloys in west Othrys chromitite indicates that S saturation had been attained. The presence of erlichmanite suggests that sulphur fugacity eventually increased significantly in both suites. Substantial fluctuations of a fluid phase, likely related to serpentinising fluids, modified the platinum-group minerals (PGM) assemblage of west Othrys, and resulted in a large diversity of secondary PGM minerals. The limited number of secondary species developed in the east Othrys indicate that secondary processes were also different in the two suites.

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Section: Petrogenetic Implicationssupporting

confidence: 59%

Investigation of Platinum-Group Minerals (PGM) from Othrys Chromitites (Greece) Using Superpanning Concentrates

et al. 2016

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“…Nonequilibrium coexistence of reduced and oxidized phases of the transition metals are characteristic of the high-temperature stages at Kudryavy [51]. (f) Finally, native iron has been documented in ophiolitic rocks such as serpentinizated dunites, peridotites, serpentinites and in associated chromitites, in several cases such as Josephine, U.S.A. [35], Sanbagawa belt, central Japan [36], Maqsad ophiolite, Oman [37], the Balangero area, Italy [38], Luobusa ophiolite, southern Tibet [3,39,40], Ray-Iz ophiolite, Polar Urals [41] and the region neighboring the study area, Skyros island, Greece [42]. In Luobusa ophiolite, southern Tibet, native iron occurs in two forms in the chromitites, as small round nodular intergrowths and as anhedral masses of acicular crystals.…”

Section: Discussionmentioning

confidence: 99%

A New Occurrence of Terrestrial Native Iron in the Earth’s Surface: The Ilia Thermogenic Travertine Case, Northwestern Euboea, Greece

et al. 2018

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Native iron has been identified in an active thermogenic travertine deposit, located at Ilia area (Euboea Island, Greece). The deposit is forming around a hot spring, which is part of a large active metallogenetic hydrothermal system depositing ore-bearing travertines. The native iron occurs in two shapes: nodules with diameter 0.4 and 0.45 cm, and angular grains with length up to tens of µm. The travertine laminae around the spherical/ovoid nodules grow smoothly, and the angular grains are trapped inside the pores of the travertine. Their mineral-chemistry is ultra-pure, containing, other than Fe, only Mn (0.34-0.38 wt.%) and Ni (≤0.05 wt.%). After evaluating all the possible environments where native iron has been reported up until today and taking under consideration all the available data concerning the study area, we propose two possible scenarios: (i) Ilia's native iron has a magmatic/hydrothermal origin i.e., it is a deep product near the magmatic chamber or a peripheral cooling igneous body that was transferred during the early stages of the geothermal field evolution, from high temperature, reduced gas-rich fluids and deposited along with other metals in permeable structural zones, at shallow levels. Later on, it was remobilized and mechanically transferred and precipitated at the Ilia's thermogenic travertine by the active lower temperatures geothermal fluids; (ii) the native iron at Ilia is remobilized from deep seated ophiolitic rocks, originated initially from reduced fluids during serpentinization processes; however, its mechanical transport seems less probable. The native iron mineral-chemistry, morphology and the presence of the other mineral phases in the same thermogenic travertine support both hypotheses.

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“…As inferred above, the Os content of laurite is a direct indicator of the T-f(S 2 ) conditions prevailing (Gervilla et al 2005) and the Ortaca ultramafic massif (Uysal et al 2005) in the ternary diagram Ru-Os-Ir (at.%), and from (B) Rhodope (Tarkian et al 1991), Skyros (Tarkian et al 1992), Othrys (Garuti et al 1999) and Vourinos (Augé 1985, 1988, Garuti & Zaccarini 1997, Kapsiotis et al 2009, 2010 Augé (1985Augé ( , 1988, Garuti & Zaccarini (1997) and Kapsiotis et al (2010), respectively. in the silicate magma during crystallization.…”

Section: Origin Of the Inverse Zoning In Laurite And Conditions Of Almentioning

confidence: 99%

“…In addition, laurite compositions in our chromitite samples from the Pindos ophiolite complex differ from those in the other ophiolitic occurrences in Greece. For example, laurite compositions from the Milia chromitites are distinct from laurite from the Vourinos chromitites (Augé 1985, 1988, Garuti & Zaccarini 1997, Kapsiotis et al 2010, the Othrys chromitites (Garuti et al 1999), Rhodope (Tarkian et al 1991) and Skyros chrome deposits (Tarkian et al 1992; Fig. 10B).…”

Section: The Pgm Of Milia Chromitites Compared To Pgm From Other Chromentioning

confidence: 99%

Chromian Spinel Composition and Platinum-Group Element Mineralogy of Chromitites From the Milia Area, Pindos Ophiolite Complex, Greece

Kapsiotis

Grammatikopoulos

Tsikouras

et al. 2009

The Canadian Mineralogist

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The chromitites of the Milia area in the Pindos ophiolite complex, in Greece, were investigated for their platinum-group mineral (PGM) content. The chromitites are massive, more rarely disseminated in texture and occur as small pods. They are composed of magnesiochromite crystals with Cr# [Cr/(Cr + Al)] between 0.80 and 0.84, and Mg# [Mg/(Mg + Fe 2+ )] between 0.54 and 0.72. The total platinum-group-element (PGE) contents in chromitites are relatively low (≤170 ppb), although they may locally be higher (up to 1059 ppb). The IPGE (Os, Ir and Ru) predominate over the PPGE (Rh, Pt and Pd). The PGM assemblage, consistent with the geochemical data, is dominated by laurite and Os-Ir-Ru alloys that occur both as single and composite grains, generally less than 15 mm in size. Laurite has a wide range of Os-for-Ru substitution [Ru/(Ru + Os): 0.42-0.99], whereas primary alloys are enriched in Ru (up to 73.80 wt.%). Some laurite crystals exhibit an anomalous pattern of zoning. Such zoning requires an inversion of the normal T-f(S 2 ) trend in magmatic systems, and is herein considered to be due to postmagmatic processes. Some Ru-rich alloy grains contain relatively high Rh and Pt abundances, similar to those of residual sulfides in mantle peridotites. This feature suggests that these alloys may represent residual PGM phases from earlier episodes of melt extraction from the severely depleted mantle unit of the Pindos ophiolite complex. Combined compositional data indicate that the Milia chromitites formed from a hydrous boninitic melt in a suprasubduction-zone environment.Keywords: chromitites, platinum-group minerals (PGM), laurite, alloys, ophiolites, Pindos, Greece. Certains grains d'alliages riches en Ru contiennent des teneurs relativement élevées en Rh et Pt, tout comme les sulfures résiduels de péridotites du manteau. Ces grains d'alliage pourraient donc représenter des MGP résiduels après l'extraction antérieure de liquide silicaté, laissant un manteau très stérile dans le complexe ophiolitique de Pinde. Les données combinées sur la composition indiquent que les chromitites de Milia se sont formées à partir d'une magma hydraté boninitique dans un milieu au dessus de la zone de subduction.(Traduit par la Rédaction)

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Platinum-group minerals and tetraauricupride in ophiolitic rocks of Skyros island, Greece

Cited by 37 publications

References 14 publications

Investigation of Platinum-Group Minerals (PGM) from Othrys Chromitites (Greece) Using Superpanning Concentrates

Investigation of Platinum-Group Minerals (PGM) from Othrys Chromitites (Greece) Using Superpanning Concentrates

A New Occurrence of Terrestrial Native Iron in the Earth’s Surface: The Ilia Thermogenic Travertine Case, Northwestern Euboea, Greece

Chromian Spinel Composition and Platinum-Group Element Mineralogy of Chromitites From the Milia Area, Pindos Ophiolite Complex, Greece

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